Modulation of the JAK/ERK/STAT signaling in melanocortin-induced inhibition of local and systemic responses to myocardial ischemia/reperfusion

Notoginsenoside R1 protects against myocardial ischemia/reperfusion injury in mice via suppressing TAK1-JNK/p38 signaling

Previous studies show that notoginsenoside R1 (NG-R1), a novel saponin isolated from Panax notoginseng, protects kidney, intestine, lung, brain and heart from ischemia-reperfusion injury. In this study we investigated the cardioprotective mechanisms of NG-R1 in myocardial ischemia/reperfusion (MI/R) injury in vivo and in vitro. MI/R injury was induced in mice by occluding the left anterior descending coronary artery for 30 min followed by 4 h reperfusion. The mice were treated with NG-R1 (25 mg/kg, i.p.) every 2 h for 3 times starting 30 min prior to ischemic surgery. We showed that NG-R1 administration significantly decreased the myocardial infarction area, alleviated myocardial cell damage and improved cardiac function in MI/R mice. In murine neonatal cardiomyocytes (CMs) subjected to hypoxia/reoxygenation (H/R) in vitro, pretreatment with NG-R1 (25 μM) significantly inhibited apoptosis. We revealed that NG-R1 suppressed the phosphorylation of transforming growth factor β-activated protein kinase 1 (TAK1), JNK and p38 in vivo and in vitro. Pretreatment with JNK agonist anisomycin or p38 agonist P79350 partially abolished the protective effects of NG-R1 in vivo and in vitro. Knockdown of TAK1 greatly ameliorated H/R-induced apoptosis of CMs, and NG-R1 pretreatment did not provide further protection in TAK1-silenced CMs under H/R injury. Overexpression of TAK1 abolished the anti-apoptotic effect of NG-R1 and diminished the inhibition of NG-R1 on JNK/p38 signaling in MI/R mice as well as in H/R-treated CMs. Collectively, NG-R1 alleviates MI/R injury by suppressing the activity of TAK1, subsequently inhibiting JNK/p38 signaling and attenuating cardiomyocyte apoptosis.

Melanocortin receptor agonist NDP-α-MSH improves cognitive deficits and microgliosis but not amyloidosis in advanced stages of AD progression in 5XFAD and 3xTg mice

Introduction

Alzheimer's disease (AD) is the most frequent cause of dementia and still lacks effective therapy. Clinical signs of AD include low levels of endogenous melanocortins (MCs) and previous studies have shown that treatment with MC analogs induces neuroprotection in the early stages of AD.

Methods

We investigated the neuroprotective role of MCs in two transgenic mouse models of severe AD using 5 and 7 month-old (mo) 5XFAD mice and 9 and 12 mo 3xTg mice. These mice were subjected to a chronic stimulation of MC receptors (MCRs) with MC analogue Nle4-D-Phe7-α-melanocyte stimulating hormone (NDP-α-MSH, 340 μg/kg, i.p.). Mouse behavior and ex-vivo histological and biochemical analyses were performed after 50 days of treatment.

Results

Our analysis demonstrated an improvement in cognitive abilities of AD mice at late stage of AD progression. We also showed that these protective effects are associated with decreased levels of hyperphosphorylated Tau but not with Aβ burden, that was unaffected in the hippocampus and in the cortex of AD mice. In addition, an age-dependent NDP effect on glial reactivity was observed only in 3xTg mice whereas a global downregulation of p38 mitogen-activated protein kinase was selectively observed in 7 mo 5XFAD and 14 mo 3xTg mice.

Conclusion

Our results suggest that MCR stimulation by NDP-α-MSH could represent a promising therapeutic strategy in managing cognitive decline also at late stage of AD, whereas the effects on neuroinflammation may be restricted to specific stages of AD progression.

Circular RNA-DENND4C in H9c2 cells relieves OGD/R-induced injury by down regulation of microRNA-320

Ischemic heart disease (IHD) is one of the most deadly diseases worldwide. To detect the regulatory mechanism, the circular RNA (circRNA)-differentially expressed in normal cells and neoplasia domain containing 4 C (DENND4C) was explored in the H9c2 cells. The circRNA-DENND4C overexpressing plasmid, si-circRNA-DENND4C and miR-320 mimic were transfected into the H9c2 cells and treated with OGD/R stimulation. We took CCK-8 method, Annexin V-FITC/PI-flow cytometer to search for viability and apoptotic ability. With the help of qRT-PCR and western blot, the expression of circRNA-DENND4C and miR-320, as well as the Bax, Cleaved PARP/caspase 3 and signal proteins were separately determined. Regulation of circRNA-DENND4C and miR-320 was confirmed by dual-luciferase reporter assay. OGD/R induced suppression of cell viability, but enhancement of apoptosis and block of ERK and mTOR pathways. Moreover, circRNA-DENND4C was up-regulated after OGD/R stimulation and augmented OGD/R-stimulated damage while circRNA-DENND4C silencing displayed opposite influences. miR-320 was negatively controlled and targeted by the circRNA-DENND4C.The overexpressed miR-320 impeded the effects of circRNA-DENND4C. Besides, circRNA-DENND4C relieved the suppression of ERK and mTOR pathways caused by OGD/R stimulation, and all promoting impacts of circRNA-DENND4C were reversed by the miR-320 mimic. Overexpressed circRNA-DENND4C in H9c2 cells attenuated OGD/R-induced injuries by the down-regulation of miR-320 through the ERK and mTOR activation.

Leptin-derived peptides block leptin-induced proliferation by reducing expression of pro-inflammatory genes in hepatocellular carcinoma cells

The obesity-regulated gene, leptin, is essential for diet. Leptin resistance causes obesity and related diseases. Certain types of diet are able to decrease leptin resistance. However, leptin has been shown to be correlated with inflammation and stimulate proliferation of various cancers. Two synthetic leptin derivatives (mimetics), OB3 and [D-Leu-4]-OB3, show more effective than leptin in reducing obesity and diabetes in mouse models. OB3 inhibits leptin-induced proliferation in ovarian cancer cells. However, effects of these mimetics in hepatocellular carcinoma (HCC) have not been investigated. In the present study, we examined the effects of OB3 and [D-Leu-4]-OB3 on cell proliferation and gene expressions in human HCC cell cultures. In contrast to what was reported for leptin, OB3 and [D-Leu-4]-OB3 reduced cell proliferation in hepatomas. Both OB3 and [D-Leu-4]-OB3 stimulated expression of pro-apoptotic genes. Both compounds also inhibited expressions of pro-inflammatory, proliferative and metastatic genes and PD-L1 expression. In combination with leptin, OB3 inhibited leptin-induced cell proliferation and expressions of pro-inflammation-, and proliferation-related genes. Furthermore, the OB3 peptide inhibited phosphoinositide 3-kinase (PI3K) activation which is essential for leptin-induced proliferation in HCC. These results indicate that OB3 and [D-Leu-4]-OB3 may have the potential to reduce leptin-related inflammation and proliferation in HCC cells.

Interleukin-34 Regulates Th1 and Th17 Cytokine Production by Activating Multiple Signaling Pathways through CSF-1R in Chicken Cell Lines

Interleukin-34 (IL-34) is a newly recognized cytokine with functions similar to macrophage colony-stimulating factor 1. It is expressed in macrophages and fibroblasts, where it induces cytokine production; however, the mechanism of chicken IL-34 (chIL-34) signaling has not been identified to date. The aim of this study was to analyze the signal transduction pathways and specific biological functions associated with chIL-34 in chicken macrophage (HD11) and fibroblast (OU2) cell lines. We found that IL-34 is a functional ligand for the colony-stimulating factor receptor (CSF-1R) in chicken cell lines. Treatment with chIL-34 increased the expression of Th1 and Th17 cytokines through phosphorylation of tyrosine and serine residues in Janus kinase (JAK) 2, tyrosine kinase 2 (TYK2), signal transducer and activator of transcription (STAT) 1, STAT3, and Src homology 2-containing tyrosine phosphatase 2 (SHP-2), which also led to phosphorylation of NF-κB1, p-mitogen-activated protein kinase kinase kinase 7 (TAK1), MyD88, suppressor of cytokine signaling 1 (SOCS1), and extracellular signal-regulated kinase 1 and 2 (ERK1/2). Taken together, these results suggest that chIL-34 functions by binding to CSF-1R and activating the JAK/STAT, nuclear factor κ B (NF-κB), and mitogen-activated protein kinase signaling pathways; these signaling events regulate cytokine expression and suggest roles for chIL-34 in innate and adaptive immunity.

Crocin prevents platelet‑derived growth factor BB‑induced vascular smooth muscle cells proliferation and phenotypic switch

The phenotypic switch of vascular smooth muscle cells (VSMCs) is a major initiating factor for atherosclerotic cardiovascular diseases. Platelet-derived growth factor-BB (PDGF-BB) initiates a number of biological processes that contribute to VSMC proliferation and phenotypic switch. Crocin, a component of saffron, has been reported to inhibit atheromatous plaque formation. However, the effects of crocin on PDGF-BB-induced VSMC proliferation and phenotypic switch remain unclear. The aim of the present study was to investigate the role of crocin on PDGF-BB-induced VSMCs proliferation and phenotypic switch and its underlying mechanisms. Cell proliferation and markers of VSMCs phenotypic switch were measured using a Cell Counting Kit-8 assay and western blot analysis, respectively. The signaling pathways involved in the effects of crocin on VSMCs were validated by western blot analysis with or without the use of specific pathway inhibitors. Crocin significantly inhibited PDGF-BB-induced VSMCs proliferation compared with the PDGF-BB only group (P<0.05). In addition, crocin significantly abrogated the PDGF-BB-induced increase in contractile protein α-smooth muscle actin, calponin and decrease in synthetic proteins osteopontin (OPN) in a concentration dependent manner (P<0.05). In addition, crocin slowed PDGF-BB-induced Janus kinase (JAK)-signal transducer and activator of transcription 3 (STAT3) and extracellular signal-regulated kinase (ERK)/Kruppel-like factor 4 (KLF4) signaling activation in VSMCs. By applying the JAK inhibitor (AG490) and ERK1/2 inhibitor (U0126), the results suggested that the crocin inhibited PDGF-BB-induced VSMCs phenotypic switch through the JAK/STAT3 and ERK/KLF4 signaling pathways. These results suggested that crocin may effectively prevent PDGF-BB-induced VSMCs proliferation and phenotypic switch and may be a promising candidate for the therapy of atherosclerotic cardiovascular diseases.

Cigarette smoke induced urocystic epithelial mesenchymal transition via MAPK pathways

Cigarette smoke has been shown to be a major risk factor for bladder cancer. Epithelial-mesenchymal transition (EMT) is a crucial process in cancer development. The role of MAPK pathways in regulating cigarette smoke-triggered urocystic EMT remains to be elucidated. Human normal urothelial cells and BALB/c mice were used as in vitro and in vivo cigarette smoke exposure models. Exposure of human normal urothelial cells to cigarette smoke induced morphological change, enhanced migratory and invasive capacities, reduced epithelial marker expression and increased mesenchymal marker expression, along with the activation of MAPK pathways. Moreover, we revealed that ERK1/2 and p38 inhibitors, but rather JNK inhibitor, effectively attenuated cigarette smoke-induced urocystic EMT. Importantly, the regulatory function of ERK1/2 and p38 pathways in cigarette smoke-triggered urocystic EMT was further confirmed in mice exposed to CS for 12 weeks. These findings could provide new insight into the molecular mechanisms of cigarette smoke-associated bladder cancer development as well as its potential intervention.

Serum Exosomes Attenuate H2O2-Induced Apoptosis in Rat H9C2 Cardiomyocytes via ERK1/2

Exosomes are small-sized vesicles that can be released from cells into the serum. Exosomes play important roles in regulating many biological processes including cell proliferation, apoptosis, cell cycle, and metabolism. However, the roles and mechanisms of plasma exosomes in the apoptosis of rat H9C2 cardiomyocytes are largely unknown. In this study, we isolated plasma exosomes as confirmed by the marker protein CD63. Using flow cytometry and western blot analysis, we found that exosomes attenuated hydrogen peroxide (H₂O₂)-induced apoptosis and improved survival of rat H9C2 cardiomyocytes. Furthermore, the anti-apoptosis effects of serum exosomes in rat H9C2 cardiomyocytes were mediated by the activation of ERK1/2 signaling pathway. These data indicated that plasma exosomes had the protective effects against cardiomyocyte apoptosis and might be a novel therapy strategy for myocardial injury.

Silencing of HJURP induces dysregulation of cell cycle and ROS metabolism in bladder cancer cells via PPARγ-SIRT1 feedback loop

Holliday Junction Recognition Protein (HJURP) is a centromeric histone chaperone involving in de novo histone H3 variant CenH3 (CENP-A) recruitment. Our transcriptome and in vivo study revealed that HJURP is significantly upregulated in bladder cancer (BCa) tissues at both mRNA and protein levels. Knockdown of HJURP inhibited proliferation and viability of BCa cell lines revealed by CCK-8, colony formation and Ki-67-staining assays, and induced apoptosis and reactive oxygen species (ROS) production, as well as triggered cell cycle arrest at G0/G1 phase possibly via loss of CENP-A. Interestingly, in the HJURP-reduced BCa cells the levels of PPARγ and acetylated-p53 were increased, while the ratio of phosphorylated/total SIRT1 protein was decreased. Moreover, after treatment of the BCa cells using PPARγ antagonist (GW9662) and SIRT1 agonist (resveratrol, RSV) respectively, thee phenotypes of cell cycle arrest, increased ROS production and inhibited proliferation rate were all rescued. Taken together, our results suggested that HJURP might regulate proliferation and apoptosis via the PPARγ-SIRT1 negative feedback loop in BCa cells.

Cardioprotection by the transfer of coronary effluent from ischaemic preconditioned rat hearts: identification of cardioprotective humoral factors

Ischaemic preconditioning (IPC) provides myocardial resistance to ischaemia/reperfusion (I/R) injuries. The protection afforded by IPC is not limited to the target tissue but extends to remote tissues, suggesting a mechanism mediated by humoral factors. The aim of the present study was to identify the humoral factors that are responsible for the cardioprotection induced by the coronary effluent transferred from IPC to naïve hearts. Isolated rat hearts were submitted to IPC (three cycles of 5 min I/R) before 30-min global ischaemia and 60-min reperfusion. The coronary effluent (Efl_IPC) collected during IPC was fractionated by ultrafiltration in different molecular weight ranges (<3, 3-5, 5-10, 10-30, 30-50, and >50 kDa) and evaluated for cardioprotective effects by perfusion before I/R in naïve hearts. Only the <3, 5-10 and <10 kDa fractions of hydrophobic eluate reduced I/R injuries. The cardioprotective effect of the 5-10 fraction was blocked by K_ATP channel blockers and a PKC inhibitor. An Efl_IPC proteomic analysis revealed 14 cytoprotection-related proteins in 4-12 kDa peptides. HSP10 perfusion protected the heart against I/R injuries. These data provide insights into the mechanisms of cardioprotection in humoral factors released by IPC. Cardioprotection is afforded by hydrophobic peptides in the 4-12 kDa size range, which activate pathways that are dependent on PKC and K_ATP. Fourteen 4-12 kDa peptides were identified, suggesting a potential therapeutic role for these molecules in ischaemic diseases. One of these, HSP10, identified by mass spectrometry, reduced I/R injuries and may be a potential candidate as a therapeutic target.

Multiple beneficial effects of melanocortin MC4 receptor agonists in experimental neurodegenerative disorders: Therapeutic perspectives

Melanocortin peptides induce neuroprotection in acute and chronic experimental neurodegenerative conditions. Melanocortins likewise counteract systemic responses to brain injuries. Furthermore, they promote neurogenesis by activating critical signaling pathways. Melanocortin-induced long-lasting improvement in synaptic activity and neurological performance, including learning and memory, sensory-motor orientation and coordinated limb use, has been consistently observed in experimental models of acute and chronic neurodegeneration. Evidence indicates that the neuroprotective and neurogenic effects of melanocortins, as well as the protection against systemic responses to a brain injury, are mediated by brain melanocortin 4 (MC₄) receptors, through an involvement of the vagus nerve. Here we discuss the targets and mechanisms underlying the multiple beneficial effects recently observed in animal models of neurodegeneration. We comment on the potential clinical usefulness of melanocortin MC₄ receptor agonists as neuroprotective and neuroregenerative agents in ischemic stroke, subarachnoid hemorrhage, traumatic brain injury, spinal cord injury, and Alzheimer's disease.

Combined Vagal Stimulation and Limb Remote Ischemic Perconditioning Enhances Cardioprotection via an Anti-inflammatory Pathway

Various combined interventions to acquire enhanced cardioprotection are prevalent focuses of current research. This randomized experiment assessed whether combined vagal stimulation perconditioning (VSPerC) and limb remote ischemic perconditioning (LRIPerC) improved cardioprotection compared to the use of either treatment alone in an in vivo rat model of myocardial ischemia/reperfusion injury. A total of 100 male Sprague Dawley rats were randomly allocated into five groups: sham group, ischemia/reperfusion (IR) group, VSPerC group, LRIPerC group, and combined VSPerC and LRIPerC (COMPerC) group. Serum enzymatic markers, inflammatory cytokines, myocardial inflammatory cytokines, and infarct size were assessed. Infarct size decreased significantly in the COMPerC group compared to the VSPerC and LRIPerC groups. Serum intercellular adhesion molecule 1 (ICAM-1) level at 120 min of reperfusion, myocardial interleukin-1 (IL-1), ICAM-1, and tumor necrosis factor α (TNF-α) levels in the ischemic region decreased significantly in the COMPerC group compared to the VSPerC group, but myocardial IL-10 levels in the nonischemic region increased markedly in the COMPerC group. Serum TNF-α levels at 30, 60, and 120 min of reperfusion; serum IL-1, IL-6, ICAM-1, and high mobility group box-1 protein (HMGB-1) levels at 120 min of reperfusion; and myocardial IL-1, IL-6, ICAM-1, and TNF-α levels in the ischemic region decreased significantly in the COMPerC group compared to the LRIPerC group. However, myocardial IL-10 levels in both ischemic and nonischemic regions were evidently higher in the COMPerC group. This study concludes that combined VSPerC and LRIPerC enhances cardioprotection compared to either treatment alone. This result is likely attributable to a more potent regulation of inflammation.

Gypenoside attenuates renal ischemia/reperfusion injury in mice by inhibition of ERK signaling

Gynostemma pentaphyllum is a traditional Chinese medicine reported to possess a wide range of health benefits. As the major component of G. pentaphyllum, gypenoside (GP) displays various anti-inflammatory and anti-oxidant properties. However, it is unclear whether GP can protect against ischemia/reperfusion (I/R)-induced renal injury, and the underlying molecular mechanisms associated with this process remain unknown. In the present study, a renal I/R injury model in C57BL/6 mice was established. It was observed that, following I/R, serum concentrations of creatinine (Cr) and blood urea nitrogen (BUN) were significantly increased (P<0.01), indicating renal injury. Pretreatment with GP (50 mg/kg) significantly inhibited I/R-induced upregulation of serum Cr and BUN (P<0.01). Furthermore, renal malondialdehyde levels were significantly reduced in the I/R+GP group, compared with the I/R group (P<0.01), whereas renal tissue superoxide dismutase activity was significantly higher in the I/R+GP group compared with the I/R group (P<0.01). Further investigation demonstrated that pretreatment with GP produced inhibitory effects on the I/R-induced production of pro-inflammatory cytokines, including interleukin (IL)-1β, IL-6, tumor necrosis factor-α and interferon-γ (P<0.01). In addition, heme oxygenase 1 (HO-1) expression levels were significantly increased in the I/R group compared with the control (P<0.01), indicating the presence of oxidative damage. However, the I/R-induced upregulation of HO-1 was significantly attenuated by pretreatment with GP (P<0.01), which also suppressed I/R-induced apoptosis by inhibiting pro-apoptotic Bax and upregulating anti-apoptotic Bcl-2 in renal cells (P<0.01). Finally, the activity of ERK signaling was significantly increased in the I/R+GP group compared with the I/R group (P<0.05), which may be associated with the protective effect of GP against I/R-induced renal cell apoptosis. To conclude, the present results suggest that GP produces a protective effect against I/R-induced renal injury as a result of its anti-inflammatory and anti-apoptotic properties.

α-Melanocyte-stimulating hormone ameliorates ocular surface dysfunctions and lesions in a scopolamine-induced dry eye model via PKA-CREB and MEK-Erk pathways

Dry eye is a highly prevalent, chronic, and multifactorial disease that compromises quality of life and generates socioeconomic burdens. The pathogenic factors of dry eye disease (DED) include tear secretion abnormalities, tear film instability, and ocular surface inflammation. An effective intervention targeting the pathogenic factors is needed to control this disease. Here we applied α-Melanocyte-stimulating hormone (α-MSH) twice a day to the ocular surface of a scopolamine-induced dry eye rat model. The results showed that α-MSH at different doses ameliorated tear secretion, tear film stability, and corneal integrity, and corrected overexpression of proinflammatory factors, TNF-α, IL-1β, and IFN-γ, in ocular surface of the dry eye rats. Moreover, α-MSH, at 10(-4) μg/μl, maintained corneal morphology, inhibited apoptosis, and restored the number and size of conjunctival goblet cells in the dry eye rats. Mechanistically, α-MSH activated both PKA-CREB and MEK-Erk pathways in the dry eye corneas and conjunctivas; pharmacological blockade of either pathway abolished α-MSH's protective effects, suggesting that both pathways are necessary for α-MSH's protection under dry eye condition. The peliotropic protective functions and explicit signaling mechanism of α-MSH warrant translation of the α-MSH-containing eye drop into a novel and effective intervention to DED.

Melanocortin peptides: potential targets in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a systemic autoimmune disease resulting in loss of self-tolerance with multiple organs, such as the kidney, skin, joints, and the central nervous system (CNS), being targeted. Numerous immunosuppressant therapies are currently being used for the treatment of SLE, but their clinical utility is somewhat variable because of the clinical heterogeneity. Melanocortins are a family of peptides derived from the common precursor protein pro-opiomelanocortin. These multifunctional peptides activate five subtypes of melanocortin receptors expressed on immune, skin, muscle, bone, and kidney cells and cells within the CNS. Melanocortin peptides have demonstrated a variety of biologic actions including immunomodulation, melanogenesis, and renoprotection. This review aims to introduce the melanocortin system and explore the mechanisms by which they may be beneficial in diseases such as SLE.

NDP-α-MSH attenuates heart and liver responses to myocardial reperfusion via the vagus nerve and JAK/ERK/STAT signaling

Melanocortin peptides afford cardioprotection during myocardial ischemia/reperfusion via janus kinases (JAK), extracellular signal-regulated kinases (ERK) and signal transducers/activators of transcription (STAT) pathways. Here we investigated whether melanocortin-induced modulation of the JAK/ERK/STAT signaling occurs via the cholinergic anti-inflammatory pathway, focusing our study on cardiac and hepatic responses to prolonged myocardial ischemia/reperfusion. Ischemia was produced in rats by ligature of the left anterior descending coronary artery for 30min; effects of ischemia/reperfusion were evaluated using Western blot of heart and liver proteins. Intravenous treatment, during coronary artery occlusion, with the melanocortin analog (Nle(4), D-Phe(7))α-melanocyte-stimulating hormone (NDP-α-MSH) induced a left ventricle up-regulation of the cardioprotective transcription factors pJAK2, pERK1/2 and pTyr-STAT3 (JAK-dependent), and a reduction in the levels of the inflammatory mediators tumor necrosis factor-α (TNF-α) and pJNK (a transcription factor also involved in apoptosis), as assessed at the end of the 2-h reperfusion period. Further, these beneficial effects of NDP-α-MSH were associated with heart over-expression of the pro-survival proteins heme oxygenase-1 (HO-1) and Bcl-XL, and decrease of ventricular arrhythmias and infarct size. In the liver NDP-α-MSH induced a decrease in the pJAK2 and pTyr-STAT3 levels, and strongly reduced pERK1/2 expression. In the liver of ischemic rats NDP-α-MSH also blunted pJNK activity and TNF-α expression, and up-regulated Bcl-XL. Bilateral cervical vagotomy prevented all effects of NDP-α-MSH, both in the heart and liver. These results indicate that melanocortins inhibit heart and liver damage triggered by prolonged myocardial ischemia/reperfusion likely, as main mechanism, via the vagus nerve-mediated modulation of the JAK/STAT/ERK signaling pathways.

Atorvastatin protects myocardium against ischemia-reperfusion arrhythmia by increasing Connexin 43 expression: A rat model

Atorvastatin has protective effects against myocardial ischemia-reperfusion injuries and ischemia-reperfusion arrhythmia. This study was designed to investigate whether atorvastatin is able to protect against myocardial ischemia-reperfusion injury by enhancing the expression of Connexin 43 (Cx43) via the activation of the phosphatidylinositol-3-kinase (PI3K)/Akt pathway and mitochondrial ATP-sensitive potassium (K(ATP)) channels. Isolated perfused rat hearts were treated with classic ischemia postconditioning (IPOST), atorvastatin, and atorvastatin combined with inhibitor of PI3K and K(ATP) channels, respectively, after 30min of LAD ischemia and then subjected to reperfusion for 120min. The QRS duration and the ischemia-reperfusion ventricular arrhythmia were assessed. The lactate dehydrogenase (LDH) and creatine kinase isoenzyme (CK-MB) levels were measured and the Cx43 expression was assessed by immunoblotting and immunohistochemistry. After 120min of reperfusion, atorvastatin and IPOST significantly decreased the QRS duration and inhibited ventricular arrhythmia. They also decreased the levels of LDH and CK-MB. Meanwhile, atorvastatin and IPOST also significantly enhanced the Cx43 expression and the phosphorylation of Cx43. Such protective effects were abolished in the presence of the inhibitor of PI3K or the inhibitor of mitochondrial K(ATP) channels. This study suggests that atorvastatin protected against myocardial ischemia-reperfusion injury and enhanced the expression of Cx43 by activating the PI3K/Akt pathway and mitochondrial K(ATP) channels.

Recombinant Human Erythropoietin Protects Myocardial Cells from Apoptosis via the Janus-Activated Kinase 2/Signal Transducer and Activator of Transcription 5 Pathway in Rats with Epilepsy

OBJECTIVE

To investigate the potential mechanisms underlying the protective effects of recombinant human erythropoietin (rhEPO) and carbamylated EPO (CEPO) against myocardial cell apoptosis in epilepsy.

METHODS

Rats were given an intra-amygdala injection of kainic acid to induce epilepsy. Groups of rats were treated with rhEPO or CEPO before induction of epilepsy, whereas additional rats were given a caudal vein injection of AG490, a selective inhibitor of Janus kinase 2 (JAK2). At different time points after seizure onset, electroencephalogram changes were recorded, and myocardium samples were taken for the detection of myocardial cell apoptosis and expression of JAK2, signal transducer and activator of transcription 5 (STAT5), caspase-3, and bcl-xl mRNAs and proteins.

RESULTS

Induction of epilepsy significantly enhanced myocardial cell apoptosis and upregulated the expression of caspase-3 and bcl-xl proteins and JAK2 and STAT5a at both the mRNA and protein levels. Pretreatment with either rhEPO or CEPO reduced the number of apoptotic cells, upregulated bcl-xl expression, and downregulated caspase-3 expression in the myocardium of epileptic rats. Both myocardial JAK2 and STAT5a mRNAs, as well as phosphorylated species of JAK2 and STAT5a, were upregulated in epileptic rats in response to rhEPO-but not to CEPO-pretreatment. AG490 treatment increased apoptosis, upregulated caspase-3 protein expression, and downregulated bcl-xl protein expression in the myocardium of epileptic rats.

CONCLUSIONS

These results indicate that myocardial cell apoptosis may contribute to myocardial injury in epilepsy. EPO protects myocardial cells from apoptosis via the JAK2/STAT5 pathway in rats with experimental epilepsy, whereas CEPO exerts antiapoptotic activity perhaps via a pathway independent of JAK2/STAT5 signaling.

Biased agonism as a novel strategy to harness the proresolving properties of melanocortin receptors without eliciting melanogenic effects

There is a need for novel approaches to control pathologies with overexuberant inflammatory reactions. Targeting melanocortin (MC) receptors represents a promising therapy for obesity and chronic inflammation, but lack of selectivity and safety concerns limit development. A new way to increase selectivity of biological effects entails the identification of biased agonists. In this study, we characterize the small molecule AP1189 as a biased agonist at receptors MC1 and MC3. Although not provoking canonical cAMP generation, AP1189 addition to MC1 or MC3, but not empty vector, transfected HEK293 cells caused ERK1/2 phosphorylation, a signaling responsible for the proefferocytic effect evoked in mouse primary macrophages. Added to macrophage cultures, AP1189 reduced cytokine release, an effect reliant on both MC1 and MC3 as evident from the use of Mc1r(-/-) and Mc3r(-/-) macrophages. No melanogenesis was induced by AP1189 in B16-F10 melanocytes. In vivo, oral AP1189 elicited anti-inflammatory actions in peritonitis and, upon administration at the peak of inflammation, accelerated the resolution phase by ∼3-fold. Finally, given the clinical efficacy of adrenocorticotropin in joint diseases, AP1189 was tested in experimental inflammatory arthritis, where this biased agonist afforded significant reduction of macroscopic and histological parameters of joint disruption. These proof-of-concept analyses with AP1189, an active oral anti-inflammatory and resolution-promoting compound, indicate that biased agonism at MC receptors is an innovative, viable approach to yield novel anti-inflammatory molecules endowed with a more favorable safety profile.

Protective effects of the melanocortin analog NDP-α-MSH in rats undergoing cardiac arrest

We previously reported that melanocortins afford cardioprotection in conditions of experimental myocardial ischemia/reperfusion, with involvement of the janus kinases (JAK), extracellular signal-regulated kinases (ERK) and signal transducers and activators of transcription (STAT) signalings. We investigated the influence of the melanocortin analog [Nle(4), D-Phe(7)]α-melanocyte-stimulating hormone (NDP-α-MSH) on short-term detrimental responses to cardiac arrest (CA) induced in rats by intravenous (i.v.) administration of potassium chloride, followed by cardiopulmonary resuscitation (CPR) plus epinephrine treatment. In CA/CPR rats i.v. treated with epinephrine (0.1 mg/kg) and returned to spontaneous circulation (48%) we recorded low values of mean arterial pressure (MAP) and heart rate (HR), alteration of hemogasanalysis parameters, left ventricle low expression of the cardioprotective transcription factors pJAK2 and pTyr-STAT3 (JAK-dependent), increased oxidative stress, up-regulation of the inflammatory mediators tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6), and down-regulation of the anti-inflammatory cytokine IL-10, as assessed at 1h and 3h after CPR. On the other hand, i.v. treatment during CPR with epinephrine plus NDP-α-MSH (340 μg/kg) almost completely restored the basal conditions of MAP and HR, reversed metabolic acidosis, induced left ventricle up-regulation of pJAK2, pTyr-STAT3 and IL-10, attenuated oxidative stress, down-regulated TNF-α and IL-6 levels, and improved survival rate by 81%. CA/CPR plus epinephrine alone or in combination with NDP-α-MSH did not affect left ventricle pSer-STAT3 (ERK1/2-dependent) and pERK1/2 levels. These results indicate that melanocortins improve return to spontaneous circulation, reverse metabolic acidosis, and inhibit heart oxidative stress and inflammatory cascade triggered by CA/CPR, likely via activation of the JAK/STAT signaling pathway.