Chronic elevation of renal venous pressure induces extensive renal venous collateral formation and modulates renal function and cardiovascular stability in rats

Sodium glucose cotransporter 2 inhibitor suppresses renal injury in rats with renal congestion

Renal congestion is an issue of cardiorenal syndrome in patients with heart failure. Recent clinical and basic studies suggest a renoprotective potential of sodium-glucose cotransporter (SGLT) 2 inhibitors. However, the effect on renal congestion and its mechanism is not fully understood. Thus, we aimed to clarify the effect of SGLT inhibition in a renal congestion model. Renal congestion was induced in the left kidney of male Sprague-Dawley rats by ligation of the inferior vena cava between the renal veins. The SGLT2 inhibitor tofogliflozin or vehicle was orally administered daily from the day before IVC ligation until two days after surgery. On the third postoperative day, both the right control kidney and the left congested kidney were harvested and analyzed. Kidney weight and water content was increased, and renal injury and fibrosis were observed in the left congested kidney. Kidney weight gain and hydration were improved with tofogliflozin treatment. Additionally, this treatment effectively reduced renal injury and fibrosis, particularly in the renal cortex. SGLT2 expression was observed in the congested kidney, but suppressed in the damaged tubular cells. Molecules associated with inflammation were increased in the congested kidney and reversed by tofogliflozin treatment. Mitochondrial dysfunction provoked by renal congestion was also improved by tofogliflozin treatment. Tofogliflozin protects against renal damage induced by renal congestion. SGLT2 inhibitors could be a candidate strategy for renal impairment associated with heart failure.

Inhibition of platelet-derived growth factor pathway suppresses tubulointerstitial injury in renal congestion

OBJECTIVE

Increased central venous pressure in congestive heart failure is responsible for renal dysfunction, which is mediated by renal venous congestion. Pericyte detachment from capillaries after renal congestion might trigger renal fibrogenesis via pericyte-myofibroblast transition (PMT). Platelet-derived growth factor receptors (PDGFRs), which are PMT indicators, were upregulated in our recently established renal congestion model. This study was designed to determine whether inhibition of the PDGFR pathway could suppress tubulointerstitial injury after renal congestion.

METHODS

The inferior vena cava between the renal veins was ligated in male Sprague-Dawley rats, inducing congestion only in the left kidney. Imatinib mesylate or vehicle were injected intraperitoneally daily from 1 day before the operation. Three days after the surgery, the effect of imatinib was assessed by physiological, morphological and molecular methods. The inhibition of PDGFRs against transforming growth factor-β1 (TGFB1)-induced fibrosis was also tested in human pericyte cell culture.

RESULTS

Increased kidney weight and renal fibrosis were observed in the congested kidneys. Upstream inferior vena cava (IVC) pressure immediately increased to around 20 mmHg after IVC ligation in both the imatinib and saline groups. Although vasa recta dilatation and pericyte detachment under renal congestion were maintained, imatinib ameliorated the increased kidney weight and suppressed renal fibrosis around the vasa recta. TGFB1-induced elevation of fibrosis markers in human pericytes was suppressed by PDGFR inhibitors at the transcriptional level.

CONCLUSION

The activation of the PDGFR pathway after renal congestion was responsible for renal congestion-induced fibrosis. This mechanism could be a candidate therapeutic target for renoprotection against renal congestion-induced tubulointerstitial injury.

Chronic, Combined Cardiac and Renal Dysfunction Exacerbates Renal Venous Pressure-Induced Suppression of Renal Function in Rats

Background and Objective

Increased renal venous pressure (RVP) is common in combined heart and kidney failure. We previously showed that acute RVP elevation depresses renal blood flow (RBF), glomerular filtration rate (GFR), and induces renal vasoconstriction in the absence of changes in blood pressure in healthy rats. We used our established rodent model of chronic combined heart and kidney failure (H/KF) to test whether RVP elevation would impair cardiovascular stability, renal perfusion and exacerbate renal dysfunction.

Methods

Male rats were subjected to 5/6 nephrectomy (SN_x or Sham) and 6% high salt diet followed 7 weeks later by ligation of the left anterior descending coronary artery (CL or Sham). Experimental groups: CL + SN_x (n = 12), Sham CL + SN_x (n = 9), CL+ Sham SN_x (n = 6), and Sham Control (n = 6). Six weeks later, anesthetized rats were subjected to an acute experiment whereupon mean arterial pressure (MAP), heart rate (HR), RVP, RBF, and GFR were measured at baseline and during elevation of RVP to 20–25 mmHg for 120 min.

Results

Baseline MAP, HR, RBF, and renal vascular conductance (RVC) were comparable among groups. Baseline GFR was significantly depressed in CL + SN_x and Sham CL + SN_x groups compared to Sham Control and CL + Sham SN_x groups. Upon RVP increase, MAP and HR fell in all groups. Increased RVP exacerbated the reduction in RBF in CL + SN_x (−6.4 ± 0.9 ml/min) compared to Sham Control (−3.7 ± 0.9 ml/min, p < 0.05) with intermediate responses in Sham CL + SN_x (−6.8 ± 1.3 ml/min) and CL + Sham SN_x (−5.1 ± 0.4 ml/min) groups. RVP increase virtually eliminated GFR in CL + SN_x (−99 ± 1%), Sham CL + SN_x (−95 ± 5%), and CL + Sham SN_x (−100%) groups compared to Sham Control (−84 ± 15% from baseline; p < 0.05). Renal vascular conductance dropped significantly upon RVP increase in rats with HF (CL + SN_x: −0.035 ± 0.011; CL + Sham SN_x: −0.050 ± 0.005 ml/min·mmHg⁻¹, p < 0.05) but not Sham CL + SN_x (−0.001 ± 0.019 ml/min·mmHg⁻¹) or Control (−0.033 ± mL/min·mmHg⁻¹).

Conclusion

Chronic combined heart and kidney failure primarily impairs renal hemodynamic stability in response to elevated RVP compared to healthy rats.