No abstract

In mice, the initial stage of nephrotoxic serum-induced nephritis (NTN) mimics antibody-mediated human glomerulonephritis. Local immune deposits generate tumor necrosis factor (TNF), which activates pro-inflammatory pathways in glomerular endothelial cells (GECs) and podocytes. Because TNF receptors mediate antibacterial defense, existing anti-TNF therapies can promote infection; however, we have previously demonstrated that different functional domains of TNF may have opposing effects. The TIP peptide mimics the lectin-like domain of TNF, and has been shown to blunt inflammation in acute lung injury without impairing TNF receptor-mediated antibacterial activity. We evaluated the impact of TIP peptide in NTN. Intraperitoneal administration of TIP peptide reduced inflammation, proteinuria, and blood urea nitrogen. The protective effect was blocked by the cyclooxygenase inhibitor indomethacin, indicating involvement of prostaglandins. Targeted glomerular delivery of TIP peptide improved pathology in moderate NTN and reduced mortality in severe NTN, indicating a local protective effect. We show that TIP peptide activates the epithelial sodium channel(ENaC), which is expressed by GEC, upon binding to the channel's a subunit. In vitro, TNF treatment of GEC activated pro-inflammatory pathways and decreased the generation of prostaglandin E2 and nitric oxide, which promote recovery from NTN. TIP peptide counteracted these effects. Despite the capacity of TIP peptide to activate ENaC, it did not increase mean arterial blood pressure in mice. In the later autologous phase of NTN, TIP peptide blunted the infiltration of Th17 cells. By countering the deleterious effects of TNF through direct actions in GEC, TIP peptide could provide a novel strategy to treat glomerular inflammation.Kidney International (2019) 95, 1359-1372; https://doi.

No abstract

Hypertension is a major modifiable risk factor for cardiovascular disease that remains suboptimally controlled despite all recent advances in biomedical research. Sex differences pertaining to development of hypertension and its pathophysiological outcomes are becoming universally recognized. Mechanistic insights into those differences can be utilized to improve the existing or develop novel therapeutic interventions for both sexes. We have previously demonstrated that excessive stimulation of Epithelial Na+ Channel (ENaC), resistant to mineralocorticoid receptor (MR) inhibition, contributes to Ang II‐induced hypertension in male mice. Given the interaction between aldosterone and estrogen signaling pathways, herein, we hypothesize that resistance to MR blockade in Ang II hypertensive subjects is sex‐specific. We combined physiological, pharmacological, biochemical and biophysical approaches to compare how MR antagonism affects renal sodium handling and blood pressure in Ang II‐infused male and female Sprague Dawley rats. Patch‐clamp electrophysiology in split‐opened collecting ducts demonstrated that systemic spironolactone administration (30 mg/kgBW·day for 14 days) only partially attenuated the stimulatory effect of Ang II infusion on ENaC in males. The activity of the channel remained at least twofold higher than in untreated normotensive controls. MR inhibition was remarkably more efficient in Ang II‐infused females, suppressing renal ENaC activity to its basal levels observed in non‐hypertensive rats. In both sexes, the reduction of ENaC activity driven by spironolactone was primarily attributed to decreased functional expression of the channel. This effect was complemented by a moderate decrease of ENaC open probability in spironolactone‐treated hypertensive females. Circulating aldosterone levels were lower in Ang II‐infused females when compared to males. This difference was further accentuated by spironolactone administration. Quantitative western‐blotting revealed that only in hypertensive females MR antagonism significantly increased renal expression of Nedd4‐2, facilitating ENaC degradation and reducing Na+ reabsorption. MR blockade did not alter the abundance of active phosphorylated forms of other renal Na+ transporters – NCC and NKCC2, in both sexes. In line with our observations on renal Na+ handling, we found that spironolactone markedly attenuated hypertension in Ang II‐infused females, while MR inhibition failed to reduce blood pressure in hypertensive males. Aldosterone antagonism did not elevate plasma K+ in all animal groups. Flow cytometry showed significantly lower levels of Th17 cells in the kidneys of spironolactone‐treated females, indicating reduced inflammatory response. Overall, our findings suggest that the action of spironolactone on ENaC‐mediated renal sodium reabsorption is sex‐specific and MR antagonism can be an effective strategy to reduce blood pressure and kidney damage in females with Ang‐II induced hypertension.Support or Funding InformationAHA 15SDG25550150This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

It is well established that cell death is a hallmark of hypertension. Apoptosis is a controlled physiologic form of cell death in which dying cells are cleared via phagocytosis limiting further tissue inflammation and damage. We have previously shown that spontaneously hypertensive rats (SHR) have greater apoptosis compared to age matched normotensive Wistar Kyoto rats. We also showed that there is a sex difference in renal cell death in SHR with females having greater renal apoptosis compared to age matched male SHR. The contribution of apoptosis to the control of blood pressure (BP) in established hypertension is unknown, however, 13 week old female SHR have a lower BP and a less pro‐inflammatory T cell profile compared to males. The goal of the current study was to test the hypothesis that greater apoptosis in female SHR contributes to the lower BP and anti‐inflammatory T cell profile vs. male SHR. Male (M) and female (F) SHR were randomized to receive vehicle (Veh) or ZVAD‐FMK, a cell permeable, non‐selective apoptosis inhibitor, from 13–15 weeks of age (1 mg/kg via IP injection 5 days/week; n=4–8) and BP was measured via telemetry. Following 2 weeks of treatment, kidney and blood were collected to measure apoptosis and the T cell profile by flow cytometry. Treatment with ZVAD for 2 weeks reduced renal apoptosis in both male and female SHR and abolished the sex difference in renal apoptosis (expressed as % total kidney cells‐ M Veh: 2.2±0.3 vs M ZVAD: 1.2±0.4; F Veh: 4.5±0.9 vs F ZVAD: 0.7±0.2; Effect of ZVAD: P<0.0001, Effect of sex: P=0.082, Interaction: P=0.0075). Inhibition of apoptosis did not alter BP in either male or female SHR (BP in mmHg in M ZVAD: 143±5; M Veh: 145±4 F ZVAD: 139±2; F Veh: 140±3 mmHg). However, inhibition of apoptosis decreased the numbers of circulating CD3+ T cells in both male (expressed as % total blood cells‐ M Veh: 12.2±1% vs M ZVAD: 10.3±1.1%) and female SHR (F Veh: 14.7±1.3% vs F ZVAD: 11.8±1.3%; Effect of ZVAD: P=0.07, Effect of sex: P=0.096, Interaction: P= 0.75). Inhibition of apoptosis also increased Tregs in female SHR (expressed as %CD3+CD4+FoxP3+ cells‐ F Veh: 6.3±0.3 vs F ZVAD: 8.1±0.1) with no effect in males (M Veh: 7.5±0.4% vs M ZVAD: 7.6±0.6%; Effect of ZVAD: P=0.025, Effect of sex: P=0.48, Interaction: P=0.041). The renal T cell profile was not altered by inhibition of apoptosis. Taken together, our data suggest that while apoptosis does not contribute to the control of BP in established hypertension in either male or female SHR, it does contribute to the pro‐inflammatory T cell profile in the blood of both sexes. Further studies will determine the contribution of apoptosis to the maturation induced increases in BP in SHR prior to the development of established hypertension.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.