Pentosan polysulfate preserves renal microvascular P2X1 receptor reactivity and autoregulatory behavior in DOCA-salt hypertensive rats

Abstract

Inflammation contributes to ANG II-associated impairment of renal autoregulation and microvascular P2X1 receptor signaling, but its role in renal autoregulation in mineralocorticoid-induced hypertension is unknown. Autoregulatory behavior was assessed using the blood-perfused juxtamedullary nephron preparation. Hypertension was induced in uninephrectomized control rats (UNx) by subcutaneous implantation of a DOCA pellet plus administration of 1% NaCl in the drinking water (DOCA-salt) for 3 wk. DOCA-salt rats developed hypertension that was unaltered by anti-inflammatory treatment with pentosan polysulfate (DOCA-salt+PPS) but was suppressed with "triple therapy" (hydrochlorothiazide, hydralazine, and reserpine; DOCA-salt+TTx). Baseline arteriolar diameters were similar across all groups. UNx rats exhibited pressure-dependent vasoconstriction with diameters declining to 69 ± 2% of control at 170 mmHg, indicating intact autoregulation. DOCA-salt treatment significantly blunted this pressure-mediated vasoconstriction. Diameters remained between 91 ± 4 and 98 ± 3% of control over 65-170 mmHg, indicating impaired autoregulation. In contrast, pressure-mediated vasoconstriction was preserved in DOCA-salt+PPS and DOCA-salt+TTx rats, reaching 77 ± 7 and 75 ± 3% of control at 170 mmHg, respectively. ATP is required for autoregulation via P2X1 receptor activation. ATP- and β,γ-methylene ATP (P2X1 receptor agonist)-mediated vasoconstriction were markedly attenuated in DOCA-salt rats compared with UNx (P < 0.05), but significantly improved by PPS or TTx (P < 0.05 vs. DOCA-salt) treatment. Arteriolar responses to adenosine and UTP (P2Y2 receptor agonist) were unaffected by DOCA-salt treatment. PPS and TTx significantly reduced MCP-1 and protein excretion in DOCA-salt rats. These results support the hypothesis that hypertension triggers inflammatory cascades but anti-inflammatory treatment preserves renal autoregulation in DOCA-salt rats, most likely by normalizing renal microvascular reactivity to P2X1 receptor activation.

Keywords: afferent arteriole; hypertension; inflammation; purinoceptors; triple therapy.

Fig. 1.

Systolic blood pressure (SBP) in DOCA-salt hypertensive rats. SBP was measured by tail-cuff plethysmography in uninephrectomized rats (UNx; circles), DOCA-salt rats (diamonds), DOCA-salt rats treated with pentosan polysulfate (PPS; DOCA-salt+PPS; 100 mg·kg⁻¹·day⁻¹, squares), and DOCA-salt rats treated with triple therapy (DOCA-salt+TTx; hydralazine, hydrochlorothiazide, and reserpine, triangles) from the metabolic studies. PPS did not alter the progression or magnitude of hypertension in DOCA-salt rats through the 21-day treatment period. TTx treatment suppressed the development of hypertension in DOCA-salt rats. Values are means ± SE. *P < 0.05 vs. SBP on day 0. †P < 0.05 vs. UNx.

Fig. 2.

Autoregulatory behavior of afferent arterioles in DOCA-salt hypertensive rats. A: afferent arteriolar response to alterations in renal perfusion pressure was measured in UNx (circles), DOCA-salt (diamonds), DOCA-salt+PPS (100 mg·kg⁻¹·day⁻¹, squares), or DOCA-salt+TTx (triangles). B: data are normalized as percentage of the control diameter at 100 mmHg. C: afferent arteriolar response to norepinephrine at the end of each experiment except that one arteriole was not assessed from the DOCA-salt or DOCA-salt+TTx group due to insufficient perfusate blood. Values are means ± SE. *P < 0.05 vs. control diameter in the same group. †P < 0.05 vs. UNx rats at the same perfusion pressure. #P < 0.05 vs. DOCA-salt+PPS at the same perfusion pressure. &P < 0.05 vs. DOCA-salt+TTx at the same perfusion pressure.

Fig. 3.

Afferent arteriolar response to ATP in DOCA-salt hypertensive rats. A: afferent arteriolar response to superfusion of ATP was assessed in UNx (circles), DOCA-salt (diamonds), DOCA-salt treated with PPS (DOCA-salt+PPS, 100 mg·kg⁻¹·day⁻¹, squares), or DOCA-salt treated with triple therapy (DOCA-salt+TTx, hydralazine, hydrochlorothiazide, and reserpine, triangles). B: data are normalized as percentage of the control diameter at 100 mmHg. Values are means ± SE. *P < 0.05 vs. control diameter in the same group. †P < 0.05 vs. UNx at the same concentration. #P < 0.05 vs. DOCA-salt+PPS at the same concentration. &P < 0.05 vs. DOCA-salt+TTx at the same concentration.

Fig. 4.

Afferent arteriolar response to β,γ-methylene ATP in DOCA-salt hypertensive rats. A: afferent arteriolar response to superfusion of β,γ-methylene ATP was assessed in UNx (circles), DOCA-salt (diamonds), DOCA-salt treated with PPS (DOCA-salt+PPS, 100 mg·kg⁻¹·day⁻¹, squares), or DOCA-salt treated with triple therapy (DOCA-salt+TTx, hydralazine, hydrochlorothiazide, and reserpine, triangles). B: data are normalized as percentage of the control diameter at 100 mmHg. Values are means ± SE. *P < 0.05 vs. control diameter in the same group. †P < 0.05 vs. UNx at the same concentration. #P < 0.05 vs. DOCA-salt+PPS at the same concentration. &P < 0.05 vs. DOCA-salt+TTx at the same concentration.

Fig. 5.

Afferent arteriolar response to UTP and adenosine in DOCA-salt hypertensive rats. A: afferent arteriolar response to superfusion of UTP was assessed in UNx (circles) and DOCA-salt (diamonds). B: afferent arteriolar response to superfusion of adenosine was assessed in UNx (circles) and DOCA-salt (diamonds). All data are expressed as percentage of the control diameter at 100 mmHg. Values are means ± SE. *P < 0.05 vs. control diameter in the same group.

Fig. 6.

Monocyte chemoattractant protein-1 (MCP-1) and proteinuria in DOCA-salt hypertensive rats. Urine (24 h) was collected on days 0, 7, 14, and 21. A: MCP-1 excretion. B: protein excretion. Values are means ± SE. †P < 0.05 vs. UNx in the same period of urine collection. #P < 0.05 vs. DOCA-salt+PPS in the same period of urine collection. &P < 0.05 vs. DOCA-salt+TTx in the same period of urine collection.