Downregulation of matrix metalloproteinase-9 by melatonin during prevention of alcohol-induced liver injury in mice

Matrix metalloproteinases (MMPs) have been implicated in inflammatory and degradative processes in several diseases. The study aims to explore the mechanism of MMP-9 regulation in alcohol-induced acute liver injury and its protection by melatonin in mice. Alcohol-induced acute liver injury was induced in female Balb/C mice by ethanol administration and protection studies were carried out with a well-known antioxidant molecule, melatonin. Degree of liver injury was monitored by histological and biochemical analysis of liver tissues. Oral administration of ethanol in mouse caused significant increase in alanine amino transferase (ALT) activity in serum. Depletion of glutathione and enhancement of lipid peroxidation as well as protein oxidation was observed in liver tissues following ethanol treatment. However, melatonin exhibited potent hepatoprotective activity by inhibiting ALT activity and oxidative stress. Additionally, MMP-9 expression was increased by ethanol in a dose and time dependent manner in liver tissue and serum. Increased secretion of proMMP-9 was strongly correlated with the expression of proinflammatory cytokines e.g., tumor necrosis factor (TNF)-α, interleukin (IL)-1β and IL6. Melatonin showed hepatoprotective role by downregulation of MMP-9 and upregulation of tissue inhibitor of metalloproteases (TIMP-1) expression in liver tissue. Nuclear factor (NF)-κB, plays an important role in inducing inflammatory genes during oxidative stress, thus the role of NF-κB in ethanol-induced liver injury was investigated. Ethanol induced nuclear translocation of NF-κB and increased degradation of inhibitor of NF-κB (IκBα) in liver tissues. Moreover, ethanol-induced NF-κB translocation into nucleus was inhibited significantly by melatonin. This is the first study to elucidate the induction of MMP-9 expression by NF-κB-dependent pathway in ethanol-induced acute liver injury in mice. This study also identifies the novel role of melatonin in hepatoprotection via MMP-9 down regulation.     

Transglutaminase 2 gene ablation protects against renal ischemic injury by blocking constant NF-κB activation

Transglutaminase 2 knockout (TGase2(-/-)) mice show significantly reduced inflammation with decreased myofibroblasts in a unilateral ureteral obstruction (UUO) model, but the mechanism remains to be clarified. Nuclear factor-κB (NF-κB) activation plays a major role in the progression of inflammation in an obstructive nephropathy model. However, the key factors extending the duration of NF-κB activation in UUO are not known. In several inflammatory diseases, we and others recently found that TGase 2 plays a key role in extending NF-κB activation, which contributes to the pathogenesis of disease. In the current study, we found that NF-κB activity in mouse embryogenic fibroblasts (MEFs) from TGase2(-/-) mice remained at the control level while the NF-κB activity of wild-type (WT) MEFs was highly increased under hypoxic stress. Using the obstructive nephropathy model, we found that NF-κB activity remained at the control level in TGase2(-/-) mouse kidney tissues, as measured by COX-2 expression, but was highly increased in WT tissues. We conclude that TGase 2 gene ablation reduces the duration of NF-κB activation in ischemic injury.     

Molecular activation of NF-κB, pro-inflammatory mediators, and signal pathways in γ-irradiated mice

The effects of γ-irradiation on inflammatory gene expression, including NF-κB activation, in the kidney of C57/BL6 mice exposed to 1–9 Gy doses of ⁶⁰Co γ-irradiation. Radiation enhanced the NF-κB activation and oxidative stress caused a dose-dependent disruption in the redox balance. The significance of this study is the new molecular information gained on γ-irradiation effects through the activation of pro-inflammatory genes by NF-κB via the MAPK signaling pathway. Considering the exquisite sensitivity of NF-κB and other pro-inflammatory mediators to the redox status, we conclude that the activation of inflammatory processes by irradiation is likely initiated by increased oxidative stress.     

A20 overexpression exerts protective effects on podocyte injury in lupus nephritis by downregulating UCH-L1

Lupus nephritis (LN), an autoimmune kidney disease caused by systemic lupus erythematosus (SLE), is the inflammation of the kidney. Although the treatment of LN is still a therapeutic challenge for many practitioners, the present study aims to provide a new insight for the treatment and management. The study aims to explore the effect of A20 on LN in relation to the nuclear factor-kappa B (NF-κB) signaling pathway. MRL/lpr mice were used as the LN mouse model. Next, A20, UCH-L1, and NF-κB expression in LN patients and MRL/lpr mice was determined. A20 was upregulated in podocytes to assess biological functions of A20 in LN. Furthermore, to further investigate the pivotal role of the NF-κB pathway in LN, the NF-κB pathway was blocked in podocytes. Next, UCH-L1 was downregulated in MRL/lpr mice to assess biological functions of UCH-L1 in LN. A20 was downregulated, whereas UCH-L1 was upregulated in LN. Overexpressed A20 declined NF-κB, UCH-L1 expression, and the extent of p65 phosphorylation. A20 overexpression or UCH-L1 inhibition increased expression of synaptoporin and nephrin but decreased desmin expression and ubiquitin accumulation level in podocytes. Moreover, A20 overexpression or UCH-L1 inhibition increased the podocyte number but decreased protein level of cleaved caspase-3, podocyte lesion improvement, decreased foot process width, glomerulus basement membrane, and foot process fusion rate. In addition, urine protein, blood urea nitrogen, serum creatinine, and ds-DNA antibody levels decreased with elevated A20 or depleted UCH-L1. Collectively, it could be concluded that A20 protects against podocyte injury in LN via UCH-L1 by inactivating the NF-κB signaling pathway.     

Activation of IKK/NF-κB provokes renal inflammatory responses in guanylyl cyclase/natriuretic peptide receptor-A gene-knockout mice

The present study was aimed at determining the consequences of the disruption of guanylyl cyclase/natriuretic peptide receptor-A (GC-A/NPRA) gene (Npr1) on proinflammatory responses of nuclear factor kappa B, inhibitory kappa B kinase, and inhibitory kappa B alpha (NF-κB, IKK, IκBα) in the kidneys of mutant mice. The results showed that the disruption of Npr1 enhanced the renal NF-κB binding activity by 3.8-fold in 0-copy (-/-) mice compared with 2-copy (+/+) mice. In parallel, IKK activity and IκBα protein phosphorylation were increased by 8- and 11-fold, respectively, in the kidneys of 0-copy mice compared with wild-type mice. Interestingly, IκBα was reduced by 80% and the expression of proinflammatory cytokines and renal fibrosis were significantly enhanced in 0-copy mice than 2-copy mice. Treatment of 0-copy mice with NF-κB inhibitors andrographolide, pyrrolidine dithiocarbamate, and etanercept showed a substantial reduction in renal fibrosis, attenuation of proinflammatory cytokines gene expression, and significantly reduced IKK activity and IkBα phosphorylation. These findings indicate that the systemic disruption of Npr1 activates the renal NF-κB pathways in 0-copy mice, which transactivates the expression of various proinflammatory cytokines to initiate renal remodeling; however, inhibition of NF-κB pathway repairs the abnormal renal pathology in mutant mice.