Apoptosis induced by withdrawal of trophic factors is mediated by p38 mitogen-activated protein kinase

Thymol Protects against 5-Fluorouracil-Induced Hepatotoxicity via the Regulation of the Akt/GSK-3β Pathway in In Vivo and In Silico Experimental Models

BACKGROUND

5-fluorouracil (5-FU) is a widely used, highly effective chemotherapeutic agent. However, its therapeutic efficacy is often limited by associated adverse effects, with hepatotoxicity being frequently reported with 5-FU therapy. Thymol is a monoterpene found in thyme (Thymus vulgaris L., Lamiaceae) and is known for its antioxidant, anti-apoptotic, and anticancer activities. This study aimed to explore the hepatoprotective activity of thymol against 5-FU-induced liver injury.

METHODS

Rats received two intraperitoneal doses of 5-FU (150 mg/kg) either alone or in combination with thymol at doses of 60 mg/kg or 120 mg/kg. Liver enzymes, oxidative stress, and apoptotic markers, in addition to histopathological changes, were assessed.

RESULTS

5-FU induced marked liver injuries as evidenced by elevated liver enzymes and histopathological changes, in addition to abnormalities of oxidative and apoptotic markers. The administration of thymol ameliorated the 5-FU-induced oxidative damage through increasing hepatic antioxidants and lowering lipid peroxidation. Apoptotic response markers such as Bax, Bcl-2, Bax/Bcl-2 ratio, and PARP were also improved. Furthermore, Western blotting analysis showed that thymol modulated the 5-FU-induced changes in the expression of Akt/GSK-3β and p44/42 MAPK (ERK1/2) signaling pathways.

CONCLUSIONS

Our research is the first to shed light on thymol's potential protective effect against 5-FU- induced hepatotoxicity by inhibiting oxidative and apoptotic pathways and modulating the Akt/ GSK-3β as well as p44/42 MAPK (ERK1/2) signaling pathways.

Interleukin 3 Inhibits Glutamate-Cytotoxicity in Neuroblastoma Cell Line

Interleukin 3 (IL-3) is a well-known pleiotropic cytokine that regulates the proliferation and differentiation of hematopoietic progenitor cells, triggering classical signaling pathways such as JAK/STAT, Ras/MAPK, and PI3K/Akt to carry out its functions. Interestingly, the IL-3 receptor is also expressed in non-hematopoietic cells, playing a crucial role in cell survival. Our previous research demonstrated the expression of the IL-3 receptor in neuron cells and its protective role in neurodegeneration. Glutamate, a principal neurotransmitter in the central nervous system, can induce cellular stress and lead to neurotoxicity when its extracellular concentrations surpass normal levels. This excessive glutamate presence is frequently observed in various neurological diseases. In this study, we uncover the protective role of IL-3 as an inhibitor of glutamate-induced cell death, analyzing the cytokine's signaling pathways during its protective effect. Specifically, we examined the relevance of JAK/STAT, Ras/MAPK, and PI3 K signaling pathways in the molecular mechanism triggered by IL-3. Our results show that the inhibition of JAK, ERK, and PI3 K signaling pathways, using pharmacological inhibitors, effectively blocked IL-3's protective role against glutamate-induced cell death. Additionally, our findings suggest that Bcl-2 and Bax proteins may be involved in the molecular mechanism triggered by IL-3. Our investigation into IL-3's ability to protect neuronal cells from glutamate-induced damage offers a promising therapeutic avenue with potential clinical implications for several neurological diseases characterized by glutamate neurotoxicity.

Deoxycholic acid inhibits ASFV replication by inhibiting MAPK signaling pathway

African swine fever (ASF) is an acute, febrile, highly contagious infection of pigs caused by the African swine fever virus (ASFV). The purpose of this study is to understand the molecular mechanism of ASFV infection and evaluate the effect of DCA on MAPK pathway, so as to provide scientific basis for the development of new antiviral drugs. The transcriptome analysis found that ASFV infection up-regulated the IL-17 and MAPK signaling pathways to facilitate viral replication. Metabolome analysis showed that DCA levels were up-regulated after ASFV infection, and that exogenous DCA could inhibit activation of the MAPK pathway by ASFV infection and thus inhibit viral replication. Dual-luciferase reporter assays were used to screen the genes of ASFV and revealed that I73R could significantly up-regulate the transcription level of AP-1 transcription factor in the MAPK pathway. Confocal microscopy demonstrated that I73R could promote AP-1 entry into the nucleus, and that DCA could inhibit the I73R-mediated nuclear entry of AP-1, inhibiting MAPK pathway, and I73R interacts with AP-1. These results indicated that DCA can inhibit ASFV-mediated activation of the MAPK pathway, thus inhibiting ASFV replication. This study provides a theoretical basis for research on ASF pathogenesis and for antiviral drug development.

Dissection of MKK6 and p38 Signaling Using Light-Activated Protein Kinases

Stress-activated signaling pathways orchestrate cellular behaviors and fates. Studying the precise role(s) of stress-activated protein kinases is challenging, because stress conditions induce adaptation and impose selection pressure. To meet this challenge, we have applied an optogenetic system with a single plasmid to express light-activated p38α or its upstream activator, MKK6, in conjunction with live-cell fluorescence microscopy. In starved cells, decaging of constitutively active p38α or MKK6 by brief exposure to UV light elicits rapid p38-mediated signaling, release of cytochrome c from mitochondria, and apoptosis with different kinetics. In parallel, light activation of p38α also suppresses autophagosome formation, similarly to stimulation with growth factors that activate PI3K/Akt/mTORC1 signaling. Active MKK6 negatively regulates serum-induced ERK activity, which is p38-independent as previously reported. Here, we reproduce that result with the one plasmid system and show that although decaging active p38α does not reduce basal ERK activity in our cells, it can block growth factor-stimulated ERK signaling in serum-starved cells. These results clarify the roles of MKK6 and p38α in dynamic signaling programs, which act in concert to actuate apoptotic death while suppressing cell survival mechanisms.

The Molecular Mechanisms of Action of Photobiomodulation Against Neurodegenerative Diseases: A Systematic Review

Neurodegenerative diseases might be slow but relentless, as we continue to fail in treating or delaying their progression. Given the complexity in the pathogenesis of these diseases, a broad-acting approach like photobiomodulation can prove promising. Photobiomodulation (PBM) uses red and infrared light for therapeutic benefits, working by stimulating growth and proliferation. The implications of photobiomodulation have been studied in several neurodegenerative disease models. It has been shown to improve cell survival, decrease apoptosis, alleviate oxidative stress, suppress inflammation, and rescue mitochondrial function. In in vivo models, it has reportedly preserved motor and cognitive skills. Beyond mitochondrial stimulation, the molecular mechanisms by which photobiomodulation protects against neurodegeneration have not been very well studied. This review has systematically been undertaken to study the effects of photobiomodulation at a molecular level and identify the different biochemical pathways and molecular changes in the process. The data showed the involvement of pathways like extracellular signal-regulated kinase (ERK), mitogen-activated protein kinase (MAPK), and protein kinase B (Akt). In addition, the expression of several genes and proteins playing different roles in the disease mechanisms was found to be influenced by PBM, such as neurotrophic factors and secretases. Studying the literature indicated that PBM can be translated to a potential therapeutic tool, acting through a spectrum of mechanisms that work together to decelerate disease progression in the organism, which is difficult to achieve through pharmacological interventions.

Strategies for Improving Photodynamic Therapy Through Pharmacological Modulation of the Immediate Early Stress Response

Photodynamic therapy (PDT) is a minimally to noninvasive treatment modality that has emerged as a promising alternative to conventional cancer treatments. PDT induces hyperoxidative stress and disrupts cellular homeostasis in photosensitized cancer cells, resulting in cell death and ultimately removal of the tumor. However, various survival pathways can be activated in sublethally afflicted cancer cells following PDT. The acute stress response is one of the known survival pathways in PDT, which is activated by reactive oxygen species and signals via ASK-1 (directly) or via TNFR (indirectly). The acute stress response can activate various other survival pathways that may entail antioxidant, pro-inflammatory, angiogenic, and proteotoxic stress responses that culminate in the cancer cell's ability to cope with redox stress and oxidative damage. This review provides an overview of the immediate early stress response in the context of PDT, mechanisms of activation by PDT, and molecular intervention strategies aimed at inhibiting survival signaling and improving PDT outcome.

Chemotherapeutic drugs: Cell death- and resistance-related signaling pathways. Are they really as smart as the tumor cells?

Chemotherapeutic drugs kill cancer cells or control their progression all over the patient's body, while radiation- and surgery-based treatments perform in a particular site. Based on their mechanisms of action, they are classified into different groups, including alkylating substrates, antimetabolite agents, anti-tumor antibiotics, inhibitors of topoisomerase I and II, mitotic inhibitors, and finally, corticosteroids. Although chemotherapeutic drugs have brought about more life expectancy, two major and severe complications during chemotherapy are chemoresistance and tumor relapse. Therefore, we aimed to review the underlying intracellular signaling pathways involved in cell death and resistance in different chemotherapeutic drug families to clarify the shortcomings in the conventional single chemotherapy applications. Moreover, we have summarized the current combination chemotherapy applications, including numerous combined-, and encapsulated-combined-chemotherapeutic drugs. We further discussed the possibilities and applications of precision medicine, machine learning, next-generation sequencing (NGS), and whole-exome sequencing (WES) in promoting cancer immunotherapies. Finally, some of the recent clinical trials concerning the application of immunotherapies and combination chemotherapies were included as well, in order to provide a practical perspective toward the future of therapies in cancer cases.

Proteomic Analyses of 3-Monochloropropanediol 1-Monooleate and 1-Monostearate Induced Testicular Toxicity in a 90 Day Sprague-Dawley Rats' Study

3-Monochloropropane 1,2-diol (3-MCPD) esters are toxicants formed during food thermal processing, and their testicular toxicities were widely reported. In this 90 day in vivo study, Sprague-Dawley rats were treated with 3-MCPD 1-monooleate at 10 and 100 mg/kg body weight (bw)/day or 1-monostearate at 15 and 150 mg/kg bw/day. Histological results indicated that testicular impairment was observed, and the level of serum testosterone was decreased dose dependently, while the levels of serum transforming growth factor beta and interferon-γ in rats' serum were increased dose dependently. To address the molecular mechanisms leading to testicular toxicities of 3-MCPD esters, testes samples were investigated with a mass spectrometry proteomic approach. The deregulated proteins affected by 3-MCPD esters include many enzymes related with the inflammatory necrosis pathways. While verifying the results in cellular level, 3-MCPD 1-monooleate and 3-MCPD 1-monostearate showed almost similar testicular cytotoxicity, and they could activate RIPK1 and MLKL pathways at the cellular level. All of these results showed the possible mechanisms about the toxicity of 3-MCPD esters in rats' testes and play a vital role in understanding the toxic effects of 3-MCPD esters both in vivo and in vitro.

The Molecular Mechanisms of Action of Photobiomodulation Against Neurodegenerative Diseases: A Systematic Review

Neurodegenerative diseases might be slow but relentless, as we continue to fail in treating or delaying their progression. Given the complexity in the pathogenesis of these diseases, a broad-acting approach like photobiomodulation can prove promising. Photobiomodulation (PBM) uses red and infrared light for therapeutic benefits, working by stimulating growth and proliferation. The implications of photobiomodulation have been studied in several neurodegenerative disease models. It has been shown to improve cell survival, decrease apoptosis, alleviate oxidative stress, suppress inflammation, and rescue mitochondrial function. In in vivo models, it has reportedly preserved motor and cognitive skills. Beyond mitochondrial stimulation, the molecular mechanisms by which photobiomodulation protects against neurodegeneration have not been very well studied. This review has systematically been undertaken to study the effects of photobiomodulation at a molecular level and identify the different biochemical pathways and molecular changes in the process. The data showed the involvement of pathways like extracellular signal-regulated kinase (ERK), mitogen-activated protein kinase (MAPK), and protein kinase B (Akt). In addition, the expression of several genes and proteins playing different roles in the disease mechanisms was found to be influenced by PBM, such as neurotrophic factors and secretases. Studying the literature indicated that PBM can be translated to a potential therapeutic tool, acting through a spectrum of mechanisms that work together to decelerate disease progression in the organism, which is difficult to achieve through pharmacological interventions.

Exploring Dysregulated Signaling Pathways in Cancer

Cancer cell biology takes advantage of identifying diverse cellular signaling pathways that are disrupted in cancer. Signaling pathways are an important means of communication from the exterior of cell to intracellular mediators, as well as intracellular interactions that govern diverse cellular processes. Oncogenic mutations or abnormal expression of signaling components disrupt the regulatory networks that govern cell function, thus enabling tumor cells to undergo dysregulated mitogenesis, to resist apoptosis, and to promote invasion to neighboring tissues. Unraveling of dysregulated signaling pathways may advance the understanding of tumor pathophysiology and lead to the improvement of targeted tumor therapy. In this review article, different signaling pathways and how their dysregulation contributes to the development of tumors have been discussed.

An overview of mammalian p38 mitogen-activated protein kinases, central regulators of cell stress and receptor signaling

The p38 family is a highly evolutionarily conserved group of mitogen-activated protein kinases (MAPKs) that is involved in and helps co-ordinate cellular responses to nearly all stressful stimuli. This review provides a succinct summary of multiple aspects of the biology, role, and substrates of the mammalian family of p38 kinases. Since p38 activity is implicated in inflammatory and other diseases, we also discuss the clinical implications and pharmaceutical approaches to inhibit p38.

Tert-Butyl Hydroperoxide Stimulated Apoptosis Independent of Prostaglandin E2 and IL-6 in the HTR-8/SVneo Human Placental Cell Line

Significant gaps exist in our knowledge of how cellular redox status, sometimes referred to as oxidative stress, impacts placental trophoblasts. The present study used tert-butyl hydroperoxide (TBHP) as a known generator of reactive oxygen species (ROS) in the extravillous trophoblast cell line HTR-8/SVneo to examine the role of cellular redox disruption of prostaglandin E₂ (PGE₂) and the cytokine IL-6 in cell death. Cells were exposed to 0, 12.5, 25, or 50 μM TBHP for 4, 8, and 24 h to ascertain effects on cell viability, caspase 3/7 activity, PGE₂ release, PTGS2 mRNA expression, and IL-6 release. Experiments with inhibitors included the cyclooxygenase inhibitor indomethacin, mitogen-activated protein kinase inhibitors (PD169316, U0126, or SP600125), or treatments to counter expected consequences of TBHP-stimulated generation of ROS (deferoxamine [DFO], butylated hydroxyanisole [BHA], and N,N'-diphenyl-1,4-phenylenediamine [DPPD]) using 24-h exposure to 50 μM TBHP. Cell viability, measured by ATP content, decreased 24% relative to controls with a 24-h exposure to 50 μM TBHP, but not at lower TBHP concentrations nor at earlier time points. Exposure to 50 μM TBHP increased caspase 3/7 activity, an indicator of apoptosis, after 8 and 24 h. Antioxidant treatment markedly reduced TBHP-stimulated caspase 3/7 activity, PGE₂ release, and IL-6 release. TBHP-stimulated IL-6 release was blocked by PD169316 but unaltered by indomethacin. These data suggest that TBHP-stimulated IL-6 release and caspase 3/7 activation were independent of PGE₂ yet were interrupted by treatments with known antioxidant properties, providing new insight into relationships between PGE₂, IL-6, and apoptosis under conditions of chemically induced cellular oxidation.

Dopamine, a key factor of mitochondrial damage and neuronal toxicity on rotenone exposure and also parkinsonic motor dysfunction-Impact of asiaticoside with a probable vesicular involvement

Persuasive evidence propose that the toxicity of dopamine in parkinsonism and the loss of dopaminergic neurons are the earliest events during the pathogenesis of Parkinson's disease (PD). In our earlier study, Asiaticoside (AS), a triterpenoid saponin isolated from Centella asiatica was shown to exert a neuroprotective effect against hemiparkinsonism, purportedly due to phosphoinositides (PI)-assisted cytodynamics and synaptic function. Here, we evaluate AS in the modulation of dopamine (DA), mitochondrial integrity and neurite variations in vitro and motor dysfunctions in vivo. PC12 cells challenged with rotenone-(ROT) (0.1 μM/mL) were exposed to AS and l-DOPA (10 mM and 20 μM/mL respectively). The protein expressions of Bax and Bcl-2 that regulate cell death were assessed following neurite length assays. Rats were distributed into 6 groups (6 rats/group): Sham, Vehicle controls, ROT-infused (6 μg/μl/kg), AS- treated (50 mg/kg/day), Drug control, and ROT + L-DOPA-treated (6 mg/kg/day) groups. At the end of the experimental period, the rats were sacrificed after performing motor behavioral analysis, and the striatum was dissected out. The contents of synaptic vesicular and cytosolic DA were analyzed. Further, the levels of striatal PI were also measured. ROT had caused significant reduction in the neurite outgrowth in the exposed PC12 cells while the tested concentrations of AS and l-DOPA can exert their protective effect on the stunted neurite growth. The levels of Bax, Bcl-2, and cytochrome c which were significantly disturbed by ROT, could also be affected by AS thereby suggesting its effect on neurons. AS treatment caused an improved motor performance, vesicular and cytosolic DA, and striatal PI. These pre-clinical findings force us to speculate that AS could be a potential drug candidate in combating ROT-induced variations that are possibly precipitated by varied vesicular trafficking of DA.

PDZRN3 protects against apoptosis in myoblasts by maintaining cyclin A2 expression

PDZRN3 is a PDZ domain-containing RING-finger family protein that functions in various developmental processes. We previously showed that expression of PDZRN3 is induced together with that of MyoD during the early phase of skeletal muscle regeneration in vivo. We here show that PDZRN3 suppresses apoptosis and promotes proliferation in myoblasts in a manner dependent on cyclin A2. Depletion of PDZRN3 in mouse C2C12 myoblasts by RNA interference reduced the proportion of Ki-67-positive cells and the level of Akt phosphorylation, implicating PDZRN3 in regulation of both cell proliferation and apoptosis. Exposure of C2C12 cells as well as of C3H10T1/2 mesenchymal stem cells and NIH-3T3 fibroblasts to various inducers of apoptosis including serum deprivation resulted in a greater increase in the amount of cleaved caspase-3 in PDZRN3-depleted cells than in control cells. The abundance of cyclin A2 was reduced in PDZRN3-depleted C2C12 myoblasts, as was that of Mre11, which contributes to the repair of DNA damage. Overexpression of cyclin A2 restored the expression of Mre11 and Ki-67 as well as attenuated caspase-3 cleavage in PDZRN3-depleted cells deprived of serum. These results indicate that PDZRN3 suppresses apoptosis and promotes proliferation in myoblasts and other cell types by maintaining cyclin A2 expression.

Neuronal p38α mediates age-associated neural stem cell exhaustion and cognitive decline

Neuronal activity regulates cognition and neural stem cell (NSC) function. The molecular pathways limiting neuronal activity during aging remain largely unknown. In this work, we show that p38MAPK activity increases in neurons with age. By using mice expressing p38α-lox and CamkII-Cre alleles (p38α∆-N), we demonstrate that genetic deletion of p38α in neurons suffices to reduce age-associated elevation of p38MAPK activity, neuronal loss and cognitive decline. Moreover, aged p38α∆-N mice present elevated numbers of NSCs in the hippocampus and the subventricular zone. These results reveal novel roles for neuronal p38MAPK in age-associated NSC exhaustion and cognitive decline.

The Role of Signaling Pathways of Inflammation and Oxidative Stress in Development of Senescence and Aging Phenotypes in Cardiovascular Disease

The ASK1-signalosome→p38 MAPK and SAPK/JNK signaling networks promote senescence (in vitro) and aging (in vivo, animal models and human cohorts) in response to oxidative stress and inflammation. These networks contribute to the promotion of age-associated cardiovascular diseases of oxidative stress and inflammation. Furthermore, their inhibition delays the onset of these cardiovascular diseases as well as senescence and aging. In this review we focus on whether the (a) ASK1-signalosome, a major center of distribution of reactive oxygen species (ROS)-mediated stress signals, plays a role in the promotion of cardiovascular diseases of oxidative stress and inflammation; (b) The ASK1-signalosome links ROS signals generated by dysfunctional mitochondrial electron transport chain complexes to the p38 MAPK stress response pathway; (c) the pathway contributes to the sensitivity and vulnerability of aged tissues to diseases of oxidative stress; and (d) the importance of inhibitors of these pathways to the development of cardioprotection and pharmaceutical interventions. We propose that the ASK1-signalosome regulates the progression of cardiovascular diseases. The resultant attenuation of the physiological characteristics of cardiomyopathies and aging by inhibition of the ASK1-signalosome network lends support to this conclusion. Importantly the ROS-mediated activation of the ASK1-signalosome p38 MAPK pathway suggests it is a major center of dissemination of the ROS signals that promote senescence, aging and cardiovascular diseases. Pharmacological intervention is, therefore, feasible through the continued identification of potent, non-toxic small molecule inhibitors of either ASK1 or p38 MAPK activity. This is a fruitful future approach to the attenuation of physiological aspects of mammalian cardiomyopathies and aging.

Cytoprotective effect of 2-carbomethoxy-2,3-epoxy-3-prenyl-1,4-naphthoquinone (CMEP-NQ) is mediated by the inhibition of BAK-dependent mitochondrial apoptosis pathway

The inhibitory mechanism of 2-carbomethoxy-2,3-epoxy-3-prenyl-1,4-naphthoquinone (CMEP-NQ) against apoptosis induced by the microtubule-damaging agents (MDAs), nocodazole (NOC) and 2-methoxyestradiol (2-MeO-E₂), or a DNA-damaging agent (DDA), camptothecin (CPT) were investigated in human Jurkat T cell clones (J/Neo and J/BCL-XL cells). Treatment of J/Neo cells with NOC, 2-MeO-E₂, or CPT caused cytotoxicity and apoptotic DNA fragmentation but these events were significantly attenuated in the presence of CMEP-NQ. Although not only MDA (NOC or 2-MeO-E₂)-induced mitotic arrest, CDK1 activation, and BCL-2, BCL-XL and BIM phosphorylation, but also DDA (CPT)-induced S-phase arrest and ATM-CHK1/CHK2-p53 pathway activation were not or were barely affected in the presence of CMEP-NQ, the levels of anti-apoptotic BAG3 and MCL-1, which were markedly downregulated after MDA- or DDA-treatment, were rather elevated by CMEP-NQ. Under the same conditions, MDA- or DDA-induced mitochondrial apoptotic events including BAK activation, mitochondrial membrane potential (Δψm) loss, caspase-9 activation, and PARP cleavage were significantly inhibited by CMEP-NQ. While MDA- or DDA-induced sub-G₁ peak and Δψm loss were abrogated in J/BCL-XL cells, MDA-induced mitotic arrest and DDA-induced S-arrest were more apparent in J/BCL-XL cells than in J/Neo cells. Simultaneously, the induced cell cycle arrest in J/BCL-XL cells was not significantly disturbed by CMEP-NQ. MDA- or DDA-treatment caused intracellular reactive oxygen species (ROS) production; however, MDA- or DDA-induced ROS production was almost completely abrogated in J/BCL-XL cells. MDA- or DDA-induced ROS production in J/Neo cells was significantly suppressed by CMEP-NQ, but the suppressive effect was hardly observed in J/BCL-XL cells. Together, these results show that CMEP-NQ efficiently protects Jurkat T cells from apoptotic cell death via the elevation of BAG3 and MCL-1 levels, which results in the inhibition of intrinsic BAK-dependent mitochondrial apoptosis pathway, as does the overexpression of BCL-XL.

Neuroprotective Effects of Proanthocyanidins, Natural Flavonoids Derived From Plants, on Rotenone-Induced Oxidative Stress and Apoptotic Cell Death in Human Neuroblastoma SH-SY5Y Cells

Proanthocyanidins (PA) are natural flavonoids widely present in many vegetables, fruits, nuts and seeds, and especially in grape seed. In the present study, we examined the neuroprotective effects of PA and the underlying molecular mechanism in rotenone model of Parkinson's disease (PD). We found that pretreatment with PA significantly reduced rotenone-induced oxidative stress in human neuroblastoma SH-SY5Y dopaminergic cells. In addition, PA markedly enhanced cell viability against rotenone neurotoxicity and considerably blocked rotenone-induced activation of caspase-9, caspase-3, and cleavage of poly (ADP-ribose) polymerase (PARP), biochemical features of apoptosis. Further study demonstrated that the anti-apoptotic effect of PA was mediated by suppressing p38, JNK, and ERK signaling, and inhibitors of these three signaling pathways reproduced the protective effect of PA separately. In summary, our results demonstrated that PA mitigated rotenone-induced ROS generation and antagonized apoptosis in SH-SY5Y cells by inhibiting p38, JNK, and ERK signaling pathways, and it may provide a new insight of PA in PD therapy.

Neonatal hyperglycemia induces cell death in the rat brain

Several studies have examined neonatal diabetes, a rare disease characterized by hyperglycemia and low insulin levels that is usually diagnosed in the first 6 month of life. Recently, the effects of diabetes on the brain have received considerable attention. In addition, hyperglycemia may perturb brain function and might be associated with neuronal death in adult rats. However, few studies have investigated the damaging effects of neonatal hyperglycemia on the rat brain during central nervous system (CNS) development, particularly the mechanisms involved in the disease. Thus, in the present work, we investigated whether neonatal hyperglycemia induced by streptozotocin (STZ) promoted cell death and altered the levels of proteins involved in survival/death pathways in the rat brain. Cell death was assessed using FluoroJade C (FJC) staining and the expression of the p38 mitogen-activated protein kinase (p38), phosphorylated-c-Jun amino-terminal kinase (p-JNK), c-Jun amino-terminal kinase (JNK), protein kinase B (Akt), phosphorylated-protein kinase B (p-Akt), glycogen synthase kinase-3β (Gsk3β), B-cell lymphoma 2 (Bcl2) and Bcl2-associated X protein (Bax) protein were measured by Western blotting. The main results of this study showed that the metabolic alterations observed in diabetic rats (hyperglycemia and hypoinsulinemia) increased p38 expression and decreased p-Akt expression, suggesting that cell survival was altered and cell death was induced, which was confirmed by FJC staining. Therefore, the metabolic conditions observed during neonatal hyperglycemia may contribute to the harmful effect of diabetes on the CNS in a crucial phase of postnatal neuronal development.

Role of the DNA repair glycosylase OGG1 in the activation of murine splenocytes

OGG1 (8-oxoguanine-DNA glycosylase) is the major DNA repair glycosylase removing the premutagenic DNA base modification 8-oxo-7,8-dihydroguanine (8-oxoG) from the genome of mammalian cells. In addition, there is accumulating evidence that OGG1 and its substrate 8-oxoG might function in the regulation of certain genes, which could account for an attenuated immune response observed in Ogg1^-/- mice in several settings. Indications for at least two different mechanisms have been obtained. Thus, OGG1 could either act as an ancillary transcription factor cooperating with the lysine-specific demethylase LSD1 or as an activator of small GTPases. Here, we analysed the activation by lipopolysaccaride (LPS) of primary splenocytes obtained from two different Ogg1^-/- mouse strains. We found that the induction of TNF-α expression was reduced in splenocytes (in particular macrophages) of both Ogg1^-/- strains. Notably, an inhibitor of LSD1, OG-L002, reduced the induction of TNF-α mRNA in splenocytes from wild-type mice to the level observed in splenocytes from Ogg1^-/- mice and had no influence in the latter cells. In contrast, inhibitors of the MAP kinases p38 and JNK as well as the antioxidant N-acetylcysteine attenuated the LPS-stimulated TNF-α expression both in the absence and presence of OGG1. The free base 8-oxo-7,8-dihydroguanine had no influence on the TNF-α expression in the splenocytes. The data demonstrate that OGG1 plays a role in an LSD1-dependent pathway of LPS-induced macrophage activation in mice.

Involvement of the MEK-ERK/p38-CREB/c-fos signaling pathway in Kir channel inhibition-induced rat retinal Müller cell gliosis

Our previous studies have demonstrated that activation of group I metabotropic glutamate receptors downregulated Kir channels in chronic ocular hypertension (COH) rats, thus contributing to Müller cell gliosis, characterized by upregulated expression of glial fibrillary acidic protein (GFAP). In the present study, we explored possible signaling pathways linking Kir channel inhibition and GFAP upregulation. In normal retinas, intravitreal injection of BaCl₂ significantly increased GFAP expression in Müller cells, which was eliminated by co-injecting mitogen-activated protein kinase (MAPK) inhibitor U0126. The protein levels of phosphorylated extracellular signal-regulated protein kinase1/2 (p-ERK1/2) and its upstream regulator, p-MEK, were significantly increased, while the levels of phosphorylated c-Jun N-terminal kinase (p-JNK) and p38 kinase (p-p38) remained unchanged. Furthermore, the protein levels of phosphorylated cAMP response element binding protein (p-CREB) and c-fos were also increased, which were blocked by co-injecting ERK inhibitor FR180204. In purified cultured rat Müller cells, BaCl₂ treatment induced similar changes in these protein levels apart from p-p38 levels and the p-p38:p38 ratio showing significant upregulation. Moreover, intravitreal injection of U0126 eliminated the upregulated GFAP expression in COH retinas. Together, these results suggest that Kir channel inhibition-induced Müller cell gliosis is mediated by the MEK-ERK/p38-CREB/c-fos signaling pathway.

Upregulation of p38 pathway accelerates proliferation and migration of MDA-MB-231 breast cancer cells

Tumor cells capture the signaling pathways used by normal tissue to promote their own survival and dissemination and among them, the NF-κB and MAPK pathways (ERK, JNK and p38). MAPK activation has ambiguous effects on tumor cell fate depending on cell type, cancer stage and the engaged MAPK isoforms. A synthetic peptide named LyeTx II, derived from the venom of the Brazilian spider Lycosa erythrognatha, was capable of increasing MDA-MB-231 aggressive breast cancer cell proliferation as indicated by MTT and BrdU (5-bromo-2'-deoxyuridine) incorporation assay and cell migration. A correlation has been established between the accelerated proliferation and migration observed in the presence of LyeTx II and the upregulation of p38 MAPK phosphorylation. The use of the selective inhibitor of p38α/β (SB203580) abrogated the peptide effect in MDA-MB-231 cells. Besides, an augment of the canonical NF-κB pathway activation considered as crucial in cancer progression was noted after cell incubation with LyeTx II. Importantly, activation of p38 and NF-κB pathways was dependent on TAK1 activity. Together, these data suggest that TAK1-p38 pathway may represent an interesting target for treatment of aggressive breast cancers.

Local synthesis of dynein cofactors matches retrograde transport to acutely changing demands

Cytoplasmic dynein mediates retrograde transport in axons, but it is unknown how its transport characteristics are regulated to meet acutely changing demands. We find that stimulus-induced retrograde transport of different cargos requires the local synthesis of different dynein cofactors. Nerve growth factor (NGF)-induced transport of large vesicles requires local synthesis of Lis1, while smaller signalling endosomes require both Lis1 and p150^Glued. Lis1 synthesis is also triggered by NGF withdrawal and required for the transport of a death signal. Association of Lis1 transcripts with the microtubule plus-end tracking protein APC is required for their translation in response to NGF stimulation but not for their axonal recruitment and translation upon NGF withdrawal. These studies reveal a critical role for local synthesis of dynein cofactors for the transport of specific cargos and identify association with RNA-binding proteins as a mechanism to establish functionally distinct pools of a single transcript species in axons.

The molecular mechanisms underlying retrograde transport in axons are only partially understood. Villarin et al. show that in cultured DRG neurons, extracellular trophic cues such as NGF dynamically regulate local protein synthesis of dynein cofactors, thus controlling retrograde trafficking in neurons.

The cannabinoid beta-caryophyllene (BCP) induces neuritogenesis in PC12 cells by a cannabinoid-receptor-independent mechanism

Beta-caryophyllene (BCP) is a phytocannabinoid whose neuroprotective activity has been mainly associated with selective activation of cannabinoid-type-2 (CB2) receptors, inhibition of microglial activation and decrease of inflammation. Here, we addressed the potential of BCP to induce neuritogenesis in PC12 cells, a model system for primary neuronal cells that express trkA receptors, respond to NGF and do not express CB2 receptors. We demonstrated that BCP increases the survival and activates the NGF-specific receptor trkA in NGF-deprived PC12 cells, without increasing the expression of NGF itself. The neuritogenic effect of BCP in PC12 cells was abolished by k252a, an inhibitor of the NGF-specific receptor trkA. Accordingly, BCP did not induce neuritogenesis in SH-SY5Y neuroblastoma cells, a neuronal model that does not express trkA receptors and do not respond to NGF. Additionally, we demonstrated that BCP increases the expression of axonal-plasticity-associated proteins (GAP-43, synapsin and synaptophysin) in PC12 cells. It is known that these proteins are up-regulated by NGF in neurons and neuron-like cells, such as PC12 cells. Altogether, these findings suggest that BCP activates trka receptors and induces neuritogenesis by a mechanism independent of NGF or cannabinoid receptors. This is the first study to show such effects of BCP and their beneficial role in neurodegenerative processes should be further investigated.

Effect of D609 on the expression of GADD45β protein: Potential inhibitory role in the growth of glioblastoma cancer stem like cells

GADD45β (Growth Arrest and DNA Damage inducible protein) is a stress activated protein which plays an important role in regulating apoptosis, proliferation, DNA repair and potentially may have a role in cancer. In this study we examined the role of anti-oxidative stress on the expression of GADD45β in glioma stem-like cells (GSC). We show that patient derived GSCs have high survival in the absence of exogenous growth factors. Addition of D609 (Tricyclodecan-9-yl-xanthogenate), a known anti-oxidative compound, to GSCs reduced the cellular ATP content with significant effects observed when GSCs were cultured in growth factor free medium. D609 exposure also resulted in a decrease in the protein and an increase in mRNA of GADD45β with a concomitant decline in the survival of cells. However, under similar conditions the phosphorylation of p38 MAP kinase (stress activated MAP kinase), a downstream target of GADD45β, was significantly enhanced in response to D609. Therefore it appears that GADD45β might play a role in glioma stem cell survival and that p38 MAP kinase may not be directly activated by GADD45β. Together these observations suggest that anti-oxidative compounds like D609 can target GADD45β which may be one strategy to curtail the growth of glioma stem like cells.

Effects of Maternal Chromium Restriction on the Long-Term Programming in MAPK Signaling Pathway of Lipid Metabolism in Mice

It is now broadly accepted that the nutritional environment in early life is a key factor in susceptibility to metabolic diseases. In this study, we evaluated the effects of maternal chromium restriction in vivo on the modulation of lipid metabolism and the mechanisms involved in this process. Sixteen pregnant C57BL mice were randomly divided into two dietary treatments: a control (C) diet group and a low chromium (L) diet group. The diet treatment was maintained through gestation and lactation period. After weaning, some of the pups continued with either the control diet or low chromium diet (CC or LL), whereas other pups switched to another diet (CL or LC). At 32 weeks of age, serum lipid metabolism, proinflammatory indexes, oxidative stress and anti-oxidant markers, and DNA methylation status in adipose tissue were measured. The results indicated that the maternal low chromium diet increased body weight, fat pad weight, serum triglyceride (TG), low-density lipoprotein cholesterol (LDL), tumor necrosis factor-α (TNF-α), malondialdehyde (MDA), and oxidized glutathione (GSSG). There was a decrease in serum reduced/oxidized glutathione (GSH/GSSG) ratio at 32 weeks of age in female offspring. From adipose tissue, we identified 1214 individual hypomethylated CpG sites and 411 individual hypermethylated CpG sites in the LC group when compared to the CC group. Pathway analysis of the differential methylation genes revealed a significant increase in hypomethylated genes in the mitogen-activated protein kinase (MAPK) signaling pathway in the LC group. Our study highlights the importance of the MAPK signaling pathway in epigenetic changes involved in the lipid metabolism of the offspring from chromium-restricted dams.

Cell-permeable p38 MAP kinase promotes migration of adult neural stem/progenitor cells

Endogenous neural stem/progenitor cells (NPCs) can migrate toward sites of injury, but the migration activity of NPCs is insufficient to regenerate damaged brain tissue. In this study, we showed that p38 MAP kinase (p38) is expressed in doublecortin-positive adult NPCs. Experiments using the p38 inhibitor SB203580 revealed that endogenous p38 participates in NPC migration. To enhance NPC migration, we generated a cell-permeable wild-type p38 protein (PTD-p38WT) in which the HIV protein transduction domain (PTD) was fused to the N-terminus of p38. Treatment with PTD-p38WT significantly promoted the random migration of adult NPCs without affecting cell survival or differentiation; this effect depended on the cell permeability and kinase activity of the fusion protein. These findings indicate that PTD-p38WT is a novel and useful tool for unraveling the roles of p38, and that this protein provides a reasonable approach for regenerating the injured brain by enhancing NPC migration.

A High-Throughput, Multi-Cell Phenotype Assay for the Identification of Novel Inhibitors of Chemotaxis/Migration

Chemotaxis and cell migration are fundamental, universal eukaryotic processes essential for biological functions such as embryogenesis, immunity, cell renewal, and wound healing, as well as for pathogenesis of many diseases including cancer metastasis and chronic inflammation. To identify novel chemotaxis inhibitors as probes for mechanistic studies and leads for development of new therapeutics, we developed a unique, unbiased phenotypic chemotaxis-dependent Dictyostelium aggregation assay for high-throughput screening using rapid, laser-scanning cytometry. Under defined conditions, individual Dictyostelium secrete chemoattractants, migrate, and aggregate. Chemotaxis is quantified by laser-scanning cytometry with a GFP marker expressed only in cells after chemotaxis/multi-cell aggregation. We applied the assay to screen 1,280 known compounds in a 1536-well plate format and identified two chemotaxis inhibitors. The chemotaxis inhibitory activities of both compounds were confirmed in both Dictyostelium and in human neutrophils in a directed EZ-TAXIscan chemotaxis assay. The compounds were also shown to inhibit migration of two human cancer cell lines in monolayer scratch assays. This test screen demonstrated that the miniaturized assay is extremely suited for high-throughput screening of very large libraries of small molecules to identify novel classes of chemotaxis/migratory inhibitors for drug development and research tools for targeting chemotactic pathways universal to humans and other systems.

Studies of selective TNF inhibitors in the treatment of brain injury from stroke and trauma: a review of the evidence to date

The brain is very actively involved in immune-inflammatory processes, and the response to several trigger factors such as trauma, hemorrhage, or ischemia causes the release of active inflammatory substances such as cytokines, which are the basis of second-level damage. During brain ischemia and after brain trauma, the intrinsic inflammatory mechanisms of the brain, as well as those of the blood, are mediated by leukocytes that communicate with each other through cytokines. A neuroinflammatory cascade has been reported to be activated after a traumatic brain injury (TBI) and this cascade is due to the release of pro- and anti-inflammatory cytokines and chemokines. Microglia are the first sources of this inflammatory cascade in the brain setting. Also in an ischemic stroke setting, an important mediator of this inflammatory reaction is tumor necrosis factor (TNF)-α, which seems to be involved in every phase of stroke-related neuronal damage such as inflammatory and prothrombotic events. TNF-α has been shown to have an important role within the central nervous system; its properties include activation of microglia and astrocytes, influence on blood–brain barrier permeability, and influences on glutamatergic transmission and synaptic plasticity. TNF-α increases the amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor density on the cell surface and simultaneously decreases expression of γ-aminobutyric acid receptor cells, and these effects are related to a direct neurotoxic effect. Several endogenous mechanisms regulate TNF-α activity during inflammatory responses. Endogenous inhibitors of TNF include prostaglandins, cyclic adenosine monophosphate, and glucocorticoids. Etanercept, a biologic TNF antagonist, has a reported effect of decreasing microglia activation in experimental models, and it has been used therapeutically in animal models of ischemic and traumatic neuronal damage. In some studies using animal models, researchers have reported a limitation of TBI-induced cerebral ischemia due to etanercept action, amelioration of brain contusion signs, as well as motor and cognitive dysfunction. On this basis, it appears that etanercept may improve outcomes of TBI by penetrating into the cerebrospinal fluid in rats, although further studies in humans are needed to confirm these interesting and suggestive experimental findings.

Rho family GTPase Chp/RhoV induces PC12 apoptotic cell death via JNK activation

Rho GTPases regulate numerous cellular processes including apoptosis. Chp/RhoV is an atypical Rho GTPase which functions are poorly understood. Here we investigated the role of Chp in regulation of cell viability using PC12 cells with inducible expression of Chp as a model. We found that expression of Chp results in apoptosis in PC12 cells. Chp-induced apoptosis was accompanied by activation of JNK signaling and both death receptor-mediated and mitochondrial apoptotic pathways as justified by caspase-8 and caspase-9 activation, respectively. Moreover, inhibition of JNK by SP600125 rescued PC12 cells from Chp-triggered cell death and attenuated activation of caspases-9 and -3/7 suggesting that activation of JNK mediates pro-apoptotic effect of Chp. Expression of Chp resulted in increased phosphorylation of c-Jun in PC12 cells, and Chp expression in HE K293 cells upregulated AP-1-dependent transcription in a JNK-dependent manner. Together results of our study reveal the role of Chp GTPase as a putative regulator of JNK-dependent apoptotic death in PC12 cells, similarly to previously described pro-apoptotic activity of the related Cdc42 and Rac1 GTPases.

Gemcitabine: metabolism and molecular mechanisms of action, sensitivity and chemoresistance in pancreatic cancer

Gemcitabine is the first-line treatment for pancreatic adenocarcinoma, but is increasingly used to treat breast, bladder, and non-small cell lung cancers. Despite such broad use, intrinsic and acquired chemoresistance is common. In general, the underlying mechanisms of chemoresistance are poorly understood. Here, current knowledge of gemcitabine metabolism, mechanisms of action, sensitivity and chemoresistance reported over the past two decades are reviewed; and we also offer new perspectives to improve gemcitabine efficacy with particular reference to the treatment of pancreatic cancer.

Hydroxyurea induces a hypersensitive apoptotic response in mouse embryonic stem cells through p38-dependent acetylation of p53

While hydroxyurea (HU) is well known to deplete dNTP pools and lead to replication fork arrest in the cell, the mechanisms by which it exerts a cell response are poorly understood. Here, our results suggest that mouse embryonic stem cells (mESCs), unlike terminally differentiated cells such as mouse embryonic fibroblasts (MEFs), rapidly respond to low concentrations of HU by p53 acetylation, leading to activation of the caspase-dependent apoptotic pathway. We show that HU treatment induces the production of nitric oxide (NO), which plays a central role in the rapid induction of apoptosis in mESCs. By contrast, reactive oxygen species, which are expressed at significantly higher levels in mESCs compared with MEFs, are not related to the HU response. Furthermore, on exposure to HU, the p38 signaling pathway becomes activated in a dose-dependent manner, and chemical inhibition of the p38 pathway attenuates HU-dependent apoptosis in mESCs. Our data reveal that acetylation of p53 as a result of HU-dependent NO production plays a key role in the induction of the apoptotic response in mESCs. Finally, p38 signaling appears to be the main pathway underlying the activation of apoptosis in mESCs in response to HU exposure.

Role of p38 MAP Kinase Signal Transduction in Solid Tumors

Mitogen-activated protein kinases (MAPKs) mediate a wide variety of cellular behaviors in response to extracellular stimuli. One of the main subgroups, the p38 MAP kinases, has been implicated in a wide range of complex biologic processes, such as cell proliferation, cell differentiation, cell death, cell migration, and invasion. Dysregulation of p38 MAPK levels in patients are associated with advanced stages and short survival in cancer patients (e.g., prostate, breast, bladder, liver, and lung cancer). p38 MAPK plays a dual role as a regulator of cell death, and it can either mediate cell survival or cell death depending not only on the type of stimulus but also in a cell type specific manner. In addition to modulating cell survival, an essential role of p38 MAPK in modulation of cell migration and invasion offers a distinct opportunity to target this pathway with respect to tumor metastasis. The specific function of p38 MAPK appears to depend not only on the cell type but also on the stimuli and/or the isoform that is activated. p38 MAPK signaling pathway is activated in response to diverse stimuli and mediates its function by components downstream of p38. Extrapolation of the knowledge gained from laboratory findings is essential to address the clinical significance of p38 MAPK signaling pathways. The goal of this review is to provide an overview on recent progress made in defining the functions of p38 MAPK pathways with respect to solid tumor biology and generate testable hypothesis with respect to the role of p38 MAPK as an attractive target for intervention of solid tumors.

Effects of culture media on the susceptibility of cells to apoptotic cell death

Whether responses of cells to extracellular environments affect the induction of apoptotic cell death is poorly understood. The current study aimed to unravel the different effects of culture media employed in vitro as extracellular environments on the susceptibility of cells to apoptosis. We found that apoptosis is stimulated to the higher levels by culturing human HeLa cells in Opti-MEM with unknown components, a medium that is specifically used for transfections, than by culturing cells in Dulbecco's modified Eagle's medium, a medium that is generally used for maintenance of cells. We showed that apoptosis is suppressed partially by culturing cells in heat-treated Opti-MEM, implicating a heat-sensitive component(s) in stimulating the apoptotic response of cells. Thus, different extracellular environments may contribute to different responses of cells to apoptosis, and this should be considered to evaluate the incidences of apoptotic cell death and could be applied to develop an efficient treatment for curing diseases such as cancer.

Flavonoids in modulation of cell survival signalling pathways

Flavonoids, a family of polyphenols, generally found in various fruits and vegetables, as well as in many plant beverages such as tea, pomegranate juice, raspberry, blueberries, and red wine. Recently, studies on flavonoids have attracted scientific attention as a potential nutritional strategy to prevent a broad range of chronic disorders. Many studies suggest that consumption of these flavonoids in sufficient amount plays neuroprotective, cardioprotective, anti-inflammatory, and chemopreventive roles. While there has been a major focus on the antioxidant properties, there is an emerging view that flavonoids and their in vivo metabolites do not act only as conventional antioxidants but may also exert modulatory actions on cellular system through direct action on various signalling pathways. These pathways include phosphoinositide 3-kinase, Akt/protein kinase B, mitogen-activated protein kinase, tyrosine kinases, and protein kinase C. Various inhibitory or stimulatory actions of flavonoids on these pathways greatly affect cellular functions by altering the phosphorylation state of targeted molecules. In addition, flavonoids also modulate various gene expressions through activation of various transcription factors. Thus, the present review will bestow a breathing overview regarding the prime role of flavonoids in modulation of survival signalling pathways at cellular system.

Functional roles of p38 mitogen-activated protein kinase in macrophage-mediated inflammatory responses

Inflammation is a natural host defensive process that is largely regulated by macrophages during the innate immune response. Mitogen-activated protein kinases (MAPKs) are proline-directed serine and threonine protein kinases that regulate many physiological and pathophysiological cell responses. p38 MAPKs are key MAPKs involved in the production of inflammatory mediators, including tumor necrosis factor-α (TNF-α) and cyclooxygenase-2 (COX-2). p38 MAPK signaling plays an essential role in regulating cellular processes, especially inflammation. In this paper, we summarize the characteristics of p38 signaling in macrophage-mediated inflammation. In addition, we discuss the potential of using inhibitors targeting p38 expression in macrophages to treat inflammatory diseases.

Sodium transport is modulated by p38 kinase-dependent cross-talk between ENaC and Na,K-ATPase in collecting duct principal cells

In relation to dietary Na(+) intake and aldosterone levels, collecting duct principal cells are exposed to large variations in Na(+) transport. In these cells, Na(+) crosses the apical membrane via epithelial Na(+) channels (ENaC) and is extruded into the interstitium by Na,K-ATPase. The activity of ENaC and Na,K-ATPase must be highly coordinated to accommodate variations in Na(+) transport and minimize fluctuations in intracellular Na(+) concentration. We hypothesized that, independent of hormonal stimulus, cross-talk between ENaC and Na,K-ATPase coordinates Na(+) transport across apical and basolateral membranes. By varying Na(+) intake in aldosterone-clamped rats and overexpressing γ-ENaC or modulating apical Na(+) availability in cultured mouse collecting duct cells, enhanced apical Na(+) entry invariably led to increased basolateral Na,K-ATPase expression and activity. In cultured collecting duct cells, enhanced apical Na(+) entry increased the basolateral cell surface expression of Na,K-ATPase by inhibiting p38 kinase-mediated endocytosis of Na,K-ATPase. Our results reveal a new role for p38 kinase in mediating cross-talk between apical Na(+) entry via ENaC and its basolateral exit via Na,K-ATPase, which may allow principal cells to maintain intracellular Na(+) concentrations within narrow limits.

Mechanism(s) Involved in Carbon Monoxide-releasing Molecule-2-mediated Cardioprotection During Ischaemia-reperfusion Injury in Isolated Rat Heart

The purpose of the present study was to determine the mechanism(s) involved in carbon monoxide-releasing molecule-2, carbon monoxide-releasing molecule-2-induced cardioprotection. We used the transition metal carbonyl compound carbon monoxide-releasing molecule-2 that can act as carbon monoxide donor in cardiac ischaemia-reperfusion injury model using isolated rat heart preparation. Langendorff's perfused rat hearts when treated with carbon monoxide-releasing molecule-2 (50 μM) for 10 min before global ischaemia exhibited significant reduction in postischaemic levels of myocardial injury markers, creatine kinase and lactate dehydrogenase in coronary effluent. Similarly, pretreatment with carbon monoxide-releasing molecule-2 showed significantly improved postischaemic recovery of heart rate, coronary flow rate, cardiodynamic parameters and reduced infarct size as compared to vehicle control hearts. Perfusion with p38 mitogen-activated protein kinase inhibitor, SB203580, a specific inhibitor of α and β isoform, before and concomitantly with carbon monoxide-releasing molecule-2 treatment abolished carbon monoxide-releasing molecule-2-induced cardioprotection. However, p38 mitogen-activated protein kinase alpha inhibitor, SCIO-469, was unable to inhibit the cardioprotective effect of carbon monoxide-releasing molecule-2. Furthermore, protective effect of carbon monoxide-releasing molecule-2 was significantly inhibited by the protein kinase C inhibitor, chelerythrine, when added before and concomitantly with carbon monoxide-releasing molecule-2. It was also observed that, perfusion with phosphatidylinositol 3-kinase inhibitor, wortmannin, before and concomitantly with carbon monoxide-releasing molecule-2 was not able to inhibit carbon monoxide-releasing molecule-2-induced cardioprotection. Interestingly, we observed that wortmannin perfusion before ischaemia and continued till reperfusion significantly inhibited carbon monoxide-releasing molecule-2-mediated cardioprotection. Our findings suggest that the carbon monoxide-releasing molecule-2 treatment may activate the p38 mitogen-activated protein kinase β and protein kinase C pathways before ischaemia and phosphatidylinositol 3-kinase pathway during reperfusion which may be responsible for the carbon monoxide-releasing molecule-2-mediated cardioprotective effect.

Baicalin attenuates acute myocardial infarction of rats via mediating the mitogen-activated protein kinase pathway

Baicalin is a bioactive ingredient from the herb and has possessed various pharmacological actions. The present study was performed to evaluate the cardioprotective potential of baicalin against myocardial infarction and explore the potential mechanism. Baicalin was intraperitoneally injected into the rats by the doses of 50, 100 and 200 mg/kg, respectively, once a day for 7 d and, 30 min after the last administration, the left coronary artery was ligated. Infarct size was measured to analyze the myocardial damage. Myocardial specific enzymes, including creatine kinase (CK), the MB isoenzyme of creatine kinase (CK-MB), lactate dehydrogenase (LDH) and cardiac troponin T (cTnT) were determined with the colorimetric method. Evidence for myocardial apoptosis was detected by caspase-3 activity measurement and Western blot analysis. We also examined the protein levels of three major subgroups of mitogen-activated protein kinases (MAPKs), namely, extracellular signal-regulated kinase (ERK), c-Jun N-terminal kinase (JNK) and p38 by immuoblotting. Our results indicated that baicalin significantly reduced the infarct size and myocardial enzymes (CK, CK-MB, LDH and cTnT). Administration of baicalin also suppressed the activity and protein expression of caspase-3. Moreover, the protein level of phosphorylated ERK (p-ERK) was found to be evidently augmented while the phosphorylated JNK (p-JNK) and phosphorylated p38 (p-p38) were strikingly diminished in infarcted rats with baicalin treatment. These findings suggest that the baicalin's cardioprotection associates with mediation of MAPK cascades in acute myocardial infarction of rats.

Diabetes and overexpression of proNGF cause retinal neurodegeneration via activation of RhoA pathway

Our previous studies showed positive correlation between accumulation of proNGF, activation of RhoA and neuronal death in diabetic models. Here, we examined the neuroprotective effects of selective inhibition of RhoA kinase in the diabetic rat retina and in a model that stably overexpressed the cleavage-resistance proNGF plasmid in the retina. Male Sprague-Dawley rats were rendered diabetic using streptozotosin or stably express cleavage-resistant proNGF plasmid. The neuroprotective effects of the intravitreal injection of RhoA kinase inhibitor Y27632 were examined in vivo. Effects of proNGF were examined in freshly isolated primary retinal ganglion cell (RGC) cultures and RGC-5 cell line. Retinal neurodegeneration was assessed by counting TUNEL-positive and Brn-3a positive retinal ganglion cells. Expression of proNGF, p75^NTR, cleaved-PARP, caspase-3 and p38MAPK/JNK were examined by Western-blot. Activation of RhoA was assessed by pull-down assay and G-LISA. Diabetes and overexpression of proNGF resulted in retinal neurodegeneration as indicated by 9- and 6-fold increase in TUNEL-positive cells, respectively. In vitro, proNGF induced 5-fold cell death in RGC-5 cell line, and it induced >10-fold cell death in primary RGC cultures. These effects were associated with significant upregulation of p75^NTR and activation of RhoA. While proNGF induced TNF-α expression in vivo, it selectively activated RhoA in primary RGC cultures and RGC-5 cell line. Inhibiting RhoA kinase with Y27632 significantly reduced diabetes- and proNGF-induced activation of proapoptotic p38MAPK/JNK, expression of cleaved-PARP and caspase-3 and prevented retinal neurodegeneration in vivo and in vitro. Taken together, these results provide compelling evidence for a causal role of proNGF in diabetes-induced retinal neurodegeneration through enhancing p75^NTR expression and direct activation of RhoA and p38MAPK/JNK apoptotic pathways.

A chemical genomic study identifying diversity in cell migration signaling in cancer cells

The aim of this study was to analyze the diversity and consistency of regulatory signaling in cancer cell migration, using a chemical genomic approach. The effects of 34 small molecular compounds were assessed quantitatively by wound healing assay in ten types of migrating cells. Hierarchical clustering was performed on the subsequent migration inhibition profile of the compounds and cancer cell types. The result was that hierarchical clustering accurately classified the compounds according to their targets. Furthermore, the cancer cells tested in this study were classified into three clusters, and the compounds were grouped into four clusters. An inhibitor of JNK suppressed all types of cell migration; however, inhibitors of ROCK, GSK-3 and p38MAPK only inhibited the migration of a subset of cell lines. Thus, our analytical system could easily distinguish between the common and cell type-specific signals responsible for cell migration.

Involvement of the p38 MAPK signaling pathway in S-phase cell-cycle arrest induced by Furazolidone in human hepatoma G2 cells

Given the previously described essential role for the p38 mitogen-activation protein kinase (p38 MAPK) signaling pathway in human hepatoma G2 cells (HepG2), we undertook the present study to investigate the role of the p38 MAPK signaling pathway in cell-cycle arrest induced by Furazolidone (FZD). The aim of this study was to determine the effects of FZD on HepG2 cells by activating and inhibiting the p38 MAPK signaling pathway. The cell cycle and proliferation of HepG2 cells treated with FZD were detected by flow cytometry and MTT assay in the presence or absence of p38 MAPK inhibitors (SB203580), respectively. Cyclin D1, cyclin D3 and CDK6 were detected by quantitative real-time PCR and western blot analysis. Our data showed that p38 MAPK became phosphorylated after stimulation with FZD. Activation of p38 MAPK could arise S-phase cell-cycle arrest and suppress cell proliferation. Simultaneously, inhibition of the p38 MAPK signaling pathway significantly prevented S-phase cell-cycle arrest, increased the percentage of cell viability and decreased the expression of cyclin D1, cyclin D3 and CDK6. These results demonstrated that FZD arose S-phase cell-cycle arrest via activating the p38 MAPK signaling pathway in HepG2 cells. Cyclin D1, cyclin D3 and CDK6 are target genes functioning at the downstream of p38 MAPK in HepG2 cells induced by FZD.