Renal denervation prevents long-term sequelae of ischemic renal injury

Renal nerve afferents drive preferential renal sympathoexcitation in response to acute renal ischemia/reperfusion in rats

Renal nerve activity is composed of afferent (sensory) and efferent (sympathetic) nerve activity. Ischemia/reperfusion (IR) of the kidney increases renal sympathetic nerve activity (rSNA) and depresses renal function. As the role of renal afferent fibers in acute renal IR is unclear, we tested the hypothesis that renal IR increases rSNA triggered by renal afferent nerves responding to acute ischemia. Two experimental series were performed in adult male Wistar rats. IR was induced by total obstruction of blood flow to the left kidney by clamping the renal artery for 60 min and reperfusion for 120 min. We recorded MAP, HR, rSNA, and splanchnic sympathetic vasomotor activity (sSNA) in 8 normal IR rats and 6 left kidney deafferented IR rats (IR ARD). Renal deafferentation was performed using capsaicin administration to the left renal nerve 2 weeks before the experiments. Blood samples were collected before ischemia and at the end of reperfusion for total and differential leukocyte counts. Renal ischemia significantly increased rSNA 23 % (20 min: 0,07 ± 0,04mVs P < 0.05) but not sSNA. The increase in rSNA was triggered by activation of renal afferent fibers, since IR significantly reduced rSNA in the IR ARD group maximal decrease in frequency 22 % (180 min: -62 ± 29Δspikes/s) and in amplitude 41 % (-0,29 ± 0, 12mVs, P < 0.05) and induced hypotension and bradycardia. However, no significant difference was observed between groups in blood leukocyte profile, but a significant reduction in renal IL-6 was found in IR ARD, suggesting a reduction in renal inflammation in deafferented IR rats. The results show that renal afferent nerves trigger a preferential increase in rSNA and inflammation in the kidney during acute IR.

The organum vasculosum of the lamina terminalis contributes to neurohumoral mechanisms of renal vascular hypertension

The organum vasculosum of the lamina terminalis (OVLT) is a forebrain circumventricular organ that modulates central autonomic control of arterial pressure and body fluid homeostasis. It has been implicated in the pathogenesis of rat models of hypertension that are driven by increased salt intake since OVLT lesion (OVLTx) attenuates both the DOCA-salt and angiotensin II-salt models. However, its contribution to the development of hypertension that is not salt-dependent, such as the 2 kidney, 1 clip (2K1C) renovascular model, is not clear. We recently reported that afferent renal denervation (ARDN) attenuates the pathogenesis of 2K1C hypertension in the rat and this was associated with a reduction of neurogenic pressor activity, water intake, vasopressin release, and renal inflammation, suggesting that afferent renal nerves, similar to OVLT, modulates central autonomic pathways that control arterial pressure and body fluid homeostasis. This idea led to the present study, which was designed to measure the effect of OVLTx on arterial pressure and body fluid homeostasis in 2K1C-HTN rats. Male Sprague-Dawley rats were randomly selected to receive OVLTx or sham operation and were instrumented 1 wk later with telemeters to continuously measure mean arterial pressure (MAP). The following week, rats received a silver clip around the left renal artery to generate 2K1C hypertension or sham-clip surgery. MAP was continuously measured for 6 wk, and once a week, rats were housed in metabolic cages for 24 h to evaluate water intake and urinary volume. Urine was analyzed for inflammatory cytokines and copeptin, a surrogate marker of vasopressin. Neurogenic pressor activity (NPA) was assessed on the last day of the protocol by measuring the peak MAP response to ganglionic blockade. Upon completion of the study, rats were euthanized and kidneys were removed for the measurement of inflammatory cytokine content. Hypertension in 2K1C rats was associated with increased NPA, water intake, vasopressin release, and renal inflammation. All of these responses were markedly attenuated or abolished in OVLTx 2K1C rats. These findings suggest that the OVLT, similar to afferent renal nerves, plays a key role in the development of hypertension, polydipsia, vasopressin release, and renal inflammation in 2K1C-HTN rats.NEW & NOTEWORTHY Renovascular hypertension (RVHT), accounting for 1%-5% of high blood pressure cases, is the most common secondary hypertension resistant to treatment. In two-kidney one-clip (2K1C) hypertensive rats, renal artery stenosis triggers sympathetic nervous system activation, increased vasopressin, water intake, and inflammation. OVLT lesions prevented these responses, similar to afferent renal denervation. This study suggests that OVLT plays a key role in 2K1C hypertension pathogenesis and interacts with afferent renal nerves. Future studies will explore the underlying mechanisms.

Sympathetic nerve promotes renal fibrosis by activating M2 macrophages through β2-AR-Gsa

Sympathetic nervous system overactivation is directly related to renal fibrosis. This study focused on the role of and mechanism by which sympathetic signaling regulates macrophage activation, as well as the contribution to renal fibrosis. Renal denervation alleviated tubular necrosis, tubulointerstitial fibrosis, and macrophage accumulation induced by unilateral ureteral obstruction and ischemia-reperfusion injury. In vitro, norepinephrine (NE) promoted macrophage alternative (M2) polarization by activating β2-adrenergic receptor (β2-AR) and heterotrimeric G stimulatory protein α-subunit (Gsa). The effects of NE-induced macrophage M2 polarization were blocked by a β2-AR selective antagonist and Gsa siRNA. Importantly, ablation of Gsa in macrophages alleviated tubulointerstitial fibrosis, macrophage accumulation, and M2 polarization in the renal ischemia-reperfusion injury model. Sympathetic nervous system overactivation regulates M2 polarization in macrophages as an important neuroimmune mechanism of renal fibrosis. The β2-AR-Gsa signaling pathway was responsible for NE-induced macrophage M2 polarization, which may be a therapeutic target for renal fibrosis.

Dual therapy with phospholipase and metalloproteinase inhibitors from Sinonatrix annularis alleviated acute kidney and liver injury caused by multiple snake venoms

Snakebite envenomation often induces acute kidney injury (AKI) and acute liver injury (ALI), leading to augmented injuries and poor rehabilitation. Phospholipase A2 (PLA2) and metalloproteinase (SVMP) present in venom are responsible for the envenomation-associated events. In this study, mice envenomed with Deinagkistrodon acutus, Naja atra, or Agkistrodon halys pallas venom exhibited typical AKI and ALI symptoms, including significantly increased plasma levels of myoglobin, free hemoglobin, uric acid, aspartate aminotransferase, and alanine aminotransferase and upregulated expression of kidney NGAL and KIM-1. These effects were significantly inhibited when the mice were pretreated with natural inhibitors of PLA2 and SVMP isolated from Sinonatrix annularis (SaPLIγ and SaMPI). The inhibitors protected the physiological structural integrity of the renal tubules and glomeruli, alleviating inflammatory infiltration and diffuse hemorrhage in the liver. Furthermore, the dual therapy alleviated oxidative stress and apoptosis in the kidneys and liver by mitigating mitochondrial damage, thereby effectively reducing the lethal effect of snake venom in the inhibitor-treated mouse model. This study showed that dual therapy with inhibitors of metalloproteinase and phospholipase can effectively prevent ALI and AKI caused by snake bites. Our findings suggest that intrinsic inhibitors present in snakes are prospective therapeutic agents for multi-organ injuries caused by snake envenoming.

Esaxerenone: blood pressure reduction and cardiorenal protection without reflex sympathetic activation in salt-loaded stroke-prone spontaneously hypertensive rats

Mineralocorticoid receptor (MR) is involved in the mechanisms of blood pressure elevation, organ fibrosis, and inflammation. MR antagonists have been used in patients with hypertension, heart failure, or chronic kidney disease. Esaxerenone, a recently approved MR blocker with a nonsteroidal structure, has demonstrated a strong blood pressure-lowering effect. However, blood pressure reduction may lead to sympathetic activation through the baroreflex. The effect of esaxerenone on the sympathetic nervous system remains unclear. We investigated the effect of esaxerenone on organ damage and the sympathetic nervous system in salt-loaded stroke-prone spontaneously hypertensive rats (SHRSP), a well-established model of essential hypertension with sympathoexcitation and organ damage. Three-week administration of esaxerenone or hydralazine successfully attenuated the blood pressure elevation. Both esaxerenone and hydralazine comparably suppressed left ventricular hypertrophy and urinary albumin excretion. However, renal fibrosis and glomerular sclerosis were suppressed by esaxerenone but not hydralazine. Furthermore, plasma norepinephrine level, a parameter of systemic sympathetic activity, was significantly increased by hydralazine but not by esaxerenone. Consistent with these findings, the activity of the control centers of sympathetic nervous system, the parvocellular region of the paraventricular nucleus in the hypothalamus and the rostral ventrolateral medulla, was enhanced by hydralazine but remained unaffected by esaxerenone. These results suggest that esaxerenone effectively lowers blood pressure without inducing reflex sympathetic nervous system activation. Moreover, the organ-protective effects of esaxerenone appear to be partially independent of its blood pressure-lowering effect. In conclusion, esaxerenone demonstrates a blood pressure-lowering effect without concurrent sympathetic activation and exerts organ-protective effects in salt-loaded SHRSP. Esaxerenone has antihypertensive and cardiorenal protective effects without reflex sympathetic activation in salt-loaded stroke-prone spontaneously hypertensive rats.

The protective role of vagus nerve stimulation in ischemia-reperfusion injury

Ischemia-reperfusion injury (IRI) encompasses the damage resulting from the restoration of blood supply following tissue ischemia. This phenomenon commonly occurs in clinical scenarios such as hemorrhagic shock, severe trauma, organ transplantation, and thrombolytic therapy. Despite its prevalence, existing treatments exhibit limited efficacy against IRI. Vagus nerve stimulation (VNS) is a widely utilized technique for modulating the autonomic nervous system. Numerous studies have demonstrated that VNS significantly reduces IRI in various organs, including the heart, brain, and liver. This article reviews the pathological processes during IRI and summarizes the role and possible mechanisms of VNS in IRI of different organs. Furthermore, this review addresses the current challenges of VNS clinical applications, providing a novel perspective on IRI treatment.

Loss of SAV1 in Kidney Proximal Tubule Induces Maladaptive Repair after Ischemia and Reperfusion Injury

Kidney ischemia and reperfusion injury (IRI) is a significant contributor to acute kidney injury (AKI), characterized by tubular injury and kidney dysfunction. Salvador family WW domain containing protein 1 (SAV1) is a key component of the Hippo pathway and plays a crucial role in the regulation of organ size and tissue regeneration. However, whether SAV1 plays a role in kidney IRI is not investigated. In this study, we investigated the role of SAV1 in kidney injury and regeneration following IRI. A proximal tubule-specific knockout of SAV1 in kidneys (SAV1ptKO) was generated, and wild-type and SAV1ptKO mice underwent kidney IRI or sham operation. Plasma creatinine and blood urea nitrogen were measured to assess kidney function. Histological studies, including periodic acid-Schiff staining and immunohistochemistry, were conducted to assess tubular injury, SAV1 expression, and cell proliferation. Western blot analysis was employed to assess the Hippo pathway-related and proliferation-related proteins. SAV1 exhibited faint expression in the proximal tubules and was predominantly expressed in the connecting tubule to the collecting duct. At 48 h after IRI, SAV1ptKO mice continued to exhibit severe kidney dysfunction, compared to attenuated kidney dysfunction in wild-type mice. Consistent with the functional data, severe tubular damage induced by kidney IRI in the cortex was significantly decreased in wild-type mice at 48 h after IRI but not in SAV1ptKO mice. Furthermore, 48 h after IRI, the number of Ki67-positive cells in the cortex was significantly higher in wild-type mice than SAV1ptKO mice. After IRI, activation and expression of Hippo pathway-related proteins were enhanced, with no significant differences observed between wild-type and SAV1ptKO mice. Notably, at 48 h after IRI, protein kinase B activation (AKT) was significantly enhanced in SAV1ptKO mice compared to wild-type mice. This study demonstrates that SAV1 deficiency in the kidney proximal tubule worsens the injury and delays kidney regeneration after IRI, potentially through the overactivation of AKT.

LncTCONS_00058568 is involved in the pathophysiologic processes mediated by P2X7R in the lower thoracic spinal cord after acute kidney injury

Acute kidney injury (AKI), a prevalent clinical syndrome, involves the participation of the nervous system in neuroimmune regulation. However, the intricate molecular mechanism that governs renal function regulation by the central nervous system (CNS) is complex and remains incompletely understood. In the present study, we found that the upregulated expression of lncTCONS_00058568 in lower thoracic spinal cord significantly ameliorated AKI-induced renal tissue injury, kidney morphology, inflammation and apoptosis, and suppressed renal sympathetic nerve activity. Mechanistically, the purinergic ionotropic P2X7 receptor (P2X7R) was overexpressed in AKI rats, whereas lncTCONS_00058568 was able to suppress the upregulation of P2X7R. In addition, RNA sequencing data revealed differentially expressed genes associated with nervous system inflammatory responses after lncTCONS_00058568 was overexpressed in AKI rats. Finally, the overexpression of lncTCONS_00058568 inhibited the activation of PI3K/Akt and NF-κB signaling pathways in spinal cord. Taken together, the results from the present study show that lncTCONS_00058568 overexpression prevented renal injury probably by inhibiting sympathetic nerve activity mediated by P2X7R in the lower spinal cord subsequent to I/R-AKI.

Neuroimmune interplay in kidney health and disease: Role of renal nerves

Renal nerves and their role in physiology and disease have been a topic of increasing interest in the past few decades. Renal inflammation contributes to many cardiorenal disease conditions, including hypertension, chronic kidney disease, and polycystic kidney disease. Much is known about the role of renal sympathetic nerves in physiology - they contribute to the regulation of sodium reabsorption, renin release, and renal vascular resistance. In contrast, far less is known about afferent, or "sensory," renal nerves, which convey signals from the kidney to the brain. While much remains unknown about these nerves in the context of normal physiology, even less is known about their contribution to disease states. Furthermore, it has become apparent that the crosstalk between renal nerves and the immune system may augment or modulate disease. Research from other fields, especially pain research, has provided critical insight into neuroimmune crosstalk. Sympathetic renal nerve activity may increase immune cell recruitment, but far less work has been done investigating the interplay between afferent renal nerves and the immune system. Evidence from other fields suggests that inflammation may augment afferent renal nerve activity. Furthermore, these nerves may exacerbate renal inflammation through the release of afferent-specific neurotransmitters.

Sympathetic Nerve Activation in Acute Kidney Injury and Cardiorenal Syndrome

The interactions between the kidney and heart are well studied and frequently lumped together as cardiorenal syndrome. It is believed that the sympathetic nervous system is involved in the mechanism of kidney injury caused by heart failure, but direct evidence is still lacking. In chronic renal fibrosis, sympathetic nerve activation was demonstrated to be harmful by unilateral ureteral obstruction and post-ischemia reperfusion injury models. On the other hand, sympathetic nerve activation seemed protective in acute kidney injury models such as ischemia reperfusion injury and lipopolysaccharide injection. Our recent investigation showed that post-ischemic renal fibrosis was attenuated when preexisting heart failure was induced by transverse aortic constriction surgery and renal denervation canceled this protection. These findings suggest sympathetic nerve activation in cardiorenal syndrome may be protective on chronic renal fibrosis development caused by ischemic an insult.

Denervation aggravates renal ischemia reperfusion injury via BMAL1-mediated Nrf2/ARE pathway

AIM

To explore the change of clock gene rhythm under renal denervation (RDN) and its effect on renal function and oxidative stress during renal ischemia-reperfusion (IR) injury.

METHOD

C57/BL6 mice were randomly divided into 4 groups at daytime 7 A M (zeitgeber time [ZT] 0) or at nighttime 7 P M (ZT12) in respectively: Sham (S) group, RDN group, IR group and RDN + IR (DIR) group. Renal pathological and functional changes were assessed by H&E staining, and serum creatinine, urea nitrogen and neutrophil gelatinase-associated lipocalin levels. Renal oxidative stress was detected by SOD and MDA levels, and renal inflammation was measured by IL-6, IL-17 A F and TNF-ɑ levels. BMAL1, CLOCK, Nrf2 and HO-1 mRNA and protein expressions were tested by qPCR and Western Blot.

RESULT

Compared with S groups, the rhythm of BMAL1, CLOCK and Nrf2 genes in the kidney were disordered in RDN groups, while renal pathological and functional indexes did not change significantly. Compared with IR groups, renal pathological and functional indexes were significantly higher in the DIR groups, as well as oxidative stress and inflammation in renal tissues. The nocturnal IR injury in the RDN kidney was the worst while the BMAL1, Nrf2 and HO-1 expressions were the highest. In DIR groups, renal injury was aggravated after the Brusatol treatment, but there was no significant improvement after the t-BHQ treatment at night, which might be consistent with the changes of Nrf2 and HO-1 protein expressions.

CONCLUSION

RDN lead to the disruption of BMAL1-mediated Nrf2 rhythm accumulation in the kidney, which reduced the renal ability to resist oxidative stress and inflammation, due to the impaired effect of activating Nrf2/ARE pathway in renal IR injury at nighttime.

The Presence of Testis Determines Aristolochic Acid-Induced Nephrotoxicity in Mice

Aristolochic acid (AA) is notorious for inducing nephrotoxicity, but the influence of sex on AA-induced kidney injury was not clear. This study sought to investigate sex differences in kidney dysfunction and tubular injury induced by AA. Male and female mice were bilaterally orchiectomized and ovariectomized, respectively. Fourteen days after gonadectomy, the mice were intraperitoneally injected with AA (10 mg/kg body weight/day) daily for 2 days and sacrificed 7 days after the first injection. Body weight, kidney function, and tubular structure were assessed. When compared between male and female non-gonadectomized mice, AA-induced body weight loss was greater in male mice than in female mice. Functional and structural damages in male kidneys were markedly induced by AA injection, but kidneys in AA-injected female mice showed no or mild damages. Ovariectomy had no effect on AA-induced nephrotoxic acute kidney injury in female mice. However, orchiectomy significantly reduced body weight loss, kidney dysfunction, and tubular injury in AA-induced nephrotoxicity in male mice. This study has demonstrated that testis causes AA-induced nephrotoxic acute kidney injury.

Repeated Administration of Cisplatin Transforms Kidney Fibroblasts through G2/M Arrest and Cellular Senescence

Cisplatin is a potent chemotherapeutic used for the treatment of many types of cancer, but it has nephrotoxic side effects leading to acute kidney injury and subsequently chronic kidney disease (CKD). Previous work has focused on acute kidney tubular injury induced by cisplatin, whereas the chronic sequelae post-injury has not been well-explored. In the present study, we established a kidney fibroblast model of CKD induced by repeated administration of cisplatin (RAC) as a clinically relevant model. In NRK-49F rat kidney fibroblasts, RAC upregulated α-smooth muscle actin (α-SMA) and fibronectin proteins, suggesting that RAC induces kidney fibroblast-to-myofibroblast transformation. RAC also enhanced cell size, including the cell attachment surface area, nuclear area, and cell volume. Furthermore, RAC induced p21 expression and senescence-associated β-galactosidase activity, suggesting that kidney fibroblasts exposed to RAC develop a senescent phenotype. Inhibition of p21 reduced cellular senescence, hypertrophy, and myofibroblast transformation induced by RAC. Intriguingly, after RAC, kidney fibroblasts were arrested at the G2/M phase. Repeated treatment with paclitaxel as an inducer of G2/M arrest upregulated p21, α-SMA, and fibronectin in the kidney fibroblasts. Taken together, these data suggest that RAC transforms kidney fibroblasts into myofibroblasts through G2/M arrest and cellular senescence.

Hepatic and proximal tubule angiotensinogen play distinct roles in kidney dysfunction, glomerular and tubular injury, and fibrosis progression

Components of the renin-angiotensin system, including angiotensinogen (AGT), are critical contributors to chronic kidney disease (CKD) development and progression. However, the specific role of tissue-derived AGTs in CKD has not been fully understood. To define the contribution of liver versus kidney AGT in the CKD development, we performed 5/6 nephrectomy (Nx), an established CKD model, in wild-type (WT), proximal tubule (PT)- or liver-specific AGT knockout (KO) mice. Nx significantly elevated intrarenal AGT expression and elevated blood pressure (BP) in WT mice. The increase of intrarenal AGT protein was completely blocked in liver-specific AGT KO mice with BP reduction, suggesting a crucial role for liver AGT in BP regulation during CKD. Nx-induced glomerular and kidney injury and dysfunction, as well as fibrosis, were all attenuated to a greater extent in liver-specific AGT KO mice compared with PT-specific AGT KO and WT mice. However, the suppression of interstitial fibrosis in PT- and liver-specific AGT KO mouse kidneys was comparable. Our findings demonstrate that liver AGT acts as a critical contributor in driving glomerular and tubular injury, renal dysfunction, and fibrosis progression, whereas the role of PT AGT was limited to interstitial fibrosis progression in chronic renal insufficiency. Our results provide new insights for the development of tissue-targeted renin-angiotensin system intervention in the treatment of CKD.NEW & NOTEWORTHY Chronic kidney disease (CKD) is a major unmet medical need with no effective treatment. Current findings demonstrate that hepatic and proximal tubule angiotensinogen have distinct roles in tubular and glomerular injury, fibrogenesis, and renal dysfunction during CKD development. As renin-angiotensin system components, including angiotensinogen, are important targets for treating CKD in the clinic, the results from our study may be applied to developing better tissue-targeted treatment strategies for CKD and other fibroproliferative diseases.

Insight on Efficacy of Renal Artery Denervation for Refractory Hypertension with Chronic Kidney Diseases: A Long-Term Follow-Up of 24-Hour Ambulatory Blood Pressure

Aims

To explore the long-term efficacy and safety of renal denervation in patients with RHT and CKD, a post hoc analysis of eGFR subgroups was completed.

Methods

Fifty-four patients with refractory hypertension with chronic kidney disease were treated with RDN and enrolled in the study. Patients were divided into three groups according to eGFR: eGFR 46–90 ml/min group, eGFR 15–45 ml/min group, and eGFR <15 ml/min group. The planned follow-up period was 48 months to assess 24 h ambulatory blood pressure, renal function, type of antihypertensive medication, and RDN complications.

Results

The ablation sites of the GFR 46–90 ml/min group and GFR 15–45 ml/min group were 32.57 ± 2.99 and 29.53 ± 5.47, respectively. No complications occurred in the GFR 46–90 ml/min group. The GFR<15 ml/min group was treated with 27.07 ± 5.59  ablation. Renal artery dissection occurred in each group of GFR 15–45 ml/min and GFR <15 ml/min. And renal stent implantation artery was performed on these two patients. No severe renal artery stenosis occurred. There were no significant differences in Scr and eGFR between the three groups at each follow-up point. Compared with baseline, SBP was significantly of each group decreased to varying degrees at each follow-up time point. SBP decreased most in the GFR 46–90 ml/min group. Compared with baseline, the type of antihypertensive drugs used in the GFR46-90 ml/min group decreased significantly except for 36 and 48 months. At 48 months' postadmission, there was a significant decrease in the type of antihypertensive medication used in the GFR15-45 ml/min group, and there was no significant decrease in the type of antihypertensive medication used in the GFR<15 ml/min group.

Conclusions

RDN can safely reduce SBP in CKD patients combined with RHT for 48 months, with the most pronounced reduction in the GFR15-45 ml/min group. The variety of antihypertensive drugs was significantly reduced after RDN. This was particularly evident in patients with GFR 15–45 ml/min.

Anesthesia and the renal sympathetic nervous system in perioperative AKI

Approximately 7% of patients undergoing non-cardiac surgery with general anesthesia develop postoperative acute kidney injury (AKI). It is well-known that general anesthesia may have an impact on renal function and water balance regulation, but the mechanisms and potential differences between anesthetics are not yet completely clear. Recently published large animal studies have demonstrated that volatile (gas) anesthesia stimulates the renal sympathetic nervous system more than intravenous propofol anesthesia, resulting in decreased water and sodium excretion and reduced renal perfusion and oxygenation. Whether this is the case also in humans remains to be clarified. Increased renal sympathetic nerve activity may impair renal excretory function and oxygenation and induce structural injury in ischemic AKI models and could therefore be a contributing factor to AKI in the perioperative setting. This review summarizes anesthetic agents' effects on the renal sympathetic nervous system that may be important in the pathogenesis of perioperative AKI.

Contribution of Afferent Renal Nerves to Cystogenesis and Arterial Pressure Regulation in a Preclinical Model of Autosomal Recessive Polycystic Kidney Disease

Polycystic kidney disease (PKD) is the most common inheritable cause of kidney failure, and the underlying mechanisms remain incompletely uncovered. Renal nerves contribute to hypertension and chronic kidney disease - frequent complications of PKD. There is limited evidence that renal nerves may contribute to cardiorenal dysfunction in PKD, and no investigations of the role of sympathetic versus afferent nerves in PKD. Afferent renal nerve activity (ARNA) is elevated in models of renal disease and fibrosis. However, it remains unknown if this is true in PKD. We tested the hypothesis that ARNA is elevated in a preclinical model of autosomal recessive PKD (ARPKD), and that targeted renal nerve ablation would attenuate cystogenesis and cardiorenal dysfunction. We tested this by performing a total (T-RDNx) or afferent (A-RDNx) denervation in 4-week-old male and female PCK rats, then quantifying renal and cardiovascular responses 6 weeks following treatment. Cystogenesis was attenuated with A-RDNx and T-RDNx vs. sham controls, highlighting a crucial role for renal afferent nerves in cystogenesis. In contrast, blood pressure was improved with T-RDNx but not A-RDNx. Importantly, treatments produced similar results in both males and females. Direct renal afferent nerve recordings revealed that ARNA was 2-fold greater in PCK rats vs. non-cystic controls and was directly correlated to cystic severity. To our knowledge, we are the first to demonstrate that PCK rats have greater ARNA than non-cystic, age-matched controls. The findings of these studies support a novel and crucial role for renal afferent innervation in cystogenesis in the PCK rat.

The Role of the Superior Cervical Sympathetic Ganglion in Ischemia Reperfusion-Induced Acute Kidney Injury in Rats

Acute kidney injury (AKI) has been found to be a serious clinical problem with high morbidity and mortality, and is associated with acute inflammatory response and sympathetic activation that subsequently play an important role in the development of AKI. It is well known that the sympathetic nervous system (SNS) and immune system intensely interact and mutually control each other in order to maintain homeostasis in response to stress or injury. Evidence has shown that the superior cervical sympathetic ganglion (SCG) participates in the bidirectional network between the immune and the SNS, and that the superior cervical ganglionectomy has protective effect on myocardial infarction, however, the role of the SCG in the setting of renal ischemic reperfusion injury has not been studied. Here, we sought to determine whether or not the SCG modulates renal ischemic reperfusion (IR) injury in rats. Our results showed that bilateral superior cervical ganglionectomy (SCGx) 14 days before IR injury markedly reduced the norepinephrine (NE) in plasma, and down-regulated the increased expression of tyrosine hydroxylase (TH) in the kidney and hypothalamus. Sympathetic denervation by SCGx in the AKI group increased the level of blood urea nitrogen (BUN) and kidney injury molecule-1 (KIM-1), and exacerbated renal pathological damage. Sympathetic denervation by SCGx in the AKI group enhanced the expression of pro-inflammatory cytokines in plasma, kidney and hypothalamus, and increased levels of Bax in denervated rats with IR injury. In addition, the levels of purinergic receptors, P2X3R and P2X7R, in the spinal cord were up-regulated in the denervated rats of the IR group. In conclusion, these results demonstrate that the sympathetic denervation by SCGx aggravated IR-induced AKI in rats via enhancing the inflammatory response, thus, the activated purinergic signaling in the spinal cord might be the potential mechanism in the aggravated renal injury.

The Interaction of Central Nervous System and Acute Kidney Injury: Pathophysiology and Clinical Perspectives

Acute kidney injury (AKI) is a common disorder in critically ill hospitalized patients. Its main pathological feature is the activation of the sympathetic nervous system and the renin-angiotensin system (RAS). This disease shows a high fatality rate. The reason is that only renal replacement therapy and supportive care can reduce the impact of the disease, but those measures cannot significantly improve the mortality. This review focused on a generalization of the interaction between acute kidney injury and the central nervous system (CNS). It was found that the CNS further contributes to kidney injury by regulating sympathetic outflow and oxidative stress in response to activation of the RAS and increased pro-inflammatory factors. Experimental studies suggested that inhibiting sympathetic activity and RAS activation in the CNS and blocking oxidative stress could effectively reduce the damage caused by AKI. Therefore, it is of significant interest to specify the mechanism on how the CNS affects AKI, as we could use such mechanism as a target for clinical interventions to further reduce the mortality and improve the complications of AKI.

Systematic Review Registration: [www.ClinicalTrials.gov], identifier [registration number].

Sympathetic Denervation Ameliorates Renal Fibrosis via Inhibition of Cellular Senescence

Objective

Continuous overactivation of the renal sympathetic nerve is considered to be an important cause of renal fibrosis. Accumulated senescent cells in the damaged kidney have metabolic activities and secrete amounts of proinflammatory factors as part of the SASP (the senescence-associated secretory phenotype), which induce chronic inflammation and fibrosis. It is still unclear whether renal sympathetic nerves affect renal inflammation and fibrosis by regulating cellular senescence. Therefore, we hypothesize that sympathetic activation in the injured kidney induces cellular senescence, which contributes to progressive renal inflammation and fibrosis.

Methods

Renal denervation was performed 2 days before the UUO (unilateral ureteral obstruction) and UIRI (unilateral ischemia-reperfusion injury) models. The effects of renal denervation on renal fibrosis and cellular senescence were observed. In vitro, cellular senescence was induced in renal proximal tubular epithelial cell lines (TKPTS cells) by treatment with norepinephrine (NE). The selective α_2A-adrenergic receptor (α_2A-AR) antagonists BRL44408 and β-arrestin2 siRNA, were administered to inhibit NE-induced cellular senescence. A significantly altered pathway was identified through immunoblotting, immunofluorescence, immunocytochemistry, and functional assays involved in mitochondrial function.

Results

Renal fibrosis and cellular senescence were significantly increased in UUO and UIRI models, which were partially reversed by renal denervation. In vitro, NE induced epithelial cells secreting proinflammatory cytokines and promoted cell senescence by activating α_2A-AR. Importantly, the effects of NE during cellular senescence were blocked by α_2A-AR selective antagonist and β-arrestin2 (downstream of α_2A-AR) siRNA.

Conclusion

Renal sympathetic activation and cellular senescence are important neurometabolic and neuroimmune mechanisms in the development of renal fibrosis. Renal sympathetic neurotransmitter NE acting on the α_2A-AR of epithelial cells promotes cellular senescence through the downstream β-arrestin2 signaling, which is a potential preventive target for renal fibrosis.

Hypothermia cannot ameliorate renal fibrosis after asphyxia in the newborn piglet

BACKGROUND

The effects of therapeutic hypothermia (TH) on renal function are not widely reported, especially in longer term animal models. The hypothesis of this study was that TH of the kidneys of hypoxic-ischemic newborn piglets would reduce pathological renal fibrosis.

METHODS

Twenty-five newborn piglets obtained within 24 h of birth were classified into a control group (n = 5), an hypoxic insult with normothermia (HI-NT) group (n = 12), and an hypoxic insult with TH (HI-TH) group (33.5 °C ± 0.5 °C for 24 h; n = 8). Five days after the insult, all piglets were sacrificed under deep anesthesia by isoflurane inhalation. The kidneys were perfused with phosphate-buffered paraformaldehyde and immersed in formalin buffer. Territory fibrosis was studied and scored in the renal medulla using Azan staining.

RESULTS

Fibrosis area scores (means ± standard deviations) based on Azan staining were 1.00 ± 0.46 in the control group, 2.85 ± 0.93 in the HI-NT group, and 3.58 ± 1.14 in the HI-TH group. The fibrosis area of the HI-NT and HI-TH groups was larger than that of the control. The HI-NT and HI-TH groups were not statistically different.

CONCLUSIONS

Renal fibrosis is affected by perinatal asphyxia and cannot be prevented by TH, based on histopathological findings.

Calcitonin gene related peptide in migraine: current therapeutics, future implications and potential off-target effects

Migraine is the second largest cause of years lost to disability globally among all diseases, with a worldwide prevalence over 1 billion. Despite the global burden of migraine, few classes of therapeutics have been specifically developed to combat migraine. After 30 years of translational research, calcitonin gene-related peptide (CGRP) inhibitors have emerged as a promising new tool in the prevention of migraine. Like all new therapeutics; however, we have limited real-world experience and CGRP has several known systemic actions that warrant consideration. This article provides a narrative review of the evidence for CGRP antagonists and summarises the known and potential side effects that should be considered.

Is the Sympathetic System Detrimental in the Setting of Septic Shock, with Antihypertensive Agents as a Counterintuitive Approach? A Clinical Proposition

Mortality in the setting of septic shock varies between 20% and 100%. Refractory septic shock leads to early circulatory failure and carries the worst prognosis. The pathophysiology is poorly understood despite studies of the microcirculatory defects and the immuno-paralysis. The acute circulatory distress is treated with volume expansion, administration of vasopressors (usually noradrenaline: NA), and inotropes. Ventilation and anti-infectious strategy shall not be discussed here. When circulation is considered, the literature is segregated between interventions directed to the systemic circulation vs. interventions directed to the micro-circulation. Our thesis is that, after stabilization of the acute cardioventilatory distress, the prolonged sympathetic hyperactivity is detrimental in the setting of septic shock. Our hypothesis is that the sympathetic hyperactivity observed in septic shock being normalized towards baseline activity will improve the microcirculation by recoupling the capillaries and the systemic circulation. Therefore, counterintuitively, antihypertensive agents such as beta-blockers or alpha-2 adrenergic agonists (clonidine, dexmedetomidine) are useful. They would reduce the noradrenaline requirements. Adjuncts (vitamins, steroids, NO donors/inhibitors, etc.) proposed to normalize the sepsis-evoked vasodilation are not reviewed. This itemized approach (systemic vs. microcirculation) requires physiological and epidemiological studies to look for reduced mortality.

Naringin and Trimetazidine Improve Baroreflex Sensitivity and Nucleus Tractus Solitarius Electrical Activity in Renal Ischemia-Reperfusion Injury

BACKGROUND

Nucleus tractus solitarius (NTS) is a brain area that plays a key role in kidney and cardiovascular regulation via baroreceptors impulses.

OBJECTIVES

The aim of this study was to evaluate the effect of naringin (NAR) and trimetazidine (TMZ) alone and their combination on NTS electrical activity and baroreceptor sensitivity (BRS) in renal ischemia- reperfusion (I/R) injury.

METHODS

Forty male Sprague-Dawley rats (200- 250 g) were allocated into 5 groups with 8 in each. 1) Sham; 2) I/R; 3) TMZ 5 mg/kg; 4) NAR 100 mg/kg; and 5) TMZ5+ NAR100. The left femoral vein was cannulated to infuse saline solution or drug and the BRS was evaluated. I/R was induced by occlusion of renal pedicles for 45 min, followed by 4 hours of reperfusion. The NTS local electroencephalogram (EEG) was recorded before, during ischemia and throughout the reperfusion. Phenylephrine was injected intravenously to evaluate BRS at the end of reperfusion time. The data were analyzed by two-way repeated measurement ANOVA followed by Tukey's post hoc test. A p-value <0.05 was considered significant.

RESULTS

NTS electrical waves did not change during ischemia time, while they significantly decreased during the entire reperfusion time. NTS electrical activity and BRS dramatically reduced in rats with I/R injury; however, administration of NAR, TMZ alone or their combination significantly improved these changes in rats with I/R injury.

CONCLUSIONS

The results showed that I/R injury leads to reduced BRS and NTS electrical activity and there may be an association between I/R and decreased BRS. In addition, NAR and TMZ are promising agents to treat I/R complications.

Renal denervation alleviates renal ischemic reperfusion injury-induced acute and chronic kidney injury in rats partly by modulating miRNAs

BACKGROUND

Renal denervation (RDN) has been used to promote kidney injury repair, whereas miRNAs have been found to be involved in the pathophysiology of renal injury. However, the miRNA alterations that occur after RDN and the related protective mechanisms remain to be determined.

METHODS

Renal ischemic reperfusion injury (IRI) rat model was established and RDN was performed. Animals were killed at 24 h and 2 weeks following the operation. Tyrosine hydroxylase (TH) levels, renal function, tubular cell apoptosis and histological sections were examined at 24 h, whereas renal fibrosis and capillary vessels were assessed at 2 weeks. Furthermore, the expression of miRNAs in the injured kidney was determined using micro-array and the target genes were analyzed.

RESULTS

We found that TH was eliminated and that renal function was improved in the denervation group at 24 h. RDN reduced tubular cell apoptosis and mitigated the histological lesion. Furthermore, an increase of capillary vessel density and reduction of renal fibrosis were observed after 2 weeks. Moreover, the numbers of miRNAs were up-regulated after RDN treatment, and the miRNAs targeted pro-angiogenic, anti-fibrotic and inflammatory pathways.

CONCLUSIONS

RDN is a reliable method for alleviating IRI-induced acute and chronic kidney injury, and modulating the miRNA-related pro-angiogenic, anti-fibrotic or inflammatory pathways involved in this process.

Preexisting heart failure with reduced ejection fraction attenuates renal fibrosis after ischemia reperfusion via sympathetic activation

Although chronic heart failure is clinically associated with acute kidney injury (AKI), the precise mechanism that connects kidney and heart remains unknown. Here, we elucidate the effect of pre-existing heart failure with reduced ejection fraction (HFrEF) on kidney via sympathetic activity, using the combining models of transverse aortic constriction (TAC) and unilateral renal ischemia reperfusion (IR). The evaluation of acute (24 h) and chronic (2 weeks) phases of renal injury following IR 8 weeks after TAC in C57BL/6 mice revealed that the development of renal fibrosis in chronic phase was significantly attenuated in TAC mice, but not in non-TAC mice, whereas no impact of pre-existing heart failure was observed in acute phase of renal IR. Expression of transforming growth factor-β, monocyte chemoattractant protein-1, and macrophage infiltration were significantly reduced in TAC mice. Lastly, to investigate the effect of sympathetic nerve activity, we performed renal sympathetic denervation two days prior to renal IR, which abrogated attenuation of renal fibrosis in TAC mice. Collectively, we demonstrate the protective effect of pre-existing HFrEF on long-term renal ischemic injury. Renal sympathetic nerve may contribute to this protection; however, further studies are needed to fully clarify the comprehensive mechanisms associated with attenuated renal fibrosis and pre-existing HFrEF.

Role of α- and β-adrenergic signaling in phenotypic targeting: significance in benign and malignant urologic disease

The urinary tract is highly innervated by autonomic nerves which are essential in urinary tract development, the production of growth factors, and the control of homeostasis. These neural signals may become dysregulated in several genitourinary (GU) disease states, both benign and malignant. Accordingly, the autonomic nervous system is a therapeutic target for several genitourinary pathologies including cancer, voiding dysfunction, and obstructing nephrolithiasis. Adrenergic receptors (adrenoceptors) are G-Protein coupled-receptors that are distributed throughout the body. The major function of α1-adrenoceptors is signaling smooth muscle contractions through GPCR and intracellular calcium influx. Pharmacologic intervention of α-and β-adrenoceptors is routinely and successfully implemented in the treatment of benign urologic illnesses, through the use of α-adrenoceptor antagonists. Furthermore, cell-based evidence recently established the antitumor effect of α1-adrenoceptor antagonists in prostate, bladder and renal tumors by reducing neovascularity and impairing growth within the tumor microenvironment via regulation of the phenotypic epithelial-mesenchymal transition (EMT). There has been a significant focus on repurposing the routinely used, Food and Drug Administration-approved α1-adrenoceptor antagonists to inhibit GU tumor growth and angiogenesis in patients with advanced prostate, bladder, and renal cancer. In this review we discuss the current evidence on (a) the signaling events of the autonomic nervous system mediated by its cognate α- and β-adrenoceptors in regulating the phenotypic landscape (EMT) of genitourinary organs; and (b) the therapeutic significance of targeting this signaling pathway in benign and malignant urologic disease. Video abstract.

Selective afferent renal denervation mitigates renal and splanchnic sympathetic nerve overactivity and renal function in chronic kidney disease-induced hypertension

BACKGROUND

Clinical and experimental evidence have shown that renal denervation, by removing both the sympathetic and afferent nerves, improves arterial hypertension and renal function in chronic kidney disease (CKD). Given the key role of renal sympathetic innervation in maintaining sodium and water homeostasis, studies have indicated that the total removal of renal nerves leads to impaired compensatory mechanisms during hemodynamic challenges.

METHOD

In the present study, we hypothesized that afferent (or sensory) fibers from the diseased kidney contribute to sympathetic overactivation to the kidney and other target organ, such as the splanchnic region, contributing to hypertension in CKD. We used a method to remove selectively the afferent renal fibers (periaxonal application of 33 mmol/l capsaicin) in a rat model of CKD, the 5/6 nephrectomy.

RESULTS

Three weeks after afferent renal denervation (ARD), we found a decrease in mean arterial pressure (∼15%) and normalization in renal and splanchnic sympathetic nerve hyperactivity in the CKD group. Interestingly, intrarenal renin--angiotensin system, as well as renal fibrosis and function and proteinuria were improved after ARD in CKD rats.

CONCLUSION

The findings demonstrate that afferent fibers contribute to the maintenance of arterial hypertension and reduced renal function that are likely to be mediated by increased sympathetic nerve activity to the renal territory as well as to other target organs in CKD.

Increased Renal Dysfunction, Apoptosis, and Fibrogenesis Through Sympathetic Hyperactivity After Focal Cerebral Infarction

Sympathetic nervous system plays an important role in secondary injury of diseases. Accumulating evidence has observed association between ischemic stroke and renal dysfunction, but the mechanisms are incompletely clear. In this study, we investigated whether sympathetic hyperactivity can cause the development of renal dysfunction, apoptosis, and fibrogenesis after focal cerebral infarction. To determine the renal consequences of focal cerebral ischemia, we subjected a mice model of transient middle cerebral artery occlusion (tMCAO) and examined systolic blood pressure, heart rate, renal structure and function, serum catecholamine, and cortisol levels, and the expression of active caspase-3 bcl-2, bax, and phosphorylated p38 MAPK after 8 weeks. We also analyzed the relationship between insular cortex infarction and acute kidney injury (AKI) in 172 acute anterior circulation ischemic stroke (ACIS) patients. Transient right middle cerebral artery occlusion induced sympathetic hyperactivity, renal dysfunction, upregulation of apoptosis, and fibrogenesis in kidneys of mice. Metoprolol treatment relieves the development of renal injury. Study in stroke patients demonstrated that insular cortex infarction, especially the right insular cortex infarction, is an independent risk factor of AKI. Focal cerebral ischemia in mice leads to the development of renal injury driven by sympathetic hyperactivity. Right insular cortex infarction is an independent risk factor of AKI in older patients. Understanding the brain-kidney interaction after stroke would have clinical implications for the treatment and overall patient outcome.

Inhibition of α2-adrenoceptor is renoprotective in 5/6 nephrectomy-induced chronic kidney injury rats

In the present study, we investigated the renoprotective effects of long-term treatment with yohimbine, an α2-adrenoceptor inhibitor, in a 5/6 nephrectomy-induced chronic kidney disease (CKD) rat model. Male Sprague-Dawley rats were randomly allocated into the following groups: sham-operated, 5/6-nephrectomized (5/6 Nx), 5/6 Nx + low or high dose of yohimbine (0.3 or 3.0 mg/L in drinking water, respectively), and 5/6 Nx + hydralazine (250 mg/L in drinking water). The 5/6 Nx group presented with renal dysfunction, hypertension, noradrenaline overproduction, and histopathological injuries. Blood pressure decreased in both the yohimbine- and hydralazine-treated groups. Treatment with high dose of yohimbine, but not hydralazine, apparently attenuated urinary protein excretion and noradrenaline concentration of renal venous plasma. Renal fibrosis and upregulated fibrosis-related gene expression were suppressed by high dose of yohimbine. Furthermore, yohimbine, but not hydralazine, treatment ameliorated the urinary concentration ability. These findings suggest that long-term yohimbine treatment can be a useful therapeutic option to prevent the progression of CKD.

Adiponectin alleviates the symptoms of ischemic renal disease by inhibiting renal cell apoptosis

AIMS

Ischemic renal disease (IRD) can cause kidney damage and eventually lead to end-stage renal disease. Adiponectin (APN), a recently discovered collagen-like protein secreted by adipose tissues, plays an important role in regulating energy metabolism and inflammation. This study aimed to explore the specific mechanism by which APN affects IRD.

MAIN METHODS

We cultured human renal tubular epithelial cells (HK-2) and created a mouse model of IRD to detect apoptosis-related indicators in vitro and in vivo.

KEY FINDINGS

Compared with those in the control group, the apoptosis rate and expression levels of Bax and Fas increased in the CoCl₂-induced hypoxia model group. However, the expression of Bcl-2 decreased, and after the combined treatment with APN, the phenomenon mentioned above was reversed. Moreover, studies have found that stanniocalcin-1 (STC-1) and uncoupling protein3 (UCP3) are also involved in the protective effect of APN. Additionally, we found that the glomeruli of the mice were significantly enlarged after the APN gene was knocked out; furthermore, the number of collagen fibers in the renal tubules, as well as the expression of the corresponding fibrogenic factors, increased significantly. More importantly, after the knockout of the APN gene, the expression of the hypoxia-inducible factors HIF-1α and HIF-1β and the apoptotic rate of renal tissue cells also increased.

SIGNIFICANCE

These results indicate that APN can alleviate the symptoms of IRD by inhibiting renal cell apoptosis. Thus, in the future, APN may be a new target for the treatment of IRD.

CHEMICAL COMPOUNDS

Cobalt chloride (PubChem CID: 24643).

Role of α2-Adrenoceptors in Hypertension: Focus on Renal Sympathetic Neurotransmitter Release, Inflammation, and Sodium Homeostasis

The kidney is extensively innervated by sympathetic nerves playing an important role in the regulation of blood pressure homeostasis. Sympathetic nerve activity is ultimately controlled by the central nervous system (CNS). Norepinephrine, the main sympathetic neurotransmitter, is released at prejunctional neuroeffector junctions in the kidney and modulates renin release, renal vascular resistance, sodium and water handling, and immune cell response. Under physiological conditions, renal sympathetic nerve activity (RSNA) is modulated by peripheral mechanisms such as the renorenal reflex, a complex interaction between efferent sympathetic nerves, central mechanism, and afferent sensory nerves. RSNA is increased in hypertension and, therefore, critical for the perpetuation of hypertension and the development of hypertensive kidney disease. Renal sympathetic neurotransmission is not only regulated by RSNA but also by prejunctional α2-adrenoceptors. Prejunctional α2-adrenoceptors serve as autoreceptors which, when activated by norepinephrine, inhibit the subsequent release of norepinephrine induced by a sympathetic nerve impulse. Deletion of α2-adrenoceptors aggravates hypertension ultimately by modulating renal pressor response and sodium handling. α2-adrenoceptors are also expressed in the vasculature, renal tubules, and immune cells and exert thereby effects related to vascular tone, sodium excretion, and inflammation. In the present review, we highlight the role of α2-adrenoceptors on renal sympathetic neurotransmission and its impact on hypertension. Moreover, we focus on physiological and pathophysiological functions mediated by non-adrenergic α2-adrenoceptors. In detail, we discuss the effects of sympathetic norepinephrine release and α2-adrenoceptor activation on renal sodium transporters, on renal vascular tone, and on immune cells in the context of hypertension and kidney disease.

Contribution of the Renal Nerves to Hypertension in a Rabbit Model of Chronic Kidney Disease

Overactivity of the sympathetic nervous system and high blood pressure are implicated in the development and progression of chronic kidney disease (CKD) and independently predict cardiovascular events in end-stage renal disease. To assess the role of renal nerves, we determined whether renal denervation (RDN) altered the hypertension and sympathoexcitation associated with a rabbit model of CKD. The model involves glomerular layer lesioning and uninephrectomy, resulting in renal function reduced by one-third and diuresis. After 3-week CKD, blood pressure was 13±2 mm Hg higher than at baseline (P<0.001), and compared with sham control rabbits, renal sympathetic nerve activity was 1.2±0.5 normalized units greater (P=0.01). The depressor response to ganglion blockade was also +8.0±3 mm Hg greater, but total norepinephrine spillover was 8.7±3.7 ng/min lower (bothP<0.05). RDN CKD rabbits only increased blood pressure by 8.0±1.5 mm Hg. Renal sympathetic activity, the response to ganglion blockade and diuresis were similar to sham denervated rabbits (non-CKD). CKD rabbits had intact renal sympathetic baroreflex gain and range, as well as normal sympathetic responses to airjet stress. However, hypoxia-induced sympathoexcitation was reduced by −9±0.4 normalized units. RDN did not alter the sympathetic response to hypoxia or airjet stress. CKD increased oxidative stress markers Nox5 and MCP-1 (monocyte chemoattractant protein-1) in the kidney, but RDN had no effect on these measures. Thus, RDN is an effective treatment for hypertension in this model of CKD without further impairing renal function or altering the normal sympathetic reflex responses to various environmental stimuli.

The Prevalence of Metabolic Acidosis in Patients with Different Stages of Chronic Kidney Disease: Single-Centre Study

BACKGROUND

Metabolic acidosis (MA) is one of the most common consequences of CKD. MA is also a risk factor of CKD progression and increased mortality in these patients.

AIM

The aim of this retrospective, cross-sectional study was to assess the prevalence of MA in different stages of CKD and renal replacement therapy (RRT) modalities - haemodialysis (HD) and peritoneal dialysis (PD). Additionally, the relationship between the prevalence of MA and aetiology of kidney disease was analysed.

METHODS

One thousand five patients in different stages of CKD, or modalities of RRT were enrolled into this single-centre cross-sectional study. Forty-one patients were ruled out because of oral bicarbonate supplementation. In the remaining 964 patients (698 CKD stages 1-5, 226 HD, 40 PD), venous blood HCO3- concentration, as well as serum Cr and urea concentrations were assessed. MA was diagnosed when blood HCO3- concentration was below 22 mmol/L.

RESULTS

The prevalence of MA increased among all stages of CKD. Patients on HD had lower prevalence of MA in comparison with CKD 5 patients with no RRT (38.5 vs. 56.0%; p = 0.02) In PD patients, the prevalence of MA was significantly lower than in HD patients (2.5 vs. 38.5%; p < 0.001). In the whole study group, there were no significant differences in the prevalence of MA between different aetiologies of CKD (glomerulonephritis 24%, hypertension 23%, diabetes 25%, and tubule-interstitial diseases 24%). Also, when only patients in stages CKD 3-5 were compared, no significant differences in the prevalence of acidosis were found (glomerulonephritis 28%, hypertension 22%, diabetes 24%, and tubule-interstitial 21%).

CONCLUSIONS

(1) MA is more frequent in patients with more advanced stages of CKD. (2) RRT reduces the prevalence of MA. (3) In PD patients, MA is rare. (4) Aetiology of CKD seems not to have a significant impact on MA prevalence.

Collecting duct cells show differential retinoic acid responses to acute versus chronic kidney injury stimuli

Retinoic acid (RA) activates RA receptors (RAR), resulting in RA response element (RARE)-dependent gene expression in renal collecting duct (CD). Emerging evidence supports a protective role for this activity in acute kidney injury (AKI) and chronic kidney disease (CKD). Herein, we examined this activity in RARE-LacZ transgenic mice and by RARE-Luciferase reporter assays in CD cells, and investigated how this activity responds to neurotransmitters and mediators of kidney injury. In RARE-LacZ mice, Adriamycin-induced heavy albuminuria was associated with reduced RA/RAR activity in CD cells. In cultured CD cells, RA/RAR activity was repressed by acetylcholine, albumin, aldosterone, angiotensin II, high glucose, cisplatin and lipopolysaccharide, but was induced by aristolochic acid I, calcitonin gene-related peptide, endothelin-1, gentamicin, norepinephrine and vasopressin. Compared with age-matched normal human CD cells, CD-derived renal cystic epithelial cells from patients with autosomal recessive polycystic kidney disease (ARPKD) had significantly lower RA/RAR activity. Synthetic RAR agonist RA-568 was more potent than RA in rescuing RA/RAR activity repressed by albumin, high glucose, angiotensin II, aldosterone, cisplatin and lipopolysaccharide. Hence, RA/RAR  in CD cells is a convergence point of regulation by neurotransmitters and mediators of kidney injury, and may be a novel therapeutic target.

Inhibition of α1-adrenoceptor reduces TGF-β1-induced epithelial-to-mesenchymal transition and attenuates UUO-induced renal fibrosis in mice

Renal fibrosis is a common pathological hallmark of chronic kidney disease (CKD). Renal sympathetic nerve activity is elevated in patients and experimental animals with CKD and contributes to renal interstitial fibrosis in obstructive nephropathy. However, the mechanisms underlying sympathetic overactivation in renal fibrosis remain unknown. Norepinephrine (NE), the main sympathetic neurotransmitter, was found to promote TGF-β1-induced epithelial-mesenchymal transition (EMT) and fibrotic gene expression in the human renal proximal epithelial cell line HK-2. Using both genetic and pharmacological approaches, we identified that NE binds Gαq-coupled α1-adrenoceptor (α1-AR) to enhance EMT of HK-2 cells by activating p38/Smad3 signaling. Inhibition of p38 diminished the NE-exaggerated EMT process and increased the fibrotic gene expression in TGF-β1-treated HK-2 cells. Moreover, the pharmacological blockade of α1-AR reduced the kidney injury and renal fibrosis in a unilateral ureteral obstruction mouse model by suppressing EMT in the kidneys. Thus, sympathetic overactivation facilitates EMT of renal epithelial cells and fibrosis via the α1-AR/p38/Smad3 signaling pathway, and α1-AR inhibition may be a promising approach toward treating renal fibrosis.

Renal ischemia/reperfusion injury: An insight on in vitro and in vivo models

Optimal tissue oxygenation is essential for its normal function. Suboptimal oxygenation or ischemia contributes to increased mortalities during various pathological conditions such as stroke, acute kidney injury (AKI), cardiac failure. Despite the rapid progression of renal tissue injury, the mechanism underlying renal ischemia/reperfusion injury (IRI) remains highly unclear. Experimental in vitro and in vivo models epitomizing the fundamental process is critical to the research of the pathogenesis of IRI and the development of plausible therapeutics. In this review, we describe the in vitro and in vivo models of IRI, ranges from proximal tubular cell lines to surgery-based animal models like clamping of both renal pedicles (bilateral IRI), clamping of one renal pedicle (unilateral IRI), clamping of one/or both renal arteries/or vein, or unilateral IRI with contralateral nephrectomy (uIRIx). Also, advanced technologies like three-dimensional kidney organoids, kidney-on-a-chip are explained. This review provides thoughtful information for establishing reliable and pertinent models for studying IRI-associated acute renal pathologies.

Post-Ischemic Renal Fibrosis Progression Is Halted by Delayed Contralateral Nephrectomy: The Involvement of Macrophage Activation

(1) Background: Successful treatment of acute kidney injury (AKI)-induced chronic kidney disease (CKD) is unresolved. We aimed to characterize the time-course of changes after contralateral nephrectomy (Nx) in a model of unilateral ischemic AKI-induced CKD with good translational utility. (2) Methods: Severe (30 min) left renal ischemia-reperfusion injury (IRI) or sham operation (S) was performed in male Naval Medical Research Institute (NMRI) mice followed by Nx or S one week later. Expression of proinflammatory, oxidative stress, injury and fibrotic markers was evaluated by RT-qPCR. (3) Results: Upon Nx, the injured kidney hardly functioned for three days, but it gradually regained function until day 14 to 21, as demonstrated by the plasma urea. Functional recovery led to a drastic reduction in inflammatory infiltration by macrophages and by decreases in macrophage chemoattractant protein-1 (MCP-1) and tumor necrosis factor-alpha (TNF-α) mRNA and most injury markers. However, without Nx, a marked upregulation of proinflammatory (TNF-α, IL-6, MCP-1 and complement-3 (C3)); oxidative stress (nuclear factor erythroid 2-related factor 2, NRF2) and fibrosis (collagen-1a1 (Col1a1) and fibronectin-1 (FN1)) genes perpetuated, and the injured kidney became completely fibrotic. Contralateral Nx delayed the development of renal failure up to 20 weeks. (4) Conclusion: Our results suggest that macrophage activation is involved in postischemic renal fibrosis, and it is drastically suppressed by contralateral nephrectomy ameliorating progression.

Cisplatin nephrotoxicity is induced via poly(ADP-ribose) polymerase activation in adult zebrafish and mice

Cisplatin is a well-known chemotherapy medication used to treat numerous cancers. However, treatment with cisplatin in cancer therapy has major side effects, such as nephrotoxic acute kidney injury. Adult vertebrate kidneys are commonly used as models of cisplatin-induced nephrotoxic acute kidney injury. Embryonic zebrafish kidney is more simplified and is composed simply of two nephrons and thus is an excellent model for the investigation of cisplatin nephrotoxicity. Here, we developed a novel model to induce cisplatin nephrotoxicity in adult zebrafish and demonstrated that intraperitoneal injection of cisplatin caused a decline in kidney proximal tubular function based on fluorescein-labeled dextran uptake and alkaline phosphatase staining. We also showed that cisplatin induced histological injury of the kidney tubules, quantified by tubular injury scores on the periodic acid-Schiff-stained kidney sections. As shown in a mouse model of cisplatin-induced nephrotoxicity, the activation of poly(ADP-ribose) polymerase (PARP), an enzyme implicated in cisplatin-induced cell death, was markedly increased after cisplatin injection in adult zebrafish. Furthermore, pharmacological inhibition of PARP using a specific PARP inhibitor PJ 34 hydrochloride (PJ34) or 3-aminobenzamide ameliorated kidney proximal tubular functional and histological damages in cisplatin-injected adult zebrafish kidneys. Administration of a combination of PARP inhibitors PJ34 and 3-aminobenzamide additively protected renal function and histology in zebrafish and mouse models of cisplatin nephrotoxicity. In conclusion, these data suggest that adult zebrafish are not only suitable for drug screening and genetic manipulation but also useful as a simplified but powerful model to study the pathophysiology of cisplatin nephrotoxicity and establish new therapies for treating human kidney diseases.

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.

Vagus Nerve Stimulation Ameliorates Renal Ischemia-Reperfusion Injury through Inhibiting NF-κB Activation and iNOS Protein Expression

OBJECTIVE

In renal ischemia/reperfusion injury (RIRI), nuclear factor κB (NF-κB (NF-κB (NF.

METHODS

Eighteen male Sprague-Dawley rats were randomly allocated into the sham group, the I/R group, and the VNS+I/R group, 6 rats per group. An RIRI model was induced by a right nephrectomy and blockade of the left renal pedicle vessels for 45 min. After 6 h of reperfusion, the blood samples and renal samples were collected. The VNS treatment was performed throughout the I/R process in the VNS+I/R group using specific parameters (20 Hz, 0.1 ms in duration, square waves) known to produce a small but reliable bradycardia. Blood was used for evaluation of renal function and inflammatory state. Renal injury was evaluated via TUNEL staining. Renal samples were harvested to evaluate renal oxidative stress, NF-κB (NF.

RESULTS

The VNS treatment reduces serum creatinine (Cr) and blood urea nitrogen (BUN) levels. Simultaneously, the levels of tumor necrosis factor alpha (TNF-α), interleukin 6 (IL-6), and interleukin 1-beta (IL-1β) were significantly increased in the I/R group, but VNS treatment markedly ameliorated this inflammatory response. Furthermore, the VNS ameliorated oxidant stress and renal injury, indicated by a decrease in 3-nitrotyrosine (3-NT) formation and MDA and MPO levels and an increase in the SOD level compared to that in the I/R group. Finally, the VNS also significantly decreases NF-κB (NF.

CONCLUSION

Our findings indicate that NF-κB activation increased iNOS expression and promoted RIRI and that VNS treatment attenuated RIRI by inhibiting iNOS expression, oxidative stress, and inflammation via NF-κB inactivation.κB (NF-κB (NF.

The sympathetic nervous system in acute kidney injury

Acute kidney injury (AKI) is frequently accompanied by activation of the sympathetic nervous system (SNS). This may result from pre-exisiting chronic diseases associated with sympathetic activation prior to AKI or it may be induced by stressors that ultimately lead to AKI such as endotoxins and arterial hypotension in circulatory shock. Conversely, sympathetic activation may also result from acute renal injury. Focusing on studies in experimental renal ischaemia and reperfusion (IR), this review summarizes the current knowledge on how the SNS is activated in IR-induced AKI and on the consequences of sympathetic activation for the development of acute renal damage. Experimental studies show beneficial effects of sympathoinhibitory interventions on renal structure and function in response to IR. However, few clinical trials obtained in scenarios that correspond to experimental IR, namely major elective surgery, showed that peri-operative treatment with centrally acting sympatholytics reduced the incidence of AKI. Apparently, discrepant findings on how sympathetic activation influences renal responses to acute IR-induced injury are discussed and future areas of research in this field are identified.

Crosstalk between the nervous system and the kidney

Under physiological states, the nervous system and the kidneys communicate with each other to maintain normal body homeostasis. However, pathological states disrupt this interaction as seen in hypertension, and kidney damage can cause impaired renorenal reflex and sodium handling. In acute kidney injury (AKI) and chronic kidney disease (CKD), damaged kidneys can have a detrimental effect on the central nervous system. CKD is an independent risk factor for cerebrovascular disease and cognitive impairment, and many factors, including retention of uremic toxins and phosphate, have been proposed as CKD-specific factors responsible for structural and functional cerebral changes in patients with CKD. However, more studies are needed to determine the precise pathogenesis. Epidemiological studies have shown that AKI is associated with a subsequent risk for developing stroke and dementia. However, recent animal studies have shown that the renal nerve contributes to kidney inflammation and fibrosis, whereas activation of the cholinergic anti-inflammatory pathway, which involves the vagus nerve, the splenic nerve, and immune cells in the spleen, has a significant renoprotective effect. Therefore, elucidating mechanisms of communication between the nervous system and the kidney enables us not only to develop new strategies to ameliorate neurological conditions associated with kidney disease but also to design safe and effective clinical interventions for kidney disease, using the neural and neuroimmune control of kidney injury and disease.

Renal Inflammation in DOCA-Salt Hypertension

Recent reports indicate that, in addition to treating hypertension, renal denervation (RDN) also mitigates renal inflammation. However, because RDN decreases renal perfusion pressure, it is unclear whether these effects are because of the direct effects of RDN on inflammatory signaling or secondary to decreased arterial pressure (AP). Therefore, this study was conducted to elucidate the contribution of renal nerves to renal inflammation in the deoxycorticosterone (DOCA)-salt rat, a model in which RDN decreases AP and abolishes renal inflammation. In Experiment 1, we assessed the temporal changes in renal inflammation by measuring renal cytokines and AP in DOCA-salt rats. Uninephrectomized (1K) adult male Sprague Dawley rats that received surgical RDN or sham (Sham) were administered DOCA (100 mg, SC) and 0.9% saline for 21 days. AP was measured by radiotelemetry, and urinary cytokine excretion was measured repeatedly. In Experiment 2, the contribution of renal nerves in renal inflammation was assessed in a 2-kidney DOCA-salt rat to control for renal perfusion pressure. DOCA-salt treatment was administered after unilateral (U-)RDN. In Experiment 1, DOCA-salt-induced increases in AP and renal inflammation (assessed by urinary cytokines) were attenuated by RDN versus Sham. In Experiment 2, GRO/KC (growth-related oncogene/keratinocyte chemoattractant), MCP (monocyte chemoattractant protein)-1, and macrophage infiltration were lower in the denervated kidney versus the contralateral Sham kidney. No differences in T-cell infiltration were observed. Together, these data support the hypothesis that renal nerves mediate, in part, the development of renal inflammation in the DOCA-salt rat independent of hypertension. The mechanisms and cell-specificity mediating these effects require further investigation.

Neuroimmune interactions and kidney disease

The autonomic nervous system plays critical roles in maintaining homeostasis in humans, directly regulating inflammation by altering the activity of the immune system. The cholinergic anti-inflammatory pathway is a well-studied neuroimmune interaction involving the vagus nerve. CD4-positive T cells expressing β2 adrenergic receptors and macrophages expressing the alpha 7 subunit of the nicotinic acetylcholine receptor in the spleen receive neurotransmitters such as norepinephrine and acetylcholine and are key mediators of the cholinergic anti-inflammatory pathway. Recent studies have demonstrated that vagus nerve stimulation, ultrasound, and restraint stress elicit protective effects against renal ischemia-reperfusion injury. These protective effects are induced primarily via activation of the cholinergic anti-inflammatory pathway. In addition to these immunological roles, nervous systems are directly related to homeostasis of renal physiology. Whole-kidney three-dimensional visualization using the tissue clearing technique CUBIC (clear, unobstructed brain/body imaging cocktails and computational analysis) has illustrated that renal sympathetic nerves are primarily distributed around arteries in the kidneys and denervated after ischemia-reperfusion injury. In contrast, artificial renal sympathetic denervation has a protective effect against kidney disease progression in murine models. Further studies are needed to elucidate how neural networks are involved in progression of kidney disease.

Cyclosporin A aggravates hydrogen peroxide-induced cell death in kidney proximal tubule epithelial cells

Cyclosporin A (CsA) does not only exert a toxic effect on kidney parenchymal cells, but also protects them against necrotic cell death by inhibiting opening of mitochondrial permeability transition pore. However, whether CsA plays a role in hydrogen peroxide-induced kidney proximal tubular cell death is currently unclear. In the present study, treatment with CsA further increased apoptosis and necrosis in HK-2 human kidney proximal tubule epithelial cells during exposure to hydrogen peroxide. In addition, hydrogen peroxide-induced p53 activation and BH3 interacting-domain death agonist (BID) expression were higher in CsA-treated cells than those in non-treated cells, whereas hydrogen peroxide-induced activation of mitogen-activated protein kinases including p38, c-Jun N-terminal kinase, and extracellular signal-regulated kinase and activation of protein kinase B were not significantly altered by treatment with CsA. In oxidant-antioxidant system, reactive oxygen species (ROS) production induced by hydrogen peroxide was further enhanced by treatment with CsA. However, expression levels of antioxidant enzymes including manganese superoxide dismutase, copper/zinc superoxide dismutase, and catalase were not altered by treatment with hydrogen peroxide or CsA. Treatment with CsA further enhanced mitochondrial membrane potential induced by exposure to hydrogen peroxide, although it did not alter endoplasmic reticulum stress based on expression of glucose-regulated protein 78 and 94. Taken together, these data suggest that CsA can aggravate hydrogen peroxide-induced cell death through p53 activation, BID expression, and ROS production.

Bioinformatics Unmasks the Maneuverers of Pain Pathways in Acute Kidney Injury

Acute Kidney injury (AKI) is one of the leading health concerns resulting in accumulation of nitrogenous as well as non-nitrogenous wastes in body and characterised by a rapid deterioration in kidney functions. Besides the major toll from the primary insult in the kidney, consequential extra-renal secondary insults endowed with the pathways of inflammatory milieu often complicates the disease outcome. Some of the known symptoms of AKI leading to clinical reporting are fatigue, loss of appetite, headache, nausea, vomiting, and pain in the flanks, wherein proinflammatory cytokines have been strongly implicated in pathogenesis of AKI and neuro-inflammation. Taking in account these clues, we have tried to decode the neuro-inflammation and pain perception phenomenon during the progression of AKI using the pathway integration and biological network strategies. The pathways and networks were generated using bioinformatics software viz. PANTHER, Genomatix and PathVisio to establish the relationship between immune and neuro related pathway in AKI. These observations envisage a neurol-renal axis that is predicted to involve calcium channels in neuro-inflammatory pathway of AKI. These observations, thus, pave a way for a new paradigm in understanding the interplay of neuro-immunological signalling in AKI.

Neuroimmunomodulation of tissue injury and disease: an expanding view of the inflammatory reflex pathway

Neuroimmunomodulation through peripheral nerve activation is an important therapeutic approach to various disorders. Central to this approach is the inflammatory reflex pathway in which the cholinergic anti-inflammatory pathway represents the efferent limb. Recent studies provide a framework for understanding this control pathway, however our understanding remains incomplete. Genetically modified mice, using optogenetics and pharmacogenomics, have been invaluable resources that will allow investigators to disentangle neural pathways that provide a unifying mechanism by which vagal nerve stimulation (and other means of stimulating the pathway) leads to an anti-inflammatory and tissue protective effect. In this review we describe disease models that contribute to our understanding of how vagal nerve stimulation attenuates inflammation and organ injury: acute kidney injury, rheumatoid arthritis, and inflammatory gastrointestinal disease. The gut microbiota contributes to health and disease and the potential role of the vagus nerve in affecting the relationship between gut microbiota and the immune system and modifying diseases remains an intriguing opportunity to attenuate local and systemic inflammation that undergird disease processes.

AKI and the Neuroimmune Axis

Neuroimmune interaction is an emerging concept, wherein the nervous system modulates the immune system and vice versa. This concept is gaining attention as a novel therapeutic target in various inflammatory diseases including acute kidney injury (AKI). Vagus nerve stimulation or treatment with pulsed ultrasound activates the cholinergic anti-inflammatory pathway to prevent AKI in mice. The kidneys are innervated by sympathetic efferent and sensory afferent neurons, and these neurons also may play a role in the modulation of inflammation in AKI. In this review, we discuss several neural circuits with respect to the control of renal inflammation and AKI as well as optogenetics as a novel tool for understanding these complex neural circuits.

Renal sympathetic nerve activation via α2-adrenergic receptors in chronic kidney disease progression

Chronic kidney disease (CKD) is increasing worldwide without an effective therapeutic strategy. Sympathetic nerve activation is implicated in CKD progression, as well as cardiovascular dysfunction. Renal denervation is beneficial for controlling blood pressure (BP) and improving renal function through reduction of sympathetic nerve activity in patients with resistant hypertension and CKD. Sympathetic neurotransmitter norepinephrine (NE) via adrenergic receptor (AR) signaling has been implicated in tissue homeostasis and various disease progressions, including CKD. Increased plasma NE level is a predictor of survival and the incidence of cardiovascular events in patients with end-stage renal disease, as well as future renal injury in subjects with normal BP and renal function. Our recent data demonstrate that NE derived from renal nerves causes renal inflammation and fibrosis progression through alpha-2 adrenergic receptors (α₂-AR) in renal fibrosis models independent of BP. Sympathetic nerve activation-associated molecular mechanisms and signals seem to be critical for the development and progression of CKD, but the exact role of sympathetic nerve activation in CKD progression remains undefined. This review explores the current knowledge of NE-α₂-AR signaling in renal diseases and offers prospective views on developing therapeutic strategies targeting NE-AR signaling in CKD progression.