Protection of early phase hepatic ischemia-reperfusion injury by cholinergic agonists

BACKGROUND: Cytokine production is critical in ischemia/reperfusion (IR) injury. Acetylcholine binds to macrophages and inhibits cytokine synthesis, through the cholinergic anti-inflammatory pathway. This study examined the role of the cholinergic pathway in cytokine production and hepatic IR- injury. METHODS: Adult male mice underwent 90-min of partial liver ischemia followed by reperfusion. The AChR agonists (1,1-dimethyl-4-phenyl-L-pioperazinium-iodide [DMPP], and nicotine) or saline-vehicle were administered i.p. before ischemia. Plasma cytokine tumor necrosis factor (TNF)-α, macrophage inflammatory protein-2, and Interleukin-6 were measured. Liver injury was assessed by plasma alanine transaminase (ALT) and liver histopathology. RESULTS: A reperfusion time-dependent hepatocellular injury occurred as was indicated by increased plasma-ALT and histopathology. The injury was associated with marked elevation of plasma cytokines/chemokines. Pre-ischemic treatment of mice with DMPP or nicotine significantly decreased plasma-ALT and cytokines after 3 h of reperfusion. After 6 h of reperfusion, the protective effect of DMPP decreased and reached a negligible level by 24 h of reperfusion, despite significantly low levels of plasma cytokines. Histopathology showed markedly diminished hepatocellular injury in DMPP- and nicotine-pretreated mice during the early-phase of hepatic-IR, which reached a level comparable to saline-treated mice at late-phase of IR. CONCLUSION: Pharmacological modulation of the cholinergic pathway provides a means to modulate cytokine production and to delay IR-induced heaptocellular injury

Lung epithelium as a sentinel and effector system in pneumonia – molecular mechanisms of pathogen recognition and signal transduction

Pneumonia, a common disease caused by a great diversity of infectious agents is responsible for enormous morbidity and mortality worldwide. The bronchial and lung epithelium comprises a large surface between host and environment and is attacked as a primary target during lung infection. Besides acting as a mechanical barrier, recent evidence suggests that the lung epithelium functions as an important sentinel system against pathogens. Equipped with transmembranous and cytosolic pathogen-sensing pattern recognition receptors the epithelium detects invading pathogens. A complex signalling results in epithelial cell activation, which essentially participates in initiation and orchestration of the subsequent innate and adaptive immune response. In this review we summarize recent progress in research focussing on molecular mechanisms of pathogen detection, host cell signal transduction, and subsequent activation of lung epithelial cells by pathogens and their virulence factors and point to open questions. The analysis of lung epithelial function in the host response in pneumonia may pave the way to the development of innovative highly needed therapeutics in pneumonia in addition to antibiotics

The role of apoptosis in pulmonary fibrosis

Apoptosis has been defined as "gene-directed cellular self-destruction" and is an active process that is tightly regulated by a number of gene products, which promote or block cell death. Apoptotic death can be triggered by a wide variety of stimuli and, importantly, not all cells necessarily undergo apoptosis in response to the same stimulus. Abnormal regulation of apoptosis has been implicated in a wide range of diseases and approaches to modifying apoptosis represent important future therapeutic strategies. Idiopathic pulmonary fibrosis (IPF) is a progressive and relentless disease involving scarring of the lung, which has been recognised as the most lethal interstitial lung disease. In the lungs of IPF patients, increased epithelial apoptosis, together with decreased apoptosis of myofibroblasts, represents persistent findings (particularly in areas of collagen deposition) supporting an interaction between altered apoptosis and the pathogenesis of the disease. Data from human tissues and animal models are refining current knowledge of the processes involved in this pathogenesis. This has challenged the dogma that IPF is purely a disease of unresolved inflammation by emphasising the central roles played by the alveolar epithelial cell and myofibroblasts and, as part of that role, the importance of altered apoptosis. Evidence suggests blockade of epithelial cell apoptosis can prevent subsequent collagen deposition, and induction of myofibroblast apoptosis, at least theoretically, would be expected to resolve ongoing fibrosis. These two concepts raise the prospect of therapeutic intervention aimed at modifying apoptosis and, thus, fibrosis in idiopathic pulmonary fibrosis