We propose that pattern recognition receptors, whose normal function is in innate immune responses, are also activated by stress-generated ligands, such as molecules released by dying cells, normal and oxidized lipids and a variety of so called """"""""danger"""""""" signals in addition to environmental toxins and pathogen associated molecular patterns. Activation of such receptors either by endogenous- (i.e. host-generated) or pathogen- generated ligands turns on stress-activated protein kinases, such as JNK, p38 MAPK and IKK, that serve as molecular transducers that contribute to development of chronic inflammatory diseases. Importantly, these pathogenic mechanisms allow the integration of environmental factors and genetic susceptibility loci that together contribute to the development of some of the most common chronic diseases, including type 2 diabetes, asthma, inflammatory bowel disease and chronic liver disease. In the previous grant period we have generated strong evidence in support of this hypothesis by focusing on the pathogenic functions of the JNK and IKK signaling pathways. We also generated a mouse model expressing the equivalent of the most common susceptibility allele for Crohn's disease, an inflammatory bowl disease whose pathogenesis is affected by genetic and environmental factors. In the present period we will focus our main effort on the pathogenic function of different classes of pattern recognition receptors as targets for stress - and injury- generated stimuli, as well as continue with our studies on the role of p38 MAPK in liver inflammation and toxicity. More specifically we will examine: 1) the role of protein kinase C isozymes and Toll like receptors (TLRs) in obesity-induced JNK activation and insulin resistance;2) the role of TLRs in toxin-induced liver injury, liver inflammation and liver cancer;3) examine the role of p38 MAPK in toxin-induced liver injury, liver inflammation and liver cancer;4) examine the mechanism by which the intracellular NOD-like receptor NOD2 leads to activation of caspase 1 and IL-lbeta secretion;5) construct a conditional mouse mutant that allows constitutive NOD2 activation and use it along with our previously generated Nod2delta33 knockin mutant to examine effects of tobacco smoke, microparticles and bacterial products on development of NOD2- modulated colonic and airway inflammation. To accomplish these aims we will use a combination of cellular biochemistry, molecular genetics and experimental pathology, an approach that has been proven effective during the previous project period.
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