Angiotensin II and the Renal Hemodynamic Response to an Isolated Increased Renal Venous Pressure in Rats

LncRNA H19: a novel player in the regulation of diabetic kidney disease

Diabetic kidney disease (DKD), one of the most severe complications of diabetes mellitus (DM), has received considerable attention owing to its increasing prevalence and contribution to chronic kidney disease (CKD) and end-stage kidney disease (ESRD). However, the use of drugs targeting DKD remains limited. Recent data suggest that long non-coding RNAs (lncRNAs) play a vital role in the development of DKD. The lncRNA H19 is the first imprinted gene, which is expressed in the embryo and down-regulated at birth, and its role in tumors has long been a subject of controversy, however, in recent years, it has received increasing attention in kidney disease. The LncRNA H19 is engaged in the pathological progression of DKD, including glomerulosclerosis and tubulointerstitial fibrosis via the induction of inflammatory responses, apoptosis, ferroptosis, pyroptosis, autophagy, and oxidative damage. In this review, we highlight the most recent research on the molecular mechanism and regulatory forms of lncRNA H19 in DKD, including epigenetic, post-transcriptional, and post-translational regulation, providing a new predictive marker and therapeutic target for the management of DKD.

Macula Densa Nitric Oxide Synthase 1 Controls Renin Release and Renin-Dependent Blood Pressure Changes

BACKGROUND

The function of macula densa nitric oxide synthase 1 (NOS1) in the regulation of renin release is controversial. This study was conducted to further elucidate the role of macula densa NOS1 in renin release and blood pressure regulation in response to salt challenges and hemorrhagic shock.

METHODS

To investigate the specific role of NOS1 in the macula densa within the kidney in response to varying sodium concentrations in the diet, tissue macula densa-specific NOS1 knockout (MD-NOS1KO) and wild type (WT) mice were subjected to sequential low (0.1% NaCl) and high (1.4% NaCl) sodium diets. Separate groups of mice, consisting of both MD-NOS1KO subgroup and WT subgroup, were induced hemorrhagic shock by retro-orbital bleeding of 12 mL blood/kg body weight. Mean arterial pressure (MAP) was measured by a radio-telemetry system. Plasma renin concentration (PRC) was measured with the radioimmunoassay for both sodium diet and hemorrhagic shock experiments.

RESULTS

PRCs were 371 ± 95 and 411 ± 68 ng/mL/hr in WT and MD-NOS1KO mice fed a normal sodium diet, respectively. Low salt intake stimulated an increase in the renin release by about 260% in WT mice (PRC = 1364 ± 217 ng/mL/hr, p < 0.0001) compared to the PRC under normal salt diet. However, the stimulation was significantly blunted in MD-NOS1KO mice (PRC = 678 ± 104 ng/mL/hr, p < 0.001). High salt intake suppressed the PRC to about 61% of the PRC level under a normal salt diet (p < 0.0001). Deletion of macula densa NOS1 further inhibited renin release to 33% of the levels of a normal salt diet. Hemorrhagic shock induced about a 3-fold increase in PRC in WT mice, but only about a 54% increase in the MD-NOS1KO mice (p < 0.0001). The MAP values were substantially greater in WT mice than in MD-NOS1KO mice within the first 6 hours following hemorrhagic shock (p < 0.001). Thus, WT mice showed a much quicker recovery in MAP than MD-NOS1KO mice.

CONCLUSIONS

Our study demonstrated that macula densa NOS1 plays an important role in mediating renin release. This mechanism is essential in maintaining blood pressure under hypovolemic situations such as hemorrhagic shock.

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.