Pentosan polysulfate treatment preserves renal autoregulation in ANG II-infused hypertensive rats via normalization of P2X₁receptor activation

Abstract

Inflammatory factors are elevated in animal and human subjects with hypertension and renal injury. We hypothesized that inflammation contributes to hypertension-induced renal injury by impairing autoregulation and microvascular reactivity to P2X(1) receptor activation. Studies were conducted in vitro using the blood-perfused juxtamedullary nephron preparation. Rats receiving ANG II (60 ng/min) infusion were treated with the anti-inflammatory agent pentosan polysulfate (PPS) for 14 days. The magnitude and progression of hypertension were similar in ANG II and ANG II+PPS-treated rats (169 ± 5 vs. 172 ± 2 mmHg). Afferent arterioles from control rats exhibited normal autoregulatory behavior with diameter decreasing from 18.4 ± 1.6 to 11.4 ± 1.7 μm when perfusion pressure was increased from 70 to 160 mmHg. In contrast, pressure-mediated vasoconstriction was markedly attenuated in ANG II-treated rats, and diameter remained essentially unchanged over the range of perfusion pressures. However, ANG II-treated rats receiving PPS exhibited normal autoregulatory behavior compared with ANG II alone rats. Arteriolar reactivity to ATP and β,γ-methylene ATP was significantly reduced in ANG II hypertensive rats compared with controls. Interestingly, PPS treatment preserved normal reactivity to P2 and P2X(1) receptor agonists despite the persistent hypertension. The maximal vasoconstriction was 79 ± 3 and 81 ± 2% of the control diameter for ATP and β,γ-methylene ATP, respectively, similar to responses in control rats. PPS treatment significantly reduced α-smooth muscle actin staining in afferent arterioles and plasma transforming growth factor-β1 concentration in ANG II-treated rats. In conclusion, PPS normalizes autoregulation without altering ANG II-induced hypertension, suggesting that inflammatory processes reduce P2X(1) receptor reactivity and thereby impair autoregulatory behavior in ANG II hypertensive rats.

Immunosuppression preserves renal autoregulatory function and microvascular P2X1 receptor reactivity in ANG II-hypertensive rats

“…In the present study, we applied MMF, an inhibitor of lymphocyte proliferation, in chronic ANG II-infused hypertensive rats and directly assessed renal autoregulatory behavior at the afferent arteriole and at the whole kidney levels. Consistent with previous in vitro studies (10,17,34), afferent arteriolar autoregulatory behavior is attenuated in ANG II-hypertensive rats. Importantly, treatment with MMF preserved normal afferent arteriolar autoregulatory behavior such that it was indistinguishable from control arterioles despite having a similar degree of hypertension development and severity as ANG II alone rats.…”

“…Hypertension was induced using osmotic mini-pumps (Alzet, Cupertino, CA) filled with ANG II (60 ng/min sc for 13-14 days, Phoenix Pharmaceuticals, Belmont, CA) as previously described (10). Four groups were studied: control, control ϩ MMF (CellCept, Roche Laboratories, Nutley, NJ), ANG II alone, and ANG II ϩ MMF.…”

“…Renal autoregulatory and microvascular reactivity studies were performed using the in vitro blood-perfused juxtamedullary nephron (JMN) preparation as described previously (10). Two identically treated rats were needed for each experiment (kidney and blood donors).…”

“…Total plasma TGF-␤1 concentration was measured using a TGF␤1 E max ImmunoAssay kit (Promega, Madison, WI), as described previously (10).…”

Purinergic signalling in the kidney in health and disease

“…The central role of the P2 system is further suggested by the fact that pressure-induced reductions in afferent arteriole diameter are abolished in P2X1-deficient mice [152]. Pharmacological [272] or pathological [119] manoeuvres that impair P2X1 receptor signalling will also blunt whole kidney autoregulation of blood flow, both in vivo and in vitro. Finally, mice with a targeted deletion of the ectonucleotidase NTPDase1 exhibit enhanced pressureinduced vasoconstriction in the mesenteric artery [183].…”