Effect of multi-glycosides of Tripterygium wilfordii on renal injury in diabetic kidney disease rats through NLRP3/caspase-1/GSDMD pyroptosis pathway / 中国中药杂志

This study investigated the effect of multi-glycosides of Tripterygium wilfordii(GTW) on renal injury in diabetic kidney disease(DKD) rats through Nod-like receptor protein 3(NLRP3)/cysteine-aspartic acid protease-1(caspase-1)/gsdermin D(GSDMD) pyroptosis pathway and the mechanism. To be specific, a total of 40 male SD rats were randomized into the normal group(n=8) and modeling group(n=34). In the modeling group, a high-sugar and high-fat diet and one-time intraperitoneal injection of streptozotocin(STZ) were used to induce DKD in rats. After successful modeling, they were randomly classified into model group, valsartan(Diovan) group, and GTW group. Normal group and model group were given normal saline, and the valsartan group and GTW group received(ig) valsartan and GTW, respectively, for 6 weeks. Blood urea nitrogen(BUN), serum creatinine(Scr), alanine ami-notransferase(ALT), albumin(ALB), and 24 hours urinary total protein(24 h-UTP) were determined by biochemical tests. The pathological changes of renal tissue were observed based on hematoxylin and eosin(HE) staining. Serum levels of interleukin-1β(IL-1β) and interleukin-18(IL-18) were detected by enzyme-linked immunosorbent assay(ELISA). Western blot was used to detect the expression of pyroptosis pathway-related proteins in renal tissue, and RT-PCR to determine the expression of pyroptosis pathway-related genes in renal tissue. Compared with the normal group, the model group showed high levels of BUN, Scr, ALT, and 24 h-UTP and serum levels of IL-1β and IL-18(P<0.01), low level of ALB(P<0.01), severe pathological damage to kidney, and high protein and mRNA levels of NLRP3, caspase-1, and GSDMD in renal tissue(P<0.01). Compared with the model group, valsartan group and GTW group had low levels of BUN, Scr, ALT, and 24 h-UTP and serum levels of IL-1β and IL-18(P<0.01), high level of ALB(P<0.01), alleviation of the pathological damage to the kidney, and low protein and mRNA levels of NLRP3, caspase-1, and GSDMD in renal tissue(P<0.01 or P<0.05). GTW may inhibit pyroptosis by decreasing the expression of NLRP3/caspase-1/GSDMD in renal tissue, thereby relieving the inflammatory response of DKD rats and the pathological injury of kidney.

Mechanisms of the UTP-induced tension in mammalian skeletal muscles

The mechanisms of UTP-induced tension in human and rat skinned fibers were investigated using isometric tension recordings, electrophysiological techniques and biochemical methods. In fast-type fibers from rat extensor digitorum longus (EDL) the UTP-induced tension: a) required previous loading of CA2+ into the sarcoplasmic reticulum (SR); b) was inhibited by previous exposure to caffeine; c) was abolished by functional disruption of the SR; d) was not affected by blockade of the SR Ca2+-release channels by ruthenium red or heparin; e) was prevented by spermidine. These data point to the SR as the target of UTP action and suggest a pathway of UTP-induced Ca2+-release independent of the ryanodine- or the IP3-sensitive Ca2+-release channels. Accordingly, UTP failed to stimulate the electrophysiological activity of ryanodine-sensitive channels, incorporated into lipid bilayers. We suggest that UTP-induced Ca2+-release might occur via the channel form of the SR Ca2+-ATPase. The UTP-induced tension in human slow-type fibers was not affected by the SR Ca2+ content or by disruption of the SR, but was accompanied by changes in the tension-pCa relationship, namely increase in maximum Ca2+-activated tension, and in apparent Ca2+-affinity of troponin. The UTP-induced tension in slow-type fibers from rat soleus was partially inhibited by Ca2+-depletion from, or by disruption of the SR, and was accompanied by changes in tension/pCa relationship, similar to those observed in human fibers. Both in skinned fibers and in isolated SR vesicles, UTP was less effective than ATP as a substrate for the SR Ca2+-ATPase. This effect might contribute to UTP-induced tension.

A comparison of the effects of UTP and ATP on the Ca2 release channel of skeletal muscle sarcoplasmic reticulum

Heavy sarcoplasmic reticulum (SR) membrane fractions from rabbit and porcine skeletal muscle were incorporated into planar lipid bilayers and the activity of the Ca2+ release channels was recorded under voltage clamp, using Cs+ as the current carrier. The effects of the nucleotides adenosine triphosphate (ATP) and uridine triphosphate (UTP) on channel activity were studied at a holding potential of +30 mV. UTP (0.1-1.0 mM) had no effect per se on the conductance or the gating properties of the Ca2+ release channels. In contrast, ATP (>0.1 mM) increased Po, the open channel probability, and both to1 and to2, the open time constants, and decreased tc1 and tc2, the closed time constants. The Ca2+ channel conductance, however, was not affected by ATP. Ruthenium red (1-2 µM), a well-known inhibitor of the SR Ca2+ release channel, abolished the ATP-induced channel activation. These electrophysiological data provide support for our contention (G. Suarez-Kurtz et al (1993). Anais da Academia Brasileira de Ciências, 65: 330) taht the UTP-induced tension in mammalian "skinned" mmuscle fibers is not due to stimulated release of SR-stored Ca2+ via the release channel