Effects of SGLT2 inhibitor and dietary NaCl on glomerular hemodynamics assessed by micropuncture in diabetic rats

It has been theorized that Na-glucose cotransporter (SGLT2) blockade slows progression of diabetic kidney disease by reducing physical strain on the glomerulus. This is the first direct measurement of intraglomerular pressure during SGLT2 blockade. Findings confirmed that SGLT2 blockade does reduce glomerular capillary pressure, that this is mediated through tubuloglomerular feedback, and that the tubuloglomerular feedback response to SGLT2 blockade involves preglomerular vasoconstriction and postglomerular vasorelaxation.

The Role of P2X7 Purinergic Receptors in the Renal Inflammation Associated with Angiotensin II-Induced Hypertension

Purinergic receptors play a central role in the renal pathophysiology of angiotensin II-induced hypertension, since elevated ATP chronically activates P2X7 receptors in this model. The changes induced by the P2X antagonist Brilliant blue G (BBG) in glomerular hemodynamics and in tubulointerstitial inflammation resulting from angiotensin II infusion were studied. Rats received angiotensin II (435 ng kg−1 min−1, 2 weeks) alone or in combination with BBG (50 mg/kg/day intraperitoneally). BBG did not modify hypertension (214.5 ± 1.4 vs. 212.7 ± 0.5 mmHg), but restored to near normal values afferent (7.03 ± 1.00 to 2.97 ± 0.27 dyn.s.cm−5) and efferent (2.62 ± 0.03 to 1.29 ± 0.09 dyn.s.cm−5) arteriolar resistances, glomerular plasma flow (79.23 ± 3.15 to 134.30 ± 1.11 nL/min), ultrafiltration coefficient (0.020 ± 0.002 to 0.036 ± 0.003 nL/min/mmHg) and single nephron glomerular filtration rate (22.28 ± 2.04 to 34.46 ± 1.54 nL/min). Angiotensin II induced overexpression of P2X7 receptors in renal tubular cells and in infiltrating T and B lymphocytes and macrophages. All inflammatory cells were increased by angiotensin II infusion and reduced by 20% to 50% (p < 0.05) by BBG administration. Increased IL-2, IL-6, TNFα, IL-1β, IL-18 and overexpression of NLRP3 inflammasome were induced by angiotensin II and suppressed by BBG. These studies suggest that P2X7 receptor-mediated renal vasoconstriction, tubulointerstitial inflammation and activation of NLRP3 inflammasome are associated with angiotensin II-induced hypertension.

The SGLT2 Inhibitor Empagliflozin Might Be a New Approach for the Prevention of Acute Kidney Injury

Three randomized control trials (Canagliflozin Cardiovascular Assessment Study, Empagliflozin Cardiovascular Outcome Event Trial in Type 2 Diabetes Mellitus Patients [EMPA-REG OUTCOME], and Dapagliflozin Effect on Cardiovascular Events-Thrombolysis in Myocardial Infarction 58 [DECLARE-TIMI 58]) showed that the sodium-glucose co-transporter 2 (SGLT2) inhibitors, originally developed as glucose-lowering drugs, are associated with a lower rate of adverse renal outcomes, such as need for renal replacement therapy, doubling of serum creatinine, and loss of glomerular filtration rate (GFR) compared to those in placebo groups. Besides, canagliflozin and empagliflozin also showed a lower risk of progression to macroalbuminuria. The EMPA-REG OUTCOME trial and DECLARE-TIMI 58 trial also indicated that these SGLT2 inhibitors might have beneficial effects on the prevention of acute kidney injury. The United States Food and Drug Administration (FDA) warned of the risk of acute kidney injury for canagliflozin and dapagliflozin. We compared canagliflozin, empagliflozin, and dapagliflozin with respect to chemical structure and pharmacological properties, to explain the observed differences in preventing acute kidney injury, and put forward the hypotheses of the potential mechanisms of different effects of SGLT2 inhibitors on acute kidney injury. Given the raising clinical use of SGLT2 inhibitors, our review should stimulate further basic science and clinical studies in order to definitively understand the role of SGLT2 inhibitors in acute kidney injury. A weakness of the clinical data obtained so far is the fact that the statements concerning acute kidney injury are just based on safety data – mainly creatine measurements. However, given the mode of action of SGLT2 blockers, initiation of a therapy with a SGLT2 blocker will cause an increase of creatine because of its effects on the tubuloglomerular feedback mechanisms/glomerular hemodynamics like RAAS blocking agents do. To really understand the potential effects of SGLT2 inhibitors, we need preclinical and clinical SGLT2 inhibitor studies focusing on all aspects of acute kidney injury – not just changes in GFR biomarkers.

Physiopathological implications of P2X1and P2X7receptors in regulation of glomerular hemodynamics in angiotensin II-induced hypertension

Deleterious effects of purinergic P2X1and P2X7receptors (P2XRs) in ANG II-dependent hypertension include increased renal vascular resistance, and impaired autoregulation and pressure natriuresis. However, their specific effects on the determinants of glomerular hemodynamics remain incompletely delineated. To investigate the P2XR contributions to altered glomerular hemodynamics in hypertension, the effects of acute blockade of P2X1R, P2X7R, and P2X4R with NF449, A438079, and PSB12054, respectively, were evaluated in ANG II-infused rats (435 ng·kg−1·min−1). P2X1R or P2X7R blockade reduced afferent (6.85 ± 1.05 vs. 2.37 ± 0.20 dyn·s−1·cm−5) and efferent (2.85 ± 0.38 vs. 0.99 ± 0.07 dyn·s−1·cm−5) arteriolar resistances, leading to increases in glomerular plasma flow (75.82 ± 5.58 vs. 206.7 ± 16.38 nl/min), ultrafiltration coefficient (0.0198 ± 0.0024 vs. 0.0512 ± 0.0046 nl·min−1·mmHg−1), and single-nephron glomerular filtration rate (22.73 ± 2.02 vs. 51.56 ± 3.87 nl/min) to near normal values. Blockade of P2X4R did not elicit effects in hypertensive rats. In normotensive sham-operated rats, only the P2X1R antagonist caused an increase plasma flow and single-nephron glomerular filtration rate, whereas the P2X4R antagonist induced glomerular vasoconstriction that was consistent with evidence that P2X4R stimulation increases release of nitric oxide from endothelial cells. Mean arterial pressure remained unchanged in both hypertensive and normotensive groups. Western blot analysis showed overexpression of P2X1R, P2X7R, and P2X4R proteins in hypertensive rats. Whereas it has been generally assumed that the altered glomerular vascular resistances in ANG II hypertension are due to AT1receptor-mediated vasoconstriction, these data indicate a predominant P2X1R and P2X7R control of glomerular hemodynamics in ANG II hypertension.