Sensing necrotic cells

The role of HMGB1 in inflammation-mediated organ injury

HMGB1 is a chromosome-binding protein that also acts as a damage-associated molecular pattern molecule. It has potent proinflammatory effects and is one of key mediators of organ injury. Evidence from research has revealed its involvement in the signaling mechanisms of Toll-like receptors and the receptor for advanced glycation end-products in organ injury. HMGB1-mediated organ injuries are acute damage including ischemic, mechanical, allograft rejection and toxicity, and chronic diseases of the heart, kidneys, lungs, and brain. Strategies against HMGB1 and its associated cellular signal pathways need to be developed and may have preventive and therapeutic potentials in organ injury.

Innate immune regulation by toll-like receptors in the brain

The innate immune system plays an important role in cerebral health and disease. In recent years the role of innate immune regulation by toll-like receptors in the brain has been highlighted. In this paper the expression of toll-like receptors and endogenous toll-like receptor ligands in the brain and their role in cerebral ischemia will be discussed. Further, the ability of systemic toll-like receptor ligands to induce cerebral inflammation will be reviewed. Finally, the capacity of toll-like receptors to both increase (sensitization) and decrease (preconditioning/tolerance) the vulnerability of the brain to damage will be disclosed. Studies investigating the role of toll-like receptors in the developing brain will be emphasized.

Expanding the clinical indications for α(1)-antitrypsin therapy

α(1)-Antitrypsin (AAT) is a 52-kDa circulating serine protease inhibitor. Production of AAT by the liver maintains 0.9-1.75 mg/mL circulating levels. During acute-phase responses, circulating AAT levels increase more than fourfold. In individuals with one of several inherited mutations in AAT, low circulating levels increase the risk for lung, liver and pancreatic destructive diseases, particularly emphysema. These individuals are treated with lifelong weekly infusions of human plasma-derived AAT. An increasing amount of evidence appears to suggest that AAT possesses not only the ability to inhibit serine proteases, such as elastase and proteinase-3 (PR-3), but also to exert antiinflammatory and tissue-protective effects independent of protease inhibition. AAT modifies dendritic cell maturation and promotes T regulatory cell differentiation, induces interleukin (IL)-1 receptor antagonist and IL-10 release, protects various cell types from cell death, inhibits caspases-1 and -3 activity and inhibits IL-1 production and activity. Importantly, unlike classic immunosuppressants, AAT allows undeterred isolated T-lymphocyte responses. On the basis of preclinical and clinical studies, AAT therapy for nondeficient individuals may interfere with disease progression in type 1 and type 2 diabetes, acute myocardial infarction, rheumatoid arthritis, inflammatory bowel disease, cystic fibrosis, transplant rejection, graft versus host disease and multiple sclerosis. AAT also appears to be antibacterial and an inhibitor of viral infections, such as influenza and human immunodeficiency virus (HIV), and is currently evaluated in clinical trials for type 1 diabetes, cystic fibrosis and graft versus host disease. Thus, AAT therapy appears to have advanced from replacement therapy, to a safe and potential treatment for a broad spectrum of inflammatory and immune-mediated diseases.

Neuronal injury induces microglial production of macrophage inflammatory protein-1α in rat corticostriatal slice cultures

Chemokines are potent chemoattractants for immune and hematopoietic cells. In the central nervous system, chemokines play an important role in inflammatory responses through activation of infiltrating leukocytes and/or resident glial cells. We previously demonstrated that N-methyl-D-aspartate (NMDA)-evoked neuronal injury induced astrocytic production of monocyte chemoattractant protein-1 (MCP-1, CCL2) via sustained activation of extracellular signal-regulated kinase (ERK) in rat organotypic slice cultures. In the present study, we examined mRNA expression and protein production of macrophage inflammatory protein-1α (MIP-1α, CCL3) induced by NMDA-evoked neuronal injury in the slice cultures. MIP-1α mRNA expression was transiently increased by NMDA treatment in a concentration-dependent manner. Double-fluorescence immunohistochemistry revealed that MIP-1α was produced predominantly in microglia. Depletion of microglial cells from the slice cultures by pretreatment with liposome-encapsulated clodronate abrogated the increase in MIP-1α mRNA expression after NMDA treatment. NMDA-induced MIP-1α mRNA expression was partially but significantly inhibited by the c-Jun N-terminal kinase inhibitor SP600125; conversely, the p38 mitogen-activated protein (MAP) kinase inhibitor SB203580 enhanced it. U0126, a MAP kinase/ERK kinase inhibitor, did not affect mRNA expression. These results, combined with our previous findings, demonstrate that NMDA-evoked neuronal injury differentially induces MIP-1α and MCP-1 production in microglia and astrocytes, respectively, through activation of different intracellular signaling pathways.