Hyperosmotic stress-induced caspase-3 activation is mediated by p38 MAPK in the hippocampus

Sulforaphene inhibits esophageal cancer progression via suppressing SCD and CDH3 expression, and activating the GADD45B-MAP2K3-p38-p53 feedback loop

Esophageal cancer is one of the most common cancer with limited therapeutic strategies, thus it is important to develop more effective strategies to against it. Sulforaphene (SFE), an isothiocyanate isolated from radish seeds, was proved to inhibit esophageal cancer progression in the current study. Flow cytometric analysis showed SFE induced cell apoptosis and cycle arrest in G2/M phase. Also, scrape motility and transwell assays presented SFE reduced esophageal cancer cell metastasis. Microarray results showed the influence of SFE on esophageal cancer cells was related with stearoyl-CoA desaturase (SCD), cadherin 3 (CDH3), mitogen-activated protein kinase kinase 3 (MAP2K3) and growth arrest and DNA damage inducible beta (GADD45B). SCD and CDH3 could promote esophageal cancer metastasis via activating the Wnt pathway, while the latter one was involved in a positive feedback loop, GADD45B-MAP2K3-p38-p53, to suppress esophageal cancer growth. GADD45B was known to be the target gene of p53, and we proved in this study, it could increase the phosphorylation level of MAP2K3 in esophageal cancer cells, activating p38 and p53 in turn. SFE treatment elevated MAP2K3 and GADD45B expression and further stimulated this feedback loop to better exert antitumor effect. In summary, these results demonstrated that SFE had the potential for developing as a chemotherapeutic agent because of its inhibitory effects on esophageal cancer metastasis and proliferation.

The Molecular Signatures of Acute-immobilization-induced Antinociception and Chronic-immobilization-induced Antinociceptive Tolerance

In the present study, the productions of antinociception induced by acute and chronic immobilization stress were compared in several animal pain models. In the acute immobilization stress model (up to 1 hr immobilization), the antinociception was produced in writhing, tail-flick, and formalin-induced pain models. In chronic immobilization stress experiment, the mouse was enforced into immobilization for 1 hr/day for 3, 7, or 14 days, then analgesic tests were performed. The antinociceptive effect was gradually reduced after 3, 7 and 14 days of immobilization stress. To delineate the molecular mechanism involved in the antinociceptive tolerance development in the chronic stress model, the expressions of some signal molecules in dorsal root ganglia (DRG), spinal cord, hippocampus, and the hypothalamus were observed in acute and chronic immobilization models. The COX-2 in DRG, p-JNK, p-AMPKα1, and p-mTOR in the spinal cord, p-P38 in the hippocampus, and p-AMPKα1 in the hypothalamus were elevated in acute immobilization stress, but were reduced gradually after 3, 7 and 14 days of immobilization stress. Our results suggest that the chronic immobilization stress causes development of tolerance to the antinociception induced by acute immobilization stress. In addition, the COX-2 in DRG, p-JNK, p-AMPKα1, and p-mTOR in the spinal cord, p-P38 in the hippocampus, and p-AMPKα1 in the hypothalamus may play important roles in the regulation of antinociception induced by acute immobilization stress and the tolerance development induced by chronic immobilization stress.

Hypertonic solution-induced preconditioning reduces inflammation and mortality rate

Background

Dysregulated inflammatory response is common cause of organ damage in critical care patients. Preconditioning/tolerance is a strategy to prevent exacerbated inflammation. The aim of this study is to analyze hypertonic saline 7.5% as a potential inducer of preconditioning that protect from a lethal dose of LPS and modulates systemic inflammatory profile in mice.

Methods

Male Balb/C mice received intravenous (i.v.) injections of Hypertonic solution (NaCl 7.5%) (0.8 ml) for 3 days, on day 8th was challenged with LPS 15 mg/kg. Controls with Saline 0.9%, urea and sorbitol were performed. Microarray of mRNA expression was analyzed from HS versus saline from macrophages to identified the pathways activated by HS.

Results

HS preconditioning reduced mortality after LPS injection as well reduced the cytokines release in plasma of the animals challenged by LPS. In order to check how HS induces a preconditioning state we measured plasma cytokines after each HS infusion. Repeated HS injections induced a state of preconditioning that reprograms the inflammatory response, resulting in reduced inflammatory cytokine production. A microarray of mRNA demonstrated that Hypertonic solution increased the expression of several genes in special Mapkbp1 and Atf3.

Conclusion

hypertonic solution induces preconditioning/tolerance reducing mortality and inflammatory response after LPS challenge.

JNK signaling pathway regulates sorbitol-induced Tau proteolysis and apoptosis in SH-SY5Y cells by targeting caspase-3

Growing evidence suggests that Diabetes Mellitus increases the risk of developing Alzheimer's disease. It is well known that hyperglycemia, a key feature of Diabetes Mellitus, may induce plasma osmolarity disturbances. Both hyperglycemia and hyperosmolarity promote the altered post-translational regulation of microtubule-associated protein Tau. Interestingly, abnormal hyperphosphorylation and cleavage of Tau have been proven to lead to the genesis of filamentous structures referred to as neurofibrillary tangles, the main pathological hallmark of Alzheimer's disease. We have previously described that hyperosmotic stress induced by sorbitol promotes Tau proteolysis and apoptosis in SH-SY5Y cells via caspase-3 activation. In order to gain insights into the regulatory mechanisms of such processes, in this work we explored the intracellular signaling pathways that regulate these events. We found that sorbitol treatment significantly enhanced the activation of conventional families of MAPK in SH-SY5Y cells. Tau proteolysis was completely prevented by JNK inhibition but not affected by either ERK1/2 or p38 MAPK blockade. Moreover, inhibition of JNK, but not ERK1/2 or p38 MAPK, efficiently prevented sorbitol-induced apoptosis and caspase-3 activation. In summary, we provide evidence that JNK signaling pathway is an upstream regulator of hyperosmotic stress-induced Tau cleavage and apoptosis in SH-SY5Y through the control of caspase-3 activation.

Mitochondrial dysfunction and oxidative stress in corneal disease

The cornea is the anterior transparent surface and the main refracting structure of the eye. Mitochondrial dysfunction and oxidative stress are implicated in the pathogenesis of inherited (e.g. Kearns Sayre Syndrome) and acquired corneal diseases (e.g. keratoconus and Fuchs endothelial corneal dystrophy). Both antioxidants and reactive oxygen species are found in the healthy cornea. There is increasing evidence of imbalance in the oxidative balance and mitochondrial function in the cornea in disease states. The cornea is vulnerable to mitochondrial dysfunction and oxidative stress due to its highly exposed position to ultraviolet radiation and high oxygen tension. The corneal endothelium is vulnerable to accumulating mitochondrial DNA (mtDNA) damage due to the post- mitotic nature of endothelial cells, yet their mitochondrial genome is continually replicating and mtDNA mutations can develop and accumulate with age. The unique physiology of the cornea predisposes this structure to oxidative damage, and there is interplay between inherited and acquired mitochondrial dysfunction, oxidative damage and a number of corneal diseases. By targeting mitochondrial dysfunction in corneal disease, emerging treatments may prevent or reduce visual loss.

Mitogen-activated protein kinase p38 induces HDAC4 degradation in hypertrophic chondrocytes

Histone deacetylase 4 (HDAC4) is a critical negative regulator for chondrocyte hypertrophy by binding to and inhibiting Runx2, a critical transcription factor for chondrocyte hypertrophy. It is unclear how HDAC4 expression and stability are regulated during growth plate development. We report here that inhibition of mitogen-activated protein kinase (MAPK) p38 by dominant negative p38 or p38 inhibitor prevents HDAC4 degradation. Mutation of a potential caspase-2 and 3 cleavage site Asp289 stabilizes HDAC4 in chondrocytes. In contrast, constitutively active MAPK kinase 6 (constitutive activator of p38) transgenic mice exhibit decreased HDAC4 content in vivo. We also observed that p38 stimulates caspase-3 activity in chondrocytes. Inhibition of p38 or caspases reduced HDAC4 degradation. HDAC4 inhibited Runx2 promoter activity in a dose-dependent manner and caspase inhibitors further enhanced this inhibition by preventing HDAC4 degradation. Overall, these results demonstrate that p38 promotes HDAC4 degradation by increasing caspase-mediated cleavage, which releases Runx2 from a repressive influence of HDAC4 and promotes the chondrocyte hypertrophy and bone formation.

Deciphering early events involved in hyperosmotic stress-induced programmed cell death in tobacco BY-2 cells

Hyperosmotic stresses represent one of the major constraints that adversely affect plants growth, development, and productivity. In this study, the focus was on early responses to hyperosmotic stress- (NaCl and sorbitol) induced reactive oxygen species (ROS) generation, cytosolic Ca(2+) concentration ([Ca(2+)]cyt) increase, ion fluxes, and mitochondrial potential variations, and on their links in pathways leading to programmed cell death (PCD). By using BY-2 tobacco cells, it was shown that both NaCl- and sorbitol-induced PCD seemed to be dependent on superoxide anion (O2·(-)) generation by NADPH-oxidase. In the case of NaCl, an early influx of sodium through non-selective cation channels participates in the development of PCD through mitochondrial dysfunction and NADPH-oxidase-dependent O2·(-) generation. This supports the hypothesis of different pathways in NaCl- and sorbitol-induced cell death. Surprisingly, other shared early responses, such as [Ca(2+)]cyt increase and singlet oxygen production, do not seem to be involved in PCD.

Protective effects of p38 MAPK inhibitor SB202190 against hippocampal apoptosis and spatial learning and memory deficits in a rat model of vascular dementia

Vascular dementia (VaD) is a common age-related neurodegenerative disease resulting from chronic hypoxia. In the present study, we examined the protective effects of p38 MAPK inhibitor SB202190 against hippocampal apoptosis and spatial learning and memory deficits in a chronic hypoperfusion rat model of VaD established by permanent bilateral carotid occlusion (2-VO). Sixty rats were randomly divided into sham-operated, VaD model, and VaD plus SB202190 groups (n = 20/group). After sham/2-VO surgery, rats were administered 0.1% DMSO (sham-operated and VaD groups) or SB202190 by intracerebroventricular injection. One week after inhibitor/vehicle treatment, hippocampal p38 MAPK phosphorylation was higher in the model group than in the SB202190 group (P < 0.01). Compared to the model group, the SB202190 group exhibited significantly shorter escape latencies in the Morris water maze hidden platform trials (P < 0.01) and longer times in the original platform quadrant during probe trials (P < 0.01). The SB202190 group also showed significantly reduced neuronal apoptosis in the hippocampus compared to VaD model rats (P < 0.01) as well as higher (antiapoptotic) Bcl-2 expression and lower (proapoptotic) caspase-3 expression (P < 0.01 for both). In conclusion, blockade of the p38 MAPK signaling pathway by SB202190 following permanent 2-OV reduced apoptosis of hippocampal neurons and rescued spatial learning and memory deficits.

The involvement of proliferation and apoptosis in the early human gonad development

Distributions of the Ki-67, TP53, caspase-3 and AIFM1 markers were histologically investigated in the 5th to 9th week developing gonads of 12 human conceptuses using immunohistochemical and immunofluorescence methods. Between the 5th and 8th developmental week, proliferation gradually increased in the surface gonad epithelium (26-52 %) and stroma (19-42 %), but then slightly decreased in the surface epithelium (35 %) during the early foetal period. In medulla, low proliferation activity decreased from 15 to 12 % between the 7th and 9th week. At earliest stages of gonadal development, primordial germ cells (PGC) were only rarely TP53 positive. In the 7th and 8th week, almost all PGC-s displayed TP53 positivity, while their number decreased in early fetal period. During the investigated period, caspase-3 reactivity gradually decreased in surface epithelium, while it increased in PGC and medulla of developing gonad AIFM1-positivity first appeared in surface gonad epithelium and then predominantly in PCG-s while caspase-3 characterized different cell populations within the developing gonad. AIFM1 and caspase-3 co-localized only during the migration of PCG-s. The number and distribution of Ki-67, TP53, caspase-3 and AIFM1 reacting cells changed coincidently with development end regression of the sex cords in indifferent and early fetal gonad. Our results indicate that the number of PGC might be controlled by balance of TP53 and AIFM1, leading to caspase-3 independent cell death. Other cell populations are probably eliminated by caspase-3-dependent cell death. Both pathways of cell death seem to operate during early human gonad development, while their intensity varies depending on the cell type and developmental period analysed.

Permissive effect of EGFR-activated pathways on RVI and their anti-apoptotic effect in hypertonicity-exposed mIMCD3 cells

Hypertonicity is a stressful stimulus leading to cell shrinkage and apoptotic cell death. Apoptosis can be prevented if cells are able to activate the mechanism of RVI (regulatory volume increase). This study in mIMCD3 cells presents evidence of a permissive role of the EGFR (epidermal growth factor receptor) on RVI, achieved for the most part through the two main EGFR-triggered signalling chains, the MAPK (mitogen-activated protein kinase)/ERK (extracellular-signal-regulated kinase) and the PI3K (phosphoinositide 3-kinase)/Akt (also known as protein kinase B) pathways. Hyperosmotic solutions (450 mosM) made by addition of NaCl, increased EGFR phosphorylation, which is prevented by GM6001 and AG1478, blockers respectively, of MMPs (matrix metalloproteinases) and EGFR. Inhibition of EGFR, ERK (PD98059) or PI3K/Akt (wortmannin) phosphorylation reduced RVI by 60, 48 and 58% respectively. The NHE (Na+/H+ exchanger) seems to be the essential mediator of this effect since (i) NHE is the main contributor to RVI, (ii) EGFR, ERK and PI3K/Akt blockers added together with the NHE blocker zoniporide reduce RVI by non-additive effects and (iii) All the blockers significantly lowered the NHE rate in cells challenged by an NH4Cl pulse. Besides reducing RVI, the inhibition of MMP, EGFR and PI3K/Akt had a strong pro-apoptotic effect increasing cell death by 2–3.7-fold. This effect was significantly lower when RVI inhibition did not involve the EGFR-PI3K/Akt pathway. These results provide evidence that Akt and its permissive effect on RVI have a predominant influence on cell survival under hypertonic conditions in IMCD3 cells. This role of Akt operates under the influence of EGFR activation, promoted by MMP.

Hydration-sensitive gene expression in brain

Dehydration has a profound influence on neuroexcitability. The mechanisms remained, however, incompletely understood. The present study addressed the effect of water deprivation on gene expression in the brain. To this end, animals were exposed to a 24 hours deprivation of drinking water and neuronal gene expression was determined by microarray technology with subsequent confirmation by RT-PCR. As a result, water deprivation was followed by significant upregulation of clathrin (light polypeptide Lcb), serum/glucocorticoid-regulated kinase (SGK) 1, and protein kinase A (PRKA) anchor protein 8-like. Water deprivation led to downregulation of janus kinase and microtubule interacting protein 1, neuronal PAS domain protein 4, thrombomodulin, purinergic receptor P2Y - G-protein coupled 13 gene, gap junction protein beta 1, neurotrophin 3, hyaluronan and proteoglycan link protein 1, G protein-coupled receptor 19, CD93 antigen, forkhead box P1, suppressor of cytokine signaling 3, apelin, immunity-related GTPase family M, serine (or cysteine) peptidase inhibitor clade B member 1a, serine (or cysteine) peptidase inhibitor clade H member 1, glutathion peroxidase 8 (putative), discs large (Drosophila) homolog-associated protein 1, zinc finger and BTB domain containing 3, and H2A histone family member V. Western blotting revealed the downregulation of forkhead box P1, serine (or cysteine) peptidase inhibitor clade H member 1, and gap junction protein beta 1 protein abundance paralleling the respective alterations of transcript levels. In conclusion, water deprivation influences the transcription of a wide variety of genes in the brain, which may participate in the orchestration of brain responses to water deprivation.

Hyperosmolarity-mediated mitochondrial dysfunction requires Transglutaminase-2 in human corneal epithelial cells

Hyperosmolar-induced ocular surface cell death is a key mitochondria-mediated event in inflammatory eye diseases. Transglutaminase (TGM)-2, a cross-linking enzyme, is purported to mediate cell death, but its link to mitochondria is unclear. In the cornea, the integrity of the epithelial cells is important for maintaining transparency of the cornea and therefore functional vision. We evaluated the role of TGM-2 and its involvement in hyperosmolarity-stimulated mitochondrial cell death in human corneal epithelial (HCE-T) cells. HCE-T cell lines stably expressing either shRNA targeting TGM-2 (shTG) or scrambled shRNA (shRNA) were constructed. Hyperosmolar conditions reduced viability and increased mitochondrial depolarization in shRNA cells. However, hyperosmolarity failed to induce mitochondrial depolarization to the same extent in shTG cells. Transient overexpression of TGM-2 resulted in very high levels of TGM-2 expression in shTG and shRNA cells. In the case of shTG cells after overexpression of TGM-2, hyperosmolarity induced the same extent of mitochondrial depolarization as similarly treated shRNA cells. Overexpression of TGM-2 also elevated transamidase activity and reduced viability. It also induced mitochondrial depolarization, increased caspase-3/7 and -9 activity, and these increases were partially suppressed by pan-caspase inhibitor Z-VAD-FMK. Corneal epithelial apoptosis via mitochondrial dysfunction after hyperosmolar stimulation is partially dependent on TGM-2. This TGM-2-dependent mechanism occurs in part via caspase-3/7 and -9. Protection against mitochondrial stress in the ocular surface targeting TGM-2 may have important implications in the survival of cells in hyperosmolar stress.

Curcumin protects against hyperosmoticity-induced IL-1beta elevation in human corneal epithelial cell via MAPK pathways

Increased tear osmolarity is an essential feature of dry eye disease. Curcumin, a natural polyphenol extracted from herb turmeric, has recently been reported to have anti-inflammatory effects. However, its anti-inflammatory effects have not been investigated in dry eye disease. It has been reported that elevated osmolarity achieved by adding sodium chloride to the culture medium of corneal epithelial cells increased the production of IL-1beta, a proinflammation cytokine. This in vitro dry eye model was used to test the anti-inflammatory effects of curcumin. In the present study, a 450 mOsM hyperosmotic medium was produced by adding sodium chloride to the culture medium to reach a final concentration of 90mM. Human corneal epithelial cells cultured in this hyperosmotic medium for 24h showed an increase of IL-1beta, IL-6 and TNF-alpha levels in the conditioned medium. IL-1beta was also upregulated at mRNA levels. Activation of p38 MAP kinase (p38), JNK MAP kinase (JNK) and NF-kappaB in cultured corneal epithelial cells were also induced by hyperosmotic conditions. Curcumin at concentrations of 1-30muM did not affect the cell viability of cultured corneal epithelial cells. Pretreatment of curcumin (5muM) completely abolished the increased production of IL-1beta induced by the hyperosmotic medium. Increased phosphorylation of p38 caused by high osmolarity was also completely abolished by curcumin, whereas the phosphorylation of JNK was only partially inhibited. SB 203580 (p38 inhibitor), but not SP 600125 (JNK inhibitor), completely suppressed hyperosmoticity-induced IL-1beta production, indicating that the inhibition of production of IL-1beta by curcumin may be achieved through the p38 signal pathway. Curcumin completely abolished a hyperosmoticity-induced increase of NF-kappaB p65. NF-kappaB inhibitor suppressed hyperosmoticity-induced IL-1beta production. p38 inhibitor suppressed hyperosmoticity-induced NF-kappaB activation, indicating that NF-kappaB activation was dependent on p38 activation. The present study suggests that curcumin might have therapeutic potential for treating dry eye disease.

Fish as model systems for the study of vertebrate apoptosis

Apoptosis is a process of pivotal importance for multi-cellular organisms and due to its implication in the development of cancer and degenerative disease it is intensively studied in humans and mammalian model systems. Invertebrate models of apoptosis have been well-studied, especially in C. elegans and D. melanogaster, but as these are evolutionarily distant from mammals the relevance of findings for human research is sometimes limited. Presently, a non-mammalian vertebrate model for studying apoptosis is missing. However, in the past few years an increasing number of studies on cell death in fish have been published and thus new model systems may emerge. This review aims at highlighting the most important of these findings, showing similarities and dissimilarities between fish and mammals, and will suggest topics for future research. In addition, the outstanding usefulness of fish as research models will be pointed out, hoping to spark future research on this exciting, often underrated group of vertebrates.