Selective inhibition of protein kinase C β2 attenuates the adaptor P66 Shc-mediated intestinal ischemia-reperfusion injury

Advancements in the study of acute lung injury resulting from intestinal ischemia/reperfusion

Intestinal ischemia/reperfusion is a prevalent pathological process that can result in intestinal dysfunction, bacterial translocation, energy metabolism disturbances, and subsequent harm to distal tissues and organs via the circulatory system. Acute lung injury frequently arises as a complication of intestinal ischemia/reperfusion, exhibiting early onset and a grim prognosis. Without appropriate preventative measures and efficacious interventions, this condition may progress to acute respiratory distress syndrome and elevate mortality rates. Nonetheless, the precise mechanisms and efficacious treatments remain elusive. This paper synthesizes recent research models and pertinent injury evaluation criteria within the realm of acute lung injury induced by intestinal ischemia/reperfusion. The objective is to investigate the roles of pathophysiological mechanisms like oxidative stress, inflammatory response, apoptosis, ferroptosis, and pyroptosis; and to assess the strengths and limitations of current therapeutic approaches for acute lung injury stemming from intestinal ischemia/reperfusion. The goal is to elucidate potential targets for enhancing recovery rates, identify suitable treatment modalities, and offer insights for translating fundamental research into clinical applications.

Exploring the Gut-Mitochondrial Axis: p66Shc Adapter Protein and Its Implications for Metabolic Disorders

This review investigates the multifaceted role of the p66Shc adaptor protein and the gut microbiota in regulating mitochondrial function and oxidative stress, and their collective impact on the pathogenesis of chronic diseases. The study delves into the molecular mechanisms by which p66Shc influences cellular stress responses through Rac1 activation, Forkhead-type transcription factors inactivation, and mitochondria-mediated apoptosis, alongside modulatory effects of gut microbiota-derived metabolites and endotoxins. Employing an integrative approach, the review synthesizes findings from a broad array of studies, including molecular biology techniques and analyses of microbial metabolites' impacts on host cellular pathways. The results underscore a complex interplay between microbial metabolites, p66Shc activation, and mitochondrial dysfunction, highlighting the significance of the gut microbiome in influencing disease outcomes through oxidative stress pathways. Conclusively, the review posits that targeting the gut microbiota-p66Shc-mitochondrial axis could offer novel therapeutic strategies for mitigating the development and progression of metabolic diseases. This underscores the potential of dietary interventions and microbiota modulation in managing oxidative stress and inflammation, pivotal factors in chronic disease etiology.

Protective Effect of Oxygen and Isoflurane in Rodent Model of Intestinal Ischemia-Reperfusion Injury

Animal research in intestinal ischemia-reperfusion injury (IRI) is mainly performed in rodent models. Previously, intraperitoneal (I.P.) injections with ketamine-xylazine mixtures were used. Nowadays, volatile anesthetics (isoflurane) are more common. However, the impact of the anesthetic method on intestinal IRI has not been investigated. We aim to analyze the different anesthetic methods and their influence on the extent of intestinal IRI in a rat model. Male Sprague-Dawley rats were used to investigate the effect of I.P. anesthesia on 60 min of intestinal ischemia and 60 min of reperfusion in comparison to hyperoxygenation (100% O₂) and volatile isoflurane anesthesia. In comparison to I.P. anesthesia with room air (21% O₂), supplying 100% O₂ improved 7-day survival by cardiovascular stabilization, reducing lactic acidosis and preventing vascular leakage. However, this had no effect on the intestinal epithelial damage, permeability, and inflammatory response observed after intestinal IRI. In contrast to I.P. + 100% O₂, isoflurane anesthesia reduced intestinal IRI by preventing ongoing low-flow reperfusion hypotension, limiting intestinal epithelial damage and permeability, and by having anti-inflammatory effects. When translating the aforementioned results of this study to clinical situations, such as intestinal ischemia or transplantation, the potential protective effects of hyperoxygenation and volatile anesthetics require further research.

Critical role of caveolin-1 in intestinal ischemia reperfusion by inhibiting protein kinase C βII

Intestinal ischemia reperfusion (I/R) is a common clinical pathological process. We previously reported that pharmacological inhibition of protein kinase C (PKC) βII with a specific inhibitor attenuated gut I/R injury. However, the endogenous regulatory mechanism of PKCβII inactivation is still unclear. Here, we explored the critical role of caveolin-1 (Cav1) in protecting against intestinal I/R injury by regulating PKCβII inactivation. PKCβII translocated to caveolae and bound with Cav1 after intestinal I/R. Cav1 was highly expressed in the intestine of mice with I/R and IEC-6 cells stimulated with hypoxia/reoxygenation (H/R). Cav1-knockout (KO) mice suffered from worse intestinal injury after I/R than wild-type (WT) mice and showed extremely low survival due to exacerbated systemic inflammatory response syndrome (SIRS) and remote organ (lung and liver) injury. Cav1 deficiency resulted in excessive PKCβII activation and increased oxidative stress and apoptosis after intestinal I/R. Full-length Cav1 scaffolding domain peptide (CSP) suppressed excessive PKCβII activation and protected the gut against oxidative stress and apoptosis due to I/R injury. In summary, Cav1 could regulate PKCβII endogenous inactivation to alleviate intestinal I/R injury. This finding may represent a novel therapeutic strategy for the prevention and treatment of intestinal I/R injury.

Oxidative Stress in Intestinal Ischemia-Reperfusion

Ischemia-reperfusion (I/R) injury is a manifestation of tissue or organ damage that is followed by ischemia and exacerbated by the return of blood flow to a previously damaged tissue or organ. The intestines are one of the most sensitive tissues and organs to I/R injury. Moreover, the adverse consequences of intestinal I/R (II/R) injury are not limited to the intestine itself and can also lead to damage of the distant tissues and organs. The mechanism of II/R is extremely complex and oxidative stress is the key link in the pathogenesis of II/R injury. This study summarizes the roles of oxidative stress and its signaling pathways involved in II/R. The signaling pathways that mitigate II/R injury include the nuclear factor erythroid-related factor 2 (Nrf2)-mediated signaling pathway, Wnt/β-catenin pathway, and phosphatidylinositol kinase 3 (PI3K)/Akt pathway; those that aggravate II/R injury include the Janus kinase/signal transducer and activator of transcription (JAK/STAT) pathway, Toll-like receptor (TLR) receptor-mediated signaling pathway, protein kinase CβII (PKCβII)/p66shc pathway, and microRNA (miRNA)/p66shc pathway; the effect of miRNA on related pathways and mitochondrial DNA translocation. The aforementioned pathways provide new ideas for further exploring the occurrence and development of II/R and more effective treatments for II/R injury.

Cellular Signal Transduction Pathways Involved in Acute Lung Injury Induced by Intestinal Ischemia-Reperfusion

Intestinal ischemia-reperfusion (II/R) injury is a common type of tissue and organ injury, secondary to intestinal and mesenteric vascular diseases. II/R is characterized by a high incidence rate and mortality. In the II/R process, intestinal barrier function is impaired and bacterial translocation leads to excessive reactive oxygen species, inflammatory cytokine release, and even apoptosis. A large number of inflammatory mediators and oxidative factors are released into the circulation, leading to severe systemic inflammation and multiple organ failure of the lung, liver, and kidney. Acute lung injury (ALI) is the most common complication, which gradually develops into acute respiratory distress syndrome and is the main cause of its high mortality. This review summarizes the signal transduction pathways and key molecules in the pathophysiological process of ALI induced by II/R injury and provides a new therapeutic basis for further exploration of the molecular mechanisms of ALI induced by II/R injury. In particular, this article will focus on the biomarkers involved in II/R-induced ALI.

circ-PRKCB acts as a ceRNA to regulate p66Shc-mediated oxidative stress in intestinal ischemia/reperfusion

Background: Oxidative stress has emerged as an essential factor in the pathogenesis of intestinal ischemia/reperfusion (I/R) injury. The adaptor protein p66Shc is a key regulator of reactive oxygen species (ROS) generation and a mediator of I/R damage in the intestine, but the upstream mechanisms that directly regulate p66Shc expression during intestinal I/R remain largely unknown. Recent studies have suggested that noncoding RNAs, such as circular RNAs (circRNAs), are important players in physiological and pathological processes based on their versatile regulatory roles in gene expression. The aim of this study was to elucidate the contribution of p66Shc to oxidative damage in intestinal I/R and to investigate the regulation of p66Shc by circRNA sponges.

Methods: Intestinal I/R was induced in mice via superior mesenteric artery (SMA) occlusion. A miR-339-5p agomir or circ-protein kinase C beta (PRKCB) siRNA was injected intravenously before I/R challenge. In addition, Caco-2 cells were subjected to hypoxia/reoxygenation (H/R) in vitro to simulate an in vivo I/R model.

Results:In vitro, p66Shc deficiency significantly reduced H/R-induced ROS overproduction by attenuating mitochondrial superoxide anion (O₂^-) levels, suppressing NADPH oxidase activity and enhancing antioxidant enzyme expression. Moreover, miR-339-5p was identified to directly regulate p66Shc expression in the intestine. Furthermore, we found that a circRNA transcribed from the PRKCB gene, named circ-PRKCB, acted as an endogenous miR-339-5p sponge to regulate p66Shc expression. circ-PRKCB silencing or miR-339-5p overexpression significantly downregulated p66Shc expression and attenuated oxidative stress levels and I/R injury in vivo and in vitro. Notably, the increased circ-PRKCB levels and decreased miR-339-5p levels associated with murine intestinal I/R were consistent with those in patients with intestinal infarction.

Conclusions: Our findings reveal a crucial role for the circ-PRKCB/miR-339-5p/p66Shc signaling pathway in regulating oxidative stress in the I/R intestine. This pathway may be a potential therapeutic target for intestinal I/R injury.

The Inhibition of Protein Kinase C β Contributes to the Pathogenesis of Preeclampsia by Activating Autophagy

Background

Preeclampsia is a devastating hypertensive disorder of pregnancy with unknown mechanism. Recent studies have considered abnormal autophagy as a new cellular mechanism for this disorder, while little is known about how autophagy is specifically involved and what factors are implicated. Here, we report a previously unrecognized preeclampsia-associated autophagic regulator, PKCβ, that is involved in placental angiogenesis.

Methods

PKCβ levels were evaluated by quantitative real-time PCR, western blotting, immunofluorescence and by the analysis of public data. The autophagy-regulating role of PKCβ inhibition in preeclampsia pathogenesis was studied in a mouse model, and in human umbilical vein endothelial cells (HUVECs) and human choriocarcinoma cells (JEG-3).

Findings

PKCβ was significantly downregulated in human preeclamptic placentas. In a mouse model, the selective inhibition of PKCβ by Ruboxistaurin was sufficient to induce preeclampsia-like symptoms, accompanied by excessive autophagic flux and a disruption in the balance of pro- and anti-angiogenic factors in mouse placentas. In contrast, autophagic inhibition by 3-methyladenine partially normalized hypertension, proteinuria and placental angiogenic imbalance in PKCβ-inhibited mice. Our in vitro experiments demonstrated that PKCβ inhibition activated autophagy, thus blocking VEGFA-induced HUVEC tube formation and resulting in the significant upregulation of sFLT1 and downregulation of VEGFA in JEG-3 cells.

Interpretation

These data support a novel model in which autophagic activation due to PKCβ inhibition leads to the impairment of angiogenesis and eventually results in preeclampsia.

Funding

Shanghai Key Program of Clinical Science and Technology Innovation, National Natural Science Foundation of China and Shanghai Medical Center of Key Programs for Female Reproductive Diseases.

Diurnal oscillations of endogenous H2O2 sustained by p66Shc regulate circadian clocks

Redox balance, an essential feature of healthy physiological steady states, is regulated by circadian clocks, but whether or how endogenous redox signalling conversely regulates clockworks in mammals remains unknown. Here, we report circadian rhythms in the levels of endogenous H₂O₂ in mammalian cells and mouse livers. Using an unbiased method to screen for H₂O₂-sensitive transcription factors, we discovered that rhythmic redox control of CLOCK directly by endogenous H₂O₂ oscillations is required for proper intracellular clock function. Importantly, perturbations in the rhythm of H₂O₂ levels induced by the loss of p66^Shc, which oscillates rhythmically in the liver and suprachiasmatic nucleus (SCN) of mice, disturb the rhythmic redox control of CLOCK function, reprogram hepatic transcriptome oscillations, lengthen the circadian period in mice and modulate light-induced clock resetting. Our findings suggest that redox signalling rhythms are intrinsically coupled to the circadian system through reversible oxidative modification of CLOCK and constitute essential mechanistic timekeeping components in mammals.

Epicatechin Gallate Protects HBMVECs from Ischemia/Reperfusion Injury through Ameliorating Apoptosis and Autophagy and Promoting Neovascularization

Green tea is one of the most beverages with antioxidants and nutrients. As one of the major components of green tea, (-)-epicatechin gallate (ECG) was evaluated for its antioxidative properties in the present study. Cell proliferation assay, tube formation, cell migration, apoptosis, and autophagy were performed in human brain microvascular endothelial cells (HBMVECs) after oxygen-glucose deprivation/reoxygenation (OGD/R) to investigate potential anti-ischemia/reperfusion injury properties of ECG in vitro. Markers of oxidative stress as ROS, LDH, MDA, and SOD were further assayed in our study. Data indicated that ECG could affect neovascularization and promote cell proliferation, tube formation, and cell migration while inhibiting apoptosis and autophagy through affecting VEGF, Bcl-2, BAX, LC3B, caspase 3, mTOR, and Beclin-1 expression. All the data suggested that ECG may be protective for the brain against ischemia/reperfusion injury by promoting neovascularization, alleviating apoptosis and autophagy, and promoting cell proliferation in HBMVECs of OGD/R.

Carvedilol alleviates diabetic cardiomyopathy in diabetic rats

Diabetic cardiomyopathy (DCM) is characterized by structural and functional changes in the myocardium. Several studies have revealed that myocardial apoptosis and fibrosis occur during DCM. Studies have also indicated that oxidative stress may be a major factor associated with the development of DCM. Protein kinase C (PKC)β₂ has been demonstrated to be activated in diabetic rats, and overexpression of PKCβ₂ in the myocardium may result in cardiac hypertrophy and fibrosis. The P66^shc adaptor protein, which is mediated by PKCβ, serves an important role in apoptosis during oxidative stress. The aim of the present study was to investigate whether the PKCβ₂/P66^shc oxidative stress pathway is associated with DCM, and to investigate the role and mechanisms of carvedilol in preserving cardiac function. Experimental diabetic rat models were induced by streptozotocin treatment accompanied by high energy intake. Carvedilol was orally administrated at a dose of 1 or 10 mg/kg/day. Cardiac function was evaluated by serum N-terminal pro-B-type natriuretic peptide level and cardiac ultrasound. Myocardial inflammation, oxidative stress, apoptosis and fibrosis were assessed by histopathological and echocardiographic analyses and tests for oxidative markers. Associated proteins and factors were examined by immunohistochemical and western blot analyses. Rats in the diabetes mellitus group exhibited significantly decreased systolic cardiac function along with elevated expression levels of phosphorylated (p)-PKCβ₂, phos-P66^shc, caspase-3, malondialdehyde, collagen type I, tumor necrosis factor-α and interleukin-1β, which were accompanied by disorder in metabolic processes. Treatment with carvedilol reversed these changes. Thus, the present results suggest that the PKCβ₂/P66^shc signaling pathway may be associated with diabetic cardiomyopathy; furthermore, carvedilol, as a novel β-receptor blocker, may protect the myocardium from injury by suppressing the myocardial inflammatory response, fibrosis, P66^shc-mediated oxidative stress and subsequent apoptosis in myocardial tissue. Consequently, carvedilol may have potential as a therapy for the treatment of DCM.

PKCβII-induced upregulation of PGP9.5 and VEGF in postoperative persistent pain in rats

Purpose

Postoperative pain is a common clinical problem. In this study, we aimed to investigate the role of protein kinase C βII (PKCβII) in the progression of postoperative pain following skin/muscle incision and retraction (SMIR) surgery.

Materials and methods

SMIR postoperative pain model was established in rats, akin to a clinical procedure. The expression level and location of p-PKCβII were observed in dorsal root ganglion (DRG) or spinal cord from SMIR-operated rats by Western blotting and immunofluorescence. In addition, the effects of PKCβII on the expression of protein gene product 9.5 (PGP9.5) or vascular endothelial growth factor (VEGF) were assessed by using pharmacological activator and inhibitor of PKCβII. Moreover, mechanical withdrawal threshold (MWT) was assessed before or after SMIR-operated rats were treated with inhibitor or activator of PKCβII.

Results

The expression of PKCβII in DRG and spinal cord was significantly increased after SMIR surgery (P < 0.001, P < 0.01) and expression of PKCβII was located in the neurons of the spinal cord, and magnocellular neurons, non-peptide neurons, and peptide neurons in DRG. Besides, compared with skin/muscle incision group, retraction caused a marked increase in the expression of PKCβII and a significant decrease of MWT (P < 0.001, P < 0.05). The activator of PKCβII greatly increased the expression of PGP9.5 and VEGF (P < 0.05, P < 0.01) and enhanced MWT (P < 0.001), while inhibitor of PKCβII decreased the expression of PGP9.5 and VEGF and attenuated MWT (P < 0.05, P < 0.01, P < 0.001).

Conclusion

Activation of PKCβII signaling pathways might be an important mechanism in the progression of postoperative pain.

MicroRNA-378 protects against intestinal ischemia/reperfusion injury via a mechanism involving the inhibition of intestinal mucosal cell apoptosis

Intestinal ischemia/reperfusion (I/R) injury remains a major clinical event and contributes to high morbidity and mortality rates, but the underlying mechanisms remain elusive. Recent studies have demonstrated that microRNAs (miRNAs) have important roles in organ I/R injury, but the changes and potential roles of miRNAs in intestinal I/R-induced intestinal injury are unclear. This study was designed to analyze the miRNA expression profiles in intestinal mucosa after I/R injury and to explore the role of target miRNA during this process. Using miRNA microarray analysis, we found changes of 19 miRNAs from the expression profile of miRNAs in a mouse model of intestinal I/R and further verified them by RT-qPCR. Here, we report that miR-378 is one of the markedly decreased miRNAs and found the putative target mRNA that is linked to cell death after applying the TargetScan, miRanda, CLIP-Seq and miRDB prediction algorithms. Our results show that the overexpression of miR-378 significantly ameliorated intestinal tissue damage in wild-type and transgenic mice and oxygen glucose deprivation/reperfusion-challenged IEC-6 cell injury. Moreover, miR-378 overexpression reduced intestinal epithelial cell apoptosis in both in vivo and in vitro ischemic models and attenuated cleaved caspase-3 expression. Collectively, our results revealed that the suppression of caspase-3 activation by miRNA-378 overexpression may be involved in the protective effects of intestinal ischemic damage. MiRNA-378 may serve as a key regulator and therapeutic target in intestinal I/R injury.

PKCζ phosphorylates TRAF2 to protect against intestinal ischemia-reperfusion-induced injury

Intestinal ischemia-reperfusion (I/R) is a common clinical problem that occurs during various clinical pathological processes. Excessive apoptosis has an indispensable role in intestinal I/R injury. Tumor necrosis factor receptor-associated factor 2 (TRAF2) and PKCζ have an essential role in apoptosis. Here, we aimed to investigate the effects of PKCζ and TRAF2 and to explore the correlation between PKCζ and TRAF2 in intestinal I/R injury. Mice were subjected to intestinal I/R injury in vivo. In vitro experiments were conducted by treating Caco-2 cells with hypoxia/reoxygenation (H/R) stimulation to simulate intestinal I/R. Intestinal tissue samples and Caco-2 cells were examined using various approaches. Intestinal I/R induced the membrane translocation and phosphorylation of PKCζ. Pretreatment with the PKCζ activator phosphatidylcholine remarkably attenuated gut injury by suppressing apoptosis. H/R induced PKCζ to combine with TRAF2, which was phosphorylated by PKCζ at Ser⁵⁵, but not at Ser¹¹, under intestinal I/R or H/R conditions. In addition, TRAF2 Ser⁵⁵ phosphorylation increased cell survival by inhibiting cell apoptosis in the H/R model. Mechanistically, TRAF2 Ser⁵⁵ phosphorylation promoted NF-κB activation but suppressed c-Jun activation in Caco-2 cells under H/R conditions. The results of this study demonstrate that the PKCζ/TRAF2 pathway represents a novel protective mechanism against intestinal I/R injury. Therefore, the PKCζ/TRAF2 pathway is a novel target for potential treatments of intestinal I/R injury-related diseases.

Protein kinase C beta II upregulates intercellular adhesion molecule-1 via mitochondrial activation in cultured endothelial cells

Activation of protein kinase C (PKC) is closely linked with endothelial dysfunction. However, the effect of PKCβII on endothelial dysfunction has not been characterized in cultured endothelial cells. Here, using adenoviral PKCβII gene transfer and pharmacological inhibitors, the role of PKCβII on endothelial dysfucntion was investigated in cultured endothelial cells. Phorbol 12-myristate 13-acetate (PMA) increased reactive oxygen species (ROS), p66shc phosphorylation, intracellular adhesion molecule-1, and monocyte adhesion, which were inhibited by PKCβi (10 nM), a selective inhibitor of PKCβII. PMA increased the phosphorylation of CREB and manganese superoxide dismutase (MnSOD), which were also inhibited by PKCβi. Gene silencing of CREB inhibited PMA-induced MnSOD expression, suggesting that CREB plays a key role in MnSOD expression. Gene silencing of PKCβII inhibited PMA-induced mitochondrial ROS, MnSOD, and ICAM-1 expression. In contrast, overexpression of PKCβII using adenoviral PKCβII increased mitochondrial ROS, MnSOD, ICAM-1, and p66shc phosphorylation in cultured endothelial cells. Finally, PKCβII-induced ICAM-1 expression was inhibited by Mito-TEMPO, a mitochondrial ROS scavenger, suggesting the involvement of mitochondrial ROS in PKC-induced vascular inflammation. Taken together, the results suggest that PKCβII plays an important role in PMA-induced endothelial dysfunction, and that the inhibition of PKCβII-dependent p66shc signaling acts as a therapeutic target for vascular inflammatory diseases.

Inhibition of p66Shc-mediated mitochondrial apoptosis via targeting prolyl-isomerase Pin1 attenuates intestinal ischemia/reperfusion injury in rats

Intestinal epithelial oxidative stress and apoptosis constitute key pathogenic mechanisms underlying intestinal ischemia/reperfusion (I/R) injury. We previously reported that the adaptor 66 kDa isoform of the adaptor molecule ShcA (p66Shc)-mediated pro-apoptotic pathway was activated after intestinal I/R. However, the upstream regulators of the p66Shc pathway involved in intestinal I/R remain to be fully identified. Here, we focused on the role of a prolyl-isomerase, peptidyl–prolyl cis–trans isomerase (Pin1), in the regulation of p66Shc activity during intestinal I/R. Intestinal I/R was induced in rats by superior mesenteric artery (SMA) occlusion. Juglone (Pin1 inhibitor) or vehicle was injected intraperitoneally before I/R challenge. Caco-2 cells were exposed to hypoxia/reoxygenation (H/R) in vitro to simulate an in vivo I/R model. We found that p66Shc was significantly up-regulated in the I/R intestine and that this up-regulation resulted in the accumulation of intestinal mitochondrial reactive oxygen species (ROS) and massive epithelial apoptosis. Moreover, intestinal I/R resulted in elevated protein expression and enzyme activity of Pin1 as well as increased interaction between Pin1 and p66Shc. This Pin1 activation was responsible for the translocation of p66Shc to the mitochondria during intestinal I/R, as Pin1 suppression by juglone or siRNA markedly blunted p66Shc mitochondrial translocation and the subsequent ROS generation and cellular apoptosis. Additionally, Pin1 inhibition alleviated gut damage and secondary lung injury, leading to improvement of survival after I/R. Collectively, our findings demonstrate for the first time that Pin1 inhibition protects against intestinal I/R injury, which could be partially attributed to the p66Shc-mediated mitochondrial apoptosis pathway. This may represent a novel prophylactic target for intestinal I/R injury.

SIRTUIN 1 ACTIVATOR SRT1720 PROTECTS AGAINST ORGAN INJURY INDUCED BY INTESTINAL ISCHEMIA-REPERFUSION

Intestinal ischemia-reperfusion (I/R) occurs in various clinical situations and causes local and remote organ injury, especially in the lungs, leading to significant morbidity and mortality. The maintenance of mitochondrial biogenesis is essential for cell survival and is regulated in part by sirtuin 1 (SIRT1), an energy-sensing enzyme. We hypothesized that SIRT1 activation with SRT1720 would reduce local and remote organ injury after intestinal I/R. Intestinal I/R was induced by the occlusion of the superior mesenteric artery of adult male C57BL/6 mice for 45 min, followed by reperfusion for 4 h. SRT1720 or vehicle was injected intravenously at the time of reperfusion. Blood, small intestine, and lung tissues were collected for analysis. The SRT1720 treatment of I/R mice resulted in a 57% increase in protein levels of succinate dehydrogenase, an index of mitochondrial mass, and a 120% increase in messenger RNA levels of mitochondrial transcription factor A, a marker for mitochondrial biogenesis. The microscopic architecture and apoptosis of the gut tissue was improved in the SRT1720-treated I/R mice. SRT1720 decreased intestinal messenger RNA levels of tumor necrosis factor-α by 60% and inducible nitric oxide synthase to baseline after I/R. Systemic inflammation, as determined by serum interleukin-6, was reduced in treated mice. Lung injury, as measured by histological architecture and myeloperoxidase activity, and lung apoptosis were also improved after the SRT1720 treatment. SRT1720 preserved mitochondrial biogenesis and mass, leading to inhibition of inflammation and oxidative stress, thereby protecting against intestinal I/R-induced injury. Thus, the SIRT1-mediated pathway is a promising target for the treatment of intestinal I/R injury.

miR-34a-5p Inhibition Alleviates Intestinal Ischemia/Reperfusion-Induced Reactive Oxygen Species Accumulation and Apoptosis via Activation of SIRT1 Signaling

AIMS

Reactive oxygen species (ROS) generation and massive epithelial apoptosis are critical in the pathogenesis of intestinal ischemia/reperfusion (I/R) injury. We previously found that the Sirtuin 1 (SIRT1)-mediated antioxidant pathway was impaired in the intestine after I/R. Here, we investigate the potential role of SIRT1-targeting microRNAs (miRNAs) in regulating ROS accumulation and apoptosis in intestinal I/R, and the important role SIRT1 involved in.

RESULTS

C57BL/6 mice were subjected to intestinal I/R induced by occlusion of the superior mesenteric artery followed by reperfusion. Caco-2 cells were incubated under hypoxia/reoxygenation condition to mimic I/R in vivo. We find that SIRT1 is gradually repressed during the early reperfusion, and that this repression results in intestinal ROS accumulation and apoptosis. Using bioinformatics analysis and real-time PCR, we demonstrate that miR-34a-5p and miR-495-3p are significantly increased among the 41 putative miRNAs that can target SIRT1. Inhibition of miR-34a-5p, but not miR-495-3p, attenuates intestinal I/R injury, as demonstrated by repressing p66shc upregulation, manganese superoxide dismutase repression, and the caspase-3 activation in vitro and in vivo; it further alleviates systemic injury, as demonstrated by reducing inflammatory cytokine release, attenuating lung and liver lesions, and improving survival. Interestingly, SIRT1 plays an indispensable role in the protection afforded by miR-34a-5p inhibition.

INNOVATION

This study provides the first evidence of miRNAs in regulating oxidative stress and apoptosis in intestinal I/R.

CONCLUSION

miR-34a-5p knockdown attenuates intestinal I/R injury through promoting SIRT1-mediated suppression of epithelial ROS accumulation and apoptosis. This may represent a novel prophylactic approach to intestinal I/R injury. Antioxid. Redox Signal. 24, 961-973.

SLA-PGN-primed dendritic cell-based vaccination induces Th17-mediated protective immunity against experimental visceral leishmaniasis: a crucial role of PKCβ

Emergence of drug resistance during visceral leishmaniasis (VL) is a major obstacle imposed during successful therapy. An effective vaccine strategy against this disease is therefore necessary. Our present study exploited the SLA (soluble leishmanial antigen) and PGN (peptidoglycan) stimulated bone marrow-derived dendritic cells (DCs) as a suitable vaccine candidate during experimental VL. SLA-PGN-stimulated DCs showed a significant decrease in hepatic and splenic parasite burden, which were associated with increased production of nitric oxide and pro-inflammatory cytokines such as IL-12, IFN-γ and IL-17. Elevated level of IL-17 was accompanied with the generation of more Th17 cells. Further studies on DC provided the evidence that these SLA-PGN-stimulated DCs played an important role in providing necessary cytokines such as IL-6, IL-23 and TGF-β for the generation of Th17 cells. Interestingly, inhibition of protein kinase C-β (PKCβ) in DCs led to decreased production of Th17 polarizing cytokines, causing reduction of the Th17 population size. Altogether, our finding highlighted the important role of DC-based PKCβ in regulation of the function and generation of Th17 cells.

MicroRNA-682-mediated downregulation of PTEN in intestinal epithelial cells ameliorates intestinal ischemia-reperfusion injury

Intestinal ischemia–reperfusion (I/R) injury causes inflammation and tissue damage and contributes to high morbidity and mortality, but the underlying mechanism remains elusive and effective therapies are still lacking. We report here a critical role of the microRNA 682 (miR-682) as a key regulator and therapeutic target in intestinal I/R injury. MiR-682 was markedly induced in intestinal epithelial cells (IECs) during intestinal ischemia in mice and in the human colonic epithelial cells during hypoxia, but was undetected rapidly after intestinal reperfusion in IEC of mice. MiR-682 induction during hypoxia was modulated by hypoxia-inducible factor-1α (HIF-1α). On lentivirus-mediated miR-682 overexpression in vivo during intestinal reperfusion or miR-682 mimic transfection in vitro during hypoxia, miR-682 decreased the expression of phosphatase and tensin homolog (PTEN) and subsequently activated nuclear translocation of nuclear factor kappa B (NF-κB) p65. Consequently, NF-κB activation by miR-682-mediated PTEN downregulation prevented reactive oxygen species (ROS) induction, inflammatory reaction, mitochondrial-mediated apoptosis and IEC apoptosis. The effect of miR-682-mediated PTEN/NF-κB pathway on IECs resulted in protection against intestinal I/R injury in mice. However, NF-κB chemical inhibitor reversed miR-682-mediated decreased PTEN expression, ROS induction, inflammation and IEC apoptosis. Collectively, these results identify a novel miR-682/PTEN/NF-κBp65 signaling pathway in IEC injury induced by I/R that could be targeted for therapy.

17β-Estradiol Abrogates Apoptosis Inhibiting PKCδ, JNK, and p66Shc Activation in C2C12 Cells

17β-Estradiol (E2) protects several non-reproductive tissues from apoptosis, including skeletal muscle. Previously, we showed that E2 at physiological concentrations prevented apoptosis induced by H2O2 in skeletal myoblasts. As we have also demonstrated a clear beneficial action of this hormone on skeletal muscle mitochondria, the present work further characterizes the signaling mechanisms modulated by E2 that are involved in mitochondria protection, which ultimately result in antiapoptosis. Here, we report that E2 through estrogen receptors (ERs) inhibited the H2O2-induced PKCδ and JNK activation, which results in the inhibition of phosphorylation and translocation to mitochondria of the adaptor protein p66Shc. In conjunction, the inhibition by the hormone of this H2O2-triggered signaling pathway results in protection of mitochondrial potential membrane. Our results provide basis for a putative mechanism by which E2 exerts beneficial effects on mitochondria, against oxidative stress, in skeletal muscle cells.

Inhibition of PKCβ2 overexpression ameliorates myocardial ischaemia/reperfusion injury in diabetic rats via restoring caveolin-3/Akt signaling

Activation of PKCβ (protein kinase Cβ) plays a critical role in myocardial I/R (ischaemia/reperfusion) injury in non-diabetic rodents. In the myocardium of diabetes, PKCβ2 overexpression is associated with increased vulnerability to post-ischaemic I/R injury with concomitantly impaired cardiomyocyte Cav (caveolin)-3 and Akt signalling compared with non-diabetic rats. We hypothesized that myocardial PKCβ overexpression in diabetes exacerbates myocardial I/R injury through impairing Cav-3/Akt signalling. Streptozotocin-induced diabetic rats were treated with the selective PKCβ inhibitor ruboxistaurin (RBX, 1 mg/kg per day) for 4 weeks, starting from 1 week after diabetes induction, before inducing myocardial I/R achieved by occluding the left descending coronary artery followed by reperfusion. Cardiac function was measured using a pressure-volume conductance system. In an in vitro study, cardiac H9C2 cells were exposed to high glucose (30 mmol/l) and subjected to hypoxia followed by reoxygenation (H/R) in the presence or absence of the selective PKCβ2 inhibitor CGP53353 (1 μmol/l), siRNAs of PKCβ2 or Cav-3 or Akt. Cell apoptosis and mitochondrial membrane potential were assessed by TUNEL (terminal deoxynucleotidyltransferase-mediated dUTP nick-end labelling) and JC-1 staining respectively. RBX significantly decreased post-ischaemic myocardial infarct size (35±5% compared with 49±3% in control, P<0.05) and attenuated cardiac dysfunction, and prevented the reduction in cardiac Cav-3 and enhanced phosphorylated/activated Akt (p-Akt) in diabetic rats (P<0.05). H/R increased cardiomyocyte injury under high glucose conditions as was evident by increased TUNEL-positive and increased JC-1 monomeric cells (P<0.05 compared with control), accompanied with increased PKCβ2 phosphorylation/activation and decreased Cav-3 expression. Either CGP53353 or PKCβ2 siRNA significantly attenuated all of these changes and enhanced p-Akt. Cav-3 gene knockdown significantly reduced p-Akt and increased post-hypoxic cellular and mitochondrial injury despite a concomitant reduction in PKCβ2 phosphorylation. PKCβ2 inhibition with RBX protects diabetic hearts from myocardial I/R injury through Cav-3-dependent activation of Akt.

Blockade of PKCβ protects against remote organ injury induced by intestinal ischemia and reperfusion via a p66shc-mediated mitochondrial apoptotic pathway

Intestinal ischemia-reperfusion (I/R) is a serious clinical dilemma with high morbidity and mortality. Remote organ damage, especially acute lung injury and liver injury are common complications that contribute to the high mortality rate. We previously demonstrated that activation of PKCβII is specifically involved in the primary injury of intestinal I/R. Considering the tissue-specific features of PKC activation, we hypothesized that some kind of PKC isoform may play important roles in the progression of secondary injury in the remote organ. Mice were studied in in vivo model of intestinal I/R. The activation of PKC isoforms were screened in the lung and liver. Interestingly, we found that PKCβII was also activated exclusively in the lung and liver after intestinal I/R. PKCβII suppression by a specific inhibitor, LY333531, significantly attenuated I/R-induced histologic damage, inflammatory cell infiltration, oxidative stress, and apoptosis in these organs, and also alleviated systemic inflammation. In addition, LY333531 markedly restrained p66shc activation, mitochondrial translocation, and binding to cytochrome-c. These resulted in the decrease of cytochrome-c release and caspase-3 cleavage, and an increase in glutathione and glutathione peroxidase. These data indicated that activated PKC isoform in the remote organ, specifically PKCβII, is the same as that in the intestine after intestinal I/R. PKCβII suppression protects against remote organ injury, which may be partially attributed to the p66shc-cytochrome-c axis. Combined with our previous study, the development of a specific inhibitor for prophylaxis against intestinal I/R is promising, to prevent multiple organ injury.

MicroRNA-424 protects against focal cerebral ischemia and reperfusion injury in mice by suppressing oxidative stress

BACKGROUND AND PURPOSE

We previously showed that the microRNA miR-424 protects against permanent cerebral ischemic injury in mice by suppressing microglia activation. This study investigated the role of miR-424 in transient cerebral ischemia in mice with a focus on oxidative stress-induced neuronal injury.

METHODS

Transient cerebral ischemia was induced in C57/BL6 mice by middle cerebral artery occlusion for 1 hour followed by reperfusion (ischemia/reperfusion). The miR-424 level in the peri-infarct cortex was quantified. Mice were also administered miR-424 angomir by intracerebroventricular injection. Cerebral infarct volume, neuronal apoptosis, and levels of oxidative stress markers and antioxidants were evaluated. In an in vitro experiment, primary cortical neurons were exposed to H2O2 and treated with miR-424 angomir, nuclear factor erythroid 2-related factor 2 siRNA, and superoxide dismutase (SOD) inhibitor; cell activity, lactate dehydrogenase release, malondialdehyde level, and manganese (Mn)SOD activity were then evaluated.

RESULTS

MiR-424 levels in the peri-infarct cortex increased at 1 and 4 hours then decreased 24 hours after reperfusion. Treatment with miR-424 decreased infarct volume and inhibited neuronal apoptosis after ischemia/reperfusion, reduced reactive oxygen species and malondialdehyde levels in the cortex, and increased the expression and activation of MnSOD as well as the expression of extracellular SOD and the redox-sensitive transcription factor nuclear factor erythroid 2-related factor. In neuronal cultures, miR-424 treatment abrogated H2O2-induced injury, as evidenced by decreased lactate dehydrogenase leakage and malondialdehyde level and increased cell viability and MnSOD activity; the protective effects of miR-424 against oxidative stress were reversed by nuclear factor erythroid 2-related factor knockdown and SOD inhibitor treatment.

CONCLUSIONS

MiR-424 protects against transient cerebral ischemia/reperfusion injury by inhibiting oxidative stress.

PKCδ promotes high glucose induced renal tubular oxidative damage via regulating activation and translocation of p66Shc

Diabetic kidney disease (DKD) is a leading cause of end-stage renal disease (ESRD). Renal tubular injury by overproduction of ROS in mitochondria plays a critical role in the pathogenesis of DKD. Evidences have shown that p66Shc was involved in renal tubular injury via mitochondrial-dependent ROS production pathway, but little is known about the upstream signaling of p66Shc that leads to tubular oxidative damage under high glucose conditions. In this study, an increased PKCδ and p66Shc activation and ROS production in renal tissues of patients with diabetic nephropathy were seen and further analysis revealed a positive correlation between the tubulointerstitial damage and p-PKCδ, p-p66Shc, and ROS production. In vitro, we investigated the phosphorylation and activation of p66Shc and PKCδ during treatment of HK-2 cells with high glucose (HG). Results showed that the activation of p66Shc and PKCδ was increased in a dose- and time-dependent manner, and this effect was suppressed by Rottlerin, a pharmacologic inhibitor of PKCδ. Moreover, PKCδ siRNA partially blocked HG-induced p66Shc phosphorylation, translocation, and ROS production in HK-2 cells. Taken together, these data suggest that activation of PKCδ promotes tubular cell injury through regulating p66Shc phosphorylation and mitochondrial translocation in HG ambient.