Role of p38 inhibition in cardiac ischemia/reperfusion injury

Stereoselective cardiotoxic effects of metconazole on zebrafish (Danio rerio) based on AGE-RAGE signalling pathway

Metconazole (MEZ) is a novel chiral triazole fungicide that is widely used to prevent and control soil-borne fungal pathogens and other fungal diseases. However, it has a long half-life in aquatic environments and thus poses potential environmental risks. This study evaluates the acute and stereoselective cardiotoxicity of MEZ in zebrafish (Danio rerio) embryos. In addition, transcriptomics, real-time quantitative PCR, enzyme activity determination, and molecular docking are performed to evaluate the molecular mechanisms underlying the cardiotoxicity of MEZ in zebrafish. MEZ decreases the heart rate while increasing the pericardial oedema rate; additionally, it induces stereoselective cardiotoxicity. 1S,5S-MEZ exhibits stronger cardiotoxicity than 1R,5R-MEZ. Furthermore, MEZ increases the expression of Ahr-associated genes and the transcription factors il6st, il1b, and AP-1. Heart development-related genes, including fbn2b, rbm24b, and tbx20 are differentially expressed. MEZ administration alters the activities of catalase, peroxidase, and glutathione-S-transferase in zebrafish larvae. Molecular docking indicates that 1R,5R-MEZ binds more strongly to the inhibitor-binding sites of p38 in the AGE-RAGE signalling pathway than to other MEZ enantiomers. Studies conducted in vivo and in silico have established the enantioselective cardiotoxicity of MEZ and its underlying mechanisms, highlighting the need to evaluate the environmental risk of chiral MEZ in aquatic organisms at the enantiomeric level.

Characterization of p38α autophosphorylation inhibitors that target the non-canonical activation pathway

p38α is a versatile protein kinase that can control numerous processes and plays important roles in the cellular responses to stress. Dysregulation of p38α signaling has been linked to several diseases including inflammation, immune disorders and cancer, suggesting that targeting p38α could be therapeutically beneficial. Over the last two decades, numerous p38α inhibitors have been developed, which showed promising effects in pre-clinical studies but results from clinical trials have been disappointing, fueling the interest in the generation of alternative mechanisms of p38α modulation. Here, we report the in silico identification of compounds that we refer to as non-canonical p38α inhibitors (NC-p38i). By combining biochemical and structural analyses, we show that NC-p38i efficiently inhibit p38α autophosphorylation but weakly affect the activity of the canonical pathway. Our results demonstrate how the structural plasticity of p38α can be leveraged to develop therapeutic opportunities targeting a subset of the functions regulated by this pathway.

Ubiquitin-specific protease 29 attenuates hepatic ischemia-reperfusion injury by mediating TGF-β-activated kinase 1 deubiquitination

Background and aims

In the course of clinical practice, hepatic ischemia/reperfusion (I/R) injury is a prevalent pathophysiological event and is caused by a combination of complex factors that involve multiple signaling pathways such as MAPK and NF-κB. USP29 is a deubiquitinating enzyme important during the development of tumors, neurological diseases, and viral immunity. However, it is unknown how USP29 contributes to hepatic I/R injury.

Methods and results

We systematically investigated the role of the USP29/TAK1-JNK/p38 signaling pathway in hepatic I/R injury. We first found reduced USP29 expression in both mouse hepatic I/R injury and the primary hepatocyte hypoxia-reoxygenation (H/R) models. We established USP29 full knockout mice (USP29-KO) and hepatocyte-specific USP29 transgenic mice (USP29-HTG), and we found that USP29 knockout significantly exacerbates the inflammatory infiltration and injury processes during hepatic I/R injury, whereas USP29 overexpression alleviates liver injury by decreasing the inflammatory response and inhibiting apoptosis. Mechanistically, RNA sequencing results showed the effects of USP29 on the MAPK pathway, and further studies revealed that USP29 interacts with TAK1 and inhibits its k63-linked polyubiquitination, thereby preventing the activation of TAK1 and its downstream signaling pathways. Consistently, 5z-7-Oxozeaneol, an inhibitor of TAK1, blocked the detrimental effects of USP29 knockout on H/R-induced hepatocyte injury, further confirming that USP29 plays a regulatory role in hepatic I/R injury by targeting TAK1.

Conclusion

Our findings imply that USP29 is a therapeutic target with promise for the management of hepatic I/R injury via TAK1-JNK/p38 pathway-dependent processes.

p38 MAPK Endogenous Inhibition Improves Neurological Deficits in Global Cerebral Ischemia/Reperfusion Mice

Cerebral ischemia/reperfusion (I/R) injury is a complex pathophysiological process that can lead to neurological function damage and the formation of cerebral infarction. The p38 MAPK pathway has attracted considerable attention in cerebral I/R injury (IRI), but little research has been carried out on its direct role in vivo. In this study, to observe the effects of p38 MAPK endogenous inhibition on cerebral IRI, p38 heterozygous knockdown (p38^KI/+) mice were used. We hypothesized that p38 signaling might be involved in I/R injury and neurological damage reduction and that neurological behavioral deficits improve when p38 MAPK is inhibited. First, we examined the neurological damage and neurological behavioral deficit effects of I/R injury in WT mice. Cerebral I/R injury was induced by the bilateral common carotid artery occlusion (BCCAO) method. The cerebral infarction area and volume were assessed and analyzed by 2,3,5-triphenyltetrazolium chloride (TTC) staining. p38 MAPK and caspase-3 were detected by western blotting. Neuronal apoptosis was measured using TUNEL staining. Neurological deficits were detected by behavioral testing. Furthermore, to assess whether these neuroprotective effects occurred when p38 MAPK was inhibited, p38 heterozygous knockdown (p38^KI/+) mice were used. We found that p38 MAPK endogenous inhibition rescued hippocampal cell apoptosis, reduced ischemic penumbra, and improved neurological behavioral deficits. These findings showed that p38 MAPK endogenous inhibition had a neuroprotective effect on IRI and that p38 MAPK may be a potential therapeutic target for cerebral IRI.

Identification of Diarylurea Inhibitors of the Cardiac-Specific Kinase TNNI3K by Designing Selectivity Against VEGFR2, p38α, and B-Raf

A series of diarylurea inhibitors of the cardiac-specific kinase TNNI3K were developed to elucidate the biological function of TNNI3K and evaluate TNNI3K as a therapeutic target for the treatment of cardiovascular diseases. Utilizing a structure-based design, enhancements in kinase selectivity were engineered into the series, capitalizing on the established X-ray crystal structures of TNNI3K, VEGFR2, p38α, and B-Raf. Our efforts culminated in the discovery of an in vivo tool compound 47 (GSK329), which exhibited desirable TNNI3K potency and rat pharmacokinetic properties as well as promising kinase selectivity against VEGFR2 (40-fold), p38α (80-fold), and B-Raf (>200-fold). Compound 47 demonstrated positive cardioprotective outcomes in a mouse model of ischemia/reperfusion cardiac injury, indicating that optimized exemplars from this series, such as 47, are favorable leads for discovering novel medicines for cardiac diseases.

Myocardial and mitochondrial effects of the anhydrase carbonic inhibitor ethoxzolamide in ischemia-reperfusion

We have previously demonstrated that inhibition of extracellularly oriented carbonic anhydrase (CA) isoforms protects the myocardium against ischemia-reperfusion injury. In this study, our aim was to assess the possible further contribution of CA intracellular isoforms examining the actions of the highly diffusible cell membrane permeant inhibitor of CA, ethoxzolamide (ETZ). Isolated rat hearts, after 20 min of stabilization, were assigned to the following groups: (1) Nonischemic control: 90 min of perfusion; (2) Ischemic control: 30 min of global ischemia and 60 min of reperfusion (R); and (3) ETZ: ETZ at a concentration of 100 μM was administered for 10 min before the onset of ischemia and then during the first 10 min of reperfusion. In additional groups, ETZ was administered in the presence of SB202190 (SB, a p38MAPK inhibitor) or chelerythrine (Chel, a protein kinase C [PKC] inhibitor). Infarct size, myocardial function, and the expression of phosphorylated forms of p38MAPK, PKCε, HSP27, and Drp1, and calcineurin Aβ content were assessed. In isolated mitochondria, the Ca2+ response, Ca2+ retention capacity, and membrane potential were measured. ETZ decreased infarct size by 60%, improved postischemic recovery of myocardial contractile and diastolic relaxation increased P-p38MAPK, P-PKCε, P-HSP27, and P-Drp1 expression, decreased calcineurin content, and normalized calcium and membrane potential parameters measured in isolated mitochondria. These effects were significantly attenuated when ETZ was administered in the presence of SB or Chel. These data show that ETZ protects the myocardium and mitochondria against ischemia-reperfusion injury through p38MAPK- and PKCε-dependent pathways and reinforces the role of CA as a possible target in the management of acute cardiac ischemic diseases.

Deficiency of myostatin protects skeletal muscle cells from ischemia reperfusion injury

Ischemia reperfusion (IR) injury plays a pivotal role in many diseases and leads to collateral damage during surgical interventions. While most studies focus on alleviating its severity in the context of brain, liver, kidney, and cardiac tissue, research as regards to skeletal muscle has not been conducted to the same extent. In the past, myostatin (MSTN), primarily known for supressing muscle growth, has been implicated in inflammatory circuits, and research provided promising results for cardiac IR injury mitigation by inhibiting MSTN cell surface receptor ACVR2B. This generated the question if interrupting MSTN signaling could temper IR injury in skeletal muscle. Examining human specimens from free myocutaneous flap transfer demonstrated increased MSTN signaling and tissue damage in terms of apoptotic activity, cell death, tissue edema, and lipid peroxidation. In subsequent in vivo Mstn^Ln/Ln IR injury models, we identified potential mechanisms linking MSTN deficiency to protective effects, among others, inhibition of p38 MAPK signaling and SERCA2a modulation. Furthermore, transcriptional profiling revealed a putative involvement of NK cells. Collectively, this work establishes a protective role of MSTN deficiency in skeletal muscle IR injury.

Post-Ischemic Treatment of Recombinant Human Secretory Leukocyte Protease Inhibitor (rhSLPI) Reduced Myocardial Ischemia/Reperfusion Injury

Myocardial ischemia/reperfusion (I/R) injury is a major cause of mortality and morbidity worldwide. Among factors contributing to I/R injury, proteolytic enzymes could also cause cellular injury, expand the injured area and induce inflammation, which then lead to cardiac dysfunction. Therefore, protease inhibition seems to provide therapeutic benefits. Previous studies showed the cardioprotective effect of secretory leukocyte protease inhibitor (SLPI) against myocardial I/R injury. However, the effect of a post-ischemic treatment with SLPI in an in vivo I/R model has never been investigated. In the present study, recombinant human (rh) SLPI (rhSLPI) was systemically injected during coronary artery occlusion or at the onset of reperfusion. The results show that post-ischemic treatment with rhSLPI could significantly reduce infarct size, Lactate Dehydrogenase (LDH) and Creatine kinase-MB (CK-MB) activity, inflammatory cytokines and protein carbonyl levels, as well as improving cardiac function. The cardioprotective effect of rhSLPI is associated with the attenuation of p38 MAPK phosphorylation, Bax, caspase-3 and -8 protein levels and enhancement of pro-survival kinase Akt and ERK1/2 phosphorylation. In summary, this is the first report showing the cardioprotective effects against myocardial I/R injury of post-ischemic treatments with rhSLPI in vivo. Thus, these results suggest that SLPI could be used as a novel therapeutic strategy to reduce myocardial I/R injury.

Inhibition of adenosine kinase attenuates myocardial ischaemia/reperfusion injury

Increased adenosine helps limit infarct size in ischaemia/reperfusion‐injured hearts. In cardiomyocytes, 90% of adenosine is catalysed by adenosine kinase (ADK) and ADK inhibition leads to higher concentrations of both intracellular adenosine and extracellular adenosine. However, the role of ADK inhibition in myocardial ischaemia/reperfusion (I/R) injury remains less obvious. We explored the role of ADK inhibition in myocardial I/R injury using mouse left anterior ligation model. To inhibit ADK, the inhibitor ABT‐702 was intraperitoneally injected or AAV9 (adeno‐associated virus)—ADK—shRNA was introduced via tail vein injection. H9c2 cells were exposed to hypoxia/reoxygenation (H/R) to elucidate the underlying mechanisms. ADK was transiently increased after myocardial I/R injury. Pharmacological or genetic ADK inhibition reduced infarct size, improved cardiac function and prevented cell apoptosis and necroptosis in I/R‐injured mouse hearts. In vitro, ADK inhibition also prevented cell apoptosis and cell necroptosis in H/R‐treated H9c2 cells. Cleaved caspase‐9, cleaved caspase‐8, cleaved caspase‐3, MLKL and the phosphorylation of MLKL and CaMKII were decreased by ADK inhibition in reperfusion‐injured cardiomyocytes. X‐linked inhibitor of apoptosis protein (XIAP), which is phosphorylated and stabilized via the adenosine receptors A2B and A1/Akt pathways, should play a central role in the effects of ADK inhibition on cell apoptosis and necroptosis. These data suggest that ADK plays an important role in myocardial I/R injury by regulating cell apoptosis and necroptosis.

Modification of ischemia/reperfusion induced infarct size by ischemic preconditioning in hypertrophied hearts

This study examined the effects of ischemic preconditioning (IP) on the ischemia/reperfusion (I/R) induced injury in normal and hypertrophied hearts. Cardiac hypertrophy in rabbits was induced by L-thyroxine (0.5 mg/kg/day for 16 days). Hearts with or without IP (3 cycles of 5 min ischemia and 10 min reperfusion) were subjected to I/R (60 min ischemia followed by 60 min reperfusion). IP reduced the I/R-induced infarct size from 68% to 24% and 57% to 33% in the normal and hypertrophied hearts, respectively. Leakage of creatine phosphokinase in the perfusate from the hypertrophied hearts due to I/R was markedly less than that form the normal hearts; IP prevented these changes. Although IP augmented the increase in phosphorylated p38-mitogen-activated protein kinase (p38-MAPK) content due to I/R, this effect was less in the hypertrophied than in the normal heart. These results suggest that reduced cardioprotection by IP of the I/R-induced injury in hypertrophied hearts may be due to reduced activation of p38-MAPK in comparison with normal hearts.

Heat Shock Protein 70 Protects the Heart from Ischemia/Reperfusion Injury through Inhibition of p38 MAPK Signaling

Background

Heat shock protein 70 (Hsp70) has been shown to exert cardioprotection. Intracellular calcium ([Ca²⁺]_i) overload induced by p38 mitogen-activated protein kinase (p38 MAPK) activation contributes to cardiac ischemia/reperfusion (I/R) injury. However, whether Hsp70 interacts with p38 MAPK signaling is unclear. Therefore, this study investigated the regulation of p38 MAPK by Hsp70 in I/R-induced cardiac injury.

Methods

Neonatal rat cardiomyocytes were subjected to oxygen-glucose deprivation for 6 h followed by 2 h reoxygenation (OGD/R), and rats underwent left anterior artery ligation for 30 min followed by 30 min of reperfusion. The p38 MAPK inhibitor (SB203580), Hsp70 inhibitor (Quercetin), and Hsp70 short hairpin RNA (shRNA) were used prior to OGD/R or I/R. Cell viability, lactate dehydrogenase (LDH) release, serum cardiac troponin I (cTnI), [Ca²⁺]_i levels, cell apoptosis, myocardial infarct size, mRNA level of IL-1β and IL-6, and protein expression of Hsp70, phosphorylated p38 MAPK (p-p38 MAPK), sarcoplasmic/endoplasmic reticulum Ca²⁺-ATPase2 (SERCA2), phosphorylated signal transducer and activator of transcription3 (p-STAT3), and cleaved caspase3 were assessed.

Results

Pretreatment with a p38 MAPK inhibitor, SB203580, significantly attenuated OGD/R-induced cell injury or I/R-induced myocardial injury, as evidenced by improved cell viability and lower LDH release, resulted in lower serum cTnI and myocardial infarct size, alleviation of [Ca²⁺]_i overload and cell apoptosis, inhibition of IL-1β and IL-6, and modulation of protein expressions of p-p38 MAPK, SERCA2, p-STAT3, and cleaved-caspase3. Knockdown of Hsp70 by shRNA exacerbated OGD/R-induced cell injury, which was effectively abolished by SB203580. Moreover, inhibition of Hsp70 by quercetin enhanced I/R-induced myocardial injury, while SB203580 pretreatment reversed the harmful effects caused by quercetin.

Conclusions

Inhibition of Hsp70 aggravates [Ca²⁺]_i overload, inflammation, and apoptosis through regulating p38 MAPK signaling during cardiac I/R injury, which may help provide novel insight into cardioprotective strategies.

Propofol post-conditioning lessens renal ischemia/reperfusion-induced acute lung injury associated with autophagy and apoptosis through MAPK signals in rats

Renal Ischemia/Reperfusion (rI/R)-induced acute lung injury (ALI) is a major problem in rI/R. The objective of the current study was to explore the defensive roles of propofol (Pro), an intravenous anesthetic, on rI/R-induced ALI through mitogen-activated protein kinase (MAPK) signaling. Rats were divided into Sham, Pro (10 mg/kg), rI/R, rI/R + Pro (5 mg/kg), and rI/R + Pro (10 mg/kg) groups. Rats were treated with Pro at 1 h after rI/R treatment. Serum and lung tissues at 24 h after rI/R were collected to evaluate morphological changes and the expression of myeloperoxidase (MPO), inflammatory cytokines, and crucial proteins in the MAPK pathway. Pro attenuated the production of mediators, resulting in reduced levels of autophagy and apoptosis by restricting the MAPK pathway in rI/R-induced ALI model. Pro represses rI/R-induced pulmonary autophagy and apoptosis by decreasing the production of inflammatory molecules, and the effects of Pro are involved in the inhibition of the MAPK pathway.

H2S attenuates injury after ischemic stroke by diminishing the assembly of CaMKII with ASK1-MKK3-p38 signaling module

Cerebral ischemia/reperfusion (I/R) injury is a leading cause of learning and memory dysfunction. Hydrogen sulfide (H₂S) has been shown to confer neuroprotection in various neurodegenerative diseases, including cerebral I/R-induced hippocampal CA1 injury. However, the underlying mechanisms have not been completely understood. In the present study, rats were pretreated with SAM/NaHS (SAM, an H₂S agonist, and NaHS, an H₂S donor) only or SAM/NaHS combined with CaM (an activator of CaMKII) prior to cerebral ischemia. The Morris water maze test demonstrated that SAM/NaHS could alleviate learning and memory impairment induced by cerebral I/R injury. Cresyl violet staining was used to show the survival of hippocampal CA1 pyramidal neurons. SAM/NaHS significantly increased the number of surviving cells, whereas CaM weakened the protection induced by SAM/NaHS. The immunohistochemistry results indicated that the number of Iba1-positive microglia significantly increased after cerebral I/R. Compared with the I/R group, the number of Iba1-positive microglia in the SAM/NaHS groups significantly decreased. Co-Immunoprecipitation and immunoblotting were conducted to demonstrate that SAM/NaHS suppressed the assembly of CaMKII with the ASK1-MKK3-p38 signal module after cerebral I/R, which decreased the phosphorylation of p38. In contrast, CaM significantly inhibited the effects of SAM/NaHS. Taken together, the results suggested that SAM/NaHS could suppress cerebral I/R injury by downregulating p38 phosphorylation via decreasing the assembly of CaMKII with the ASK1-MKK3-p38 signal module.

A novel small molecule compound VCP979 improves ventricular remodeling in murine models of myocardial ischemia/reperfusion injury

Persistent ventricular remodeling following myocardial ischemia/reperfusion (MI/R) injury results in functional decompensation and eventual progression to heart failure. VCP979, a novel small‑molecule compound developed in‑house, possesses anti‑inflammatory and anti‑fibrotic activities. In the present study, no significant pathological effect was observed following the administration of VCP979 on multiple organs in mice and no difference of aspartate transaminase/alanine aminotransferase/lactate dehydrogenase levels was found in murine serum. Treatment with VCP979 ameliorated cardiac dysfunction, pathological myocardial fibrosis and hypertrophy in murine MI/R injury models. The administration of VCP979 also inhibited the infiltration of inflammatory cells and the pro‑inflammatory cytokine expression in hearts post MI/R injury. Further results revealed that the addition of VCP979 prevented the primary neonatal cardiac fibroblasts (NCFs) from Angiotensin II (Ang II)‑induced collagen synthesis and neonatal cardiac myocytes (NCMs) hypertrophy. In addition, VCP979 attenuated the activation of p38‑mitogen‑activated protein kinase in both Ang II‑induced NCFs and hearts subjected to MI/R injury. These findings indicated that the novel small‑molecule compound VCP979 can improve ventricular remodeling in murine hearts against MI/R injury, suggesting its potential therapeutic function in patients subjected to MI/R injury.

Combination of metformin and p38 MAPK inhibitor, SB203580, reduced myocardial ischemia/reperfusion injury in non-obese type 2 diabetic Goto-Kakizaki rats

Diabetic cardiomyopathy, especially myocardial ischemia reperfusion (I/R) injury, is a major cause of morbidity and mortality in type 2 diabetic patients. The increasing of basal p38 MAP Kinase (p38 MAPK) activation is a major factor that aggravates cardiac death on diabetic cardiomyopathy. In addition, metformin also shows cardio-protective effects on myocardial ischemia/reperfusion injury. In this study, we investigated the effect of the combination between metformin and p38 MAPK inhibitor (SB203580) in diabetic rats subjected to I/R injury. H9c2 cells were induced into a hyperglycemic condition and treated with metformin, SB203580 or the combination of metformin and SB203580. In addition, cells in both the presence and absence of drug treatment were subjected to simulated ischemia/reperfusion injury. Cell viability and cellular reactive oxygen species (ROS) were determined. Moreover, the Goto-Kakizaki (GK) rats were treated with metformin, SB203580, and the combination of metformin and SB203580 for 4 weeks. Diabetic parameters and cardiac functions were assessed. Finally, rat hearts were induced ischemia/reperfusion injury for the purpose of infarct size analysis and determination of signal transduction. A high-glucose condition did not reduce cell viability but significantly increased ROS production and significantly decreased cell viability after induced sI/R. Treatment using drugs was shown to reduce ROS generation and cardiac cell death. The GK rats displayed diabetic phenotype by increasing diabetic parameters and these parameters were significantly decreased when treated with drugs. Treatment with metformin or SB203580 could significantly reduce the infarct size. Interestingly, the combination of metformin and SB203580 could enhance cardio-protective ability. Myocardial I/R injury significantly increased p38 MAPK phosphorylation, Bax/Bcl-2 ratio and caspase-3 level. Treatment with drugs significantly decreased the p38 MAPK phosphorylation, Bax/Bcl-2 ratio, caspase-3 level and increased Akt phosphorylation. In conclusion, using the combination of metformin and SB203580 shows positive cardio-protective effects on diabetic ischemic cardiomyopathy.

l-α-Lysophosphatidylinositol (LPI) aggravates myocardial ischemia/reperfusion injury via a GPR55/ROCK-dependent pathway

The phospholipid l-α-lysophosphatidylinositol (LPI), an endogenous ligand for GPR55, is elevated in patients with acute coronary syndrome, and a GPR55 antagonist cannabidiol (CBD) reduces experimental ischemia/reperfusion (I/R) injury. While LPI activates multiple signaling pathways, little is known about which ones are important in cardiomyocytes. In this study we explored whether activation of the Rho kinase/ROCK/p38 MAPK pathway is responsible for LPI-induced extension of I/R injury. Using a high-throughput screening method (dynamic mass redistribution; DMR), mouse- and human-induced pluripotent stem cell (iPSC) cardiomyocytes exposed to LPI were shown to exhibit a rapid, sustained, and concentration-dependent (1 nmol L-1-30 μmol L-1) cellular response. Y-27632 (ROCK inhibitor; 10 & 50 μmol L-1) and CBD (1 μmol L-1) both abolished the DMR response to LPI (10 μmol L-1). In murine iPSC cardiomyocytes, LPI-induced ROCK and p38 MAPK phosphorylation, both of which were prevented by Y-27632 and CBD, but did not induce JNK activation or cleavage of caspase-3. In hearts isolated from wild type (WT) mice subjected to 30 minutes global I/R, LPI (10 μmol L-1) administered via the coronary circulation increased infarct size when applied prior to ischemia onset, but not when given at the time of reperfusion. The exacerbation of tissue injury by LPI was not seen in hearts from GPR55-/- mice or in the presence of Y-27632, confirming that injury is mediated via the GPR55/ROCK/p38 MAPK pathway. These findings suggest that raised levels of LPI in the vicinity of a developing infarct may worsen the outcome of AMI.

Protective Effect of Ethyl Pyruvate against Myocardial Ischemia Reperfusion Injury through Regulations of ROS-Related NLRP3 Inflammasome Activation

Emerging evidence indicates the pronounced role of inflammasome activation linked to reactive oxygen species (ROS) in the sterile inflammatory response triggered by ischemia/reperfusion (I/R) injury. Ethyl pyruvate (EP) is an antioxidant and conveys myocardial protection against I/R injury, while the exact mechanisms remain elusive. We aimed to investigate the effect of EP on myocardial I/R injury through mechanisms related to ROS and inflammasome regulation. The rats were randomly assigned to four groups: (1) sham, (2) I/R-control (IRC), (3) EP-pretreatment + I/R, and (4) I/R + EP-posttreatment. I/R was induced by a 30 min ligation of the left anterior descending artery followed by 4 h of reperfusion. EP (50 mg/kg) was administered intraperitoneally at 1 h before ischemia (pretreatment) or upon reperfusion (posttreatment). Both pre- and post-EP treatment resulted in significant reductions in myocardial infarct size (by 34% and 31%, respectively) and neutrophil infiltration. I/R-induced myocardial expressions of NADPH oxidase-4, carnitine palmitoyltransferase 1A, and thioredoxin-interacting protein (TXNIP) were mitigated by EP. EP treatment was associated with diminished inflammasome activation (NOD-like receptor 3 (NLRP3), apoptosis-associated speck-like protein, and caspase-1) and interleukin-1β induced by I/R. I/R-induced phosphorylation of ERK and p38 were also mitigated with EP treatments. In H9c2 cells, hypoxia-induced TXNIP and NLRP3 expressions were inhibited by EP and to a lesser degree by U0126 (MEK inhibitor) and SB203580 (p38 inhibitor) as well. EP's downstream protective mechanisms in myocardial I/R injury would include mitigation of ROS-mediated NLRP3 inflammasome upregulation and its associated pathways, partly via inhibition of hypoxia-induced phosphorylation of ERK and p38.

Protective Effects of Arabinogalactan-Peptide Isolated from Wheat Flour against Myocardial Injury in an Ischemia/Reperfusion Rat Model

We have previously shown that supplementation of wheat with hot-water extract reduces myocardial injury by inhibiting apoptosis in a rat model of myocardial infarction (MI). Arabinogalactan-peptide (AGP), a cell wall polysaccharide of wheat, was also responsible for the protection. However, the underlying mechanisms were not elucidated. In this study, we investigated the underlying mechanisms for how AGP supplementation reduces myocardial injury. First, we isolated highly pure AGP from all-purpose wheat flour. We supplemented rats with AGP at a dose of 100 mg/kg/d for 3 days, and subjected the rats to ischemia (30 min) through ligation of the left anterior descending coronary artery followed by reperfusion (3 h) through a release of the ligation. Supplementation with AGP significantly reduced the infarct size in the heart. In addition, AGP intake inhibited the apoptotic cascade, determined through decreased mitogen-activated protein kinases (p38 and c-Jun N-terminal kinase) phosphorylation, decreased Bcl-2-associated X protein/B-cell lymphoma ratios, and decreased generation of nicked DNA, which was confirmed through western blotting and terminal deoxynucleotidyltransferase-mediated dUTP nick-end labeling staining. These findings indicate that AGP intake can protect against myocardial injury. Traditionally, consumption of dietary fiber such as AGP has been shown to reduce MI risk by inhibiting preocclusion steps through reducing risk factors. Our findings suggest that AGP intake can also reduce MI risk by inhibiting postocclusion steps. This study describes a better dietary recommendation and new prevention strategy for reducing MI risk through regular consumption of wheat rich in AGP.

Understanding the Multitarget Pharmacological Mechanism of the Traditional Mongolian Common Herb Pair GuangZao-RouDouKou Acting on Coronary Heart Disease Based on a Bioinformatics Approach

GuangZao and RouDouKou (Fructus Choerospondiatis and Nutmeg, FCN) are one of the most common herb pairs in traditional Mongolian medicine for the treatment of coronary heart disease (CHD). However, evidence for the protective effect of FCN is limited, and its underlying mechanism of action remains unclear. The present study employed a network pharmacology approach to identify the potentially active ingredients and synergistic effects of the herb pair FCN as traditional Mongolian medicine. We predicted the targets of all available FCN ingredients with PharmMapper, SWISS, and SuperPred Server and clustered CHD-related targets from the DrugBank and the OMIM database. We also evaluated the links between herbal ingredients and pharmacological actions to explore the potential mechanism of action of FCN. We found that FCN targets a network of CHD-related key processes, including stress responses, cell adhesion and connections, angiogenesis, cell apoptosis and necrosis, the endocrine system, inflammatory and immune responses, and other biological processes. To confirm the predicted results, we investigated the protective effect of FCN on isoproterenol- (ISO-) induced myocardial ischemia in rats. Pathological assessment indicated that FCN inhibits apoptosis and inflammatory responses involving the myocardium. Quantitative real-time polymerase chain reaction (qRT-PCR) and western blotting analyses demonstrated the therapeutic effects of FCN on ISO-induced myocardial ischemia rats, possibly via regulating stress and inflammatory responses and inhibiting cardiomyocyte apoptosis. The findings of the present study indicate that bioinformatics combined with experimental verification provide a credible and objective method to elucidate the complex multitarget mechanism of action of FCN.

Caspase recruitment domain-containing protein 9 (CARD9) knockout reduces regional ischemia/reperfusion injury through an attenuated inflammatory response

Ischemic heart disease remains a leading cause of morbidity and mortality in the United States. Interventional reperfusion induces further damage to the ischemic myocardium through neutrophil infiltration and acute inflammation. As caspase recruitment domain-containing protein 9 (CARD9) plays a critical role in innate immune response and inflammation, we hypothesized that CARD9 knockout would provide protection against ischemia and reperfusion (I/R) injury through attenuation of acute inflammatory responses. C57BL/6 wild-type (WT) and CARD9^-/- mice were subjected to 45 min left anterior descending (LAD) coronary artery occlusion followed by 24-h reperfusion. Area at risk (AAR) and infarct size were measured by Evans blue and triphenyltetrazolium chloride (TTC) staining. Frozen heart sections were stained with anti-mouse GR-1 antibody to detect infiltrated neutrophils. Concentrations of cytokines/chemokines TNF-α, IL-6, CXCL-1 and MCP-1 were determined in heart tissue homogenate and serum by ELISA assay. Western immunoblotting analyses were performed to measure the phosphorylation of p38 MAPK. Our results indicate that following I/R, infarct size was significantly smaller in CARD9^-/- mice compared to WT. The number of infiltrated neutrophils was significantly lower in CARD9^-/- mice compared to WT. Levels of TNF-α, IL-6, CXCL-1 and MCP-1 were significantly reduced in heart tissue and serum from CARD9^-/- mice compared to WT. CARD9^-/- mice also exhibited significantly lower levels of phosphorylated p38 MAPK. Taken together, our results suggest that CARD9 knockout protects the heart from ischemia/reperfusion (I/R) injury, possibly through reduction of neutrophil infiltration and attenuation of CARD9-associated acute inflammatory signaling.

Overexpression and pre-treatment of recombinant human Secretory Leukocyte Protease Inhibitor (rhSLPI) reduces an in vitro ischemia/reperfusion injury in rat cardiac myoblast (H9c2) cell

One of the major causes of cardiac cell death during myocardial ischemia is the oversecretion of protease enzymes surrounding the ischemic tissue. Therefore, inhibition of the protease activity could be an alternative strategy for preventing the expansion of the injured area. In the present study, we investigated the effects of Secretory Leukocyte Protease Inhibitor (SLPI), by means of overexpression and treatment of recombinant human SLPI (rhSLPI) in an in vitro model. Rat cardiac myoblast (H9c2) cells overexpressing rhSLPI were generated by gene delivery using pCMV2-SLPI-HA plasmid. The rhSLPI-H9c2 cells, mock transfected cells, and wild-type (WT) control were subjected to simulated ischemia/reperfusion (sI/R). Moreover, the treatment of rhSLPI in H9c2 cells was also performed under sI/R conditions. The results showed that overexpression of rhSLPI in H9c2 cells significantly reduced sI/R-induced cell death and injury, intracellular ROS level, and increased Akt phosphorylation, when compared to WT and mock transfection (p <0.05). Treatment of rhSLPI prior to sI/R reduced cardiac cell death and injury, and intra-cellular ROS level. In addition, 400 ng/ml rhSLPI treatment, prior to sI, significantly inhibited p38 MAPK phosphorylation and rhSLPI at 400-1000 ng/ml could increase Akt phosphorylation.

The cardioprotective effects of secretory leukocyte protease inhibitor against myocardial ischemia/reperfusion injury

Protease enzymes generated from injured cells and leukocytes are the primary cause of myocardial cell damage following ischemia/reperfusion (I/R). The inhibition of protease enzyme activity via the administration of particular drugs may reduce injury and potentially save patients' lives. The aim of the current study was to investigate the cardioprotective effects of treatment with recombinant human secretory leukocyte protease inhibitor (rhSLPI) on in vitro and ex vivo models of myocardial I/R injury. rhSLPI was applied to isolated adult rat ventricular myocytes (ARVMs) subjected to simulated I/R and to ex vivo murine hearts prior to I/R injury. Cellular injury, cell viability, reactive oxygen species (ROS) levels, and levels of associated proteins were assessed. The results demonstrated that administration of rhSLPI prior to or during sI/R significantly reduced the death and injury of ARVMs and significantly reduced intracellular ROS levels in ARVMs during H₂O₂ stimulation. In addition, treatment of ARVMs with rhSLPI significantly attenuated p38 mitogen-activated protein kinase (MAPK) activation and increased the activation of Akt. Furthermore, pretreatment of ex vivo murine hearts with rhSLPI prior to I/R significantly decreased infarct size, attenuated p38 MAPK activation and increased Akt phosphorylation. The results of the current study demonstrated that treatment with rhSLPI induced a cardioprotective effect and reduced ARVM injury and death, intracellular ROS levels and infarct size. rhSLPI also attenuated p38 MAPK phosphorylation and activated Akt phosphorylation. These results suggest that rhSLPI may be developed as a novel therapeutic strategy of treating ischemic heart disease.

Inflammation: A Novel Therapeutic Target/Direction in Atherosclerosis

Over the past two decades, the viewpoint of atherosclerosis has been replaced gradually by a lipid-driven, chronic, low-grade inflammatory disease of the arterial wall. Current treatment of atherosclerosis is focused on limiting its risk factors, such as hyperlipidemia or hypertension. However, treatment targeting the inflammatory nature of atherosclerosis is still very limited and deserves further attention to fight atherosclerosis successfully. Here, we review the current development of inflammation and atherosclerosis to discuss novel insights and potential targets in atherosclerosis, and to address drug discovery based on anti-inflammatory strategy in atherosclerotic disease.

Prdx1 alleviates cardiomyocyte apoptosis through ROS-activated MAPK pathway during myocardial ischemia/reperfusion injury

Apoptosis induced by oxidative stress blocks the recovery of heart function in myocardial ischemia reperfusion injury (MIRI). Peroxiredoxin 1 (Prdx1) inhibits oxidative stress. However, the expression and function of Prdx1 in MIRI are unclear. In present study, Prdx1 protein level increased in rat MIRI model, associated with cardiomyocyte apoptosis. Cultured rat embryonic ventricular myocardial H9c2 cells with hypoxia/reoxygenation (H/R) treatment was utilized to mimic MIRI in vitro, showing that H/R treatment increased the ratio of p-p38/p38, p-JNK/JNK and apoptosis index. But Prdx1 ameliorate the up-regulation of p-p38/p38 ratio and p-JNK/JNK ratio, as well as decreased H9c2 cell apoptosis. SB203580 (p38 inhibitor) and SP600125 (JNK inhibitor) inhibited H9c2 cell apoptosis, and at the same time Prdx1 down-regulated the activation of p38 MAPK and JNK during H/R treatment. In addition, a ROS scavenger N-acetyl-l-cysteine (NAC) down-regulated the protein level of p-p38, p-JNK and Prdx1, and H9c2 cell apoptosis. In summary, these findings indicated that Prdx1 inhibited MAPK pathway induced cells apoptosis, and ROS is the upstream regulator of H/R induced apoptosis.

Luteolin: A Flavonoid that Has Multiple Cardio-Protective Effects and Its Molecular Mechanisms

Cardiovascular disease (CVD) has become the leading cause of morbidity and mortality worldwide. A well-monitored diet with a sufficient intake of fruits and vegetables has been confirmed as a primary prevention of CVD. Plant constituents such as flavonoids have been shown to confer healthy benefits. Luteolin (Lut), a kind of flavonoid, possesses anti-oxidative, anti-tumor, and anti-inflammatory properties. Recent scientific literature has reported the cardiac protective effects of Lut in vitro and in vivo. Therefore, the aim of this review is to provide an update and detailed overview with cardio-protective molecular mechanisms of Lut with a focus on multiple intrinsic and extrinsic effectors. We further explore how these mechanisms participate in ischemia/reperfusion (I/R) injury, heart failure (HF) and atherosclerosis (AS). A proper understanding of the cardiovascular protective effects and the relative mechanisms of Lut may provide the possibility of new drug design and development for CVD. With the previous studies mainly focused on basic research, we need to advance the prospects of its further clinical utilization against CVD, large prospective clinical trials of Lut are needed to observe its therapeutic effects on patients with I/R injury, HF and AS, especially on the effective therapeutic dosage, and safety of long-term administration.

The Renin-Angiotensin System Regulates Neurodegeneration in a Mouse Model of Optic Neuritis

The major role of the renin-angiotensin system (RAS), including that of angiotensin II (Ang II), the principal effector molecule, in the cardiovascular system is well known. Increasing evidence suggests that the RAS also plays a role in the development of autoimmune diseases. Optic neuritis (ie, inflammation of the optic nerve, with retinal ganglion cell loss) is strongly associated with multiple sclerosis. We investigated the effects of candesartan, an Ang II receptor antagonist, on optic neuritis in experimental autoimmune encephalomyelitis (EAE), an animal model of multiple sclerosis. The Ang II concentration was increased in the early phase of EAE. Oral administration of candesartan markedly attenuated demyelination of the optic nerve and spinal cord and reduced retinal ganglion cell loss and visual impairment in mice with EAE. In vitro analyses revealed that Ang II up-regulated the expression of Toll-like receptor (TLR)-4 in astrocytes via the NF-κB pathway. In addition, Ang II treatment enhanced lipopolysaccharide-induced production of monocyte chemoattractant protein 1 in astrocytes, and pretreatment with candesartan or SN50, an NF-κB inhibitor, suppressed the effects of Ang II. The novel pathway of RAS-NF-κB-TLR4 in glial cells identified in the present study may be a valid therapeutic target for neurodegeneration in neuroinflammatory diseases.

Luteolin Enhances Sarcoplasmic Reticulum Ca2+-ATPase Activity through p38 MAPK Signaling thus Improving Rat Cardiac Function after Ischemia/Reperfusion

Background/Aims: A major challenge for current therapeutic strategies against ischemia/reperfusion (I/R) is the lack of effective drugs. Considering luteolin enhances the activity of sarcoplasmic reticulum Ca2+-ATPase (SERCA2a) to improve the systolic/diastolic function of rat hearts and cardiomyocytes during the I/R process, we studied the regulatory function of the p38 MAPK pathway in this protective mechanism. Methods: Isolated cardiomyocytes and perfused hearts were separately divided into five groups and used to investigate I/R. The phosphorylation of p38 and phospholamban (p-PLB), the levels and activity of SERCA2a and the levels of proteins related to apoptosis were measured. Apoptotic cells were assessed using the TUNEL assay. Single-cell shortening, Ca2+ transients, and the decay of the mitochondrial membrane potential (Δψm) were detected. Results: The p38 MAPK pathway was activated during the I/R process, and inhibiting it with SB203580 promoted p-PLB, which enhanced the activity of SERCA2a and relieved the calcium overload to promote the recovery of the Δψm and reduce cardiomyocyte apoptosis in I/R. Luteolin also suppressed the activation of the p38 MAPK pathway and showed cardioprotective effects during I/R injury. Conclusions: We conclude that luteolin enhances SERCA2a activity to improve systolic/diastolic function during I/R in rat hearts and cardiomyocytes by attenuating the inhibitive effects of the p38 pathway on p-PLB.

CARD9 knockout ameliorates myocardial dysfunction associated with high fat diet-induced obesity

Obesity is associated with chronic inflammation which plays a critical role in the development of cardiovascular dysfunction. Because the adaptor protein caspase recruitment domain-containing protein 9 (CARD9) in macrophages regulates innate immune responses via activation of pro-inflammatory cytokines, we hypothesize that CARD9 mediates the pro-inflammatory signaling associated with obesity en route to myocardial dysfunction. C57BL/6 wild-type (WT) and CARD9(-/-) mice were fed normal diet (ND, 12% fat) or a high fat diet (HFD, 45% fat) for 5months. At the end of 5-month HFD feeding, cardiac function was evaluated using echocardiography. Cardiomyocytes were isolated and contractile properties were measured. Immunofluorescence was performed to detect macrophage infiltration in the heart. Heart tissue homogenates, plasma, and supernatants from isolated macrophages were collected to measure the concentrations of pro-inflammatory cytokines using ELISA kits. Western immunoblotting analyses were performed on heart tissue homogenates and isolated macrophages to explore the underlying signaling mechanism(s). CARD9 knockout alleviated HFD-induced insulin resistance and glucose intolerance, prevented myocardial dysfunction with preserved cardiac fractional shortening and cardiomyocyte contractile properties. CARD9 knockout also significantly decreased the number of infiltrated macrophages in the heart with reduced myocardium-, plasma-, and macrophage-derived cytokines including IL-6, IL-1β and TNFα. Finally, CARD9 knockout abrogated the increase of p38 MAPK phosphorylation, the decrease of LC3BII/LC3BI ratio and the up-regulation of p62 expression in the heart induced by HFD feeding and restored cardiac autophagy signaling. In conclusion, CARD9 knockout ameliorates myocardial dysfunction associated with HFD-induced obesity, potentially through reduction of macrophage infiltration, suppression of p38 MAPK phosphorylation, and preservation of autophagy in the heart.

The p38 MAP kinase pathway modulates the hypoxia response and glutamate receptor trafficking in aging neurons

Neurons are sensitive to low oxygen (hypoxia) and employ a conserved pathway to combat its effects. Here, we show that p38 MAP Kinase (MAPK) modulates this hypoxia response pathway in C. elegans. Mutants lacking p38 MAPK components pmk-1 or sek-1 resemble mutants lacking the hypoxia response component and prolyl hydroxylase egl-9, with impaired subcellular localization of Mint orthologue LIN-10, internalization of glutamate receptor GLR-1, and depression of GLR-1-mediated behaviors. Loss of p38 MAPK impairs EGL-9 protein localization in neurons and activates the hypoxia-inducible transcription factor HIF-1, suggesting that p38 MAPK inhibits the hypoxia response pathway through EGL-9. As animals age, p38 MAPK levels decrease, resulting in GLR-1 internalization; this age-dependent downregulation can be prevented through either p38 MAPK overexpression or removal of CDK-5, an antagonizing kinase. Our findings demonstrate that p38 MAPK inhibits the hypoxia response pathway and determines how aging neurons respond to hypoxia through a novel mechanism.

DOI:http://dx.doi.org/10.7554/eLife.12010.001

The brain accounts for 2% of our body weight, but consumes about 20% of our oxygen intake. This oxygen gluttony is due to the tremendous appetite of brain cells for energy, which neurons satisfy through oxygen-dependent (aerobic) metabolism. As a result, the loss of oxygen to the brain during a stroke, heart attack, or due to another medical condition can be very damaging to cells in the brain.

Human and other animal cells use a communication system called the hypoxia response pathway to sense oxygen and trigger a protective response when oxygen is low. This pathway includes an enzyme called prolyl hydroxylase, which senses oxygen and modifies another protein in the pathway that regulates the production of enzymes involved in metabolism. This alters the balance of enzymes involved in aerobic and oxygen-independent (anaerobic) metabolism in the cell. However, it is not clear how the activity of the prolyl hydroxylase is regulated.

Much of our knowledge about the hypoxia response pathway has been gained from studies using a small worm called C. elegans. This worm uses the pathway to cope with hypoxia in the harsh environment of the soil. Mutant worms that lack the prolyl hydroxylase have several abnormalities including higher levels of anaerobic metabolism even in the presence of oxygen, and defects in the connections between neurons.

Park and Rongo used C. elegans to study the pathway in more detail. The experiments show that another enzyme called p38 MAPK activates the prolyl hydroxylase. Mutant worms that lack this enzyme have similar abnormalities in the hypoxia response pathway as animals that lack the prolyl hydroxylase. In normal worms, decreasing levels of p38 MAPK as the animals grow older contribute to the decline in the nervous system. The p38 MAPK enzyme appears to work by regulating the activity of the prolyl hydroxylase and its location inside neurons.

These findings provide a new target for the development of drugs that may help to protect us from tissue damage caused by hypoxia. Future challenges are to find out what activates p38 MAPK, and how it influences the location of prolyl hydroxylase in neurons.

DOI:http://dx.doi.org/10.7554/eLife.12010.002

Modulation of p38 kinase by DUSP4 is important in regulating cardiovascular function under oxidative stress

Over-activation of p38 is implicated in many cardiovascular diseases (CVDs), including myocardial infarction, hypertrophy, heart failure, and ischemic heart disease. Numerous therapeutic interventions for CVDs have been directed toward the inhibition of the p38 mitogen-activated protein kinase activation that contributes to the detrimental effect after ischemia/reperfusion (I/R) injuries. However, the efficacy of these treatments is far from ideal, as they lack specificity and are associated with high toxicity. Previously, we demonstrated that N-acetyl cysteine (NAC) pretreatment up-regulates DUSP4 expression in endothelial cells, regulating p38 and ERK1/2 activities, and thus providing a protective effect against oxidative stress. Here, endothelial cells under hypoxia/reoxygenation (H/R) insult and isolated heart I/R injury were used to investigate the role of DUSP4 in the modulation of the p38 pathway. In rat endothelial cells, DUSP4 is time-dependently degraded by H/R (0.25 ± 0.07-fold change of control after 2h H/R). Its degradation is closely associated with hyperphosphorylation of p38 (2.1 ± 0.36-fold change) and cell apoptosis, as indicated by the increase in cells immunopositive for cleaved caspase-3 (12.59 ± 3.38%) or TUNEL labeling (29.46 ± 3.75%). The inhibition of p38 kinase activity with 20 µM SB203580 during H/R prevents H/R-induced apoptosis, assessed via TUNEL (12.99 ± 1.89%). Conversely, DUSP4 gene silencing in endothelial cells augments their sensitivity to H/R-induced apoptosis (45.81 ± 5.23%). This sensitivity is diminished via the inhibition of p38 activity (total apoptotic cells drop to 17.47 ± 1.45%). Interestingly, DUSP4 gene silencing contributes to the increase in superoxide generation from cells. Isolated Langendorff-perfused mouse hearts were subjected to global I/R injury. DUSP4(-/-) hearts had significantly larger infarct size than WT. The increase in I/R-induced infarct in DUSP4(-/-) mice significantly correlates with reduced functional recovery (assessed by RPP%, LVDP%, HR%, and dP/dtmax) as well as lower CF% and a higher initial LVEDP. From immunoblotting analysis, it is evident that p38 is significantly overactivated in DUSP4(-/-) mice after I/R injury. The activation of cleaved caspase-3 is seen in both WT and DUSP4(-/-) I/R hearts. Infusion of a p38 inhibitor prior to ischemia and during the reperfusion improves both WT and DUSP4(-/-) cardiac function. Therefore, the identification of p38 kinase modulation by DUSP4 provides a novel therapeutic target for oxidant-induced diseases, especially myocardial infarction.

Inhibition of p38 MAPK activation protects cardiac mitochondria from ischemia/reperfusion injury

CONTEXT

Cardiac cell death and fatal arrhythmias during myocardial ischemia/reperfusion (I/R) can be reduced by p38 MAPK inhibition. However, the effects of p38 MAPK inhibition on cardiac mitochondria have not been investigated.

OBJECTIVE

We tested the hypothesis that p38 MAPK inhibition at different times during I/R protects cardiac mitochondrial functions.

MATERIALS AND METHODS

Adult Wistar rats were subjected to 30 min of left anterior descending coronary artery (LAD) occlusion, followed by 120 min of reperfusion. A 2 mg/kg bolus infusion of p38 MAPK inhibitor, SB203580, was given before or during ischemia, or at reperfusion. Mitochondrial function and ultrastructure were assessed and Western blots were performed.

RESULTS

Administration of SB203580 at any time point of I/R significantly attenuated the mitochondrial ultrastructure change, mitochondrial swelling, by increasing the absorbance at 540 nm (I/R control 0.42 ± 0.03; pretreatment 0.58 ± 0.04; during ischemia 0.49 ± 0.02; at reperfusion 0.51 ± 0.02, p < 0.05), similar to reactive oxygen species (ROS) generation (I/R control 1300 ± 48; pretreatment 1150 ± 30; during ischemia 1000 ± 50; at reperfusion 1050 ± 55, p < 0.05). Only SB203580 given before or during ischemia attenuated mitochondrial membrane depolarization (I/R control 0.78 ± 0.04; pretreatment 1.02 ± 0.03; during ischemia 1.05 ± 0.12, p < 0.05). In addition, pre-treatment of SB203580 significantly reduced the phosphorylation of p53, CREB, Bax, cytochrome c, and cleaved caspase 3.

DISCUSSION AND CONCLUSION

The results from this study showed for the first time that p38 MAPK inhibition protects mitochondria from I/R injury.

Pretreatment with pPolyHb attenuates H2O2-induced endothelial cell injury through inhibition of JNK/p38 MAPK pathway by upregulation of heme oxygenase-1

Polymerized porcine hemoglobin (pPolyHb) exhibits a protective effect on ischemia/reperfusion of organ grafts. A series of experiments were performed to explore the underlying cytoprotective mechanisms of pPolyHb pretreatment on H2O2-induced cell death and apoptosis. The results showed that the pretreatment augmented heme oxygenase-1 (HO-1) expression, and at the same time, decreased the phosphorylation of JNK/p38 mitogen-activated protein kinase (MAPK) and intracellular ROS generation in H2O2-treated HUVECs. Moreover, the inhibition of HO-1 expression by tin porphyrin (SnPP) abolished the protective effects of pPolyHb, which suggested that the cytoprotective effect of pPolyHb involves upregulating HO-1 and subsequently decreasing the phosphorylation of the JNK and p38 MAPK and ROS generation.

Effects of antidepressants on IP-10 production in LPS-activated THP-1 human monocytes

Major depressive disorder and cardiovascular disease are common serious illnesses worldwide. Selective serotonin reuptake inhibitors and norepinephrine-dopamine reuptake inhibitors may reduce the mortality of cardiovascular disease patients with comorbid depression. Interferon-γ-inducible protein 10 (IP-10), a type 1 T helper cell (Th1)-related chemokine, contributes to manifestations of atherosclerosis during cardiovascular inflammations; however, the pathophysiological mechanisms linking cardiovascular disease and effective antidepressants have remained elusive. We investigated the in vitro effects of six different classes of antidepressants on the IP-10 chemokine expression in lipopolysaccharide (LPS)-stimulated monocytes, and their detailed intracellular mechanisms. The human monocytes were pretreated with antidepressants (10⁻⁸–10⁻⁵ M) before LPS-stimulation. IP-10 was measured by enzyme-linked immunosorbent assay (ELISA) and then intracellular signaling was investigated using Western blotting and chromatin immunoprecipitation. Fluoxetine and bupropion suppressed LPS-induced IP-10 expression in monocytes, and they had no cytotoxic effects. Furthermore, fluoxetine inhibited LPS-induced IP-10 expression via the mitogen-activated protein kinase (MAPK)-p38 pathway. Fluoxetine and bupropion could not only treat depression but also reduce Th1-related chemokine IP-10 production in human monocytes. Our results may indicate a possible mechanism related to how particular antidepressants reduce the risk of cardiovascular disease.

Allosteric enhancement of MAP kinase p38α's activity and substrate selectivity by docking interactions

Mitogen-activated protein kinases (MAPKs) are essential to intracellular signal transduction. MAPKs anchor their pathway-specific substrates through so-called 'docking interactions' at locations distal from the active site. Docking interactions ensure efficient substrate recognition, but their contribution to the kinase reaction itself remains unclear. Herein, we use solution NMR to analyze the interaction between dually phosphorylated, active human p38α and the C-terminal fragments of its substrate MK2. p38α phosphorylation and ATP loading collaboratively induce the active conformation; subsequently, p38α accommodates MK2 phosphoacceptor residues in its active site. The docking interaction enhances binding of ATP and the phosphoacceptor to p38α, accelerating the phosphotransfer reaction. Thus, the docking interaction enhances p38α's enzymatic activity toward pathway-specific substrates allosterically as well as by the anchor effect. These findings clarify how MAPK cascades are organized in cells, even under ATP-depleted conditions often associated with environmental stress.

Crystal structure of the p38α MAP kinase in complex with a docking peptide from TAB1

The mitogen-activated protein kinase (MAPK) p38α is a key regulator in many cellular processes, whose activity is tightly regulated by upstream kinases, phosphatases and other regulators. Transforming growth factor-β activated kinase 1 (TAK1) is an upstream kinase in p38α signaling, and its full activation requires a specific activator, the TAK1-binding protein (TAB1). TAB1 was also shown to be an inducer of p38α's autophosphorylation and/or a substrate driving the feedback control of p38α signaling. Here we determined the complex structure of the unphosphorylated p38α and a docking peptide of TAB1, which shows that the TAB1 peptide binds to the classical MAPK docking groove and induces long-range conformational changes on p38α. Our structural and biochemical analyses suggest that TAB1 is a reasonable substrate of p38α, yet the interaction between the docking peptide and p38α may not be sufficient to trigger trans-autophosphorylation of p38α.

Inhibition of ASK1-p38 pathway prevents neural cell death following optic nerve injury

Optic nerve injury (ONI) induces retinal ganglion cell (RGC) death and optic nerve atrophy that lead to visual loss. Apoptosis signal-regulating kinase 1 (ASK1) is an evolutionarily conserved mitogen-activated protein kinase (MAPK) kinase kinase and has an important role in stress-induced RGC apoptosis. In this study, we found that ONI-induced p38 activation and RGC loss were suppressed in ASK1-deficient mice. Sequential in vivo retinal imaging revealed that post-ONI treatment with a p38 inhibitor into the eyeball was effective for RGC protection. ONI-induced monocyte chemotactic protein-1 production in RGCs and microglial accumulation around RGCs were suppressed in ASK1-deficient mice. In addition, the productions of tumor necrosis factor and inducible nitric oxide synthase in microglia were decreased when the ASK1-p38 pathway was blocked. These results suggest that ASK1 activation in both neural and glial cells is involved in neural cell death, and that pharmacological interruption of ASK1-p38 pathways could be beneficial in the treatment of ONI.