Protective effect of ischemic preconditioning on ischemia/reperfusion-induced acute kidney injury through sympathetic nervous system in rats

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.

Chronic Limb Remote Ischemic Conditioning may have an Antihypertensive Effect in Patients with Hypertension

Hypertension is the leading preventable risk factor for all-cause morbidity and mortality worldwide. Despite antihypertensive medications have been available for decades, a big challenge we are facing is to increase the blood pressure (BP) control rate among the population. Therefore, it is necessary to search for new antihypertensive means to reduce the burden of disease caused by hypertension. Limb remote ischemic conditioning (LRIC) can trigger endogenous protective effects through transient and repeated ischemia on the limb to protect specific organs and tissues including the brain, heart, and kidney. The mechanisms of LRIC involve the regulation of the autonomic nervous system, releasing humoral factors, improvement of vascular endothelial function, and modulation of immune/inflammatory responses. These underlying mechanisms of LRIC may restrain the pathogenesis of hypertension through multiple pathways theoretically, leading to a potential decline in BP. Several existing studies have explored the impact of LRIC on BP, however, controversial findings were reported. To explore the potential antihypertensive effect of LRIC and the underlying mechanisms, we systematically reviewed the relevant articles to provide an insight into the novel therapy of hypertension.

Interactions between remote ischemic conditioning and post-stroke sleep regulation

Sleep disturbances are common in patients with stroke, and sleep quality has a critical role in the onset and outcome of stroke. Poor sleep exacerbates neurological injury, impedes nerve regeneration, and elicits serious complications. Thus, exploring a therapy suitable for patients with stroke and sleep disturbances is imperative. As a multi-targeted nonpharmacological intervention, remote ischemic conditioning can reduce the ischemic size of the brain, improve the functional outcome of stroke, and increase sleep duration. Preclinical/clinical evidence showed that this method can inhibit the inflammatory response, mediate the signal transductions of adenosine, activate the efferents of the vagal nerve, and reset the circadian clocks, all of which are involved in sleep regulation. In particular, cytokines tumor necrosis factor α (TNFα) and adenosine are sleep factors, and electrical vagal nerve stimulation can improve insomnia. On the basis of the common mechanisms of remote ischemic conditioning and sleep regulation, a causal relationship was proposed between remote ischemic conditioning and post-stroke sleep quality.

The Impact of Remote Ischaemic Conditioning on Beat-to-Beat Heart Rate Variability Circadian Rhythm in Healthy Adults

BACKGROUND

Remote ischaemic conditioning (RIC) is an intervention that may exert a protective effect over multiple tissues or organs by regulating neuronal signal transduction. Heart rate variability (HRV) can assess the state of the autonomic nervous system. However, whether RIC can also regulate HRV in humans remains unknown.

METHOD

This was a self-controlled interventional study in which serial beat-to-beat monitoring was performed at the same seven time points (7, 9, and 11 AM; 2, 5, and 8 PM; and 8 AM on the next day) with or without RIC in 50 healthy adults. The seven time points on the RIC day were defined as baseline, 1 hour, 3 hours, 6 hours, 9 hours, 12 hours, and 24 hours after RIC. The RIC protocol consisted of 4×5-minute inflation/deflation in one arm and one thigh cuff at 200 mmHg pressure from 7:20 to 8 AM. This study is registered on ClinicalTrials.gov (NCT02965547).

RESULTS

We included 50 healthy adult volunteers (aged 34.54±12.01 years, 22 men [44%], all Asian). The variables analysed in frequency-domain measures performed as power of low-frequency in normalised units (0.04-0.15 Hz), high-frequency in normalised units (0.15-0.40 Hz), and ratio of low frequency to high frequency. The time-domain parameters standard deviation (SD) of all normal to normal (NN) intervals (SDNN), mean of the 5-minute SD of the NN intervals, SD of the consecutive 5-minute averages of NN intervals, and the root mean square of successive differences of NN intervals, and time-domain parameters calculated from Poincaré plots, SD of the short diagonal axis in Poincaré plot (SD1), SD of the long diagonal axis in Poincaré plot (SD2), and SD1/SD2 were also obtained. The SDNN and SD2 significantly increased 1 hour after RIC (p=0.029 and p=0.045, respectively). Additionally, the SD2 increased a second time 12 hours after RIC (p=0.041), which represented inhibited sympathetic activity.

CONCLUSIONS

Heart rate variability increase and sympathetic inhibition induced by RIC appeared both on the early and delayed protective window of RIC, which may indicate some of the underlying mechanisms by which RIC may offer protection.

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.

Ischemic preconditioning improved renal ischemia/reperfusion injury and hyperglycemia

Renal ischemia/reperfusion (I/R) is an alternation of renal hemodynamics, which results in diverse postischemic responses and eventually acute kidney injury. Although renal ischemic preconditioning (IPC) is known to protect the kidney from I/R injury, the precise renoprotective mechanisms are not completely understood. The multiple renoprotective effects of IPC underscore the importance in understanding molecular mechanisms and the targets of action involved. This study aimed to identify the biochemical changes in renal I/R injury and investigate the renoprotective mechanisms of IPC. Herein, renal I/R was produced in adult male Sprague-Dawley rats through the bilateral ligation of renal pedicles for 45 min, followed by reperfusion for 24 h. For the IPC group, rats were subjected to three cycles of 2-min ischemia, followed by a 5-min reperfusion, 15 min prior to renal I/R. Our data confirmed the beneficial effects that IPC has on renal I/R injury. IPC-mediated renoprotection was associated with the resolution of oxidative stress, inflammation, apoptosis, and hyperglycemia. Among the numerous signaling molecules involved in the renoprotective mechanisms of IPC, an elevated protein expression of Nrf2, HO-1, LC3 II conversion, along with Atg12 and protein phosphorylation of AMPK, as well as a decreased protein phosphorylation of ERK, p38 MAPK, and Akt and NF-κB DNA binding activity were identified. Importantly, the post renal I/R overproduction of counter-regulatory hormones, impaired hepatic insulin action, and augmented hepatic gluconeogenesis were improved through IPC. As counter-regulatory hormones have been implicated in the induction of oxidative stress, inflammation, apoptosis, impaired insulin action, hyperglycemia, and tissue destruction, our findings suggest that counter-regulatory hormones may well be valuable targets of IPC for combatting renal I/R injury. © 2018 IUBMB Life, 71(3):321-329, 2019.

Relationship between sleep-disordered breathing and renal dysfunction in acute coronary syndrome

BACKGROUND

Sleep-disordered breathing (SDB) is associated with cardiovascular complications. However, the effect of SDB on renal function in patients with acute coronary syndrome (ACS) treated by percutaneous coronary intervention (PCI) remains unclear.

METHODS

We enrolled 154 consecutive ACS patients without heart failure. A sleep study was performed immediately after PCI.

RESULTS

The mean apnea-hypopnea index (AHI) was 16.4±13.1, and 33 patients (21%) had severe SDB, defined as AHI≥25. Estimated glomerular filtration rate (eGFR) values on admission (60±12mL/min/1.73m² vs. 67±17mL/min/1.73m², p=0.046) and at discharge (54±15mL/min/1.73m² vs. 63±15mL/min/1.73m², p=0.002) were lower in patients with severe SDB than in those patients without severe SDB. Multiple linear regression analysis showed that AHIs were significantly correlated with absolute changes in eGFR values from admission to discharge (β=0.201, p=0.004). Median 24-h urinary noradrenaline excretion measured on the same day of the sleep study was higher [297 (interquartile range {IQR}: 232-472) vs. 174 (IQR: 107-318)μg/day, p=0.021] in patients with severe SDB. On multivariate logistic regression analysis, the presence of severe SDB was a significant predictor (adjusted odds ratio 3.76, 95% confidence interval 1.06-13.9, p=0.047) for eGFR of less than 45mL/min/1.73m² at discharge. This association was independent of age, eGFR on admission, and a presentation of ST-segment elevation myocardial infarction.

CONCLUSION

In patients with ACS who undergo PCI, severe SDB is associated with impaired renal function on admission and its deterioration during hospitalization. Further studies will be needed to conclude that SDB would be a therapeutic target in ACS.

Sympathetic nervous response to ischemia-reperfusion injury in humans is altered with remote ischemic preconditioning

Sympathetic neural activation may be detrimentally involved in tissue injury caused by ischemia-reperfusion (IR). We examined the effects of experimental IR in the forearm on sympathetic nerve response, finger reactive hyperemia, and oxidative stress, and the protection afforded by applying remote ischemic preconditioning (RIPC). Ischemia was induced in the forearm for 20 min in healthy volunteers. RIPC was induced by applying two cycles, 5 min each, of ischemia and reperfusion to the upper leg immediately before IR. We examined muscle sympathetic nerve activity (MSNA) in the contralateral leg using microneurography, finger reactive hyperemia [ischemic reactive hyperemia index (RHI)], erythrocyte production of reduced gluthathione (GSH), and plasma nitric oxide (NO) concentration. In controls (no RIPC; n = 15), IR increased MSNA in the early and late phase of ischemia (70% at 5 min; 101% at 15 min). In subjects who underwent RIPC (n = 15), the increase in MSNA was delayed to the late phase of ischemia and increased only by 40%. GSH increased during ischemia in the control group (P = 0.05), but not in those who underwent RIPC. Nitrate and nitrite concentration, taken as an index of NO availability, decreased during the reperfusion period in control individuals (P < 0.05), while no change was observed in those who underwent RIPC. Experimental IR did not affect RHI in the control condition, but a significant vasodilatory response occurred in the RIPC group (P < 0.05). RIPC attenuated ischemia-induced sympathetic activation, prevented the production of an erythrocyte marker of oxidative stress and the reduction of NO availability, and ameliorated RHI.

Molecular Mechanisms of Renal Ischemic Conditioning Strategies

Ischemia-reperfusion injury is the leading cause of acute kidney injury in a variety of clinical settings such as renal transplantation and hypovolemic and/or septic shock. Strategies to reduce ischemia-reperfusion injury are obviously clinically relevant. Ischemic conditioning is an inherent part of the renal defense mechanism against ischemia and can be triggered by short periods of intermittent ischemia and reperfusion. Understanding the signaling transduction pathways of renal ischemic conditioning can promote further clinical translation and pharmacological advancements in this era. This review summarizes research on the molecular mechanisms underlying both local and remote ischemic pre-, per- and postconditioning of the kidney. The different types of conditioning strategies in the kidney recruit similar powerful pro-survival mechanisms. Likewise, renal ischemic conditioning mobilizes many of the same protective signaling pathways as in other organs, but differences are recognized.

Resveratrol neuroprotection in stroke and traumatic CNS injury

Resveratrol, a stilbene formed in many plants in response to various stressors, elicits multiple beneficial effects in vertebrates. Particularly, resveratrol was shown to have therapeutic properties in cancer, atherosclerosis and neurodegeneration. Resveratrol-induced benefits are modulated by multiple synergistic pathways that control oxidative stress, inflammation and cell death. Despite the lack of a definitive mechanism, both in vivo and in vitro studies suggest that resveratrol can induce a neuroprotective state when administered acutely or prior to experimental injury to the CNS. In this review, we discuss the neuroprotective potential of resveratrol in stroke, traumatic brain injury and spinal cord injury, with a focus on the molecular pathways responsible for this protection.