Tetramethylpyrazine alleviates acute kidney injury by inhibiting NLRP3/HIF­1α and apoptosis.

The aim of the present study was to investigate the protective effect and underlying mechanism of tetramethylpyrazine (TMP) on renal ischemia reperfusion injury (RIRI) in rats, which refers to the injury caused by the restoration of blood supply and reperfusion of the kidney after a period of ischemia. Sprague­Dawley rats were randomly divided into a Sham group, renal ischemia­reperfusion (I/R) group and TMP group. TMP hydrochloride (40 mg/kg, 6 h intervals) was given via intraperitoneal injection immediately after reperfusion in the TMP group, after 24 h the kidney tissues were taken for follow­up experiments. Pathological changes in the kidney tissues were observed by periodic acid­Schiff staining. Renal function was assessed by measuring levels of serum creatinine and blood urea nitrogen, and inflammatory cytokines tumor necrosis factor (TNF)­α and interleukin (IL)­6. Renal cell apoptosis was detected by TUNEL­DAPI double staining, mRNA and protein changes were analyzed by reverse transcription­quantitative PCR and western blotting. Cell viability was measured using a CCK­8 assay. It was found that the renal tissues of the sham operation group were notably abnormal, and the renal tissues of the I/R group were damaged, while the renal tissues of the TMP group were less damaged compared with those of the I/R group. Compared with the I/R group, the serum creatinine and blood urea nitrogen levels in the TMP group were low (all P<0.05), levels of inflammatory cytokines TNF­α and IL­6 decreased, the apoptotic rate was low (all P<0.05), and the relative expression levels of nucleotide­oligomerization domain­like receptor 3 (NLRP3) protein and mRNA in renal tissues were low (all P<0.05). The expression levels of hypoxia­inducible factor 1­α and NLRP3 increased after oxygen and glucose deprivation (OGD), and reduced after treatment with OGD and TMP (all P<0.05). It was concluded that TMP can reduce renal injury and improve renal function in RIRI rats, and its mechanism may be related to the reduction of NLRP3 expression in renal tissues.

Tob2 Inhibits TLR-Induced Inflammatory Responses by Association with TRAF6 and MyD88.

Optimal activation of TLR pathways is crucial for the initiation of inflammatory responses and eliminating invading micro-organisms. However, excessive of TLR activation may lead to autoimmune and inflammatory diseases. Thus, TLR pathways should be tightly controlled. In this study, we identify Tob2, a Tob/BTG family member, as a suppressor of TLR pathways. Tob2 deficiency enhances TLR-induced NF-κB and MAPK activation and promotes the expression of proinflammatory cytokines in primary peritoneal macrophages of C57BL/6 mice. Furthermore, Tob2-defective C57BL/6 mice may be more susceptible to endotoxemic shock in vivo. Mechanistically, Tob2 interacts with TRAF6 and MyD88 and thus inhibits signaling from the MyD88-TRAF6 complex in primary peritoneal macrophages and HEK293T cells. Therefore, our results uncover a regulatory mechanism of TLR pathways and provide a potential target for the intervention of diseases with excessive TLR activation.

Ligustrazine ameliorates acute kidney injury through downregulation of NOD2­mediated inflammation.

Ligustrazine has been used to alleviate clinical acute kidney injury (AKI); however, the underlying molecular mechanisms are poorly understood. In order to further elucidate the molecular mechanism underlying its occurrence, the role of nucleotide­binding oligomerization domain­containing 2 (NOD2) in AKI was investigated in the present study, and the results indicated that ligustrazine exerts an important protective effect against AKI in vivo by inhibiting the upregulation of NOD2 expression and reducing apoptosis of kidney cells following ischemia/reperfusion injury in rat models. Furthermore, the inhibitory role of ligustrazine on the upregulation of NOD2 and apoptosis of kidney cells induced by CoCl2 and oxygen and glucose deprivation followed by reoxygenation was investigated in in vitro experiments. The effect of ligustrazine on NOD2 downregulation was partially blocked by inhibiting autophagy. To the best of our knowledge, the results of the present study are the first to provide evidence that ligustrazine can inhibit NOD2­mediated inflammation to protect against renal injury, which may be in part attributed to the induction of autophagy. These findings may help design and develop new approaches and therapeutic strategies for AKI to prevent the deterioration of renal function.

NLRP3 inflammasome negatively regulates podocyte autophagy in diabetic nephropathy.

Inflammasome mechanisms are recognized as a key pathophysiology of diabetic nephropathy (DN). The nucleotide-oligomerization domain-like receptor 3 (NLRP3) inflammasome has attracted the most attention. Autophagy as a conserved intracellular catabolic pathway plays essential roles in the maintenance of podocytes. Although autophagy was involved in preventing excessive inflammatory responses in kidney diseases, a clear understanding of the regulation of NLRP3 inflammasome on autophagy in glomerular damage in DN is still lacking. In this study, we focused on the effect of the activation of NLRP3 inflammasome on the suppression of podocyte autophagy and aimed to investigate the role of autophagy in podocyte injury in DN. Podocyte autophagy has been confirmed to be inhibited in high-fat diet/streptozotocin (HFD/STZ)-induced DN mice, and NLRP3 has been found to be upregulated in both mice and human DN biopsies and in vitro. Activation of NLRP3 inflammasome exacerbated podocyte autophagy and reduced podocyte nephrin expression, while silencing of NLRP3 efficiently restored podocyte autophagy and ameliorated podocyte injury induced by high glucose. The results showed that NLRP3 was a negative regulator of autophagy and suggested that restoration of podocyte autophagy by inactivation of NLRP3 under high glucose could reduce podocyte injury. Proper modification of autophagy and inflammasome has the potential to benefit the kidney in DN.

Interleukin-18 binding protein attenuates renal injury of adriamycin-induced mouse nephropathy.

Nephrotic syndrome is one of the most common kidney diseases in children, most of which were caused by minimal change disease, which could be typically reversible with the use of corticosteroid therapy in steroid-sensitive nephrotic syndrome. At the same time, there still exist some side effects caused by drugs and steroid-resistant nephrotic syndrome. It's urgent to investigate more accurate treatment to improve the situation. In this study, we chose mice model by adriamycin to observe the effect of IL-18BP intervention. It was shown that (1) weak general conditions appeared after adriamycin administration; (2) Proteinuria showed up after adriamycin-administration and then decreased with IL-18 binding protein intervention; (3) the level of triglyceride, cholesterol, IL-18, IFN-γ, and TNF-α in the IL-18 binding protein intervening group were significantly lower than those in the adriamycin-minimal change disease MCD group (all P < 0.01), and the levels of serum total protein, albumin, and IL-4 were significantly higher than those in the adriamycin-minimal change disease MCD group (P < 0.05, P < 0.01, P < 0.05); (4) ultramicrostructural examination demonstrated wide fusion of foot processes of glomerular epithelial cells in adriamycin-minimal change disease MCD mice, while only focal fusion occurred in IL-18 binding protein intervening mice. In conclusion, IL-18BP repaired the proteinurine, histopathological injury of kidney, and the induction of serum cytokines in mice models of minimal change disease induced by adriamycin.

Apocynin inhibited NLRP3/XIAP signalling to alleviate renal fibrotic injury in rat diabetic nephropathy.

AIMS: In this animal study, we tried to test the hypothesis that apocynin could play an anti-inflammation role by inhibiting NLRP3/X-linked inhibitor of apoptosis protein (XIAP) signalling and have an effect on antifibrosis in rats with diabetic nephropathy. MAIN METHODS: Diabetic nephropathy rats were induced by tail-vein injection of streptozotocin at 60 mg/kg body weight in sodium citrate buffer (0.01 M, pH 4.5) with unrestricted access to food/water for 12 weeks, and rats with blood glucose levels above 18.0 mM were considered diabetic; the damage index for glomerular mesangial cells damage index was calculated by morphological examinations; protein and mRNA changes were analysed by western blotting immunohistochemistry and real-time quantitative polymerase chain reaction; interstitial fibrosis was assessed and scored using Masson's staining. KEY FINDINGS: In rats with diabetic nephropathy, apocynin (1) reduced renal injury and improved renal function; (2) downregulated the expression of NLRP3 in renal cortex; (3) downregulated the expression of XIAP in renal cortex; and (4) attenuated renal fibrosis. SIGNIFICANCE: As an inhibitor of reactive oxygen species (ROS), apocynin could downregulate the expression of NLRP3 and XIAP, and alleviate renal fibrosis, which meant not only that ROS was one type of ligands of NLRP3, but also that ROS mechanism and NLRP3 activation might be therapeutic targets in the treatment of diabetic nephropathy in the future.