Lethal CD4 T Cell Responses Induced by Vaccination Against Staphylococcus aureus Bacteremia.

Multiple candidate vaccines against Staphylococcus aureus infections have failed in clinical trials. Analysis of a recent prematurely halted vaccine trial revealed increased mortality rates among vaccine recipients in whom postsurgical S. aureus infection developed, emphasizing the potential for induction of detrimental immune responses and the need to better understand the requirements for protective immunity against S. aureus. These failures of single-antigen vaccines have prompted ongoing development of multicomponent vaccines to target the multitude of S. aureus virulence factors. In the current study, we used lethally irradiated S. aureus as a model multicomponent vaccine and showed that vaccination of mice decreased survival in a bacteremia challenge model. These deleterious effects were due to a CD4 T-cell-dependent interferon γ response and could be prevented by inhibiting development of this response during vaccination. Our results identify the potential for vaccination to induce pathological immune responses, and they have implications for recent vaccine failures and the design of future staphylococcal vaccines.

Fibulin-1 and fibrinogen in human atherosclerotic lesions.

Fibulin-1 is a fibrinogen-binding blood protein and a component of many extracellular matrices (ECM) including those of blood vessels. In this study, the deposition patterns of fibulin-1 and fibrinogen were examined in human coronary artery atherosclerotic lesions excised by atherectomy from 20 patients. Fibulin-1 deposition was found to be closely overlapping with fibrinogen located within the atherosclerotic lesions and in regions containing fresh thrombi. Pronounced intracellular fibulin-1 immunostaining was apparent in lesion areas rich in macrophages and foam cells, although THP-1 macrophages and foam cells were found not to express fibulin-1. Strong ECM deposition of fibulin-1 was observed in acellular atheromatous and myxomatous regions. By contrast, fibulin-1 was present at relatively low levels in the ECM associated with smooth muscle cells within and outside of lesions and was not detected in sclerotic regions. These results reveal the pattern of fibulin-1 within human atherosclerotic lesions and highlight the potential for fibulin-1, perhaps derived from the blood and acting in conjunction with fibrinogen, to play a role in the etiology and cardiovascular disease progression, particularly with respect to thrombotic aspects of atherosclerosis.

Improving endothelial healing with novel chimeric mitogens.

BACKGROUND: Chimeric proteins may be used to direct cell-specific activity. Heparin-binding growth-associated molecule (HBGAM) binds to cell receptors that are relatively more robust on endothelial cells, and it may confer endothelial cell selectivity to potent angiogens such as fibroblast growth factor-1 (FGF-1). METHODS: By ligating fibroblast growth factor or its potent mutant, S130K, to HBGAM, we tested their effect on re-endothelialization after angioplasty injury by using a canine model. RESULTS: Both HBGAM/S130K- and HBGAM/FGF-1-treated arteries had increased neointimal mitotic index and re-endothelialization rates at 30 days compared with control arteries without inducing a significant increase in the neointimal thickness or the ratio of neointimal to medial thickness between treatment and control groups. CONCLUSION: HBGAM/S130K and HBGAM/FGF-1 facilitates endothelial healing without myointimal thickening after canine carotid artery balloon angioplasty injury. Application of these growth factors in fibrin glue may improve endothelialization clinically after angioplasty or endarterectomy.

Cardiac pathologic effects of azidothymidine (AZT) in Mg-deficient mice.

Treatment of HIV with AZT (zidovudine) may have toxic side effects as a result of multiple mechanisms. It is known that patients with AIDS may suffer from magnesium deficiency (MgD). We studied selected biochemical and histopathologic consequences of AZT administration (0.7 mg/mL in drinking water) with concurrent Mg-deficient (20% of normal) diet in male C57Bl/6N mice for 3 wk. Significant decreases in red blood cell glutathione (GSH) were evident in the Mg-deficient mice with or without AZT treatment, suggesting compromised antioxidant capacity in the blood. Although MgD alone led to a 1.9-fold increase in plasma thromboxane B(2) (TXB(2), derived from the highly vasoconstrictive TXA(2)), AZT + MgD increased the TXB(2) level 3.5-fold. AZT (+/-MgD) provoked prominent hepatic damage expressed by distortion of lobular architecture, nuclear and cellular swelling, and inflammatory lesions and loss of hepatocytes. AZT alone caused mild cardiac lesions, resulting in partial cardiac fibrosis, especially in the atrium. AZT + MgD caused only scattered small-size cardiac lesions consisting of microscopic foci of inflammatory infiltrates in the ventricles but led to more prominent lesions, fibrosis, and scars in the atrium. MgD or AZT alone caused varying degrees of skeletal muscle degeneration; in combination, more intense degeneration and regeneration of muscle cells were evident. In conclusion, it is suggested that both the decreased blood GSH and elevated plasma TXA(2) might contribute, at least in part, to the aggravated pathological damages observed in the atrium and skeletal muscle of the AZT-treated Mg-deficient mice.

The opioid antagonist naltrexone blocks acute endotoxic shock by inhibiting tumor necrosis factor-alpha production.

Septic shock is believed to be a consequence of excessive stimulation of the immune system by bacterial toxins that results in systemic overproduction of proinflammatory cytokines, including tumor necrosis factor-alpha (TNF-alpha), IL-1, and IL-6. Various studies have shown that TNF-alpha, a major mediator of septic shock, induces tissue injury, loss of blood pressure, organ failure, and ultimately death. Administration of the opioid antagonist naloxone has been reported to reverse opiate-mediated hypotension, promote organ perfusion and increase patient survival. In this study, we examined the mechanism by which the opioid receptor antagonist, naltrexone, modulates the septic shock response in BALB/c mice after injection with lipopolysaccharide (LPS) or staphylococcal enterotoxin B (SEB) in combination with d-galactosamine (d-gal), or with agonistic anti-Fas antibody (Jo2) alone. Each of these treatments induced rapid-onset, acute shock, and ultimately mortality (6-9h after injection), although different mechanisms are involved. Administration of the opioid antagonist naltrexone protected mice from shock induced by LPS+d-gal, but not SEB+d-gal or Jo2 antibody, a protective effect that was reversed by morphine. Naltrexone significantly inhibited the production of TNF-alpha induced by LPS, but not SEB in vivo. When bone marrow-derived, splenic or peritoneal macrophages were treated with LPS in vitro, administration of naltrexone had no direct effect on TNF-alpha production. These results suggest that naltrexone is capable of preventing LPS-induced septic shock mortality by indirect inhibition of TNF-alpha production in vivo.

Dietary flaxseed meal reduces proteinuria and ameliorates nephropathy in an animal model of type II diabetes mellitus.

BACKGROUND: Evidence is emerging that varying the type or source of dietary protein intake can have beneficial effects on chronic renal disease. Consumption of soybean and soy-based food products, as the source of plant protein, can retard the development and progression of chronic renal disease. We studied the obese spontaneously hypertensive/NIH-corpulent (SHR/N-cp) rat, a model of obesity and type II diabetes mellitus that consistently develops nephropathy resembling diabetic nephropathy. We specifically sought to determine whether changing the source of protein intake from animal protein, casein, to plant protein in the form of either soy protein concentrate or flaxseed protein in the diet has a different impact on renal function and nephropathy in this model. METHODS: Male obese SHR/N-cp rats were randomly assigned to one of three diets containing either 20% casein, 20% soy protein concentrate, or 20% flaxseed meal. Except for the protein source, all three diets were identical and contained similar amounts of protein, fat, carbohydrates, minerals, and vitamins. All animals were maintained on these diets for 6 months. At the end of the study, blood sampling and 24-hour urine collections were performed for renal functional measurements, and the kidneys were harvested and examined for histologic evaluation. RESULTS: All three groups had similar amounts of food intake and body weight gain and exhibited fasting hyperglycemia and hyperinsulinemia. Plasma glucose levels did not differ among the three groups, but plasma insulin concentration was significantly lower in rats fed flaxseed meal than those fed either casein or soy protein concentrate. Mean plasma creatinine, creatinine clearance, and urinary urea excretion also did not differ significantly between the three groups. By contrast, urinary protein excretion was significantly lower (P < 0.01) in rats fed flaxseed than in rats fed either casein or soy protein concentrate. Morphologic analysis of renal structural lesions showed that the percentage of abnormal glomeruli with mesangial expansion and the tubulointerstitial score (an index of severity of tubulointerstitial damage) were significantly reduced in rats fed flaxmeal compared to those fed casein or soy protein concentrate. CONCLUSION: We conclude that dietary protein substitution with flaxseed meal reduces proteinuria and glomerular and tubulointerstitial lesions in obese SHR/N-cp rats and that flaxseed meal is more effective than soy protein in reducing proteinuria and renal histologic abnormalities in this model. The reduction in proteinuria and renal injury was independent of the amount of protein intake and glycemic control. Which dietary component(s) present in flaxseed meal is (are) responsible for the renal protective effect remains to be determined.

Loss of proteolytically processed filaggrin caused by epidermal deletion of Matriptase/MT-SP1.

Profilaggrin is a large epidermal polyprotein that is proteolytically processed during keratinocyte differentiation to release multiple filaggrin monomer units as well as a calcium-binding regulatory NH2-terminal filaggrin S-100 protein. We show that epidermal deficiency of the transmembrane serine protease Matriptase/MT-SP1 perturbs lipid matrix formation, cornified envelope morphogenesis, and stratum corneum desquamation. Surprisingly, proteomic analysis of Matriptase/MT-SP1-deficient epidermis revealed the selective loss of both proteolytically processed filaggrin monomer units and the NH2-terminal filaggrin S-100 regulatory protein. This was associated with a profound accumulation of profilaggrin and aberrant profilaggrin-processing products in the stratum corneum. The data identify keratinocyte Matriptase/MT-SP1 as an essential component of the profilaggrin-processing pathway and a key regulator of terminal epidermal differentiation.

Role of SHP-2 tyrosine phosphatase in the DNA damage-induced cell death response.

SHP-2, a ubiquitously expressed Src hmology 2 (SH2) domain-containing tyrosine phosphatase, plays a critical role in the regulation of growth factor and cytokine signal transduction. Here we report a novel function of this phosphatase in DNA damage-induced cellular responses. Mutant embryonic fibroblast cells lacking functional SHP-2 showed significantly decreased apoptosis in response to DNA damage. Following cisplatin treatment, induction of p73 and its downstream effector p21(Cip1) was essentially blocked in SHP-2 mutant cells. Further investigation revealed that activation of the nuclear tyrosine kinase c-Abl, an essential mediator in DNA damage induction of p73, was impaired in the mutant cells, suggesting a functional requirement of SHP-2 in c-Abl activation. Consistent with this observation, the effect of overexpression of c-Abl kinase in SHP-2 mutant cells on sensitizing the cells to DNA damage-induced death was abolished. Additionally, we found that in embryonic fibroblast cells 30-40% of SHP-2 was localized in the nuclei, and that a fraction of nuclear SHP-2 was constitutively associated with c-Abl via its SH3 domain. Phosphatase activity of nuclear but not cytoplasmic SHP-2 was significantly enhanced in response to DNA damage. These results together suggest a novel nuclear function for SHP-2 phosphatase in the regulation of DNA damage-induced apoptotic responses.

Matriptase/MT-SP1 is required for postnatal survival, epidermal barrier function, hair follicle development, and thymic homeostasis.

Matriptase/MT-SP1 is a novel tumor-associated type II transmembrane serine protease that is highly expressed in the epidermis, thymic stroma, and other epithelia. A null mutation was introduced into the Matriptase/MT-SP1 gene of mice to determine the role of Matriptase/MT-SP1 in epidermal development and neoplasia. Matriptase/MT-SP1-deficient mice developed to term but uniformly died within 48 h of birth. All epidermal surfaces of newborn mice were grossly abnormal with a dry, red, shiny, and wrinkled appearance. Matriptase/MT-SP1-deficiency caused striking malformations of the stratum corneum, characterized by dysmorphic and pleomorphic corneocytes and the absence of vesicular bodies in transitional layer cells. This aberrant skin development seriously compromised both inward and outward epidermal barrier function, leading to the rapid and fatal dehydration of Matriptase/MT-SP1-deficient pups. Loss of Matriptase/MT-SP1 also seriously affected hair follicle development resulting in generalized follicular hypoplasia, absence of erupted vibrissae, lack of vibrissal hair canal formation, ingrown vibrissae, and wholesale abortion of vibrissal follicles. Furthermore, Matriptase/MT-SP1-deficiency resulted in dramatically increased thymocyte apoptosis, and depletion of thymocytes. This study demonstrates that Matriptase/MT-SP1 has pleiotropic functions in the development of the epidermis, hair follicles, and cellular immune system.