The sympathetic nervous system in the pathogenesis of acute renal failure

Renal Sympathetic Nerve-Derived Signaling in Acute and Chronic kidney Diseases

The kidney is innervated by afferent sensory and efferent sympathetic nerve fibers. Norepinephrine (NE) is the primary neurotransmitter for post-ganglionic sympathetic adrenergic nerves, and its signaling, regulated through adrenergic receptors (AR), modulates renal function and pathophysiology under disease conditions. Renal sympathetic overactivity and increased NE level are commonly seen in chronic kidney disease (CKD) and are critical factors in the progression of renal disease. Blockade of sympathetic nerve-derived signaling by renal denervation or AR blockade in clinical and experimental studies demonstrates that renal nerves and its downstream signaling contribute to progression of acute kidney injury (AKI) to CKD and fibrogenesis. This review summarizes our current knowledge of the role of renal sympathetic nerve and adrenergic receptors in AKI, AKI to CKD transition and CKDand provides new insights into the therapeutic potential of intervening in its signaling pathways.

Effect of monoamine oxidase inhibitors on ischaemia/reperfusion-induced acute kidney injury in rats

Increases in renal sympathetic nerve activity during ischaemia and renal venous norepinephrine levels after reperfusion play important roles in the development of ischaemia/reperfusion-induced acute kidney injury. In the present study, we examined the effect of isatin, an endogenous monoamine oxidase inhibitor, on renal venous norepinephrine levels, superoxide production after reperfusion, and ischaemia/reperfusion-induced acute kidney injury. Ischaemia/reperfusion-induced acute kidney injury was accomplished by clamping the left renal artery and vein for 45min, followed by reperfusion, 2 weeks after contralateral nephrectomy. Renal superoxide production and norepinephrine overflow were elevated and significant renal tissue damage was observed following ischaemia/reperfusion injury. Intravenous injection of isatin (10mg/kg) at 5min before ischaemia increased the renal venous plasma norepinephrine level after reperfusion and aggravated ischaemia/reperfusion-induced renal dysfunction and histological damage. The excessive superoxide production after reperfusion was significantly suppressed by isatin administration, indicating that the inhibition of oxidative deamination effectively suppressed superoxide production. These data suggest that the exacerbation effect of isatin is associated, at least in part, with increased norepinephrine levels but not with superoxide production. To the best of our knowledge, this is the first report of isatin involvement in the pathogenesis and/or development of acute kidney injury.

Role of TRPV1 channels in ischemia/reperfusion-induced acute kidney injury

OBJECTIVES

Transient receptor potential vanilloid 1 (TRPV1) -positive sensory nerves are widely distributed in the kidney, suggesting that TRPV1-mediated action may participate in the regulation of renal function under pathophysiological conditions. Stimulation of TRPV1 channels protects against ischemia/reperfusion (I/R)-induced acute kidney injury (AKI). However, it is unknown whether inhibition of these channels is detrimental in AKI or not. We tested the role of TRPV1 channels in I/R-induced AKI by modulating these channels with capsaicin (TRPV1 agonist), capsazepine (TRPV1 antagonist) and using Trpv1-/- mice.

METHODS AND RESULTS

Anesthetized C57BL/6 mice were subjected to 25 min of renal ischemia and 24 hrs of reperfusion. Mice were pretreated with capsaicin (0.3 mg/kg body weight) or capsazepine (50 mg/kg body weight). Capsaicin ameliorated the outcome of AKI, as measured by serum creatinine levels, tubular damage,neutrophil gelatinase-associated lipocalin (NGAL) abundance and Ly-6B.2 positive polymorphonuclear inflammatory cells in injured kidneys. Neither capsazepine nor deficiency of TRPV1 did deteriorate renal function or histology after AKI. Measurements of endovanilloids in kidney tissue indicate that 20-hydroxyeicosatetraeonic acid (20-HETE) or epoxyeicosatrienoic acids (EETs) are unlikely involved in the beneficial effects of capsaicin on I/R-induced AKI.

CONCLUSIONS

Activation of TRPV1 channels ameliorates I/R-induced AKI, but inhibition of these channels does not affect the outcome of AKI. Our results may have clinical implications for long-term safety of renal denervation to treat resistant hypertension in man, with respect to the function of primary sensory nerves in the response of the kidney to ischemic stimuli.

Renal denervation prevents long-term sequelae of ischemic renal injury

Signals that drive interstitial fibrogenesis after renal ischemia reperfusion injury remain undefined. Sympathetic activation is manifest even in the early clinical stages of chronic kidney disease and is directly related to disease severity. A role for renal nerves in renal interstitial fibrogenesis in the setting of ischemia reperfusion injury has not been studied. In male 129S1/SvImJ mice, ischemia reperfusion injury induced tubulointerstitial fibrosis as indicated by collagen deposition and profibrotic protein expression 4 to 16 days after the injury.. Leukocyte influx, proinflammatory protein expression, oxidative stress, apoptosis, and cell cycle arrest at G2/M phase were enhanced after ischemia reperfusion injury. Renal denervation at the time of injury or up to 1 day post-injury improved histology, decreased proinflammatory/profibrotic responses and apoptosis, and prevented G2/M cell cycle arrest in the kidney. Treatment with afferent nerve-derived calcitonin gene-related peptide (CGRP) or efferent nerve-derived norepinephrine in denervated and ischemia reperfusion injury-induced kidneys mimicked innervation, restored inflammation and fibrosis, induced G2/M arrest, and enhanced TGF-β1 activation. Blocking norepinephrine or CGRP function using respective receptor blockers prevented these effects. Consistent with the in vivo study, treatment with either norepinephrine or CGRP induced G2/M cell cycle arrest in HK-2 proximal tubule cells, whereas antagonists against their respective receptors prevented G2/M arrest. Thus, renal nerve stimulation is a primary mechanism and renal nerve-derived factors drive epithelial cell cycle arrest and the inflammatory cascade causing interstitial fibrogenesis after ischemia reperfusion injury.

Histomorphometric and sympathetic innervation of the human renal artery: A cadaveric study

Background and Aim:

Renal artery stenosis (RAS) and acute renal failure may be due to the intimal hyperplasia and sympathetic fibers of the renal artery (RA), respectively. The purpose of this study was to characterize arterial wall and sympathetic innervation of the human RA.

Materials and Methods:

Fifty-two fresh human RA samples (proximal part) were collected from 26 cadavers (19 males and 7 females), between the ages of 19 and 83 years, during autopsy. Samples were divided into three age groups: Group 1, 19-40 years; Group 2, 41-60 years; Group 3, over 61 years. 5-μm thick sections of each sample were taken and stained with hematoxylin-eosin and Verhoeff-Van Gieson. Five out of 52 samples were processed for tyrosine hydroxylase (TH) immunostaining.

Results:

Our histological studies revealed that tunica media of RA showed smooth muscle cells and fine irregularly arranged elastic fibers. Intimal hyperplasia was the most common finding. The present study showed that thickness of tunica intima and media were found to increase with age. Sympathetic nerves were present in the tunica adventitia and outer media of the RA. The mean adventitial and sympathetic nerve fiber areas were found to be 0.595 and 0.071 mm², respectively. Sympathetic index (SI) to RA was calculated by dividing the sympathetic fiber area by the adventitial area of the RA. SI of RA was found to be 0.140.

Conclusion:

We conclude that RA showed the structure of musculo-elastic artery. SI may be used for the analysis of sympathetic fiber related problems of the human RA or kidneys.

Moxonidine prevents ischemia/reperfusion-induced renal injury in rats

Enhancement of renal sympathetic nerve activity during renal ischemia and its consequent effect on norepinephrine overflow from nerve endings after reperfusion play important roles in the development of ischemic acute kidney injury. In the present study, we evaluated whether moxonidine, an alpha(2)-adrenaline/I(1)-imidazoline receptor agonist which is known to elicit sympathoinhibitory action, would prevent the post-ischemic renal injury. Ischemic acute kidney injury was induced by clamping the left renal artery and vein for 45 min followed by reperfusion, 2 weeks after contralateral nephrectomy. Intravenous (i.v.) injection of moxonidine at a dose of 360 nmol/kg to ischemic acute kidney injury rats suppressed the enhanced renal sympathetic nerve activity during the ischemic period, to a degree similar to findings with intracerebroventricular (i.c.v.) injection of moxonidine at a dose of 36 nmol/kg. On the other hand, suppressive effects of the i.v. treatment on renal venous norepinephrine overflow, renal dysfunction and tissue injury in the post-ischemic kidney were significantly greater than those elicited by the i.c.v. treatment. These results suggest that renoprotective effects of moxonidine on ischemic acute kidney injury probably result from its suppressive action on the ischemia-enhanced renal sympathetic nerve activity followed by norepinephrine spillover from the nerve endings of the post-ischemic kidney.

Selective antagonism of the postsynaptic alpha(1)-adrenoceptor is protective against ischemic acute renal failure in rats

We investigated the effects of prazosin, an alpha(1)-adrenoceptor antagonist, on the pathogenesis of ischemic acute renal failure in rats. Ischemic acute renal failure was induced by occlusion of the left renal artery and vein for 45 min followed by reperfusion, 2 weeks after contralateral nephrectomy. An in vivo microdialysis study revealed that renal interstitial norepinephrine levels were increased with the ischemia/reperfusion (n=3). Renal function in vehicle-treated acute renal failure rats markedly decreased 1 day after reperfusion (n=6), compared with those in sham-operated control animals (n=6). Pre-ischemic treatment with prazosin (100 microg/kg, i.v.) markedly and significantly attenuated the ischemia/reperfusion-induced renal dysfunction (n=6). Histopathological examination of the kidney of vehicle-treated acute renal failure rats revealed severe renal damage, which was also significantly suppressed by pre-ischemic treatment with 100 microg/kg prazosin. The same dose of prazosin given after reperfusion failed to improve the ischemia/reperfusion-induced renal dysfunction (n=6), in contrast to cases of the pre-ischemic treatment with this agent. The administration of prazosin before ischemia did not influence the elevation of renal venous plasma norepinephrine levels (n=6), which were observed both immediately and 1 day after reperfusion. From these findings, we suggest that norepinephrine released excessively from the post-ischemic kidney is involved in the pathogenesis of ischemic acute renal failure, probably acting at the postsynaptic alpha(1)-adrenoceptors.

Renoprotective Effects of l-Carnosine on Ischemia/Reperfusion-Induced Renal Injury in Rats

We examined the renoprotective effects of l-carnosine (beta-alanyl-l-histidine) on ischemia/reperfusion (I/R)-induced acute renal failure (ARF) in rats. Ischemic ARF was induced by occlusion of the left renal artery and vein for 45 min followed by reperfusion, 2 weeks after contralateral nephrectomy. In vehicle (0.9% saline)-treated rats, renal sympathetic nerve activity (RSNA) was significantly augmented during the renal ischemia, and renal function was markedly decreased at 24 h after reperfusion. Intracerebroventricular injection of l-carnosine (1.5 and 5 pmol/rat) to ischemic ARF rats dose-dependently suppressed the augmented RSNA during ischemia and the renal injury at 24 h after reperfusion. N-alpha-Acetyl-l-carnosine [N-acetyl-beta-alanyl-l-histidine; 5 pmol/rat intracerebroventricular (i.c.v.)], which is resistant to enzymatic hydrolysis by carnosinase, did not affect the renal injury, and l-histidine (5 pmol/rat i.c.v.), a metabolite cleaved from l-carnosine by carnosinase, ameliorated the I/R-induced renal injury. Furthermore, a selective histamine H(3) receptor antagonist, thioperamide (30 nmol/rat i.c.v.) eliminated the preventing effects by l-carnosine (15 nmol/rat intravenously) on ischemic ARF. In contrast, a selective H(3) receptor agonist, R-alpha-methylhistamine (5 pmol/rat i.c.v.), prevented the I/R-induced renal injury as well as l-carnosine (5 pmol/rat) did. These results indicate that l-carnosine prevents the development of I/R-induced renal injury, and the effect is accompanied by suppressing the enhanced RSNA during ischemia. In addition, the present findings suggest that the renoprotective effect of l-carnosine on ischemic ARF is induced by its conversion to l-histidine and l-histamine and is mediated through the activation of histamine H(3) receptors in the central nervous system.

Retraction：Dietary Supplementation of L-Carnosine Prevents Ischemia/Reperfusion-Induced Renal Injury in Rats

The effects of dietary supplementation of L-carnosine (beta-alanyl-L-histidine) on ischemia/reperfusion-induced acute renal failure (ARF) in rats were examined. Ischemic ARF was induced by occlusion of the left renal artery and vein for 45 min followed by reperfusion, 2 weeks after contralateral nephrectomy. Renal functional parameters such as blood urea nitrogen, plasma creatinine, creatinine clearance, urine flow, urinary osmolality and fractional excretion of sodium were measured. Renal function in ARF rats markedly decreased at 1 d after reperfusion. Prior feeding of L-carnosine-containing diet (0.0001 w/w%) for 2 weeks attenuated the ischemia/reperfusion-induced renal dysfunction. Histopathological examination of the kidney of ARF rats revealed severe renal damages, such as tubular necrosis, proteinaceous casts in tubuli and medullary congestion, which were also significantly suppressed by the dietary supplementation of L-carnosine. These findings strongly suggest that L-carnosine supplementation is useful as a prophylactic treatment in the development of the ischemic ARF.

Tempol Protects against Ischemic Acute Renal Failure by Inhibiting Renal Noradrenaline Overflow and Endothelin-1 Overproduction

The effects of tempol, a superoxide dismutase mimetic, on ischemia/reperfusion-induced acute renal failure (ARF), noradrenaline (NA) overflow and endothelin-1 (ET-1) overproduction in rats were examined. Ischemic ARF was induced by occlusion of the left renal artery and vein for 45 min followed by reperfusion, 2 weeks after contralateral nephrectomy. Renal functional parameters such as blood urea nitrogen, plasma creatinine concentration, and fractional excretion of sodium, NA concentrations in renal venous plasma, and renal ET-1 contents were determined. Renal function in ARF rats markedly decreased at 1 d after reperfusion. Pre-ischemic treatment with tempol (10, 100 mg/kg, i.v.) dose-dependently attenuated the ischemia/reperfusion-induced renal dysfunction. Histopathological examination of the kidney of ARF rats revealed severe renal damages, such as tubular necrosis, proteinaceous casts in tubuli and medullary congestion, which were also significantly suppressed by the tempol treatment. There was a significant increase in NA concentrations in renal venous plasma after the ischemia/reperfusion, and this increase was markedly suppressed by the treatment with tempol. In addition, tempol treatment significantly attenuated the increment of ET-1 content in the kidney exposed to the ischemia/reperfusion. These findings suggest that tempol improves the post-ischemic renal injury by inhibiting the neural activity of renal sympathetic nerve and ET-1 overproduction.

The role of renal sympathetic nervous system in the pathogenesis of ischemic acute renal failure

We investigated the role of renal sympathetic nervous system in the progression of ischemia/reperfusion-induced acute renal failure in rats. Acute renal failure was induced by clamping the left renal artery and vein for 45 min followed by reperfusion, 2 weeks after the contralateral nephrectomy. Renal venous plasma norepinephrine concentrations markedly and significantly increased immediately after reperfusion, thereafter, the increased level declined but remained higher even at 24 h after reperfusion. Renal sympathetic nerve activity was significantly augmented during the renal ischemia. Renal denervation or the administration of pentolinium, a ganglion blocking agent, (5 mg/kg i.v.) at 5 min before ischemia attenuated the ischemia/reperfusion-induced renal dysfunction and histological damage, such as proteinaceous casts in tubuli and tubular necrosis. The elevation of renal venous norepinephrine levels after reperfusion was suppressed by renal denervation or pentolinium treatment. Thus, a surgical or pharmacological blockade of renal sympathetic nerve prevents the progression of ischemia/reperfusion-induced acute renal failure, thereby suggesting that renal sympathetic nervous system plays an important role in the development of the ischemic acute renal failure.

Preventive effect of L-carnosine on ischemia/reperfusion-induced acute renal failure in rats

We investigated the effect of L-carnosine (beta-alanyl-L-histidine) on ischemic acute renal failure in rats. Ischemic acute renal failure was induced by occlusion of the left renal artery and vein for 45 min followed by reperfusion, 2 weeks after contralateral nephrectomy. Renal function in untreated acute renal failure rats markedly decreased at 1 day after reperfusion. Pre-ischemic treatment with L-carnosine dose-dependently (1, 10 microg/kg, i.v.) attenuated the ischemia/reperfusion-induced renal dysfunction. Histopathological examination of the kidney of untreated acute renal failure rats revealed severe renal damage, which was significantly suppressed by pre-treatment with L-carnosine, at each dose given. In untreated acute renal failure rats, norepinephrine concentrations in renal venous plasma remarkably increased within 2 min after reperfusion and thereafter rapidly decreased. Pre-ischemic treatment with L-carnosine at a dose of 10 microg/kg significantly depressed the elevated norepinephrine level. On the other hand, although the higher dose of L-carnosine given 5 min after reperfusion tended to ameliorate the renal dysfunction after reperfusion, the improvement was moderate compared with those seen in pre-ischemic treatment. These results indicate that L-carnosine prevents the development of ischemia/reperfusion-induced renal injury, and the effect is accompanied by suppression of the enhanced norepinephrine release in the kidney immediately after reperfusion. Thus, the preventing effect of L-carnosine on ischemic acute renal failure is probably through the suppression of enhanced renal sympathetic nerve activity induced by ischemia/reperfusion.