8B), as compared to JNK2 ASO-treated wild-type mice

8B), as compared to JNK2 ASO-treated wild-type mice. isoforms have distinct effects on steatohepatitis with JNK1 promoting steatosis Rabbit Polyclonal to FGFR1/2 and hepatitis and JNK2 inhibiting hepatocyte cell death by blocking the mitochondrial death pathway. and but not null mice, indicating that JNK1 specifically functions in the development of this disease.6 JNK1 has also been demonstrated to mediate the development of obesity and insulin resistance in BT-11 both high fat diet (HFD)-fed and genetically obese mouse models.4 JNK2 was reportedly not involved in these processes, but subsequent studies in mice haploinsufficient for and null for suggested that JNK2 may also promote the development of obesity and insulin resistance.7 These mice and test and defined as knockout mice although and has differential effects on c-Jun phosphorylation. (A) Total protein was isolated from your livers of regular diet (RD)- and HFD-fed mice and immunoblotted with antibodies for phospho-JNK (P-JNK), total JNK, phospho-c-Jun (P-c-Jun) and total c-Jun. Stripped blots were reprobed for PDI. (B) Protein isolated from HFD-fed wild-type (WT) and null mice experienced significant decreases in serum ALT levels (Fig. 8A), and the numbers of TUNEL positive cells (Fig. 8B), as compared to JNK2 ASO-treated wild-type mice. Thus, the increase in Bim expression that resulted from JNK2 inhibition mediated the increase in liver injury in HFD-fed mice. Open in a separate window Fig. 8 null mice are guarded from your increase in liver injury and cell death induced by a JNK2 knockdown. (A) Serum ALT levels in HFD-fed wild-type mice (WT) treated with the JNK1 or JNK2 ASO and null mice that did not occur in ASO-treated mice, or to disparate functions of JNK2 in developing versus established insulin resistance. A similar explanation likely underlies the differences between our findings and those of Tuncman null mice haploinsufficient for null mice experienced a significant, but partial, reduction in liver injury and cell death. The partial nature of the effect may have been secondary to increased Bax translocation that promoted mitochondrial death pathway activation impartial of Bim. JNK2-dependent promotion of liver injury in HFD-fed mice by activation of the mitochondrial death pathway is in direct opposition to our findings in a model of toxin-induced liver injury in which JNK2 functioned to inhibit this pathway.18 These differences point to the complexity of JNK function in the liver and likely reflect the effects of different types of injury, the time course of the injury, crosstalk with other signaling pathways and possible extrahepatic effects of JNK. The findings from your ASO-treated animals demonstrate that HFD-induced BT-11 steatohepatitis in mice is usually quickly reversible. Despite the fact that approximately two weeks of injections were required to accomplish a JNK knockdown, a dramatic decrease in steatohepatitis was achieved with only four weeks of therapy. The rapidity of this effect is further evidence of the critical nature of JNK1 activation in steatohepatitis and the potential efficacy of anti-JNK therapy in the treatment of this disease. The findings demonstrate that this JNK isoforms have differential functions in insulin resistance and steatohepatitis. Both JNK forms contributed to insulin resistance, however, JNK1 promoted both hepatic excess fat accumulation and injury whereas JNK2 was uninvolved in the steatosis and inhibited liver injury. Significantly the findings demonstrate that anti-JNK therapy can reverse chronic steatohepatitis in the absence of any reduction in the stimulus for the disease, a high excess fat diet. Kinase inhibitors are already employed BT-11 in the treatment of human diseases, 37 and JNK inhibitors have successfully reversed diabetes in animals.5 Our findings suggest that steatohepatitis can also be treated with this approach but that therapy will have to be targeted specifically to the JNK1 isoform. Inhibiting JNK2 may be effective in increasing insulin sensitivity but have detrimental effects on the associated liver disease. Acknowledgements We thank Neil Kaplowitz for his helpful suggestions, Xiao-Ming Yin for the Bid antibody and Richard Stockert for the PDI antibody. Supported by NIH grants DK061498 (MJC) and DK020541 and an American Liver Foundation Postdoctoral Research Fellowship Award (RS). Abbreviations ASOantisense oligonucleotideHFDhigh excess fat dietHOMAhomeostasis model assessment of insulin resistanceJNKc-Jun N-terminal kinaseNAFLDnonalcoholic fatty liver diseasePBSphosphate-buffered salinePDIprotein disulfide isomeraseTGtriglyceride.