Elevated sympathetic activity changes renal function and accelerates the development of hypertension. Principles of sympatho-renal interactions in chronic hypertension are reviewed. Alterations in the ontogeny of the sympathetic nervous system and the kidney, inherited abnormalities in sensory receptor function and exaggerated responsiveness to mental stress contribute to inappropriately high sympathetic activity in primary or essential hypertension. Careful characterization of clinical study populations shows that elevated sympathetic activity and "essential" hypertension are not unequivocally associated. Prospective clinical studies which investigate a broader array of physiological functions and experiments in recombinant inbred rodents with less traumatic nerve recording techniques than currently available will help to define under which conditions elevated sympathetic activity is indeed a cause of primary hypertension. Signals arising from the kidney which activate the renin-angiotensin system and afferent renal nerves increase sympathetic activity. These mechanisms importantly contribute to the pathogenesis of hypertension secondary to renal artery stenosis and end-stage renal disease.

The present study was designed to test the hypothesis that NADPH oxidase inhibition with apocynin would lower blood pressure and improve endothelial function in spontaneously hypertensive rats (SHRs). Although apocyin effectively dilated arterial segments in vitro, it failed to lower blood pressure or improve endothelial function. Further experiments were performed in normotensive rats and in NADPH oxidase subunit knock-out mice to test if apocynin-induced vasodilation depends on NADPH oxidase inhibition at all. SHRs were treated with apocynin orally or i.v. Arterial pressure was recorded directly. Rat and mouse arterial function was investigated in vitro by small vessel wire myography. NADPH oxidase activity was measured in human granulocytes and in rat vascular preparations. Rho kinase activity was determined by Western blot analysis. Apocynin did not reduce arterial pressure acutely in SHR when given at 50, 100, or 150 mg kg⁻¹ day⁻¹ orally over 1-week intervals or when given i.v. Apocynin potently inhibited granulocyte NADPH oxidase but not vascular NADPH-oxidase-dependent oxygen radical formation unless exogenous peroxidase was added to vascular preparations. Apocynin dilated rat intrarenal and coronary arteries independently of pharmacological interventions that reduce vascular superoxide radical abundance and actions. Aortic rings from p47phox^−/− mice were more sensitive to apocynin-induced dilation than wild-type aortic rings. Rho kinase inhibition reduced or prevented the inhibitory effect of apocynin on agonist-induced vasoconstriction and apocynin inhibited the phosphorylation of Rho kinase substrates. Apocynin per se does not inhibit vascular NADPH-oxidase-dependent superoxide formation. Its in vitro vasodilator actions are not due to NADPH oxidase inhibition but may be explained at least in part by inhibition of Rho kinase activity. The discrepancy between apocynin-induced vasodilation in vitro and the failure of apocynin to lower arterial pressure in SHR suggests opposing effects on arterial pressure-regulating systems in vivo. Its use as a pharmacological tool to investigate vascular NADPH oxidase should be discontinued.

This review is focused on the mechanisms that regulate health, disease and aging redox status, the signal pathways that counteract oxidative and reductive stress, the role of food components and additives with antioxidant properties (curcumin, polyphenols, vitamins, carotenoids, flavonoids, etc.), and the role of the hormones irisin and melatonin in the redox homeostasis of animal and human cells. The correlations between the deviation from optimal redox conditions and inflammation, allergic, aging and autoimmune responses are discussed. Special attention is given to the vascular system, kidney, liver and brain oxidative stress processes. The role of hydrogen peroxide as an intracellular and paracrine signal molecule is also reviewed. The cyanotoxins β-N-methylamino-l-alanine (BMAA), cylindrospermopsin, microcystins and nodularins are introduced as potentially dangerous food and environment pro-oxidants.

We investigated whether arterial pressure in spontaneously hypertensive rats (SHR) can be normalized by a kidney graft from normotensive histocompatible donors. In addition, the effect of differential genetic predisposition to hypertension of recipients of an SHR kidney on the development of post-transplantation hypertension was studied. SHR were transplanted with a kidney from congenic rats (BB.1K) homozygous for a 2 cM segment of SHR chromosome 20, including the major histocompatibility complex class Ia and class II genes. BB.1K and F1 hybrids (F1H, SHR × Wistar–Kyoto rats) were transplanted with an SHR kidney and the development of renal post-transplantation hypertension was monitored. Thirty days after renal transplantation, mean arterial pressure (MAP) was 116 ± 4 mmHg in SHR with a BB.1K kidney (n = 8) versus 168 ± 2 mmHg in sham-operated SHR (n = 10);P < 0.001. Cumulative renal sodium balance (mmol/100 g body weight) over 21 days after bilateral nephrectomy was 6.8 ± 0.6 in SHR with a BB.1K kidney versus 10.8 ± 1.6 in sham-operated SHR (P < 0.05). Within 60 days of transplantation, MAP increased in BB.1K and in F1H transplanted with an SHR kidney (n = 7 per group) by 38 ± 5 mmHg and 43 ± 8 mmHg, respectively. In SHR, arterial pressure can be normalized by a kidney graft from normotensive donors. The genetic predisposition of the recipients to hypertension does not modify the rate and the extent of the arterial pressure rise induced by an SHR kidney graft.

Objectives: Increased renal vascular resistance contributes to the pathogenesis of hypertension. The new Rho kinase (ROCK) inhibitor SAR407899 more potently lowers arterial pressure than the commercially available ROCK inhibitor Y27623. We tested whether ROCK inhibition more effectively reduced agonist-induced vasoconstriction in renal than in nonrenal resistance arteries and if SAR407899 more potently inhibits agonist-induced vasoconstriction than Y27632. Methods: The effects of the ROCK inhibitors on endothelin-1 (ET-1) induced vasoconstriction were investigated in isolated renal and coronary arteries from lean, normotensive Dark Agouti and obese, type 2 diabetic Zucker diabetic fatty (ZDF) rats as well as in isolated human resistance arteries from the kidney and thymus. Vascular ROCK mRNA abundance was studied by real-time PCR (RT-PCR). Results: ET-1-induced constriction depended more on ROCK in rat and human renal resistance arteries than in rat coronary or human thymic arteries, respectively. SAR407899 was more effective than Y27632 in reducing ET-1-induced vasoconstriction in ZDF rat renal resistance arteries. Maximum ET-1-induced vasoconstriction in SAR407899-treated and Y27632-treated human renal resistance arteries was 23 ± 5 and 48 ± 6% of control values, respectively. Transcripts of both ROCK isoforms were detected in rat and human renal resistance arteries. In human thymic arteries, only the ROCK2 transcript was found. Conclusion: ET-1-induced vasoconstriction is more ROCK-dependent in renal than in nonrenal resistance arteries. SAR407899 causes a greater inhibition of ET-1-induced vasoconstriction in renal resistance arteries from ZDF rats and patients than Y27632. The greater efficacy in renal vessels may contribute to the higher antihypertensive potency of SAR407899 compared with Y27632.

The effects of neonatal sympathectomy of donors or recipients on posttransplantation arterial pressure were investigated in spontaneously hypertensive rats (SHR) by renal transplantation experiments. Conscious mean arterial pressure (MAP) and renal vascular resistance were 136 ± 1 mmHg and 15.5 ± 1.2 mmHg · ml−1 · min · g in sympathectomized SHR ( n = 8) vs. 158 ± 4 mmHg ( P < 0.001) and 20.8 ± 1.1 mmHg · ml−1 · min · g ( P < 0.05) in controls ( n = 10). Seven weeks after transplantation of a kidney from neonatally sympathectomized SHR donors, MAP in SHR recipients ( n = 10) was 20 mmHg lower than in controls transplanted with a kidney from hydralazine-treated SHR ( n = 10) ( P < 0.05) associated with reduced sodium sensitivity of MAP. Neonatal sympathectomy also lowered MAP in F1-hybrids (F1H; SHR × Wistar-Kyoto rats). Within 6 wk after transplantation, renal grafts from untreated SHR increased MAP by 20 mmHg in sympathectomized F1H ( n = 10) and by 35 mmHg in sham-treated F1H ( n = 8) ( P < 0.05). Neonatal sympathectomy induces chronic changes in SHR kidney function leading to a MAP reduction even when extrarenal sympathetic tone is restored. Generalized reduction in sympathetic tone resets the kidney-fluid system to reduced MAP and blunts the extent of arterial pressure rise induced by an SHR kidney graft.