P16INK4a deletion alleviates contrast-induced acute kidney injury by ameliorating renal cell apoptosis and suppressing inflammation and oxidative stress

Contrast-induced acute kidney injury (CI-AKI) is the third leading cause of hospital-acquired acute kidney injury. Cellular senescence is associated with CI-AKI. P16INK4a (p16) is a cell cycle regulator and link to aging and senescence. We found that the expression of p16 was elevated in CI-AKI renal tissues, however its role in CI-AKI remains insufficiently understood. In this study, we used p16 knockout (p16KO) mice and wild-type (WT) littermates to establish CI-AKI mice model to elucidate the impact of p16 on CI-AKI. The results showed that serum creatinine (SCr), blood urea nitrogen (BUN), and serum neutrophil gelatinase-associated lipocalin (NGAL) levels were markedly reduced in p16KO CI-AKI mice. Both immunohistochemistry and western blot analyses confirmed that p16 knockout alleviated renal cell apoptosis. Furthermore, interleukin (IL)-1β, IL-6, and tumor necrosis factor-α (TNF-α) were attenuated by downregulating NLRP3 and NF-κB inflammasomes. Additionally, ROS levels were diminished via activating Nrf2/Keap-1 pathway in p16KO CI-AKI mice. Collectively, our findings suggest that p16 deletion exerts protective effects against apoptosis, inflammation, and oxidative stress in CI-AKI mice model, p16 deletion might be a potential therapeutic strategy for ameliorating CI-AKI.

Swimming Exercise Ameliorates Hypertension-Induced Kidney Dysfunction via Alleviating Renal Interstitial Fibrosis and Apoptosis

BACKGROUND

Hypertensive nephropathy is one of the major causes of ESRD. Exercise has been considered a nonpathological therapy for hypertension and its complications, yet mechanisms remain unclear. We sought to investigate whether periodic swimming could ameliorate hypertension-induced kidney dysfunction and its underlying mechanisms.

METHODS

Four-week male spontaneously hypertensive rats (SHRs) were randomly divided into the hypertension group (SHR, n = 8) and exercise group (SE, n = 8, 60 min swimming/day, 6 days per week, for 8 weeks). Wistar-Kyoto rats (WKY, n = 8) were served as a sedentary normotensive group. Bodyweight and blood pressure (BP) were recorded weekly. After 8-week sedentary or swimming exercise, lipids profile, BUN, and Cr were measured. The renal interstitial fibrosis was examined by the histopathological analysis using Masson's trichrome staining and hematoxylin and eosin staining. The kidney cell apoptosis was tested by TUNEL staining. The expressions of critical proteins responsible for the TGF-β1/Smad signaling of fibrosis, that is, TGF-β1, Smad2/3, and Smad7, as well as apoptosis related proteins, Bax and Bcl-2 in kidney cortex tissues were measured.

RESULTS

The 8-week swimming exercise reduced BP and bodyweight, lowered concentrations of BUN, and serum Cr, compared with SHR. Exercise remarkably inhibited hypertension-induced tubular degeneration, cellular cluster, and tubular cell swelling as well as glomerular degeneration in the kidney cortical tissues, attenuated renal interstitial fibrosis, and renal cell apoptosis. Moreover, expressions of TGF-β1, Smad2/3, and Bax were higher in the SHR than the WKY, which were significantly suppressed by the exercise. In contrast, hypertension-reduced expressions of Smad7 and Bcl-2 were enhanced by the swimming exercise. Strong correlations were found between kidney function indices, blood lipids, and key protein expressions.

CONCLUSION

Our results demonstrate beneficial effects of the periodic swimming on ameliorating hypertension-induced kidney dysfunction highlighting the potential of swimming exercise as a nonpathological therapy for early prevention of hypertension-caused kidney diseases.

Renal cells apoptosis and Bax, Bcl-2 expression in rats with severe acute pancreatitis

AIM: To explore the roles of renal cell apoptosis and expression of Bax and Bcl-2 in renal injury in rats with severe acute pancreatitis (SAP).

METHODS: Thirty rats were randomized into sham operation (SO, n = 15) and SAP group (n = 15). The model of SAP was established by retrograde injection of 50 g/L sodium taurocholate into the biliopancreatic duct in the rats. Serum creatinine (Cr) and blood urea nitrogen (BUN) were determined 6, 12, and 18 h after injection. The pathological changes were observed by light and electron microscopy. The apoptosis of renal cells was determined by TUNEL method, and the expression of Bax and Bcl-2 was detected by immunohistochemical staining (SABC assay).

RESULTS: As compared with those in SO group at the same phase, serum Cr and BUN in SAP group increased markedly. Significant injuries of renal tissue were observed under light and electron microscope.The apoptotic index of renal glomerular cells increased significantly 6, 12, 18 h after injection (3.2±1.1 vs 0.8±0.1, P <0.05; 3.9±1.8 vs 0.9±0.1, P <0.05; 4.8±1.7 vs 0.8±0.2, P <0.01, respectively). The apoptotic index of renal tubule cells also increased significantly (9.8±1.1 vs 1.3±0.5, P <0.01; 12.6±2.3 vs 1.2±0.3, P <0.01; 15.7±2.6 vs 1.3±0.3, P <0.01, respectively). The expression of Bax in renal glomerulus and tubule increased significantly at 6, 12, 18 h, respectively (glomerulus: 3.05±0.86 vs 1.01±0.04, P <0.05; 3.37±1.13 vs 1.06±0.05, P <0.05; 4.11±1.24 vs 1.09±0.03, P <0.05; tubule: 8.17±2.16 vs 1.53±0.07, P <0.01; 12.92±1.81 vs 1.61±0.05, P <0.01; 13.08±2.53 vs 1.59±0.05, P <0.01), and increased continuously. Bcl-2 was mainly expressed in the regions of renal tubule, and it also increased in SAP group at 6, 12, 18 h, respectively (3.38±1.07 vs 1.58±0.02, P <0.05; 4.26±1.13 vs 1.59±0.06, P <0.05; 7.21±1.04 vs 1.61±0.02, P <0.01). The level of Bcl-2 expression in renal glomerulus was higher in SAP group than that in SO group at 6, 12, 18 h, respectively (2.18±0.65 vs 1.04±0.02; 2.42±0.63 vs 1.03±0.05, P <0.05; 2.69±0.47 vs 1.08±0.04, P <0.05), but decreased with the duration of the injuries.

CONCLUSION: Renal cell apoptosis, which relates to the up-regulated expression of Bax and downed regulated expression of Bcl-2, may be involved in the pathogenesis of renal injury in patients with SAP.