Loss of fatty acid binding protein 3 ameliorates lipopolysaccharide-induced inflammation and endothelial dysfunction

Circulating fatty acid-binding protein 3 (FABP3) is an effective biomarker of myocardial injury and peripheral artery disease (PAD). The endothelium, which forms the inner most layer of every blood vessel, is exposed to higher levels of FABP3 in PAD or following myocardial injury, but the pathophysiological role of endothelial FABP3, the effect of FABP3 exposure on endothelial cells, and related mechanisms are unknown. Here, we aimed to evaluate the pathophysiological role of endothelial FABP3 and related mechanisms in vitro. Our molecular and functional in vitro analyses show that (1) FABP3 is basally expressed in endothelial cells; (2) inflammatory stress in the form of lipopolysaccharide (LPS) upregulated endothelial FABP3 expression; (3) loss of endogenous FABP3 protected endothelial cells against LPS-induced endothelial dysfunction; however, exogenous FABP3 exposure exacerbated LPS-induced inflammation; (4) loss of endogenous FABP3 protected against LPS-induced endothelial dysfunction by promoting cell survival and anti-inflammatory and pro-angiogenic signaling pathways. Together, these findings suggest that gain-of endothelial FABP3 exacerbates, whereas loss-of endothelial FABP3 inhibits LPS-induced endothelial dysfunction by promoting cell survival and anti-inflammatory and pro-angiogenic signaling. We propose that an increased circulating FABP3 in myocardial injury or PAD patients may be detrimental to endothelial function, and therefore, therapies aimed at inhibiting FABP3 may improve endothelial function in diseased states.

Adverse effects of SYP-3343 on zebrafish development via ROS-mediated mitochondrial dysfunction

As a newly-invented and highly-efficiency strobilurin fungicide, pyraoxystrobin (SYP-3343) has been recognized as a highly poisonous toxin for a variety of aquatic organisms. Nevertheless, the developmental toxicity and potential mechanism of SYP-3343 have not been well-documented. The results showed that SYP-3343 was relatively stable and maintained within the range of 20 % in 24 h, and the LC₅₀ value to embryos at 72 hpf was 17.13 μg/L. The zebrafish embryotoxicity induced by 1, 2, 4, and 8 μg/L SYP-3343 is demonstrated by repressive embryo incubation, enhancive mortality rate, abnormal heart rate, malformed morphological characteristic, and impaired spontaneous coiling, indicating SYP-3343 mostly exerted its toxicity in a dose- and time-dependent manner. Besides SYP-3343 was critically involved in regulating cell cycle, mitochondrial membrane potential, and reactive oxygen species production as well as zebrafish primary cells apoptosis, which can be mitigated using antioxidant N-acetyl-L-cysteine. A significant change occurred in total protein content, the biochemical indices, and antioxidant capacities owing to SYP-3343 exposure. Additionally, SYP-3343 altered the mRNA levels of heart development-, mitochondrial function-, and apoptosis-related genes in zebrafish embryos. These results indicated that SYP-3343 induced apoptosis accompanying reactive oxygen species-initiated mitochondrial dysfunction in zebrafish embryos.

Tetrahydrocurcumin improves lipopolysaccharide-induced myocardial dysfunction by inhibiting oxidative stress and inflammation via JNK/ERK signaling pathway regulation

BACKGROUND

Acute myocardial dysfunction in patients with sepsis is attributed to oxidative stress, inflammation, and cardiomyocyte loss; however, specific drugs for its prevention are still lacking. Tetrahydrocurcumin (THC) has been proven to contribute to the prevention of various cardiovascular diseases by decreasing oxidative stress and inflammation. This study was performed to investigate the functions and mechanism of action of THC in septic cardiomyopathy.

METHODS

After the oral administration of THC (120 mg/kg) for 5 consecutive days, a mouse model of sepsis was established via intraperitoneal lipopolysaccharide (LPS, 10 mg/kg) injection. Following this, cardiac function was assessed, pathological section staining was performed, and inflammatory markers were detected.

RESULTS

Myocardial systolic function was severely compromised in parallel with the accumulation of reactive oxygen species and enhanced cardiomyocyte apoptosis in mice with sepsis. These adverse changes were markedly reversed in response to THC treatment in septic mice as well as in LPS-treated H9c2 cells. Mechanistically, THC inhibited the release of pro-inflammatory cytokines, including tumor necrosis factor alpha, interleukin (IL)-1β, and IL-6, by upregulating mitogen-activated protein kinase phosphatase 1, to block the phosphorylation of c-Jun N-terminal kinase (JNK) and extracellular signal-regulated protein kinase (ERK). Additionally, THC enhanced the levels of antioxidant proteins, including nuclear factor-erythroid 2-related factor 2, superoxide dismutase 2, and NAD(P)H quinone oxidoreductase 1, while decreasing gp91^phox expression. Furthermore, upon THC treatment, Bcl-2 expression was significantly increased, along with a decline in Bax and cleaved caspase-3 expression, which reduced cardiomyocyte loss.

CONCLUSION

Our findings indicate that THC exhibited protective potential against septic cardiomyopathy by reducing oxidative stress and inflammation through the regulation of JNK/ERK signaling. The findings of this study provide a basis for the further evaluation of THC as a therapeutic agent against septic cardiomyopathy.

O-GlcNAc modification regulates MTA1 transcriptional activity during breast cancer cell genotoxic adaptation

BACKGROUND

Chromatin modifier metastasis-associated protein 1 (MTA1), closely associated with tumor angiogenesis in breast cancer, plays an important role in gene expression and cancer cell behavior. Recently, an association between O-GlcNAc transferase (OGT) and MTA1 was identified by mass spectroscopy. However, the potential relationship between MTA1 and O-GlcNAc modification has not yet explored.

METHODS

In the current study, the role of MTA1 and its O-GlcNAc modification in breast cancer cell genotoxic adaptation was investigated through quantitative proteomics, chromatin immunoprecipitation followed by sequencing (ChIP-seq), transcriptome analysis, and loss- and gain-of-function experiments.

RESULTS

We demonstrate that the O-GlcNAc modification promotes MTA1 to interaction with chromatin and thus changes the expression of target genes, contributing to breast cancer cell genotoxic adaptation. MTA1 is modified with O-GlcNAc residues at serine (S) residues S237/S241/S246 in adriamycin-adaptive breast cancer cells, and this modification improves the genome-wide interactions of MTA1 with gene promotor regions by enhancing its association with nucleosome remodeling and histone deacetylation (NuRD) complex. Further, O-GlcNAc modification modulates MTA1 chromatin binding, influencing the specific transcriptional regulation of genes involved in the adaptation of breast cancer cells to genotoxic stress.

CONCLUSIONS

Our findings reveal a previously unrecognized role for O-GlcNAc-modified MTA1 in transcriptional regulation and suggest that the O-GlcNAc modification is a key to the molecular regulation of chemoresistance in breast cancers.

C16, a novel sinomenine derivatives, promoted macrophage reprogramming toward M2-like phenotype and protected mice from endotoxemia

Macrophage plays a critical part in host defense, tissue repair, and anti-inflammation; Macrophage reprogramming is responsible for disease development or regression. We aimed to clarify the effect of sinomenine-4-hydroxy-palmitate (C16), on macrophage reprogramming and anti-inflammatory in endotoxemia model. According to a structure modification of SIN (Sinomenine), C16 was found. Then, based on the endotoxin model, the mice liver and kidney toxicity was evaluated and serum cytokines level of IL-6 (Interleukin-6), TNF-α (Tumor necrosis factor-α), and IL-1β (Interleukin-1β) were measured by ELISA (Enzyme linked immunosorbent assay). Then, we confirmed the effect of C16 on macrophages reprogramming, we used the flow cytometry to test the effect of C16 on macrophages apoptosis in vitro. Then, iNOS (Inducible nitric oxide synthase), M1-type related cytokines, such as IL-1β, TNF-α, and M2-type related cytokines, such as Arg-1 (Arginase-1), CD206, Fizz1, and Ym1 was detected, which expressed in ANA-1 and primary peritoneal macrophages. To further explore the molecular mechanism of C16 in reprogramming of macrophages from M1 toward M2 phenotype, the expression of STAT1 (signal transducer and activator of Transcription 1), STAT3, ERK1/2 (extracellular signal regulated kinase1/2), AKT, p38, and its corresponding phosphorylation were determined by western blot. Our results demonstrated that C16 improved the survival rate of LPS- (lipopolysaccharide) challenged mice and decreased the inflammatory cytokines expression; After C16 treatment, the expression of M1 phenotype correlation factors decreased significantly, while the expression of M2 phenotype correlation factors increased significantly at different levels compared with normal group. It indicated that C16 reprogram macrophages phenotype from M1 toward M2 following LPS stimulus. Furthermore, the results also showed that C16 showed anti-inflammatory effect by inhibiting LPS-induced p38, AKT and STAT1 phosphorylation and contributing ERK1/2 activation. C16 promoted macrophage reprogramming toward M2-like phenotype via p-p38/p-AKT or STAT1 signals pathway and C16 might be a valid candidate for inflammatory disease.

Regulatory role of the TLR4/JNK signaling pathway in sepsis‑induced myocardial dysfunction

Sepsis is a life-threatening organ dysfunction caused by a dysregulated host response to infection, and is a leading cause of mortality worldwide. Myocardial dysfunction is associated with poor prognosis in patients with sepsis and contributes to a high risk of mortality. However, the pathophysiological mechanisms underlying sepsis-induced myocardial dysfunction are not completely understood. The aim of the present study was to investigate the role of toll-like receptor 4 (TLR4)/c-Jun N-terminal kinase (JNK) signaling in pro-inflammatory cytokine expression and cardiac dysfunction during lipopolysaccharide (LPS)-induced sepsis in mice. C57BL/6 mice were pretreated with TAK-242 or saline for 1 h and then subjected to LPS (12 mg/kg, intraperitoneal) treatment. Cardiac function was assessed using an echocardiogram. The morphological changes of the myocardium were examined by hematoxylin and eosin staining and transmission electron microscopy. The serum protein levels of cardiac troponin I (cTnI) and tumor necrosis factor-α (TNF-α) were determined by an enzyme-linked immunosorbent assay (ELISA). The TLR4 and JNK mRNA levels were analyzed via reverse transcription-quantitative PCR. TLR4, JNK and phosphorylated-JNK protein levels were measured by western blotting. In response to LPS, the activation of TLR4 and JNK in the myocardium was upregulated. There were significant increases in the serum levels of TNF-α and cTnI, as well as histopathological changes in the myocardium and suppressed cardiac function, following LPS stimulation. Inhibition of TLR4 activation using TAK-242 led to a decrease in the activation of JNK and reduced the protein expression of TNF-α in plasma, and alleviated histological myocardial injury and improved cardiac function during sepsis in mice. The present data suggested that the TLR4/JNK signaling pathway played a critical role in regulating the production of pro-inflammatory cytokines and myocardial dysfunction induced by LPS.

Myc is involved in Genistein protecting against LPS-induced myocarditis in vitro through mediating MAPK/JNK signaling pathway

BACKGROUND

Genistein is widely used as a pharmacological compound as well as a food additive. However, the pharmaceutical effects of Genistein on myocarditis and its potential mechanisms have not been studied in detail.

METHODS

H9c2 cells were continuously stimulated by lipopolysaccharide (LPS) for 12 h to simulate the in vitro model of myocarditis injury. DrugBank, String, and GEO dataset were used to investigate specific genes that interacting with Genistein. KEGG and GO enrichment analysis were employed to explore Myc-related signaling pathways. Biological behaviors of H9c2 cells were observed with the support of cell counting kit-8, MTT and flow cytometry. Expression levels of cytokines including TNF-α and ILs were evaluated by enzyme-linked immunosorbent assay. Western blot was applied to detect the expression of Myc and MAPK pathway related proteins.

RESULTS

Genistein alleviated the damage of H9c2 cells subjected to LPS from the perspective of elevating cells growth ability, and inhibiting cells apoptosis and inflammatory response. Through bioinformatics analysis, we identified Myc as the potential target of Genistein in myocarditis, and MAPK as the signaling pathway. Significantly, Myc was highly up-regulated in myocarditis samples. More importantly, by performing biological experiments, we discovered that Genistein relieved H9c2 cells apoptosis and inflammatory reaction which caused by LPS stimulation through inhibiting Myc expression. Additionally, the marked augmentation of p-P38 MAPK and p-JNK expression in LPS-induced cardiomyocyte model were blocked by Genistein and si-Myc.

CONCLUSIONS

Our research revealed that Myc mediated the protective effects of Genistein on H9c2 cells damage caused by LPS partly through modulation of MAPK/JNK signaling pathway.

MMP-1 promotes osteogenic differentiation of human bone marrow mesenchymal stem cells via the JNK and ERK pathway

Enhancing the functions of mesenchymal stem cells (MSCs) is considered a potential approach for promoting tissue regeneration. In this study, we investigated the effects of Matrix Metalloproteinase-1 (MMP-1) on bone marrow mesenchymal stem cells (BMSCs) and its mechanism. Our results showed that knockdown of MMP-1 impeded scratch closure, attenuated proliferation, inhibited ALP activity, ALP denser staining and mineralization in vitro, and decreased expression of RUNX2, OSX, OPN and OCN in BMSCs, while 20 ng/mL recombinant human MMP-1 protein (rhMMP-1) significantly accelerated scratch closure, enhanced proliferation, ALP activity, ALP denser staining and mineralization in vitro, and increased expression of RUNX2, OSX, OPN and OCN. In addition, knockdown of MMP-1 inhibited the expression of phosphorylated c-Jun N-terminal kinase (p-JNK) and phosphorylated extracellular regulated protein kinases (p-ERK), while 20 ng/mL rhMMP-1 increased the expression of p-JNK and p-ERK in BMSCs. Furthermore, inhibition of c-Jun N-terminal kinase (JNK) and extracellular regulated protein kinases (ERK) by their inhibitor SP600125 and PD98059 dramatically blocked MMP-1-enhanced ALP activity and mineralization in BMSCs. Our results revealed that MMP-1 could accelerate the osteogenic differentiation potentials of BMSCs via the JNK and ERK pathway, providing the mechanism underlying MSC biology and identifying a potential target for improving bone tissue regeneration.

Down-regulation of long non-coding RNA MALAT1 inhibits granulosa cell proliferation in endometriosis by up-regulating P21 via activation of the ERK/MAPK pathway

STUDY QUESTION

Is there a specific mechanism underlying the association between lung adenocarcinoma transcript 1 (MALAT1) and endometriosis-related infertility?

SUMMARY ANSWER

The down-regulation of MALAT1 in endometriosis granulosa cells (GCs) may have an adverse effect on the growth and development of oocytes by inhibiting GC proliferation, due to cell cycle-dependent mechanisms that enhance P21 expression through activation of the extracellular signal-regulated kinase (ERK)/mitogen-activated protein kinase (MAPK) pathway.

WHAT IS KNOWN ALREADY

The association between endometriosis and infertility is well supported throughout the literature, and endometriosis per se and its surgical treatment have an adverse effect on the ovarian reserve and on oocyte development. MALAT1, one of the most extensively expressed and evolutionarily conserved transcripts, has been implicated to play a role in human development and many diseases. However, little is known about the role of MALAT1 long non-coding RNA (lncRNA) in endometriosis and its associated infertility.

STUDY DESIGN, SIZE, DURATION

We measured MALAT1 lncRNA expression levels in GCs from 52 endometriosis patients and 52 controls. Also, MALAT1 was knocked down in a human GC tumor-derived cell line, KGN, to investigate the role of MALAT1 and its molecular mechanism in cell proliferation.

PARTICIPANTS/MATERIALS, SETTING, METHODS

GCs were collected from women with or without endometriosis undergoing IVF or ICSI treatment. All endometriosis patients were diagnosed by laparoscopy or laparotomy, and control patients were limited to male factor or tubal disease and had a normal ovarian reserve. Quantitative real-time PCR (qRT-PCR) was used to measure the differential expression levels of MALAT1 lncRNA between endometriosis patients and controls. The receiver operating characteristic (ROC) curve was drawn to evaluate the diagnostic values of MALAT1 in endometriosis. In the KGN cell line, MALAT1 was knocked down with locked nucleic acid GapmeRs. Cell counting kit-8 assays, ethynyl-2-deoxyuridine assays and flow cytometry were used to study the role of MALAT1 in cell proliferation and cell-cycle progression, and western blotting was performed to detect the potential underlying mechanism.

MAIN RESULTS AND THE ROLE OF CHANCE

We first found that MALAT1 lncRNA was significantly down-regulated in endometriosis GCs and was associated with the antral follicle count (R = 0.376, P < 0.001 versus control). In addition, MALAT1 lncRNA levels were significantly lower in the GCs of infertile women with advanced stages of endometriosis (P = 0.01 versus control). The ROC curves illustrated strong separation between all the endometriosis patients and the control group (AUC: 0.705; 95% CI: 0.606-0.804; P < 0.001), Stage I-II and control group (AUC: 0.651; 95% CI: 0.536-0.767; P = 0.016), and Stage III-IV and control group (AUC: 0.827; 95% CI: 0.718-0.936; P < 0.001). MALAT1 lncRNA was primarily localized in the nuclei of GCs. We found a negative correlation between MALAT1 lncRNA and P21 mRNA in the GCs from patients (R = -0.628; P < 0.001). MALAT1 knockdown in KGN cells inhibited cell proliferation and cell-cycle progression. In addition, MALAT1 knockdown induced an increase in both the mRNA and protein levels of P21, and of P53, phosphorylated ERK1/2 (p-ERK1/2) and phosphorylated c-Jun N-terminal protein kinase (p-JNK) protein levels, as well as causing a decrease in cyclin dependent kinase 2 (CDK2), cyclin D1 and p-P38 MAPK protein levels. Furthermore, inhibition of the ERK/MAPK pathway with U0126, the up-regulation of p-ERK1/2, P21 and P53, and the down-regulation of CDK2 and cyclin D1 by the knockdown of MALAT1 were all attenuated by MALAT1 knockdown. Therefore, MALAT1 may regulate GC proliferation through P21/P53-dependent control of the cell cycle, and the ERK/MAPK pathway participates in this process.

LARGE SCALE DATA

None.

LIMITATIONS, REASONS FOR CAUTION

The hormonal treatment used in IVF and surgical removal of endometriotic lesions may have altered MALAT1 expression in GCs. The ovarian granulosa-like tumor cell line, KGN, was used for further functional and mechanistic studies due to the difficulties in obtaining human GCs in sizable amounts and maintaining primary cultures.

WIDER IMPLICATIONS OF THE FINDINGS

Our finding represents the first example of an lncRNA-based mechanism in endometriosis GCs. Women with endometriosis show altered MALAT1 expression levels in GCs that may impair fertility by regulating the function of GCs. Therefore, analysis of MALAT1 and its molecular mechanisms of action provide new insights into the pathogenesis of endometriosis and its associated infertility.

STUDY FUNDING/COMPETING INTEREST(s)

This work was supported by the National Natural Science Foundation of China (grant number: 81671524) and the National key research and development program of China (grant number: 2017YFC1001100). The authors declare there is no conflict of interest.

Mechanism of Metformin on LPS-Induced Bacterial Myocarditis

Aims:

Metformin is commonly used to treat type 2 diabetes mellitus; however, in recent years, it was found to play a potential role in the protection of myocardial injury. In this study, we intended to investigate whether metformin had protective effects on bacterial myocarditis.

Methods and Results:

We stimulated rat cardiac myoblast H9c2 cells with lipopolysaccharide (LPS) and administrated with metformin. The results showed that cell viability after LPS stimulation was greatly reduced. The expression levels of phosphorylated p38 mitogen-activated protein kinases (MAPK) and c-Jun N-terminal kinases (JNK), nuclear factor (NF)-κB (NF-κB), BAX, and cleaved Caspase3 were significantly increased, while the expression of antiapoptotic protein Bcl-2 showed a prominent decrease compared to control. Nevertheless, the cells activity increased remarkably after metformin administration, and the expression levels of intracellular related proteins showed the opposite trend to that of the LPS group.

Conclusion:

We demonstrate that LPS stimulation may activate intracellular MAPK/JNK and NF-κB signaling pathways and thus induce cell apoptosis. In contrast, metformin reduced apoptosis by inhibiting this signaling pathway and increasing the expression level of Bcl-2. Moreover, it was found that metformin could enhance the ability of cells to antagonize redox damage by regulating the activities of superoxide dismutase and lactate dehydrogenase and subsequently promote the recovery of cardiomyocyte function.

Bone Marrow Mesenchymal Stem Cells Combat Lipopolysaccharide-Induced Sepsis in Rats via Amendment of P38-MAPK Signaling Cascade

Sepsis is a systemic inflammatory disorder which often occurs during extremely stressful conditions such as trauma, burn, shock, and infection. This study investigated the curative effects of bone marrow-derived mesenchymal stem cells (BM-MSCs) against hepatic, renal, and pulmonary responses caused by a single administration of lipopolysaccharide (LPS) (10 mg/kg, i.p) in rats. Treatment with BM-MSCs (5 × 10⁵ in 0.1 ml PBS, i.p.) 3 h after LPS antagonized the LPS-induced increment of the liver enzymes (ALT, AST) and kidney functions (BUN, sCr). BM-MSCs decreased tissue levels of P38-MAPK, NF-κB, STAT-3, TNF-α, IL-1β, iNOS, Bax together with elevation of the anti-inflammatory cytokine IL-10 and the anti-apoptotic biomarker Bcl-2. Meanwhile, rats exhibited marked reduction of the broncho-alveolar lavage fluid levels of TNF-α, IL-1β, and IFN-γ. Interestingly, BM-MSCs normalized both broncho-alveolar lavage fluid (BALF) neutrophils count and lung wet/dry ratios. Briefly, these findings may provide a preclinical platform for the management of LPS-induced sepsis using BM-MSCs via their ameliorative anti-inflammatory, anti-oxidant, and anti-apoptotic potentials.

Hirudin Protects Ang II-Induced Myocardial Fibroblasts Fibrosis by Inhibiting the Extracellular Signal-Regulated Kinase1/2 (ERK1/2) Pathway

BACKGROUND Myocardial fibrosis is closely related to all types of cardiovascular diseases. Hirudin is widely used in the prevention and treatment of cardiovascular diseases and cancers. In this study, we examined the potential role(s) and mechanism of hirudin in angiotensin II (Ang II)-induced myocardial fibrosis. MATERIAL AND METHODS The viability of myocardial fibroblasts, and reactive oxygen species (ROS) rates were measured respectively using cell counting kit-8 (CCK-8) and flow cytometry. Malondialdehyde (MDA) content, the activities of lactate dehydrogenase (LDH), and superoxide dismutase (SOD) were detected by the respective kits. The mRNA and protein levels of fibrosis-related factors were separately assessed by qRT-PCR and western blot. RESULTS Our data revealed that hirudin suppressed the viability of myocardial fibroblasts, and that it relieved the proliferation induced by Ang II in a dose-dependent manner. We also found that hirudin reduced ROS production, LDH activity, and MDA content; however, it enhanced SOD activity. Moreover, while hirudin significantly downregulated the levels of matrix metalloproteinase-2 (MMP-2), MMP-9, fibronectin (FN), transforming growth factor beta 1 (TGF-β1), collagen-I (COL-I), and COL-III, it upregulated the expression level of tissue inhibitor of metalloproteinases-2 (TIMP-2). Furthermore, phosphorylated extracellular signal-regulated kinase1/2 (p-ERK1/2) was decreased by hirudin, compared to the Ang-II group. CONCLUSIONS Hirudin depressed Ang II-induced myocardial fibroblasts via inhibiting oxidative stress, regulating fibrosis-related factors, and repressing the ERK1/2 pathway.

Crucial Role of miR-433 in Regulating Cardiac Fibrosis

Dysregulation of microRNAs has been implicated in many cardiovascular diseases including fibrosis. Here we report that miR-433 was consistently elevated in three models of heart disease with prominent cardiac fibrosis, and was enriched in fibroblasts compared to cardiomyocytes. Forced expression of miR-433 in neonatal rat cardiac fibroblasts increased proliferation and their differentiation into myofibroblasts as determined by EdU incorporation, α-SMA staining, and expression levels of fibrosis-associated genes. Conversely, inhibition of miR-433 exhibited opposite results. AZIN1 and JNK1 were identified as two target genes of miR-433. Decreased level of AZIN1 activated TGF-β1 while down-regulation of JNK1 resulted in activation of ERK and p38 kinase leading to Smad3 activation and ultimately cardiac fibrosis. Importantly, systemic neutralization of miR-433 or adeno-associated virus 9 (AAV9)-mediated cardiac transfer of a miR-433 sponge attenuated cardiac fibrosis and ventricular dysfunction following myocardial infarction. Thus, our work suggests that miR-433 is a potential target for amelioration of cardiac fibrosis.

North American ginseng inhibits myocardial NOX2-ERK1/2 signaling and tumor necrosis factor-α expression in endotoxemia

Sepsis is a systemic inflammatory response to infection with a high mortality but has no specific treatment despite decades of research. North American (NA) ginseng (Panax quinquefolius) is a popular natural health product with anti-oxidant and anti-inflammatory properties. The aim of the present study was to investigate the effects of NA ginseng on pro-inflammatory cytokine expression and cardiac function in endotoxemia, a model of sepsis. Mice were challenged with lipopolysaccharide (LPS) to induce endotoxemia. Myocardial expression of tumor necrosis factor-alpha (TNF-α), a major pro-inflammatory cytokine that causes cardiac dysfunction, was upregulated in mice with endotoxemia, which was accompanied by increases in NOX2 expression, superoxide generation and ERK1/2 phosphorylation. Notably, pretreatment with NA ginseng aqueous extract (50mg/kg/day, oral gavage) for 5days significantly inhibited NOX2 expression, superoxide generation, ERK1/2 phosphorylation and TNF-α expression in the heart during endotoxemia. Importantly, cardiac function and survival in endotoxemic mice were significantly improved. Additionally, pretreatment with ginseng extract inhibited superoxide generation, ERK1/2 phosphorylation and TNF-α expression induced by LPS in cultured cardiomyocytes. We conclude that NA ginseng inhibits myocardial NOX2-ERK1/2-TNF-α signaling pathway and improves cardiac function in endotoxemia, suggesting that NA ginseng may have the potential in the prevention of clinical sepsis.

LncRNA-HOTAIR promotes TNF-α production in cardiomyocytes of LPS-induced sepsis mice by activating NF-κB pathway

BACKGROUND

Mounting studies have illustrated an important role of HOTAIR in cancer progress, but few studies have reported its function in cardiac disease, including cardiac-associated sepsis. This study aimed to investigate the function of HOTAIR in sepsis, involving its association with the level of tumor necrosis factor-alpha (TNF-α), an important inducer of myocardial dysfunction during LPS-induced sepsis.

METHODS

Sepsis mice model was established by LPS administration, and myocardial dysfunction was evaluated with hemodynamic parameters. HOTAIR expression in isolated cardiomyocytes and TNF-α production in the circulation were detected, as well as the protein levels of phosphorylated p65. HL-1 cells were subjected to LPS treatment in vitro for functional studies, including luciferase report assays for NF-κB activity.

RESULTS

HOTAIR expression was significantly upregulated in cardiomyocytes from sepsis mice, in line with increased TNF-α production and p65 phosphorylation, while similar results were also observed in LPS treated HL-1 cells, which was then reversed by HOTAIR interference. Functional studies demonstrated that HOTAIR showed positive regulation on p65 phosphorylation and NF-κB activation, while HOTAIR-induced TNF-α production was repressed by NF-κB inhibitor. Further in vivo studies confirmed that HOTAIR silence can improve cardiac function of sepsis mice, and markedly decreased TNF-α production in the circulation.

CONCLUSION

HOTAIR upregulation in cardiomyocytes of LPS-induced sepsis mice promoted TNF-α production in the circulation by activating NF-κB, involving the phosphorylation of NF-κB p65 subunit. Moreover, HOTAIR silence preserved cardiac function of sepsis mice during LPS-induced sepsis.

Slack sodium-activated potassium channel membrane expression requires p38 mitogen-activated protein kinase phosphorylation

p38 MAPK has long been understood as an inducible kinase under conditions of cellular stress, but there is now increasing evidence to support its role in the regulation of neuronal function. Several phosphorylation targets have been identified, an appreciable number of which are ion channels, implicating the possible involvement of p38 MAPK in neuronal excitability. The KNa channel Slack is an important protein to be studied as it is highly and ubiquitously expressed in DRG neurons and is important in the maintenance of their firing accommodation. We sought to examine if the Slack channel could be a substrate of p38 MAPK activity. First, we found that the Slack C-terminus contains two putative p38 MAPK phosphorylation sites that are highly conserved across species. Second, we show via electrophysiology experiments that KNa currents and further, Slack currents, are subject to tonic modulation by p38 MAPK. Third, biochemical approaches revealed that Slack channel regulation by p38 MAPK occurs through direct phosphorylation at the two putative sites of interaction, and mutating both sites prevented surface expression of Slack channels. Based on these results, we conclude that p38 MAPK is an obligate regulator of Slack channel function via the trafficking of channels into the membrane. The present study identifies Slack KNa channels as p38 MAPK substrates.

Expression of TNF-α and CD44 is implicated in poor prognosis, cancer cell invasion, metastasis and resistance to the sunitinib treatment in clear cell renal cell carcinomas

Tumor necrosis factor-α (TNF-α) is involved in epithelial-mesenchymal transition (EMT) and expression of CD44, a cancer stem cell marker, in several cancers. This study was performed to clarify the significance of TNF-α and CD44 in clear cell renal cell carcinomas (ccRCCs). Expression of TNF-α and CD44 was examined by immunohistochemistry in 120 ccRCCs. Involvement of TNF-α in EMT and induction of CD44 was analyzed by monitoring expression of EMT-related genes and CD44, and invasion in cultured ccRCC cell lines. TNF-α and CD44 were immunolocalized mainly to carcinoma cells of high-grade ccRCCs with positive correlations with primary tumor stage. A positive correlation was also obtained between TNF-α and CD44 expression, and co-upregulation of TNF-α and CD44 was associated with primary tumor stage, distant metastasis, and poor prognosis. TNF-α enhanced migration and invasion of ccRCC cells together with down-regulation of E-cadherin expression and up-regulation of matrix metalloproteinase 9 and CD44 expression. TNF-α also up-regulated the expression of TNF-α itself in ccRCC cells. Among the 25 ccRCC patients treated with sunitinib for metastatic disease, high CD44 expression was associated with poor treatment outcome. Importantly, residual carcinoma cells in the sunitinib-treated metastatic ccRCCs were strongly positive for CD44, and the CD44 expression was significantly higher in the tumors from the sunitinib-treated patients than in those from untreated ones. Our data show that TNF-α plays an important role in progression of ccRCCs by inducing EMT and CD44 expression, and suggest that CD44 induced by TNF-α may be involved in the resistance to the sunitinib treatment.

MLK3 is part of a feedback mechanism that regulates different cellular responses to reactive oxygen species

Reactive oxygen species (ROS) influence diverse cellular processes, including proliferation and apoptosis. Both endogenous and exogenous ROS activate signaling through mitogen-activated proteins kinase (MAPK) pathways, including those involving extracellular signal-regulated kinases (ERKs) or c-Jun N-terminal kinases (JNKs). Whereas low concentrations of ROS generally stimulate proliferation, high concentrations result in cell death. We found that low concentrations of ROS induced activating phosphorylation of ERKs, whereas high concentrations of ROS induced activating phosphorylation of JNKs. Mixed lineage kinase 3 (MLK3, also known as MAP3K11) directly phosphorylates JNKs and may control activation of ERKs. Mathematical modeling of MAPK networks revealed a positive feedback loop involving MLK3 that determined the relative phosphorylation of ERKs and JNKs by ROS. Cells exposed to an MLK3 inhibitor or cells in which MLK3 was knocked down showed increased activation of ERKs and decreased activation of JNKs and were resistant to cell death when exposed to high concentrations of ROS. Thus, the data indicated that MLK3 is a critical factor controlling the activity of kinase networks that control the cellular responses to different concentrations of ROS.

MAP Kinase cross talks in oxidative stress-induced impairment of insulin secretion. Involvement in the protective activity of quercetin

Insulin secretion preservation is a major issue for the prevention or treatment of type 2 diabetes. We previously showed on β-cells that quercetin (Q), but not resveratrol (R) or N-acetyl cysteine (NAC), amplified glucose-induced insulin secretion in a calcium- and ERK1/2-dependent manner. Quercetin, but not resveratrol or NAC, also protected β-cell function and hyperamplified ERK1/2 phosphorylation in oxidative stress conditions. As quercetin may interfere with other stress-activated protein kinases (JNK and p38 MAPK), we further explored MAPK cross talks and their relationships with the mechanism of the protective effect of quercetin against oxidative stress. In INS-1 insulin-secreting β-cells, using pharmacological inhibitors of MAPK pathways, we found that under oxidative stress (50 μm H2O2) and glucose-stimulating insulin secretion conditions: (i) p38 MAPK phosphorylation was increased and regulated by ERK1/2 (positively) and JNK (negatively), although p38 MAPK activation did not seem to play any significant role in oxidative stress-induced insulin secretion impairment; (ii) the JNK pathway appeared to inhibit both ERK1/2 activation and insulin secretion, although JNK phosphorylation was not significantly changed in our experimental conditions; (iii) the functionality of β-cell in the presence of oxidative stress was closely linked to the level of ERK1/2 activation, (iv) quercetin, resveratrol, or NAC inhibited H2O2 -induced p38 MAPK phosphorylation. The preservation of β-cell function against oxidative stress appears dependent on the balance between ERK1/2 and JNK activation. The protecting effect of quercetin appears due to ERK1/2 hyperactivation, possibly induced by L-type calcium channel opening as we recently showed.

Gene deletion of protein tyrosine phosphatase 1B protects against sepsis-induced cardiovascular dysfunction and mortality

OBJECTIVE

Cardiovascular dysfunction is a major cause of mortality in patients with sepsis. Recently, we showed that gene deletion or pharmacological inhibition of protein tyrosine phosphatase 1B (PTP1B) improves endothelial dysfunction and reduces the severity of experimental heart failure. However, the cardiovascular effect of PTP1B invalidation in sepsis is unknown. Thus, we explored the beneficial therapeutic effect of PTP1B gene deletion on lipopolysaccharide (LPS)-induced cardiovascular dysfunction, inflammation, and mortality.

APPROACH AND RESULTS

PTP1B(-/-) or wild-type mice received LPS (15 mg/kg) or vehicle followed by subcutaneous fluid resuscitation (saline, 30 mL/kg). α-1-dependent constriction and endothelium-dependent dilatation, assessed on isolated perfused mesenteric arteries, were impaired 8 hours after LPS and significantly improved in PTP1B(-/-) mice. This was associated with reduced vascular expression of interleukin1-β, intercellular adhesion molecule-1, vascular cell adhesion molecule-1, cyclooxygenase-2, and inducible nitric oxide synthase mRNA. PTP1B gene deletion also limited LPS-induced cardiac dysfunction assessed by echocardiography, left ventricular pressure-volume curves, and in isolated perfused hearts. PTP1B(-/-) mice also displayed reduced LPS-induced cardiac expression of tumor necrosis factor-α, interleukin1-β, intercellular adhesion molecule-1, vascular cell adhesion molecule-1, and Gp91phox, as well as of several markers of cellular infiltration. PTP1B deficiency also reduced cardiac P38 and extracellular signal-regulated protein kinase 1 and 2 phosphorylation and increased phospholamban phosphorylation. Finally, PTP1B(-/-) mice displayed a markedly reduced LPS-induced mortality, an effect also observed using a pharmacological PTP1B inhibitor. PTP1B deletion also improved survival in a cecal ligation puncture model of sepsis.

CONCLUSIONS

PTP1B gene deletion protects against septic shock-induced cardiovascular dysfunction and mortality, and this may be the result of the profound reduction of cardiovascular inflammation. PTP1B is an attractive target for the treatment of sepsis.

Recombinant human annexin A5 inhibits proinflammatory response and improves cardiac function and survival in mice with endotoxemia

OBJECTIVES

Annexin A5 is a 35-kDa protein with high affinity binding to negatively charged phospholipids. However, its effects on sepsis are not known. Our aim was to study the effects of annexin A5 on myocardial tumor necrosis factor-α expression, cardiac function, and animal survival in endotoxemia.

DESIGN

Prospective experimental study.

SETTING

University laboratory.

SUBJECTS

Adult male C57BL/6 mice.

INTERVENTIONS

Mice were challenged with lipopolysaccharide (4 or 20 mg/kg, i.p.) to induce endotoxemia with and without recombinant human annexin A5 treatment (5 or 10 μg/kg, i.v.). Cytokine expression and cardiac function were assessed, and animal survival was monitored.

MEASUREMENTS AND MAIN RESULTS

Treatment with annexin A5 inhibited myocardial mitogen-activated protein kinase, and nuclear factor-κB activation in mice with endotoxemia. Furthermore, annexin A5-treated animals showed significant reductions in myocardial and plasma levels of tumor necrosis factor-α and interleukin-1β while cardiac function was significantly improved during endotoxemia. Additionally, 5-day animal survival was significantly improved by either an immediate or a 4-hour delayed annexin A5 treatment after lipopolysaccharide challenge. Importantly, annexin A5 dose-dependently inhibited lipopolysaccharide binding to a toll-like receptor-4/myeloid differentiation factor 2 fusion protein.

CONCLUSIONS

Annexin A5 treatment decreases cytokine expression and improves cardiac function and survival during endotoxemia. These effects of annexin A5 are mediated by its ability to inhibit lipopolysaccharide binding to toll-like receptor-4, leading to reductions in mitogen-activated protein kinase and Akt signaling. Our study suggests that annexin A5 may have therapeutic potential in the treatment of sepsis.

Myocyte signalling in leucocyte recruitment to the heart

Myocardial damage, by different noxious causes, triggers an inflammatory reaction driving post-injury repair mechanisms and chronic remodelling processes that are largely detrimental to cardiac function. Cardiomyocytes have recently emerged as key players in orchestrating this inflammatory response. Injured cardiomyocytes release damage-associated molecular pattern molecules, such as high-mobility group box 1 (HMGB1), DNA fragments, heat shock proteins, and matricellular proteins, which instruct surrounding healthy cadiomyocytes to produce inflammatory mediators. These mediators, mainly interleukin (IL)-1β, IL-6, macrophage chemoattractant protein (MCP)-1, and tumour necrosis factor α (TNF-α), in turn activate versatile signalling networks within surviving cardiomyocytes and trigger leucocyte activation and recruitment. In this review, we will focus on recently characterized signalling pathways activated in cardiomyocytes that mediate inflammatory responses during myocardial infarction, hypertensive heart disease, and myocarditis.

α₁ adrenoceptor activation by norepinephrine inhibits LPS-induced cardiomyocyte TNF-α production via modulating ERK1/2 and NF-κB pathway

Cardiomyocyte tumour necrosis factor α (TNF-α) production contributes to myocardial depression during sepsis. This study was designed to observe the effect of norepinephrine (NE) on lipopolysaccharide (LPS)-induced cardiomyocyte TNF-α expression and to further investigate the underlying mechanisms in neonatal rat cardiomyocytes and endotoxaemic mice. In cultured neonatal rat cardiomyocytes, NE inhibited LPS-induced TNF-α production in a dose-dependent manner. α₁- adrenoceptor (AR) antagonist (prazosin), but neither β₁- nor β₂-AR antagonist, abrogated the inhibitory effect of NE on LPS-stimulated TNF-α production. Furthermore, phenylephrine (PE), an α₁-AR agonist, also suppressed LPS-induced TNF-α production. NE inhibited p38 phosphorylation and NF-κB activation, but enhanced extracellular signal-regulated kinase 1/2 (ERK1/2) phosphorylation and c-Fos expression in LPS-treated cardiomyocytes, all of which were reversed by prazosin pre-treatment. To determine whether ERK1/2 regulates c-Fos expression, p38 phosphorylation, NF-κB activation and TNF-α production, cardiomyocytes were also treated with U0126, a selective ERK1/2 inhibitor. Treatment with U0126 reversed the effects of NE on c-Fos expression, p38 mitogen-activated protein kinase (MAPK) phosphorylation and TNF-α production, but not NF-κB activation in LPS-challenged cardiomyocytes. In addition, pre-treatment with SB202190, a p38 MAPK inhibitor, partly inhibited LPS-induced TNF-α production in cardiomyocytes. In endotoxaemic mice, PE promoted myocardial ERK1/2 phosphorylation and c-Fos expression, inhibited p38 phosphorylation and IκBα degradation, reduced myocardial TNF-α production and prevented LPS-provoked cardiac dysfunction. Altogether, these findings indicate that activation of α₁-AR by NE suppresses LPS-induced cardiomyocyte TNF-α expression and improves cardiac dysfunction during endotoxaemia via promoting myocardial ERK phosphorylation and suppressing NF-κB activation.

ERK/PP1a/PLB/SERCA2a and JNK pathways are involved in luteolin-mediated protection of rat hearts and cardiomyocytes following ischemia/reperfusion

Luteolin has long been used in traditional Chinese medicine for treatment of various diseases. Recent studies have suggested that administration of luteolin yields cardioprotective effects during ischemia/reperfusion (I/R) in rats. However, the precise mechanisms of this action remain unclear. The aim of this study is to confirm that luteolin-mediated extracellular signal regulated kinase (ERK1/2) and c-Jun N-terminal kinase (JNK) pathways are responsible for their cardioprotective effects during I/R. Wistar rats were divided into the following groups: (i) DMSO group (DMSO); (ii) I/R group (I/R); (iii) luteolin+I/R group (Lut+I/R); (iv) ERK1/2 inhibitor PD98059+I/R group (PD+I/R); (v) PD98059+luteolin+I/R group (PD+Lut+I/R); and (vi) JNK inhibitor SP600125+I/R group (SP+I/R). The following properties were measured: contractile function of isolated heart and cardiomyocytes; infarct size; the release of lactate dehydrogenase (LDH); the percentage of apoptotic cells; the expression levels of Bcl-2 and Bax; and phosphorylation status of ERK1/2, JNK, type 1 protein phosphatase (PP1a), phospholamban (PLB) and sarcoplasmic reticulum Ca²⁺-ATPase (SERCA2a). Our data showed that pretreatment with luteolin or SP600125 significantly improved the contraction of the isolated heart and cardiomyocytes, reduced infarct size and LDH activity, decreased the rate of apoptosis and increased the Bcl-2/Bax ratio. However, pretreatment with PD98059 alone before I/R had no effect on the above indexes. Further, these consequences of luteolin pretreatment were abrogated by co-administration of PD98059. We also found that pretreatment with PD98059 caused a significant increase in JNK expression, and SP600125 could cause ERK1/2 activation during I/R. In addition, we are the first to demonstrate that luteolin affects PP1a expression, which results in the up-regulation of the PLB, thereby relieving its inhibition of SERCA2a. These results showed that luteolin improves cardiomyocyte contractile function after I/R injury by an ERK1/2-PP1a-PLB-SERCA2a-mediated mechanism independent of JNK signaling pathway.

Si Shen Wan Inhibits mRNA Expression of Apoptosis-Related Molecules in p38 MAPK Signal Pathway in Mice with Colitis

Si Shen Wan (SSW) is used to effectively treat ulcerative colitis (UC) as a formula of traditional Chinese medicine. To explore the mechanism of SSW-inhibited apoptosis of colonic epithelial cell, the study observed mRNA expression of apoptosis-related molecules in p38 MAPK signal pathway in colonic mucosa in colitis mice treated with SSW. Experimental colitis was induced by 2,4,6-trinitrobenzene sulfonic acid (TNBS) in mice; meanwhile, the mice were administrated daily either SSW (5 g/kg) or p38 MAPK inhibitor (2 mg/kg) or vehicle (physiological saline) for 10 days. While microscopical evaluation was observed, apoptosis rate of colonic epithelial cell and mRNA expression of apoptosis-related molecules were tested. Compared with colitis mice without treatment, SSW alleviated colonic mucosal injuries and decreased apoptosis rate of colonic epithelial cell, while the mRNA expressions of p38 MAPK, p53, caspase-3, c-jun, c-fos, Bax, and TNF- α were decreased in the colonic mucosa in colitis mice treated with SSW, and Bcl-2 mRNA and the ratio of Bcl-2/Bax were increased. The present study demonstrated that SSW inhibited mRNA expression of apoptosis-related molecules in p38 MAPK signal pathway to downregulate colonic epithelial cells apoptosis in colonic mucosa in mice with colitis.

MAPKs and signal transduction in the control of gastrointestinal epithelial cell proliferation and differentiation

Mitogen-activated protein kinase (MAPK) pathways are activated by several stimuli and transduce the signal inside cells, generating diverse responses including cell proliferation, differentiation, migration and apoptosis. Each MAPK cascade comprises a series of molecules, and regulation takes place at different levels. They communicate with each other and with additional pathways, creating a signaling network that is important for cell fate determination. In this review, we focus on ERK, JNK, p38 and ERK5, the major MAPKs, and their interactions with PI3K-Akt, TGFβ/Smad and Wnt/β-catenin pathways. More importantly, we describe how MAPKs regulate cell proliferation and differentiation in the rapidly renewing epithelia that lines the gastrointestinal tract and, finally, we highlight the recent findings on nutritional aspects that affect MAPK transduction cascades.

Extracellular HSP60 induces inflammation through activating and up-regulating TLRs in cardiomyocytes

AIMS

The molecular events leading from cardiomyocyte ischaemia to inflammatory cytokine production are not well understood. We previously found that heat shock protein 60 (HSP60) appeared in extracellular space after cardiomyocyte ischaemia. This study examined the activation and regulation of toll-like receptors (TLRs) by HSP60 in cardiomyocytes.

METHODS AND RESULTS

Cytokine production and TLRs regulation mediated by TLRs signalling were examined in response to exogenous HSP60 (exHSP60) and endogenous HSP60 (enHSP60) released extracellularly under ischaemia. The results showed that exHSP60 induced inflammatory cytokine production in adult rat cardiomyocytes and H9c2 cells (a standard cardiac cell line derived from embryonic cells), through a pathway dependent on TLR4, myeloid differentiation factor 88 (MyD88), p38, and nuclear factor-κB (NF-κB). Further study revealed up-regulated expression of both TLR2 and TLR4 by exHSP60, which was dependent on the activation of TLR4, MyD88, c-Jun NH2-terminal kinase (JNK), and NF-κB, but not on p38. In myocytes exposed to ischaemia, enHSP60 was released into the media, and triggered cytokine production and TLR2/4 overexpression, through the same pathways as exHSP60. In rats subjected to LAD ligation, the released enHSP60 contributed to cytokine production and TLR2/4 overexpression in the ischaemic myocardium.

CONCLUSION

Extracellular HSP60 induces cytokine production via TLR4-MyD88-p38/NF-κB pathway, and up-regulates TLR2/4 expression via TLR4-MyD88-JNK/NF-κB pathway. Both pathways contribute to myocardial inflammation induced by ischaemia.

MAPK signaling drives inflammation in LPS-stimulated cardiomyocytes: the route of crosstalk to G-protein-coupled receptors

Profound cardiovascular dysfunction is an important cause of mortality from septic shock. The molecular underpinnings of cardiac dysfunction during the inflammatory surge of early sepsis are not fully understood. MAPKs are important signal transducers mediating inflammation whereas G-protein signaling pathways modulate the cardiac response to stress. Using H9c2 cardiomyocytes, we investigated the interaction of MAPK and G-protein signaling in a sepsis model to test the hypothesis that the cardiomyocyte inflammatory response is controlled by MAPKs via G-protein-mediated events. We found that LPS stimulated proinflammatory cytokine production was markedly exacerbated by siRNA knockdown of the MAPK negative regulator Mkp-1. Cytokine production was blunted when cells were treated with p38 inhibitor. Two important cellular signaling molecules typically regulated by G-protein-coupled receptors, cAMP and PKC activity, were also stimulated by LPS and inflammatory cytokines TNF-α and IL-6, through a process regulated by Mkp-1 and p38. Interestingly, neutralizing antibodies against Gα_s and Gα_q blocked the increase in cellular cAMP and PKC activation, respectively, in response to inflammatory stimuli, indicating a critical role of G-protein coupled receptors in this process. LPS stimulation increased COX-2 in H9c2 cells, which also express prostaglandin receptors. Blockade of G-protein-coupled EP4 prostaglandin receptor by AH 23848 prevented LPS-induced cAMP increase. These data implicate MAPKs and G-proteins in the cardiomyocyte inflammatory response to LPS as well as crosstalk via COX-2-generated PGE₂. These data add to our understanding of the pathogenesis of septic shock and have the potential to guide the selection of future therapeutics.

Crosstalk and signaling switches in mitogen-activated protein kinase cascades

Mitogen-activated protein kinase (MAPK) cascades control cell fate decisions, such as proliferation, differentiation, and apoptosis by integrating and processing intra- and extracellular cues. However, similar MAPK kinetic profiles can be associated with opposing cellular decisions depending on cell type, signal strength, and dynamics. This implies that signaling by each individual MAPK cascade has to be considered in the context of the entire MAPK network. Here, we develop a dynamic model of feedback and crosstalk for the three major MAPK cascades; extracellular signal-regulated kinase (ERK), p38 mitogen-activated protein kinase (p38), c-Jun N-terminal kinase (JNK), and also include input from protein kinase B (AKT) signaling. Focusing on the bistable activation characteristics of the JNK pathway, this model explains how pathway crosstalk harmonizes different MAPK responses resulting in pivotal cell fate decisions. We show that JNK can switch from a transient to sustained activity due to multiple positive feedback loops. Once activated, positive feedback locks JNK in a highly active state and promotes cell death. The switch is modulated by the ERK, p38, and AKT pathways. ERK activation enhances the dual specificity phosphatase (DUSP) mediated dephosphorylation of JNK and shifts the threshold of the apoptotic switch to higher inputs. Activation of p38 restores the threshold by inhibiting ERK activity via the PP1 or PP2A phosphatases. Finally, AKT activation inhibits the JNK positive feedback, thus abrogating the apoptotic switch and allowing only proliferative signaling. Our model facilitates understanding of how cancerous deregulations disturb MAPK signal processing and provides explanations for certain drug resistances. We highlight a critical role of DUSP1 and DUSP2 expression patterns in facilitating the switching of JNK activity and show how oncogene induced ERK hyperactivity prevents the normal apoptotic switch explaining the failure of certain drugs to induce apoptosis.

Differential sensitivity to LPS-induced myocardial dysfunction in the isolated brown Norway and Dahl S rat hearts: roles of mitochondrial function, NF-κB activation, and TNF-α production

Recently, we reported that Brown Norway (BN) rats were more resistant to lipopolysaccharide (LPS)-induced myocardial dysfunction than Dahl S (SS) rats. This differential sensitivity was exemplified by reduced production of proinflammatory cytokines and diminished nuclear factor-κB pathway activation. To further clarify the mechanisms of different susceptibility of these two strains to endotoxin, this study was designed to examine the alterations of cardiac and mitochondrial bioenergetics, proinflammatory cytokines, and signaling pathways after hearts were isolated and exposed to LPS ex vivo. Isolated BN and SS hearts were perfused with LPS (4 μg/mL) for 30 min in the Langendorff preparation. Lipopolysaccharide depressed cardiac function as evident by reduced left ventricular developed pressure and decreased peak rate of contraction and relaxation in SS hearts but not in BN hearts. These findings are consistent with our previous in-vivo data. Under complex I substrates, a higher oxygen consumption and hydrogen peroxide (H2O2) production were observed in mitochondria from SS hearts than those from BN hearts. Lipopolysaccharide significantly increased H2O2 levels in both SS and BN heart mitochondria; however, the increase in oxygen consumption and H2O2 production in BN heart mitochondria was much lower than that in SS heart mitochondria. In addition, LPS significantly decreased complex I activity in SS hearts but not in BN hearts. Furthermore, LPS induced higher levels of tumor necrosis factor-α and increased phosphorylation of IκκB and p65 more in SS hearts than in BN hearts. Our results clearly demonstrate that less mitochondrial dysfunction combined with a reduced production of tumor necrosis factor-α and diminished activation of nuclear factor-κB are involved in the mechanisms by which isolated BN hearts were more resistant to LPS-induced myocardial dysfunction.

Mitogen-activated protein kinase phosphatase-1 inhibits myocardial TNF-α expression and improves cardiac function during endotoxemia

AIMS

Myocardial tumour necrosis factor-α (TNF-α) expression induces cardiac dysfunction in endotoxemia. The aim of this study was to investigate the role of mitogen-activated protein kinase phosphatase-1 (MKP1) pathway in myocardial TNF-α expression and cardiac function during endotoxemia.

METHODS AND RESULTS

Lipopolysaccharide (LPS) increased MKP1 expression in the myocardium in vivo and in cultured neonatal cardiomyocytes in vitro. LPS-induced extracellular signal-regulated kinase (ERK) 1/2 and p38 phosphorylation in the myocardium was prolonged in MKP1(-/-) mice. Myocardial TNF-α mRNA and protein levels were enhanced in MKP1(-/-) compared with wild-type (WT) mice in endotoxemia, leading to a further decrease in cardiac function. To study if Rac1/p21-activated kinase 1 (PAK1) signalling regulates MKP1 expression, cardiomyocytes were treated with LPS. Inhibition of Rac1 and PAK1 by a dominant negative Rac1 adenovirus (Ad-Rac1N17) and PAK1 siRNA, respectively, blocked LPS-induced MKP1 expression in cardiomyocytes. PAK1 siRNA also decreased p38 and c-Jun N-terminal kinase (JNK) activation, and TNF-α expression induced by LPS. Furthermore, deficiency in either Rac1 or JNK1 decreased myocardial MKP1 expression in endotoxemic mice.

CONCLUSION

LPS activates the Rac1/PAK1 pathway, which increases myocardial MKP1 expression via JNK1. MKP1 attenuates ERK1/2 and p38 activation, inhibits myocardial TNF-α expression, and improves cardiac function in endotoxemia. Thus, MKP1 represents an important negative feedback mechanism limiting pro-inflammatory response in the heart during sepsis.

Targeted inhibition of calpain reduces myocardial hypertrophy and fibrosis in mouse models of type 1 diabetes

OBJECTIVE

Recently we have shown that calpain-1 activation contributes to cardiomyocyte apoptosis induced by hyperglycemia. This study was undertaken to investigate whether targeted disruption of calpain would reduce myocardial hypertrophy and fibrosis in mouse models of type 1 diabetes.

RESEARCH DESIGN AND METHODS

Diabetes in mice was induced by injection of streptozotocin (STZ), and OVE26 mice were also used as a type 1 diabetic model. The function of calpain was genetically manipulated by cardiomyocyte-specific knockout Capn4 in mice and the use of calpastatin transgenic mice. Myocardial hypertrophy and fibrosis were investigated 2 and 5 months after STZ injection or in OVE26 diabetic mice at the age of 5 months. Cultured isolated adult mouse cardiac fibroblast cells were also investigated under high glucose conditions.

RESULTS

Calpain activity, cardiomyocyte cross-sectional areas, and myocardial collagen deposition were significantly increased in both STZ-induced and OVE26 diabetic hearts, and these were accompanied by elevated expression of hypertrophic and fibrotic collagen genes. Deficiency of Capn4 or overexpression of calpastatin reduced myocardial hypertrophy and fibrosis in both diabetic models, leading to the improvement of myocardial function. These effects were associated with a normalization of the nuclear factor of activated T-cell nuclear factor-κB and matrix metalloproteinase (MMP) activities in diabetic hearts. In cultured cardiac fibroblasts, high glucose-induced proliferation and MMP activities were prevented by calpain inhibition.

CONCLUSIONS

Myocardial hypertrophy and fibrosis in diabetic mice are attenuated by reduction of calpain function. Thus targeted inhibition of calpain represents a potential novel therapeutic strategy for reversing diabetic cardiomyopathy.

Inhibition of c-Jun-N-terminal kinase increases cardiac peroxisome proliferator-activated receptor alpha expression and fatty acid oxidation and prevents lipopolysaccharide-induced heart dysfunction

Septic shock results from bacterial infection and is associated with multi-organ failure, high mortality, and cardiac dysfunction. Sepsis causes both myocardial inflammation and energy depletion. We hypothesized that reduced cardiac energy production is a primary cause of ventricular dysfunction in sepsis. The JNK pathway is activated in sepsis and has also been implicated in impaired fatty acid oxidation in several tissues. Therefore, we tested whether JNK activation inhibits cardiac fatty acid oxidation and whether blocking JNK would restore fatty acid oxidation during LPS treatment. LPS treatment of C57BL/6 mice and adenovirus-mediated activation of the JNK pathway in cardiomyocytes inhibited peroxisome proliferator-activated receptor α expression and fatty acid oxidation. Surprisingly, none of the adaptive responses that have been described in other types of heart failure, such as increased glucose utilization, reduced αMHC:βMHC ratio or induction of certain microRNAs, occurred in LPS-treated mice. Treatment of C57BL/6 mice with a general JNK inhibitor (SP600125) increased fatty acid oxidation in mice and a cardiomyocyte-derived cell line. JNK inhibition also prevented LPS-mediated reduction in fatty acid oxidation and cardiac dysfunction. Inflammation was not alleviated in LPS-treated mice that received the JNK inhibitor. We conclude that activation of JNK signaling reduces fatty acid oxidation and prevents the peroxisome proliferator-activated receptor α down-regulation that occurs with LPS.

Female stem cells are superior to males in preserving myocardial function following endotoxemia

Mesenchymal stem cells (MSCs) may offer therapeutic benefit in the setting of sepsis and endotoxemia. Previous studies suggest that MSCs from female donors may possess better protective capabilities than their male counterparts. The present study examined whether female MSCs may offer a greater protective advantage in the setting of endotoxemic cardiac dysfunction compared with male MSCs. Adult male Sprague-Dawley rats were injected intraperitoneally with LPS and then treated with intraperitoneal injections of either saline, female MSCs, or male MSCs. Hearts and serum were then collected for analysis of myocardial function, myocardial protein, and myocardial and serum cytokines. Compared with male MSC or vehicle-treated animals, female MSC treatment resulted in greater preservation of myocardial function (P < 0.001). Serum and myocardial levels of all measured cytokines were comparable between rats given MSCs from male or female donors but substantially improved over rats given vehicle (P < 0.05). Reduced myocardial inflammation correlated with reduced levels of phosphorylated p38 MAPK expression in the myocardium of animals injected with MSCs of either sex (P < 0.05). The Bcl-xL/Bax ratio was increased to a greater extent following treatment with female MSCs vs. male MSCs (P < 0.05). Intraperitoneal administration of MSCs is effective in limiting myocardial inflammation and dysfunction in the rat endotoxemia model. Compared with treatment with their male counterparts, MSC treatment from female donors is associated with greater cardiac protection against acute endotoxemic injury.

Nitric oxide and calcium signaling regulate myocardial tumor necrosis factor-α expression and cardiac function in sepsis

Myocardial tumor necrosis factor-alpha (TNF-alpha), a proinflammatory cytokine, is a critical inducer of myocardial dysfunction in sepsis. The purpose of this review is to summarize the mechanisms through which TNF-alpha production is regulated in cardiomyocytes in response to lipopolysaccharide (LPS), a key pathogen-associated molecular pattern (PAMP) in sepsis. These mechanisms include Nox2-containing NAD(P)H oxidase, phospholipase C (PLC)gamma1, and Ca2+ signaling pathways. Activation of these pathways increases TNF-alpha expression via activation of extracellular signal-regulated kinases 1 and 2 (ERK1/2) and p38 mitogen-activated protein kinase (MAPK). Conversely, activation of c-Jun NH2-terminal kinase 1 (JNK1) negatively regulates TNF-alpha production through inhibition of ERK1/2 and p38 MAPK activity. Interestingly, endothelial nitric oxide synthase (eNOS) promotes TNF-alpha expression by enhancing p38 MAPK activation, whereas neuronal NOS (nNOS) inhibits TNF-alpha production by reducing Ca2+-dependent ERK1/2 activity. Therefore, the JNK1 and nNOS inhibitory pathways represent a "brake" that limits myocardial TNF-alpha expression in sepsis. Further understanding of these signal transduction mechanisms may lead to novel pharmacological therapies in sepsis.

Disruption of Rac1 signaling reduces ischemia-reperfusion injury in the diabetic heart by inhibiting calpain

Diabetes increases myocardial ischemia/reperfusion (I/R) injury. However, the underlying mechanisms remain incompletely understood. This study investigated the role of Rac1 signaling and calpain in exacerbated I/R injury in diabetic hearts. Mice with cardiac-specific deletion of Rac1 (Rac1-ko) and transgenic mice with cardiac-specific superoxide dismutase-2 (SOD2) or calpastatin overexpression were rendered diabetic with streptozotocin. Isolated perfused hearts were subjected to global I/R. After I/R, Rac1 activity was significantly enhanced in diabetic compared with nondiabetic hearts. Diabetic hearts displayed more severe I/R injury than nondiabetic hearts, as evidenced by more lactate dehydrogenase release and apoptosis and decreased cardiac function. These adverse impacts of diabetes were abrogated in Rac1-ko hearts or by perfusion with the Rac1 inhibitor NSC23766. In an in vivo I/R mouse model, infarct size was much smaller in diabetic Rac1-ko compared with wild-type mice. Inhibition of Rac1 signaling prevented NADPH oxidase activation, reactive oxygen species production, and protein carbonyl accumulation, leading to inhibition of calpain activation. Furthermore, SOD2 or calpastatin overexpression significantly reduced I/R injury in diabetic hearts and improved cardiac function after I/R. In summary, Rac1 activation increases I/R injury in diabetic hearts and the role of Rac1 signaling is mediated, at least in part, through calpain activation.

High-mobility group box 1 (HMGB1) downregulates cardiac transient outward potassium current (Ito) through downregulation of Kv4.2 and Kv4.3 channel transcripts and proteins

Transient outward potassium currents (I(to)) are major early repolarization currents in shaping cardiac action potential (AP). Downregulation of I(to) contributes to AP configuration alteration in myocardial infarction (MI) and numerous other heart diseases. High-mobility group box 1 (HMGB1), a proinflammatory cytokine, has been reported to increase dramatically in the serum of patients with MI, participating in ischemia-reperfusion injury and recovery of post-infarction failing heart. This study investigated the possible role of HMGB1 in regulating cardiac I(to) and electrical stability. HMGB1 treatment for 24h significantly inhibited the current densities of heterologously expressed Kv4.3 and Kv4.2 in COS-7 cells and native I(to) in neonatal rat ventricular myocytes (NRVMs) in a dose-dependent manner. HMGB1 decreased the mRNA and protein levels of the I(to) alpha subunits Kv4.2 and Kv4.3 channels, but not the beta subunit KChIP2 and KCNE2 in NRVMs. The receptor binding domain (150-186 amino acid residues) responsible for receptor of advanced glycation end product (RAGE) binding similarly inhibited I(to)(,) while treatment with soluble RAGE that blocks binding of ligands to cell-surface RAGE partially restored I(to) current density and Kv4 protein expressions. Box A which possesses no proinflammatory activity of HMGB1 still remained part of the I(to) suppression effect. In addition to downregulating I(to), HMGB1 modestly inhibited L-type Ca(2+) current, but not I(K1). The AP duration (APD) was slightly prolonged by HMGB1 treatment. These results collectively establish HMGB1 as a novel pathological factor downregulating I(to) partially through HMGB1-RAGE interaction, providing new insights into the potential molecular mechanisms underlying the electrical remodeling in MI.

miR133a regulates cardiomyocyte hypertrophy in diabetes

BACKGROUND

Diabetic cardiomyopathy, characterized by cardiac hypertrophy and contractile dysfunction, eventually leads to heart failure. We have previously shown that alterations of a number of key molecules are involved in producing cardiomyocyte hypertrophy in diabetes. The aim of the present study was to determine whether microRNAs (miRNA) play a role in mediating altered gene expression and structural/functional deficits in the heart in diabetes.

METHODS

STZ-induced diabetic mice were haemodynamically investigated after 2 months of diabetes to establish the development of cardiomyopathy. The tissues were then examined for gene expression and microRNA analysis. We further investigated neonatal rat cardiomyocytes to identify the mechanisms of glucose-induced hypertrophy and the potential role of miR133a.

RESULTS

Diabetic mice showed myocardial contractile dysfunction and augmented mRNA expression of atrial and brain natriuretic peptides (ANP, BNP), MEF2A and MEF2C, SGK1 and IGF1R compared to age- and sex-matched controls. Cardiac tissues from these mice showed alteration of multiple miRNAs by array analysis including miR133a, which was confirmed by RT-PCR. In vitro exposure of cardiomyocytes to high levels of glucose produced hypertrophic changes and reduced expression of miRNA133a. Finally, transfection of miR133a mimics prevented altered gene expression and hypertrophic changes.

CONCLUSION

Data from these studies demonstrate a novel glucose-induced mechanism regulating gene expression and cardiomyocyte hypertrophy in diabetes which is mediated through miR133a.

The alarmin cytokine, high mobility group box 1, is produced by viable cardiomyocytes and mediates the lipopolysaccharide-induced myocardial dysfunction via a TLR4/phosphatidylinositol 3-kinase gamma pathway

High mobility group box 1 (HMGB1) is an alarmin actively secreted by immune cells and passively released by necrotic nonimmune cells. HMGB1 has been implicated in both cardiac contractile dysfunction and the lethality associated with sepsis/endotoxemia. The aim of the current study was to assess whether viable cardiomyocytes could produce HMGB1 and whether HMGB1 can affect myocardial contractility. LPS was used as a model of sepsis/endotoxemia in mice and isolated cardiac myocytes. LPS increased myocardial expression of HMGB1 in vivo (immunohistochemistry) and production and secretion of HMGB1 by viable cardiac myocytes in vitro (Western). LPS increased the phosphorylation status of PI3Kgamma in cardiac myocytes, an effect not observed in TLR4(-/-) myocytes. Genetic (PI3Kgamma(-/-)) or pharmacologic (AS605240) blockade of PI3Kgamma ameliorated the LPS-induced 1) cardiomyocyte production and secretion of HMGB1 in vitro and 2) HMGB1 expression in the myocardium in vivo. The LPS-induced depression of myocardial contractility was prevented by the HMGB1 antagonist, A-box. Genetic (PI3Kgamma(-/-)) or pharmacologic (AS605240) blockade of PI3Kgamma ameliorated the LPS-induced decrease in myocardial contractility. No evidence of inflammatory infiltrate was noted in any of the in vivo studies. The findings of the current study indicate that 1) LPS can induce HMGB1 secretion by viable cardiac myocytes through a TLR4/PI3Kgamma signaling pathway, and 2) HMGB1 plays a role in the LPS-induced myocardial contractile dysfunction. The results of the current study also have broader implications (i.e., that viable parenchymal cells, such as cardiac myocytes, participate in the alarmin response).

Fos proteins suppress dextran sulfate sodium-induced colitis through inhibition of NF-kappaB

The Fos family proteins, c-Fos and Fra-1, are components of the dimeric transcription factor AP-1, which is typically composed of Fos and Jun family proteins. We have previously shown that mice lacking c-Fos (Fos(-/-) mice) respond more strongly to LPS injection than do wild-type (wt) controls. We then examined the sensitivity of Fos(-/-) mice to acute inflammatory stress in a dextran sulfate sodium (DSS)-induced colitis model. We found that Fos(-/-) mice exhibited more severe weight loss, bleeding, diarrhea, and colon shortening than did wt mice, in association with higher TNF-alpha production and NF-kappaB activity in colon segments of DSS-treated Fos(-/-) mice. Furthermore, NF-kappaB inhibition suppressed severe DSS-induced colitis in Fos(-/-) mice. In contrast, Fra-1 transgenic (Tg) mice responded poorly to LPS injection, and Fra-1-overexpressing macrophages and fibroblasts showed reduced production of proinflammatory cytokines, NO, and NF-kappaB activity. Remarkably, in the DSS-induced colitis model, Fra-1 Tg mice showed less severe clinical scores of colitis than did wt mice. Consistently, proinflammatory cytokine production and NF-kappaB activity in colon segments of DSS-treated Fra-1 Tg mice were lower than in wt controls. These findings reveal that the absence of c-Fos and overexpression of Fra-1 respectively enhance and suppress the activation of NF-kappaB in DSS-induced inflammatory stress. In this paper, we propose that AP-1 transcription factors containing c-Fos or Fra-1 are negative regulators of NF-kappaB-mediated stress responses.

Cardiomyocyte-specific overexpression of human stem cell factor improves cardiac function and survival after myocardial infarction in mice

BACKGROUND

Soluble stem cell factor (SCF) has been shown to mobilize bone marrow stem cells and improve cardiac repair after myocardial infarction (MI). However, the effect of membrane-associated SCF on cardiac remodeling after MI is not known. The present study investigated the effects of cardiomyocyte-specific overexpression of the membrane-associated isoform of human SCF (hSCF) on cardiac function after MI.

METHODS AND RESULTS

A novel mouse model with tetracycline-inducible and cardiac-specific overexpression of membrane-associated hSCF was generated. MI was induced by left coronary artery ligation. Thirty-day mortality after MI was decreased in hSCF/tetracycline transactivator (tTA) compared with wild-type mice. In vivo cardiac function was significantly improved in hSCF/tTA mice at 5 and 30 days after MI compared with wild-type mice. Endothelial progenitor cell recruitment and capillary density were increased and myocardial apoptosis was decreased in the peri-infarct area of hSCF/tTA mice. Myocyte size was decreased in hSCF/tTA mice 30 days after MI compared with WT mice. Furthermore, hSCF overexpression promoted de novo angiogenesis as assessed by matrigel implantation into the left ventricular myocardium.

CONCLUSIONS

Cardiomyocyte-specific overexpression of hSCF improves myocardial function and survival after MI. These beneficial effects of hSCF may result from increases in endothelial progenitor cell recruitment and neovascularization and decreases in myocardial apoptosis and cardiac remodeling.