MAPK14 Activation Research Articles

The role of miR-128-3p through MAPK14 activation in the apoptosis of GC2 spermatocyte cell line following heat stress.

MicroRNAs play a crucial role in the regulation of spermatogenesis. For example, miR-128-3p expression is known to decrease significantly after testicular hyperthermia, but the regulatory effect of this change on the spermatogenesis damage caused by heat stress remains unclear. This study aimed to verify whether the target gene of miR-128-3p is MAPK14, which affects spermatogenic cell proliferation and apoptosis under testicular hyperthermia. Mouse testis and GC2 spermatocyte cell line heat stress models were established. miR-128-3p expression before and after heat stress was analyzed by reverse transcription polymerase chain reaction. MAPK14 and p-MAPK14 expression was detected by Western blot, and cell apoptosis was analyzed by Annexin V-FITC/PI. Subsequently, miR-128-3p inhibitors and mimics were used to interfere with spermatocytes before and after heat stress, respectively, for correlation detection. Compared with the control group, the heat stress group showed decreased miR-128-3p expression, increased p-MAPK14 expression, and decreased cell proliferation activity. In the GC2-spd cell line in vitro, miR-128-3p inhibitors were found to upregulate p-MAPK14 expression, reduce cell proliferation activity, and increase apoptosis, consistent with the results obtained in the heat treatment alone. Furthermore, miR-128-3p mimics transfected in the GC2 cells after heat stress reduced p-MAPK14 expression, alleviated the decrease in cell proliferation, and decreased the apoptosis level. The downregulation of miR-128-3p expression plays an important role in spermatogenesis damages after testicular hyperthermia, which is probably attributable to the activation of the MAPK signaling pathway. Downregulated miR-128-3p expression induces the apoptosis and inhibits the proliferation of spermatogenic cells by promoting MAPK14 phosphorylation.

ROS amplification drives mouse spermatogonial stem cell self-renewal.

Reactive oxygen species (ROS) play critical roles in self-renewal division for various stem cell types. However, it remains unclear how ROS signals are integrated with self-renewal machinery. Here, we report that the MAPK14/MAPK7/BCL6B pathway creates a positive feedback loop to drive spermatogonial stem cell (SSC) self-renewal via ROS amplification. The activation of MAPK14 induced MAPK7 phosphorylation in cultured SSCs, and targeted deletion of Mapk14 or Mapk7 resulted in significant SSC deficiency after spermatogonial transplantation. The activation of this signaling pathway not only induced Nox1 but also increased ROS levels. Chemical screening of MAPK7 targets revealed many ROS-dependent spermatogonial transcription factors, of which BCL6B was found to initiate ROS production by increasing Nox1 expression via ETV5-induced nuclear translocation. Because hydrogen peroxide or Nox1 transfection also induced BCL6B nuclear translocation, our results suggest that BCL6B initiates and amplifies ROS signals to activate ROS-dependent spermatogonial transcription factors by forming a positive feedback loop.

Vascular smooth muscle-MAPK14 is required for neointimal hyperplasia by suppressing VSMC differentiation and inducing proliferation and inflammation

Injury-induced stenosis is a serious vascular complication. We previously reported that p38α (MAPK14), a redox-regulated p38MAPK family member was a negative regulator of the VSMC contractile phenotype in vitro. Here we evaluated the function of VSMC-MAPK14 in vivo in injury-induced neointima hyperplasia and the underlying mechanism using an inducible SMC-MAPK14 knockout mouse line (iSMC-MAPK14-/-). We show that MAPK14 expression and activity were induced in VSMCs after carotid artery ligation injury in mice and ex vivo cultured human saphenous veins. While the vasculature from iSMC-MAPK14-/- mice was indistinguishable from wildtype littermate controls at baseline, these mice exhibited reduced neointima formation following carotid artery ligation injury. Concomitantly, there was an increased VSMC contractile protein expression in the injured vessels and a decrease in proliferating cells. Blockade of MAPK14 through a selective inhibitor suppressed, while activation of MAPK14 by forced expression of an upstream MAPK14 kinase promoted VSMC proliferation in cultured VSMCs. Genome wide RNA array combined with VSMC lineage tracing studies uncovered that vascular injury evoked robust inflammatory responses including the activation of proinflammatory gene expression and accumulation of CD45 positive inflammatory cells, which were attenuated in iSMC-MAPK14-/- mice. Using multiple pharmacological and molecular approaches to manipulate MAPK14 pathway, we further confirmed the critical role of MAPK14 in activating proinflammatory gene expression in cultured VSMCs, which occurs in a p65/NFkB-dependent pathway. Finally, we found that NOX4 contributes to MAPK14 suppression of the VSMC contractile phenotype. Our results revealed that VSMC-MAPK14 is required for injury-induced neointima formation, likely through suppressing VSMC differentiation and promoting VSMC proliferation and inflammation. Our study will provide mechanistic insights into therapeutic strategies for mitigation of vascular stenosis.

Abstract 082: High Fat Diet Promotes Haplotype Dependent Differential Transcriptional Regulation of the Human Angiotensinogen Gene

Angiotensinogen (AGT) is the only known precursor to angiotensin II. Systemic renin angiotensin aldosterone system (RAAS) is activated in human and experimental models of obesity. RAAS activation in obesity is linked to the development of cardiovascular pathophysiologies. We have identified polymorphisms in 2.5 Kb promoter of human angiotensinogen gene (hAGT) that forms two haplotype (Hap) blocks: -6A/G (-1670A/G, -1562C/T, -1561T/C) and -217A/G (-532T/C, -793A/G, -1074T/C,& -1178G/A). Hap -6A/-217A (Hap -6A) is associated with human hypertension whereas, Hap -6G/-217G (Hap -6G) reduces cardiovascular risk. Here, we examine high fat diet-mediated allele-specific transcriptional regulation of the hAGT gene in adipose tissue, in vivo, in transgenic (TG) mice engineered with either haplotype of the hAGT gene. Twelve-week-old male TG mice with Hap –6A or –6G were fed normal diet (10% kcal as fat) and high fat diet (60% kcal as fat) for 10 weeks. Using Q - RT PCR and western blot we show increased hAGT expression in adipose tissue of the Hap -6A-TG mice after high fat diet than control diet (Hap -6A-0.68±0.04 vs. Hap -6G- 0.33±0.03 A.U., p<0.05). ChIP assay shows greater chromatin binding of GR, MR, CEBPβ and STAT3 transcriptional factors (Hap -6A- 0.80±0.04 vs. Hap -6G- 0.26±0.06 A.U., p<0.05) to the hAGT transgenes in Hap -6A TG mice after high fat diet. No significant change was observed in the endogenous mouse AGT gene. In addition, after high fat diet, change ([[Unable to Display Character: ∆]]) in inflammatory and redox markers was significantly (p<0.05) greater in TG mice with Hap I including, IL1 (4.6±0.8 vs. 2.1±0.49 fold), IL6 (4.0±0.69 vs. 2.1±0.2 fold) and NOX1 (8.3±0.4 vs. 2.5±0.6 fold). This is accompanied by reduction in levels of antioxidant defenses (SOD1: 0.97±0.0 vs. 1.4±0.1 fold; HO1: 0.77±0.1 vs. 1.3±0.2 fold) & activation of MAPK14 and ERK1/2 signaling. Taken together, our results show that SNPs in the hAGT Hap -6A favor high fat diet induced binding of transcriptional factors GR, MR, CEBP-β and STAT3 that lead to elevated expression of the hAGT in expanded mass of the adipose tissue. This also activates the RAAS with pathophysiological implications including, phosphorylation of kinases such as MAPK14 and ERK2, increase in tissue pro-inflammatory and oxidative stress molecules.

Abstract 192: High Fat Diet Promotes Haplotype Dependent Differential Transcriptional Regulation of the Human Angiotensinogen Gene

Angiotensinogen (AGT) is the only known precursor to angiotensin II. Systemic renin angiotensin aldosterone system (RAAS) is activated in human and experimental models of obesity. RAAS activation in obesity is linked to the development of cardiovascular pathophysiologies. We have identified polymorphisms in 2.5 Kb promoter of human angiotensinogen gene (hAGT) that forms two haplotype (Hap) blocks: -6A/G (-1670A/G, -1562C/T, -1561T/C) and -217A/G (-532T/C, -793A/G, -1074T/C,& -1178G/A). Hap -6A/-217A (Hap -6A) is associated with human hypertension whereas, Hap -6G/-217G (Hap -6G) reduces cardiovascular risk. Here, we examine high fat diet-mediated allele-specific transcriptional regulation of the hAGT gene in adipose tissue, in vivo, in transgenic (TG) mice engineered with either haplotype of the hAGT gene. Twelve-week-old male TG mice with Hap –6A or –6G were fed normal diet (10% kcal as fat) and high fat diet (60% kcal as fat) for 10 weeks. Using Q - RT PCR and western blot we show increased hAGT expression in adipose tissue of the Hap -6A-TG mice after high fat diet than control diet (Hap -6A-0.68±0.04 vs. Hap -6G- 0.33±0.03 A.U., p<0.05). ChIP assay shows greater chromatin binding of GR, MR, CEBPβ and STAT3 transcriptional factors (Hap -6A- 0.80±0.04 vs. Hap -6G- 0.26±0.06 A.U., p<0.05) to the hAGT transgenes in Hap -6A TG mice after high fat diet. No significant change was observed in the endogenous mouse AGT gene. In addition, after high fat diet, change ([[Unable to Display Character: ∆]]) in inflammatory and redox markers was significantly (p<0.05) greater in TG mice with Hap I including, IL1 (4.6±0.8 vs. 2.1±0.49 fold), IL6 (4.0±0.69 vs. 2.1±0.2 fold) and NOX1 (8.3±0.4 vs. 2.5±0.6 fold). This is accompanied by reduction in levels of antioxidant defenses (SOD1: 0.97±0.0 vs. 1.4±0.1 fold; HO1: 0.77±0.1 vs. 1.3±0.2 fold) & activation of MAPK14 and ERK1/2 signaling. Taken together, our results show that SNPs in the hAGT Hap -6A favor high fat diet induced binding of transcriptional factors GR, MR, CEBP-β and STAT3 that lead to elevated expression of the hAGT in expanded mass of the adipose tissue. This also activates the RAAS with pathophysiological implications including, phosphorylation of kinases such as MAPK14 and ERK2, increase in tissue pro-inflammatory and oxidative stress molecules.

VPAC2 receptor agonist BAY 55-9837 increases SMN protein levels and moderates disease phenotype in severe spinal muscular atrophy mouse models

BackgroundSpinal Muscular Atrophy (SMA) is one of the most common inherited causes of infant death and is caused by the loss of functional survival motor neuron (SMN) protein due to mutations or deletion in the SMN1 gene. One of the treatment strategies for SMA is to induce the expression of the protein from the homologous SMN2 gene, a rescuing paralog for SMA.Methods and resultsHere we demonstrate the promise of pharmacological modulation of SMN2 gene by BAY 55-9837, an agonist of the vasoactive intestinal peptide receptor 2 (VPAC2), a member of G protein coupled receptor family. Treatment with BAY 55-9837 lead to induction of SMN protein levels via activation of MAPK14 or p38 pathway in vitro. Importantly, BAY 55-9837 also ameliorated disease phenotype in severe SMA mouse models.ConclusionOur findings suggest the VPAC2 pathway is a potential SMA therapeutic target.

Bovine spermatozoa react to in vitro heat stress by activating the mitogen-activated protein kinase 14 signalling pathway

Heat stress has long been recognised as a cause of subfertility in farm animals. The objectives of the present study were to elucidate the effect of heat stress on sperm function and involvement of the mitogen-activated protein kinase (MAPK) 14 signalling pathway. Spermatozoa incubated for 4 h at a physiological temperature (38.5°C) exhibited significantly (P<0.05) reduced motility, plasma membrane integrity and mitochondrial potential compared with non-incubated spermatozoa; the reductions in these parameters were more severe following incubation at a hyperthermic (41°C) temperature (P<0.01). Percentages of fertilisation and embryo development were highly affected in spermatozoa incubated at 41°C compared with non-incubated spermatozoa (P<0.01). Similarly, embryo quality was adversely affected by sperm incubation at 41°C, as indicated by a higher apoptotic cell ratio in Day 7 blastocysts compared with that in the non-incubated control group (14.6% vs 6.7%, respectively; P<0.01). Using SB203580 (10 µgmL(-1)), a specific inhibitor of the p38 MAPK pathway, during sperm hyperthermia reduced MAPK14 activation (24.9% vs 35.6%), increased sperm motility (45.8% vs 26.5%) and reduced DNA fragmentation (16.9% vs 23.4%) compared with the untreated control group, but did not improve subsequent fertilisation and embryo development. In conclusion, heat stress significantly affects the potential of spermatozoa to penetrate oocytes, as well as subsequent embryo development and quality. Notably, the data show that the MAPK14 signalling pathway is largely involved in heat-induced sperm damage. However, further research is needed to elucidate other signalling pathways possibly involved in heat-induced sperm damage.

Abstract 3445: The role of p38/MAPK14 in cerebellar granule neuron precursor proliferation and medulloblastoma

Abstract Development of the cerbellum occurs primarily postnatally and is marked by a rapid proliferation of cerebellar granule neuron precursors (CGNPs). This proliferation requires the activity of the mitogen Sonic Hedgehog (Shh). CGNPs are proposed to be the cells of origin for some classes of medulloblastoma (MB), the most common solid pediatric tumor, making their proliferation an attractive target for cancer therapy. Since MAP kinases play important roles in many aspects of development, proliferation, and cancer, we investigated if any of the three major classes of MAP kinases were involved in Shh-driven CGNP proliferation. We have previously shown that p42/p44 ERK MAP kinases are not involved in Shh signaling in CGNP proliferation. We have also shown that JNK/SAP kinases are not involved in Shh-driven proliferation. However, p38/MAPK14 is induced and activated in proliferating CGNPs compared to CGNPs that exit the cell cycle and differentiate in the absence of Shh. Other known pathway components upstream and downstream of MAPK14, such as ASK1, MKK3 and ATF-2, are also activated in the presence of Shh. Antioxidants such as lipoic acid and n-acetyl-cysteine that relieve oxidative stress reduced Shh-induced activation of MAPK14 and caused a marked decrease in CGNP proliferation measured by Ki67 and BrdU staining. Knocking down p38 in CGNPs also causes a marked decrease in Shh-dependent proliferation and an increase in apoptosis, which indicates a role for MAPK14 in CGNP survival. We are currently investigating the mechanism of Shh regulation of p38 MAPK pathway, which will lead to a better understanding of CGNP proliferation, cerebellar development, and MB progression. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 3445. doi:10.1158/1538-7445.AM2011-3445

MAPK14 Cooperates with MAPK3/1 to Regulate Endothelin-1-Mediated Prostaglandin Synthase 2 Induction and Survival in Leiomyoma but Not in Normal Myometrial Cells1

We recently reported that in ELT3 uterine leiomyoma cells, but not in normal myometrial cells, endothelin (ET)-1 exerts a survival effect insensitive to MAPK3/1(ERK1/2) inhibition. In the present work, we investigated the potential role of MAPK14 (p38) in this ET-1-mediated effect. We demonstrated that, in ELT3, but not in normal myometrial cells, ET-1 activated MAPK14. Data based on pharmacological and siRNA approaches indicate that ETA and ETB receptors contributed to the activation of MAPK14 by ET-1 through a mechanism involving Gi protein, but not PI3-kinase. The inhibition of MAPK3/1 by U0126 did not affect the activation of MAPK14 by ET-1. Conversely, the inhibition of MAPK14 by SB203580 and the down-regulation of MAP2K3/MAP2K6 (kinases upstream of MAPK14) by specific siRNA did not alter the activation of MAPK3/1. These data indicate that MAPK14 was activated by ET-1 independently from MAPK3/1. Furthermore, ET-1 increased protein expression of prostaglandin synthase 2 (PTGS2 or COX2), prostaglandin E2 (PGE2) production, and subsequent ELT3 cell survival. The inhibition of PTGS2 induction and subsequent survival induced by ET-1 required the coinhibition of MAPK14 and MAPK3/1. Our findings provide evidence that ET-1 activated MAPK14 only in ELT3 cells, but not in normal myometrial cells. This MAPK14 activation was required, in addition to MAPK3/1 in ET-1-mediated survival through the COX2/prostaglandin axis, and may explain the absence of ET-1 antiapoptotic effect in normal myometrial cells. Our data reinforce the role of ET-1 and associated signaling pathways in leiomyoma pathology.

Abstract LB-13: The role of p38/MAPK14 in Sonic Hedgehog-driven CGNP proliferation

Abstract Development of the cerbellum occurs primarily postnatally and is marked by a rapid proliferation of cerebellar granule neuron precursors (CGNPs). This proliferation requires the activity of the mitogen Sonic Hedgehog (Shh). The rapid proliferation stage of CGNPs has led to speculation that they are the cells of origin for some classes of medulloblastoma, the most common solid pediatric tumor. Since MAP kinases play important roles in many aspects of development, proliferation, and cancer we investigated if any of the three major classes of MAP kinases were involved in Shh-driven CGNP proliferation. We have previously shown that p42/p44 ERK MAP kinases are not involved in Shh signaling in CGNP proliferation. We have also shown that JNK/SAP kinases are not involved in Shh-driven proliferation. However, p38/MAPK14 is induced and activated in proliferating CGNPs compared to CGNPs that exit the cell cycle and differentiate in the absence of Shh. Other known pathway components upstream and downstream of MAPK14, such as ASK1, MKK3 and ATF-2, are also activated in the presence of Shh. Antioxidants such as lipoic acid and n-acetyl-cysteine that relieve oxidative stress reduced Shh-induced activation of MAPK14 and caused a marked decrease in CGNP proliferation measured by Ki67 and BrdU staining. We are currently investigating the role of oxidative stress and MAPK14 in CGNP proliferation by over-expressing and knocking down MAPK14 in CGNPs under oxidative stress conditions. Preliminary data suggests that knocking down MAPK14 reduces CGNP proliferation. Elucidating the role of MAPK14 pathway in CGNP proliferation will not only help us understand normal cerebellum development but may also lead to possible therapies for diseases where constitutive Shh signaling has been shown to play a role such as some classes of medulloblastoma and Gorlin's syndrome. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr LB-13.

Mitogen-Activated Protein Kinase Signaling in Male Germ Cell Apoptosis in the Rat1

Programmed germ cell death is critical for functional spermatogenesis. Increased germ cell apoptosis can be triggered by various regulatory stimuli, including testicular hyperthermia or deprivation of gonadotropins and intratesticular testosterone. We have previously shown the involvement of the mitogen-activated protein kinase (MAPK) 14 in apoptotic signaling of male germ cells across species after hormone deprivation. This study investigates the role of MAPK14 in germ cell apoptosis in rats triggered by testicular hyperthermia. The contributions of the MAPK1/3 and the MAPK8 to male germ cell death were also examined after this intervention. We show that 1) testicular hyperthermia results in induction of both MAPK1/3 and MAPK14 but not MAPK8; 2) inhibition of MAPK1/3 has no effect on the incidence of heat-induced germ cell apoptosis, suggesting that MAPK1/3 signaling may be dispensable for heat-induced male germ cell apoptosis; and 3) activation of MAPK14 and BCL2 phosphorylation are critical for heat-induced male germ cell apoptosis in rats. Thus, unlike the hormone deprivation model, heat stress through activation of the MAPK14 signaling promotes germ cell apoptosis by provoking BCL2 phosphorylation, leading to its inactivation and the subsequent activation of the mitochondria-dependent death pathway. These novel findings point to a critical role of MAPK14 in stage- and cell-specific activation of male germ cell apoptosis triggered by hormone deprivation or heat stress.

Transforming Growth Factor B1 Stimulated DNA Synthesis in the Granulosa Cells of Preantral Follicles: Negative Interaction with Epidermal Growth Factor1

EGF or TGFB1 alone stimulates but together attenuate granulosa cell DNA synthesis. Intact preantral follicles from hamsters were cultured with TGFB1, EGF, or both to reveal the mechanisms of such unique regulation. Follicular CCND2 (also known as cyclin D2), CDKN1B (also known as p27(kip1)), and the involvement of appropriate signaling intermediaries and kinases were examined. TGFB1, acting via SMAD2 and SMAD3, antagonized the degradation of CCND2 protein by blocking its phosphorylation. In contrast, TGFB1 supported CDKN1B degradation by involving MAPK14 (also known as p38 Map Kinase) and PKC, resulting in CDK4 activation and DNA synthesis. EGF via MAPK3/1 maintained functional levels of CCND2 through CCND2 synthesis as well as degradation. EGF and TGFB1 together inhibited CDK4 activation and DNA synthesis. EGF attenuated TGFB1 stimulated phosphorylation of SMAD3, TGFB1-induced activation of MAPK14 and PKC, and TGFB1 suppression of CCND2 degradation. In contrast, TGFB1 suppressed EGF-induced increase in CCND2 mRNA levels. The final outcome was CCND2 degradation without replenishment and decreased activities of MAPK14 and PKC leading to suppression of CDK4 activation. The results indicate that each growth factor involves a separate mechanism to maintain an effective level of CCND2 in granulosa cells for the activation of CDK4 and induction of DNA synthesis. However, their simultaneous action is inhibitory to follicular DNA synthesis because they counteract each other's activity by interfering at specific sites. Because both EGF and TGFB1 are present in granulosa cells, this mechanism may explain how their effects are temporally modulated for granulosa cell proliferation and folliculogenesis.