This is where the fish lives.

The fun starts around 7:30...

c-dif: all hands on poop deck

Clostridium difficile was first described over 75 years ago by Hall and O'Toole, and initially named 'Bacillus difficilis' not because of its virulence but rather because of the difficulty culturing the bacteria ex vivo. They found that this bacteria asymptomatically colonized 40-70% of neonates within the first month of birth. In fact, c-dif is a slow-growing, indolent bacteria whose morbidity has been unleashed exclusively by iatrogenic eradication of gut flora by (you guessed it) doctors. It turns out that c-dif's relative inactivity makes it insensitive to most standard antibiotics; therefore when a patient is treated broadly with a penicillin, cephalosporin, or fluoroquinolone for a pneumonia or cholecystitis, the coast becomes clear for c-dif to spread and do its damage. The damage is done primarily by thenefarious work of 2 toxins, appropriately named c-dif toxin A and toxin B (CDTa and CDTb, respectively). These toxins disrupt the actin cytoskeleton-stabilized tight junctions between intestinal epithelialcells via UDP-glucose-dependent glycosylation and inactivation of Rho and Ras protiens, leading to epithelial sloughing and subsequent inflammation.

Over the years, the liberal use of antibiotics in hospitals has driven increasing virulence of c-dif, such that a hospital stay of 2 days or longer now results in a 10% risk of contracting c-dif colitis. The risk appears to be highest in the elderly, possibly because of their impaired immune response. This virulence began to progress to the point that c-dif outbreaks began to emerge in the community and in absence of recent antibiotic therapy, first in Hungary in 2004 but quickly in the US by 2006, and particularly in patients on gastric acid-suppressive therapies.

One of the main concerns with controlling c-dif infections is the frequency of recurrence (20-33% after the first infection, 65% or higher in those with more than 1 occurence). And while c-dif colitis is treatable with either metronidazole or vancomycin, antibiotic efficacy decreases in subsequent recurrences. Recurrent c-dif appears to be more virulent based on upregulation of CDTa and b toxins; yet this may also be a key to its treatment. One of the fun things about emerging therapies for c-dif is how 2 of the most promising therapies are about as different as can be: recombinant humanized monoclonal antibody therapy versus....someone else's poop.

The high-tech answer: passive and active immunization.

The first hint that the immune system might be of some help in fighting off recurrent c-dif came from a study in 2000 published in the New England Journal. In it, Kyne and colleagues showed that patients who had c-dif colonization without infection had high serum levels of antibodies against toxin A. They followed it up with a study published in Lancet one year later in which they showed that following acute c-dif infection, the patients who were 'immune' to recurrence made IgM antibodies against toxin A within 3 days. Similar results were later shown for c-dif toxin B. It took about 6 years for fully humanized monoclonal antibodies to be made against both toxins and shown to protect hamsters from recurrent c-dif (Infect Immun. 2006, 74(11): 6339-47).

4 years later, in 2010, a landmark study published in NEJM showed that administration of mAb against both toxins A and B resulted in a relative risk reduction of 70% in patients with 1 episode of c-dif colitis and 80% in patients with more than 1 prior episode. The inherent problem with this strategy is that it provides only passive immunity, and therefore patients would require frequent infusions. A more lasting solution would be to induce active immunity in patients with vaccination against target peptide antigens. In 2003, a vaccine composed of immunogenic portions of toxin A was able to induce significant titers of IgG in patients, and case reports of 3 patients with severe recurrent c-dif colitis showed that two out of three patients who were vaccinated generated high titers of antibodies to both CDTB and CDTA and induced remission without recurrence. A phase II trial in patients aged 18-85 with 1+ prior episode of c-dif colitis is currently underway.

The low-tech option: your poo, please.

The other potential solution to c-dif is simple, logical, fairly gross, and impressively efficacious. It goes by the name of "fecal flora reconstitution," which is a fancy way of saying "poop transfusion." It's based on two major ideas: first, that patients who succumb to c-dif infections have not only a poor immune response to c-dif, but commensal gut flora that don't protect them against c-dif overgrowth, and second, that the best way to overcome a deadly, but frankly wimpy bacteria like c-dif is to re-introduce a set of much more competitive gut flora. Thus: poop transfusions. It's simple; check the donor for communicable diseases as well as a history of c-dif exposure, liquefy their feces in non-bacteriostatic saline, dump it into a colonoscope, administer the donor feces at the level of the ileum, have the patient take immodium to maximize contact time between the new flora and the gut epithelium, and watch the magic happen.

And, for the most part, it does. Almost every study, despite variability, demonstrates sustained responses in refractory patients with only one dose in >90% of patients, and response to a 2nd dose in the majority of the 10% of patients who don't respond initially. The point? if you can get over slightly stomach-turning concept, its an incredible, cost-effective solution to an iatrogenic problem. And its sure to make one bond in your life stronger - after all, once you share poop, what can't you share?

***

I'll leave you this election night, in which 4/10 voters verbalized support for the "death panel" touting Tea Party, with the thoughts of David Meltzer of the University of Chicago's department of Medicine and Economics, on the need to accept rationing for what it is (a fact of life in the health care system) so that we can have some real debate, not over whether we should ration (a healthcare system without it is ludicrous) but rather, who should be in charge.

love me some notebook!

i bet his name isn't mike...that's why he's confused when i say 'mike'...

so i've been reading some things.

and why have i chosen to headline this post with a totally badass previously not seen photo from Empire Strikes Back? Yeah, like someone needs a reason to do that.

The Tea Party

So...I know the dialogue on this is pretty uninteresting. But I did read a few pretty interesting articles that, while not addressing the Tea Party per se (a narrative that is kind of played out) deals with the importance of the ascension of the Tea Party:

Sean Wilentz of the New Yorker kicks things off by rehashing the ol' "history repeats itself" with specific reference to the Tea Party and how it owes its roots directly to the John Birch Society and a man named Willard Skousen, whose ideologies revolved around surprising tenets such as equating the Ivy League with the Illuminati (I wish.) The piece also touches on Glenn Beck's carrying forward of Skousen's paranoid interpretations of the politicians of his day. Perhaps more interesting, however, is his description of William Buckley's efforts to recenter the Republican party (pretty sad when you have to look to a McCarthyist to be the GOP flagbearer, but still). Wilentz depicts Ronald Reagan's shrewd ability to consolidate Buckley's pragmatic conservatism into Republican victories, a step forward for the GOP that was ignored during the Gingrich "Contract for America" resurgence in 1994 and positively obliterated by the Tea Party surge in 2010.

Matt Taibbi, to my great joy, takes advantage of the greater leeway he is offered by Rolling Stone. "Let me get this straight," he says to David, a Tea Party tax protestor. "You've been picking up a check from the government for decades, as a tax assessor, and your wife is on Medicare. How can you complain about the welfare state?" Of course, I love that gonzo journalism stuff, but the real good stuff is in Taibbi's detailing of the Tea Party, and its mascot Rand Paul's roots as an unrecognizable perversion of Ron Paul's libertarian rallies in 2008. Ultimately, Taibbi offers us a chilling reminder that the co-opting, subjugation, and assimilation of taxpayer fury into corporate sponsored gridlock is the essence of our modern political system:

The bad news is that the Tea Party's political outrage is being appropriated, with thanks, by the Goldmans and the BPs of the world. The good news, if you want to look at it that way, is that those interests mostly have us by the balls anyway, no matter who wins on Election Day. That's the reality; the rest of this is just noise. It's just that it's a lot of noise, and there's no telling when it's ever going to end.

Finally, Todd Purdum of Vanity Fair talks about the challenge that John Boehner, a somewhat pragmatic dealmaker in his old days who sold his soul to the Tea Party early on, will face. Purdum notes that Boehner may be one of the few remaining hopes for Republican pragmatists sure to be overwhelmed by a sea of incoming partisan fury:

Boehner is, in the end, a most unlikely candidate to lead any kind of revolution. He is a traditionalist, and an institutionalist, and, Lord knows, he is anything but a fresh face. He is the captive of forces more powerful than himself, and he has evidenced a form of Stockholm syndrome, which his captors may or may not find convincing. The pitiful reality of contemporary Washington is that institutional perspective is in such short supply that anyone with even a smidgen of it might pass for having qualities of statesmanship. If John Boehner is a statesman, he’s one who starts from an unenviable position: neither the leader his party may really want nor the kind his country most needs.

Obama and Pals

I think this piece by Tim Dickinson may be the most important, however. In it, he tells us all to get off of our enormously high horse, and realized that our president has made almost unfathomably large pieces of legislative progress in his first 2 years:

But if the passions of Obama's base have been deflated by the compromises he made to secure historic gains like the Recovery Act, health care reform and Wall Street regulation, that gloom cannot obscure the essential point: This president has delivered more sweeping, progressive change in 20 months than the previous two Democratic administrations did in 12 years. "When you look at what will last in history," historian Doris Kearns Goodwin tells Rolling Stone, "Obama has more notches on the presidential belt." In fact, when the history of this administration is written, Obama's opening act is likely to be judged as more impressive than any president's — Democrat or Republican — since the mid-1960s. "If you're looking at the first-two-year legislative record," says Ornstein, "you really don't have any rivals since Lyndon Johnson — and that includes Ronald Reagan."

It is, rather, the talking points war that has been lost by the Obama administration. In some ways, I think of them as these kind of insular policy nerds, who have always just made the best available decision and figured people would come around to realize the value of their pragmatism. Unfortunately, they overlooked the fact that modern consumers don't simply value sensationalism over rationalism; they actually invert the two and elevate people who have either barely, or not even, graduated from college, to the level of pundits.

Malcolm Gladwell describes one such ambitious accomplishment/failed narrative: the auto bailout. He describes the fairly impressive turnound of GM, something that was news to me (I guess I'm victimized by the news cycle as much as anyone else). This is all couched within a story about the power struggle between Steven Rattner, the private equity maven hired to oversee the auto bailout, and Rick Wagoner, the villainized former CEO of GM who flew his chartered jet to Washington to ask for taxpayer money, yet is more responsible for GM's turnaround than Rattner.

Honestly, the piece on Sean Parker was pretty lame, so I'll end by saying that you absolutely have to check out 'Abstract City,' Cristoph Niemann's blog on the New York Times. Some of his stuff, including his visual chronicle of a trip overseas and his Lego interpretation of New York, are transcendent.

Back to science next time!

non-science?

yep! i read other stuff! i do! such as...

- glenn beck

- the tea party

- barack obama

- cristoph niemann

- general motors

<-- jon boehner

- and sean parker!

- yay!

- this photo is kind of creepy.

You should be dancing and that ain't no dark sarcasm.

holy melanoma!

The mantra of treating melanoma has been the same as many other malignancies (colon, lung, ovarian, etc.): catch it before it spreads. What has separated melanoma, other than the fact that it is readily detectable with excellent prognosis as an in situ malignancy, once metastasized (which occurs in 20-25% of all melanomas), the prognosis has been almost incomparably poor.The life expectancy of a patient with stage IV malignant melanoma is less than one year, with fewer than 15% of patients surviving three years.Until recently, exisiting therapies for metastatic melanoma offered little hope of disease-free survival. The most promising therapies as recent as five years ago revolved around broad-scale harnessing of the immune system:

IL2 (proleukin) is a well-known T cell survival and proliferation signal, and has been shown to induce partial responses in 10-20% of patients (though few patients go into complete remission). The method of activity is presumed to be expansion of antitumor T cells. However, this therapy is associated with sepsis-mimicking complications such as severe hypotension and vascular leak syndrome.

IFNg is produced by NK cells as well as activated CD4 and CD8 T cells and drives both anti-viral and anti-tumor immunity by driving a number of transcriptional changes, including enhanced MHC-I presentation on all cells and maturation of macrophages and dendritic cells. It is one of the prime effector cytokines of Th1 CD4+ T cells.

While both of these therapeutic options are quite limited in their efficacy, the fact that they both act by broadly stimulating T cell effector functions suggested that enhancing antigen-specific T cell responses might provide mortality benefits in metastatic melanoma. So, here are some of the interesting and diverse treatment modalities under exploration:

Immunomodulatory therapy

The new therapies being explored in this vein expand upon the possibilities raised by recombinant IL-2 and IFN-g therapy by potentiating endogenous T cell antitumor activity. Drug developers have tried many interesting ways to boost the endogenous response:

Block suppressive T cell signals: CTLA-4 is expressed on T cells and upregulated following activation. It has a higher affinity for its ligand, B7, than the co-stimulatory molecule CD28, whose ligation is required for full T cell activation. By outcompeting CD28, CTLA-4 limits the duration of T cell signaling and maintains homeostasis. Mice lacking CTLA-4 die rapidly of multi-system autoimmune disease, suggesting that this homeostasis is critical to preventing autoimmunity. However, in patients with unresectable metastatic melanoma, it was felt that removing this suppressive T cell signal might increase reactivity towards low-affinity tumor antigens. Indeed, evidence supporting this was provided in a recent study by Hodi and associates published in the New England Journal.

In it, ipilimumab, a blocking antibody to CTLA-4, nearly doubled median survival (10 months vs. 6.4 month), and increased 1 year survival from 25% to 45%. Interesting, the limiting side effect for these patients was skin fibrosis and inflammatory diarrhea similar in histopathology to graft-versus-host disease and likely representing unchecked autoimmune reactivity seen in

earlier mouse studies and controlled in these patients with either high-dose steroids or TNFa inhibitors.

Improve T cell priming: Immunogenic peptides derived from melanoma cells were shown to induce tumor-infiltrating lymphocytes which led to tumor regression over fifteen years ago.

Unfortunately, vaccination with gp100 or other highly immunogenic peptides has proven disappointing. Recent efforts have focused on improving peptide delivery to lymph nodes in order to maximally prime anti-tumor T cells.

A recent paper in the Journal of Clinical Investigation used a bacterial vector, Listeria monocytogenes,for this process with the rationale that bacteria would activate toll-like receptor signaling and enhance dendritic cell maturation, and that Listeria's natural tropism for the liver would improve T cell homing to the liver, a common site of melanoma metastasis.Researchers were able to effectively target Listeria to dendritic cells, engineer effective DC activation, drive CTL generation against the melanoma antigen MART-1 as well as CD4 T cells against the antigen ESO-1, which drove effective tumor rejection in a mouse model. Key to the utility of this mechanism is ensuring that the vector's virulence is completely neutralized.

Improve immune cell homing: Somebody really clever came up with this novel idea: of creating a lytic herpes simplex virus which also expresses granulocyte-macrophage colony stimulating factor (GM-CSF); they then directly inject this virus into accessible tumors. A phase II trial of this was published in the Journal of Clinical Oncology last December; unbelievably, it seems to work, improving 1 year survival to greater than 50%. While likely not curative, it provides a fascinating method of decreasing metastatic tumor burden.

Adoptive Transfer of tumor-specific T cells: generation of tumor-infiltrating CD8 T lymphocytes has long thought to be the main mechanism of inducing tumor killing. About 4 years ago, a study in the Journal of Clinical Oncology demonstrated that adoptive transfer of Melan-A-specific CTLs did induce partial or complete responses in 27% of patients; however, these responses were complicated by both eosinophilia and tumor progression in which surviving tumor cells lost their melan-A expression, suggesting that CTLs alone may not be sufficient to control tumor growth.

Given the critical role of CD4 T cells in enhancing CD8 T cell survival and priming, the role of tumor-specific CD4 T cells has been a recent subject of interest. In a study published in NEJM in 2008, a case report from the Fred Hutchinson Institute in Seattle described a patient with metastatic melanoma expressing the immunogenic antigens MART, MAGE-3, ESO-1, but not gp100. Peripheral T cells were isolated from the patient and stimulated with dendritic cells pulsed with ESO-1. After ESO-1-specific CD4 T cells grew out, they were restimulated and expanded multiple times in vitro before being transferred adoptively into the patient. Follow-up 2 months later showed complete resolution of pulmonary and nodal disease and suppression of new metastasis; the patient remained disease free 2 years later at the time of publication. 2 more points here are quite interesting:

1) tumor analysis demonstrated regression despite the fact that not all tumor cells expressed the ESO-1 antigen.

2) Consistent with this, harvesting of the patient's peripheral blood cells revealed expansion of T cells specific not only for ESO-1, but for MART and MAGE-3, but not gp100. This is consistent with the concept known as "antigen spreading" in which ESO-1 expressing cells were killed, taken up by antigen presenting cells, and then induced activation of T cells against other immunogenic tumor peptides.

Growth factor signal inhibitors

In a totally separate direction, massive gene chip analyses have been performed to try to identify novel aberrant signaling pathways activated in melanoma T cells. A few years ago, it was revealed that 40-60% of melanomas carry a mutation in B-Raf, a serine-threonine kinase in the MAP kinase pathway. 90% of these mutations result in a glutamic acid for valine substitution (V600E) which results in constitutive activation. Plexxikon, an orally bioavailable inhibitor of mutant-BRAF, was recently used in a phase I trial for patients with metastatic melanoma which had this mutation. The phase I study (not placebo-controlled) resulted in an 81% response rate and has significantly increased progression-free survival (total survival could not be assessed at the time of publication). Analysis of tumor cells showed that the drug repressed MAP kinase activation, cell cycle activation, and tumor cell proliferation. Notably, this mutation is also seen in anaplastic thyroid cancer; phase I trials assessing response rates is underway.

I wonder how many people actually made it to the end of this?

tonight's project: melanoma

To be worked on while I watch Jonathan Sanchez and Roy Oswalt battle it out.

ok, who's hasselbeck?

ok, this was awesome, and i loved inception.

solving amyloidosis

First described by none other than Rudolph Virchow (pictured, rocking a killer beard) in 1853 in reference to abnormal extracellular material found in the liver on autopsy, amyloidosis refers to the accumulation of misfolded extracellular proteins that are deposited in tissue as bundles of beta-sheet, fibrillar insoluble aggregates and ultimately result in end-organ pathology. It is seen in numerous diseases which can be stratified as follows:

Diseases in which amyloid accumulation is critical to pathogenesis: Alzheimer's disease (APP accumulation in the brain), Creutzfeldt-Jacob Disease (PrP accumulation in the brain), dialysis-associated amyloidosis (beta-2 microglobulin accumulation in the joint spaces), and senile/systemic amyloidosis (transthyretin accumulation in the brain, heart, and kidney).

Diseases in which amyloidosis is a disease-modifying side effect: multiple myeloma (accumulation of immunoglobulin light chain in kidneys and peripheral nerves), and reactive amyloidosis of chronic inflammatory disease (amyloid A accumulation).

How does amyloidosis occur? When proteins are initially translated from mRNA, their three-dimensional structure is determined by specific interactions of the amino acid side chains. With the assistance of chaperone proteins, newly produced polypeptides assemble into the secondary, tertiary, and quatenary structure at the lowest energy configuration. However, certain proteins may have more than one low-energy state, depending on the protein microenvironment: the properly assembled, functional assembly, and a misfolded assembly driven by hydrogen bonding between the amide and carbonyl groups of the main amino acid chain, which is facilitated when the polypeptides are layered in antiparallel linear sheets in which the N and C termini are oriented in opposite directions. Therefore, there are 2 major issues of concern:

1) What type of proteins are susceptible to misfolding? Certain intrinsically susceptible proteins such as transthyretin, proteins that acquire a susceptible point mutation, as seen in hereditary amyloidosis, and proteins that achieve saturating concentrations in serum, such as beta-2 microglobulin in dialysis patients.

2) What conditions support pathologic misfolding of the aforementioned proteins? Conditions that interfere with weak peptide interactions (low pH, accumulation of free radical species, high temperature).

It is important (foreshadowing) to note that amyloid accumulations are not composed simply of these fibrillar beta-sheets. A critical component of amyloid is SAP, a glycoprotein that binds the common conformation of amyloid fibrils and which is protected against proteolysis, making amyloid fibrils resistant to degradation.

The presenting symptoms of amyloidosis depend on the primary tissue in which amyloid is deposited, despite the fact that in patients with amyloidosis, autopsy routinely demonstrates some degree of deposition in every organ system. Perhaps because of this, the most common initial presenting symptoms (although not that which leads to diagnosis) in patients with amyloidosis are fatigue and weight loss. End-organ damage in amyloidosis is primary caused by tissue distortion, although there may a role for an inflammatory response to deposited amyloid as well. The most common organs affected are the heart and kidneys, but other organs can be affected as well:

Renal amyloidosis often presents with the nephrotic syndrome, with renal failure, proteinuria, hyperlipidemia, and hypoalbuminemia.

Cardiac amyloidosis often presents as a restrictive cardiomyopathy with signs of right-sided heart failure (elevated jugular venous pulses, hepatic congestion, and peripheral edema). EKG often shows low voltage, and echocardiography often reveals concentric hypertrophy with elevated filling pressures. Patients may present with an MI despite no coronary artery disease. Amyloid infiltration often has a predilection for the cardiac conduction system resulting in bradyarrhythmias and even asystole.

Neuropathies are usually autonomic (orthostatic hypotension) or sensory (carpal tunnel or symmetric, distal, painful sensory neuropathies).

GI symptoms are often secondary to enteric dysfunction, resulting in constipation and/or diarrhea, but diffuse infiltration can often result in malabsorption

Vascular infiltration results in friable blood vessels, presenting as easy bruising, with the characteristic "raccoon eyes" (spontaneous periorbital bruising following rubbing of the eyes or nose-blowing).

Soft tissue involvement results in macroglossia, submandibular enlargement.

Diagnosis is classically obtained by either involved organ or abdominal fat pad biopsy. Following Congo-Red staining of tissue, apple-green birefringence under polarized light is pathognomonic. Once found, patients should be evaluated for occult plasma cell dyscrasias, transthyretin mutations, or collagen vascular disease.

Treatment of amyloidosis has been notoriously difficult, and has revolved around reducing the rate of synthesis of the amyloidogenic protein. This is based on the idea that slow resorption of amyloid components by tissue-resident macrophages is opposed by constant renewal of amyloid protein. This has proven to be notoriously difficult, other than cases in which the culprit disease (multiple myeloma, collagen vascular disease) can be treated. Vaccination against the amyloidogenic variants of A-beta peptides in Alzheimer's Disease showed some promise in early mouse studies, but has been largely disappointing in human clinical trials. Because of this, overall prognosis of patients with amyloidosis has been overwhelmingly poor.

So why have I wasted this much breath on this topic? Because there's been a breakthrough, that's why!!

We salute you, Mark Pepys' lab at the University College London! Because you did something awesome. You realized that SAP (remember??) is critical for the stability of amyloid fibrils in vivo. You then developed a proline-based compound, CPHPC (the full name is too long), which effectively binds and depletes circulating human SAP (a component of C-reactive protein) and leaves only SAP which is bound to amyloid. You then treated this residual sap with a specific IgG antibody. Right off the bat, you showed that CPHPC followed by anti-SAP treatment significantly reduced tissue amyloid burden without any significant adverse effects in mice with human SAP-induced amyloid A-driven angiopathy (a mouse model for inflammatory amyloidosis). You then carefully demonstrated the mechanism by which this occurs:

- 24 hours after antibody treatment, you show mononuclear, primarily macrophage infiltration of amyloid accumulations, as indicated by F4/80 staining in (b).
- 48 hours after treatment, you show coalescence of macrophages into multinucleated giant cells containing amyloid within endocytic compartments, as seen in (e).
- 96 hours after, you show that diminished, fragmented amyloid fibrils are largely contained within multinucleate giant cells, as seen in (d).
-Finally, you demonstrate that this process is not only macrophage dependent, but also Fc and C3 dependent, providing a step-by-step mechanism for complement mediated clearance.

What else is there to say? With a humanized monoclonal anti-SAP antibody already being tested, this work may ultimately constitute a paradigm shift in the treatment of this disease.

Stay tuned for my next post, about hormones! The lady kinds!

the NFL

Why don't we start with a few deep thoughts from NFL Pittsburgh Steeler linebacker James Harrison, following a particularly vicious hit on the Cleveland Browns' receiver Josh Cribbs:

The crown of Harrison's helmet slammed into the left side of Cribbs' helmet as the receiver was running a Wildcat formation play, causing Cribbs to crumple face-first into the turf. He appeared to be momentarily knocked out. Because Cribbs was a runner, such helmet-to-helmet contact is permissible. "I thought Cribbs was asleep," Harrison said. "A hit like that geeks you up, especially when you find out the guy is not really hurt, he's just sleeping. He's knocked out but he's going to be OK."

Awesome. Now, my first response upon reading this was to immediately Wikipedia James Harrison, because I was absolutely dying to find out the extent of his higher education. And, oh, man, I was so not disappointed. I had forgotten that this was the same guy who in 2009, after the Steelers won the Super Bowl, was the lone member to decline an invitation to the White House. At the time, he said, "This is how I feel — if you want to see the Pittsburgh Steelers, invite us when we don't win the Super Bowl. As far as I'm concerned, he [Obama] would've invited Arizona if they had won." Which, I suppose, is true.

Despite astute observations such as those above, Harrison somehow missed the plethora of medical studies linking serial head trauma to neurocognitive impairment. Many of these studies were published in the Journal of the American Medical Association, including the first description in 1928 by a pathologist from New Jersey, Harrison (ha!) Martland, who noted a "punch-drunk" personality change in long-term boxers. Many years later, a seminal report in JAMA from 1984 (pictured) demonstrated a clear association between boxers, cerebral atrophy on CT, and impaired neurocognitive and neuropsychiatric testing with an emphasis on poor memory performance.

JAMA continued to build on these reports, and began extending their observations to another sport rife with cerebral trauma: American football. In 2003, they published a report on collegiate football players that demonstrated an additive effect to head trauma; with progressive concussions, recovery time to full neurological function increased exponentially. This followed strong experimental data in which mice subjected to repeated mild trauma suffered progressive neurological damage as a result (J Neurosurg, 2001 Nov;95(5):859-70). Follow-up studies suggested that football players with 3 or more concussions over their careers were five times more likely to show signs of mild cognitive impairment, a frequent precursor of Alzeimer's Disease.

This correlative data was provided with a histopathologic correlative in 2005 when analysis of the brain of a recently deceased football player revealed "chronic traumatic encephalopathy with many diffuse amyloid plaques as well as sparse neurofibrillary tangles and tau-positive neuritic threads in neocortical areas. " As reported in the New York Times, five subsequent autopsies of NFL veterans who died between age 36 and 50 all revealed evidence of so-named "chronic traumatic encephalopathy," with tau and amyloid deposition that was otherwise never seen in brains of people this young. As the neuropathologist Daniel Perl from Mount Sinai School of Medicine noted,

"Something is clearly abnormal in these athletes' brains...in the most extreme cases the extent of tau pathology is just unbelievable."

An excellent review in The New England Journal of Medicine summarizes the pathophysiologic mechanism as follows: following head trauma, sudden movement produces rotational injury, damaging the long axons that connect different brain regions. This results in pathologic deposition of soluble amyloid-beta peptide as soon as two hours after injury. Ultimately, this results in accelerated formation neurofibrillary tangles seen generally in older patients with dementia as well as these patients.

This and countless other reports must have been part of the inspiration for a furious piece written by Malcolm Gladwell last year in the New Yorker in which he wondered if football and dogfighting were all that different. Gladwell speaks of the countless circulating stories of bizarre and ultimately self-destructive behavior of football players following retirement:

Mike Webster, the longtime Pittsburgh Steeler and one of the greatest players in N.F.L. history, ended his life a recluse, sleeping on the floor of the Pittsburgh Amtrak station. Another former Pittsburgh Steeler, Terry Long, drifted into chaos and killed himself four years ago by drinking antifreeze. Andre Waters, a former defensive back for the Philadelphia Eagles, sank into depression and pleaded with his girlfriend—“I need help, somebody help me”—before shooting himself in the head.

“There is something wrong with this group as a cohort,” Dr. Omalu [the pathologist at U. Pittsburgh who performed the first autopsy of an NFL player showing tauopathy] says. “They forget things. They have slurred speech. I have had an N.F.L. player come up to me at a funeral and tell me he can’t find his way home. I have wives who call me and say, ‘My husband was a very good man. Now he drinks all the time. I don’t know why his behavior changed.’ I have wives call me and say, ‘My husband was a nice guy. Now he’s getting abusive.’ I had someone call me and say, ‘My husband went back to law school after football and became a lawyer. Now he can’t do his job. People are suing him.’”

Gladwell goes on to note the data demonstrating the clear risk posed to football players due not only to their full concussions, but countless subconcussive head injuries. Ultimately, he, I think rightly, lays the blame at the feet of the NFL as an organization, which, despite claims to the contrary, applauds the tenacity of hard-hitting players such as Harrison, Ray Lewis, or Brian Dawkins and lionizes "warriors" who "play through injuries" and "never miss a start." A culture such as this, in which players are taught that approval (and salary) comes with masking or minimizing injury, betrays the best interest of the players. Gladwell concludes with anecdote of a young player during practice whose concussive symptoms are so severe that he is losing consciousness while sitting in a tub of ice-cold water, yet insists on returning to practice. He notes:

That moment in the cold tub represented a betrayal of trust. He had taken the hit on behalf of his team. He was then left to pass out in the cold tub, and to deal—ten and twenty years down the road—with the consequences. No amount of money or assurances about risk freely assumed can change the fact that, in this moment, an essential bond had been broken. What football must confront, in the end, is not just the problem of injuries or scientific findings. It is the fact that there is something profoundly awry in the relationship between the players and the game.

The mixed nature of the messages sent by the league could not be clearer than in the case I first mentioned, in which James Harrison was not flagged for the hit he put on Josh Cribbs, yet is being fined $75,000 for his actions. The league wants to permit the type of violent play for which fans clamor, yet have the appearance of chastising such choices. It's reminiscent of Obama's waffling on the "right versus wisdom" of the mosque at Ground Zero. It's no wonder that Harrison, 2008's NFL Defensive Player of the Year, now being subtly undermined as a dirty player, is considering retirement. He's the cuckhold, not the true villain.

dementia pugilistica

Forthcoming.

neutrophil chemotaxis

Neutrophils are the first of the innate immune system to arrive on the scene following tissue injury. This tremendous paper by McDonald and colleagues elegantly delineates the three-step process by which this happens.

First, using a thermal injury model that causes tissue necrosis (marked by propridium iodide, red), a labelled, soluble dextran that marks tissue vasculature (blue), the authors show that neutrophils hone expertly to the site of tissue necrosis primary via an intravascular, rather than an extravascular path (aka, they follow tracks marked by vasculature delineated in blue). The authors note that neutrophils take the longest possible intravascular tract, even at the expense of taking the shortest track; they hypothesize that this reduces potential collateral damage that could be exerted by neutrophils trafficking through healthy tissue on the way to a damaged focus.

The authors also show that tissue necrosis results in unique extracellular release of ATP, which is normally restricted to within cells. Extracellular ATP then activates the receptor P2X7-R on tissue-resident macrophages and stimulates them to produce pro-inflammatory cytokines such as IL-1B. Local endothelial cells then respond to this inflammation and upregulate expression of the integrin molecule ICAM-1; it is expression of these integrins which causes neutrophils to stick to the endothelium proximal to the necrotic focus; however, neither ATP nor IL-1B is responsible for actually attracting neutrophils to areas of necrosis, only adhesion at the focus.

Second, the authors then map out the pathway by which neutrophils arrive at the necrotic focus. The inflammation generated by tissue-resident macrophages drives expression of not only ICAM-1 but also the chemokinetic ligand MIP-2 (macrophage inflammatory protein 2), otherwise known as CXCL2. The authors clearly demonstrate that, unlike ICAM-1, MIP-2 is expressed on endothelial cells in a gradient that serves as a potent chemokinetic signal for neutrophils to the edge of the necrotic focus. Interestingly, however, the authors note that endothelial cells within 150 microns of the necrotic center do not express MIP-2, and neutrophils migrate in a pattern that is independent of exogenous MIP-2 expression in the necrotic center, suggesting that an overriding signal drives neutrophil chemotaxis within the proximal 150 microns of the necrotic focus.

Once neutrophils get within 150 microns of the necrotic focus, then what happens? The authors finally demonstrate that necrotic cells release so-called damage-associated molecular patterns (DAMPs), which are generated from fragments of cellular mitochondria. DAMPs share significant homology with pathogen-associated molecular patterns (PAMPs), which are derived from bacterial fragments; this should come as no surprise, as bacteria are thought to be evolutionary precursors of eukaryotic mitochondria. These DAMPs activate signaling through formylated peptide receptors on neutrophils, which serve as an overriding signal to drive the remaining migration of neutrophils to the necrotic focus.

i gotta start posting again.

And im going to start by reading the above article in the latest issue of Science and commenting on it. Tonight.