In this study we addressed the role of the nuclear factor (NF)-kappaB1/p50 subunit in chronic injury of the liver by determining the inflammatory and fibrotic responses of nfkappab1-null mice in an experimental model that mimics chronic liver disease. Mice received repeated hepatic injuries throughout 12 weeks by intraperitoneal injection of the hepatotoxin carbon tetrachloride. In response nfkappab1(-/-) mice developed more severe neutrophilic inflammation and fibrosis compared to nfkappab1(+/+) mice. This phenotype was associated with elevated hepatic expression of tumor necrosis factor (TNF)-alpha, which was localized to regions of the liver associated with inflammation and fibrosis. Hepatic stellate cells are important regulators of hepatic inflammatory and fibrogenic events but normally do not express TNF-alpha. Hepatic stellate cells derived from nfkappab1(-/-) mice expressed TNF-alpha promoter activity, mRNA, and protein. By contrast the expression of other NF-kappaB-responsive genes (ICAM1 and interleukin-6) was similar between nfkappab1(-/-) and nfkappab1(+/+) cells. We provide experimental evidence that the inappropriate expression of TNF-alpha by nfkappab1(-/-) cells is because of lack of a p50-dependent histone deacetylase 1 (HDAC1)-mediated repression of TNF-alpha gene transcription. Taken together these data indicate that the p50 NF-kappaB subunit plays a critical protective role in the injured liver by limiting the expression of TNF-alpha and its recruitment of inflammatory cells.

Activation of transcription factors plays a pivotal role in many signal transduction pathways. Of particular interest is NF-kappaB, which is present in the cytoplasm in an inactive form, where it can be activated in response to many different stress conditions such as infection, inflammation, heat shock etc. It has also been associated with apoptosis and tissue repair. Modulation of signal transduction events that mediate activation of NF-kappaB seems to have a great potential in not only treating many disease conditions, but also in tissue repair. The present review article is an attempt to put together many different conditions where the NF-kappaB activation pathway appears to be crucial in transducing signals under stress conditions, and to explore the possibility of its modulation as a targeted treatment modality.

Toll-like receptors (TLRs) comprise a clan of proteins involved in identification and triggering a suitable response against pathogenic attacks. As lung is steadily exposed to multiple infectious agents, antigens and host-derived danger signals, the inhabiting stromal and myeloid cells of the lung express an aggregate of TLRs which perceive the endogenously derived damage-associated molecular patterns (DAMPs) along with pathogen associated molecular patterns (PAMPs) and trigger the TLR-associated signalling events involved in host defence. Thus, they form an imperative component of host defence activation in case of microbial infections as well as noninfectious pulmonary disorders such as interstitial lung disease, acute lung injury and airways disease, such as COPD and asthma. They also play an equally important role in lung cancer. Targeting the TLR signalling network would pave ways to the design of more reliable and effective vaccines against infectious agents and control deadly infections, desensitize allergens and reduce inflammation. Moreover, TLR agonists may act as adjuvants by increasing the efficiency of cancer vaccines, thereby contributing their role in treatment of lung cancer too. Overall, TLRs present a compelling and expeditiously bolstered area of research and addressing their signalling events would be of significant use in pulmonary diseases.

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The most frequently reported symptom of exposure to high altitude is loss of body mass and decreased performance which has been attributed to altered protein metabolism affecting skeletal muscles mass. The present study explores the mechanism of chronic hypobaric hypoxia mediated skeletal muscle wasting by evaluating changes in protein turnover and various proteolytic pathways. Male Sprague-Dawley rats weighing about 200 g were exposed to hypobaric hypoxia (7,620 m) for different durations of exposure. Physical performance of rats was measured by treadmill running experiments. Protein synthesis, protein degradation rates were determined by (14)C-Leucine incorporation and tyrosine release, respectively. Chymotrypsin-like enzyme activity of the ubiquitin-proteasome pathway and calpains were studied fluorimetrically as well as using western blots. Declined physical performance by more than 20%, in terms of time taken in exhaustion on treadmill, following chronic hypobaric hypoxia was observed. Compared to 1.5-fold increase in protein synthesis, the increase in protein degradation was much higher (five-folds), which consequently resulted in skeletal muscle mass loss. Myofibrillar protein level declined from 46.79 ± 1.49 mg/g tissue at sea level to 37.36 ± 1.153 (P < 0.05) at high altitude. However, the reduction in sarcoplasmic proteins was less as compared to myofibrillar protein. Upregulation of Ub-proteasome pathway (five-fold over control) and calpains (three-fold) has been found to be important factors for the enhanced protein degradation rate. The study provided strong evidences suggesting that elevated protein turnover rate lead to skeletal muscle atrophy under chronic hypobaric hypoxia via ubiquitin-proteasome pathway and calpains.

Although aberrant miRNA signatures are associated with diabetes, yet, the status and role of altered miRNAs in the diabetic skeletal muscle is currently poorly understood. Here, we report that 41 miRNAs are altered in the diabetic gastrocnemius skeletal muscle and of these, miR-135a that is identified as a critical regulator of myogenesis, is significantly up-regulated. IRS2 is predicted as its potential putative target and its levels are down-regulated in the diabetic gastrocnemius skeletal muscle. In C2C12 cells, while miR-135a levels decreased during differentiation, IRS2 levels were up-regulated. miR-135a significantly reduced IRS2 protein levels and its 3'UTR luciferase reporter activity and these were blunted by the miR-135a inhibitor and mutation in the miR-135a binding site. Knock-down of endogenous miR-135a levels increased IRS2 at the mRNA and protein levels. miR-135a also attenuated insulin stimulated phosphorylation and activation of PI3Kp85α and Akt and glucose uptake. miR-135a levels were also found to be elevated in the human diabetic skeletal muscle. In-vivo silencing of miR-135a alleviated hyperglycemia, improved glucose tolerance and significantly restored the levels of IRS2 and p-Akt in the gastrocnemius skeletal muscle of db/db mice without any effect on their hepatic levels. These suggest that miR-135a targets IRS2 levels by binding to its 3'UTR and this interaction regulates skeletal muscle insulin signaling.

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