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1.
IL-6, a proinflammatory cytokine, has been implicated in the development of vascular diseases. We previously demonstrated that mechanical stress can initiate signaling pathways leading to smooth muscle cell (SMC) proliferation and apoptosis, but little is known concerning cyclic stress-induced inflammatory response. To explore the role of stretch in the upregulation of cytokine expression in SMCs we performed RNase protection assay for a panel of cytokines and found that mechanical stress resulted in a time-dependent induction of IL-6 mRNA but not other cytokines, e.g., IL-1alpha, IL-1beta, IL-6, IL-10, IL-12p35, IL-12p40, IL-18, IFN-gamma, and macrophage migration inhibitory factor (MIF). This induction also correlated with elevated IL-6 protein levels in the supernatant. Pretreatment of the cells with NF-kappaB inhibitors inhibited NF-kappaB activity and resulted in marked inhibition (50%) of IL-6 protein. Moreover, SMC lines stably expressing dominant-negative Ras (RasN17) or Rac (RacN17) exhibited a remarkable decrease in p38 MAPK activity and IL-6 mRNA induction by mechanical stress. Furthermore, a significant inhibition of 30 and 40% in IL-6 protein was observed in SMCs pretreated with inhibitors of p38 MAPK and ERK1/2, respectively, but not JNK. Interestingly, SMCs isolated from PKC-delta-deficient mice exhibited higher levels of IL-6 compared with wild-type cells. Finally, high levels of IL-6 expression were observed in atherosclerotic lesions of vein bypass grafts, which are related to altered biomechanical stress. Our findings demonstrate that biomechanical stress-induced IL-6 expression occurs via a mechanism that involves Ras/Rac/p38 MAPK/NF-kappaB/NF-IL6 signaling pathways, which is downregulated by PKC-delta, and suggest that modulation of this event contributes to the pathogenesis of atherosclerosis.  相似文献   

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Mammalian cells respond to environmental stress by activating a variety of protein kinases critical for cellular signal transmission, such as the epidermal growth factor receptor (EGFR) tyrosine kinase and different members of the mitogen-activated protein kinase (MAPK) family. EGFR activation by stress stimuli was previously thought to occur independently of stimulation by extracellular ligands. Here, we provide evidence that osmotic and oxidative stresses induce a metalloprotease activity leading to cell surface cleavage of pro-heparin-binding EGF (pro-HB-EGF) and subsequent EGFR activation. This ligand-dependent EGFR signal resulted from stress-induced activation of the MAPK p38 in human carcinoma cells and was mediated by the metalloproteases ADAM9, -10, and -17. Furthermore, stress-induced EGFR activation induced downstream signaling through the MAPKs extracellular signal-regulated kinases 1 and 2 and JNK. Interestingly, apoptosis induced by treatment of tumor cells with doxorubicin was strongly enhanced by blocking HB-EGF function. Together, our data provide novel insights into the mammalian stress response, suggesting a broad mechanistic relevance of a p38-ADAM-HB-EGF-EGFR-dependent pathway and its potential significance for tumor cells in evasion of chemotherapeutic agent-induced apoptosis.  相似文献   

4.

Aims

This study was designed to demonstrate simultaneous increases in proliferation and apoptosis of vascular smooth muscle cells (VSMCs) leading to accelerated vein graft remodeling and to explore the underlying mechanisms.

Methods

Vein grafts were performed in non-diabetic and diabetic mice. The cultured quiescent VSMCs were subjected to mechanical stretch stress (SS) and/or advanced glycosylation end products (AGEs). Harvested vein grafts and treated VSMCs were used to detect cell proliferation, apoptosis, mitogen-activated protein kinases (MAPKs) activation and SM-α-actin expression.

Results

Significantly thicker vessel walls and greater increases in proliferation and apoptosis were observed in diabetic vein grafts than those in non-diabetic. Both SS and AGEs were found to induce different activation of three members of MAPKs and simultaneous increases in proliferation and apoptosis of VSMCs, and combined treatment with both had a synergistic effect. VSMCs with strong SM-α-actin expression represented more activated JNKs or p38MAPK, and cell apoptosis, while the cells with weak SM-α-actin expression demonstrated preferential activation of ERKs and cell proliferation. In contrast, inhibition of MAPKs signals triggered significant decreases in VSMC proliferation, and apoptosis. Treatment of the cells with RNA interference of receptor of AGEs (RAGE) also resulted in significant decreases in both proliferation and apoptosis.

Conclusions

Increased pressure-induced SS triggers simultaneous increases in proliferation and apoptosis of VSMCs in the vein grafts leading to vein arterializations, which can be synergistically accelerated by high glucose-induced AGEs resulting in vein graft atherosclerosis. Either SS or AGEs and their combination induce simultaneous increases in proliferation and apoptosis of VSMCs via different activation of three members of MAPKs resulting from different VSMC subtypes classified by SM-α-actin expression levels.  相似文献   

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Molecular aspects of mechanical stress-induced cardiac hypertrophy   总被引:1,自引:0,他引:1  
To elucidate the signal transduction pathway from external stimuli to nuclear gene expression in mechanical stress-induced cardiac hypertrophy, we examined the time course of activation of protein kinases such as Raf-1 kinase (Raf-1), mitogen-activated protein kinase kinase (MAPKK), MAP kinases (MAPKs) and 90-kDa ribosomal S6 kinase (p90rsk) in neonatal rat cardiomyocytes. Mechanical stretch rapidly activated Raf-1 and its maximal activation was observed at 1–2 min after stretch. The activity of MAPKK was also increased by stretch, with a peak at 5 min after stretch. In addition, MAPKs and p90rsk were maximally activated at 8 min and at 10–30 min after stretch, respectively. Next, the relationship between mechanical stress-induced hypertrophy and the cardiac renin-angiotensin system was investigated. When the stretch-conditioned culture medium was transferred to the culture dish of non-stretched cardiac myocytes, the medium activated MAPK activity slightly but significantly, and the activation was completely blocked by the type 1 angiotensin II receptor antagonist, CV-11974. However, activation of Raf-1 and MAPKs provoked by stretching cardiomyocytes was only partially suppressed by pretreatment with CV-11974. These results suggest that mechanical stress activates the protein kinase cascade of phosphorylation in cardiac myocytes in the order of Raf-1, MAPKK, MAPKs and p90rsk, and that angiotensin II, which is secreted from stretched myocytes, activates a part of these protein kinases.Abbreviations MAPK mitogen-activated protein kinase - MAPKK MAP kinase kinase - Raf-1 - Raf- 1 kinase p90rsk, 90 kDa ribosomal S6 kinase; AngII - angiotensin II - MAPKKK MAP kinase kinase kinase - rMAPK recombinant MAPKK fused to gluthathione S transferase - MMAKK recombinant MAPK fused to maltose binding protein - MBP myelin basic protein - ACE angiotensin-converting enzyme  相似文献   

7.
Mechanical stress has detrimental effects on cartilaginous endplate chondrocytes due to apoptosis in vivo and in vitro. In this study, we investigated the possible apoptosis signaling pathways induced by mechanical stress in cultured rat cervical endplate chondrocytes. Static mechanical load significantly reduced cell viability in a time- and load-dependent manner, as demonstrated by the Cell Counting Kit-8 (CCK-8) assay. Chondrocyte apoptosis induced by mechanical stress was confirmed by annexin V/propidium iodide (PI) staining and terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL). Western blot analysis revealed that static load-induced chondrocyte apoptosis was accompanied by increased phosphorylation of c-Jun N-terminal kinase (JNK), extracellular signal-regulated kinase 1/2 (ERK1/2), and p38 mitogen-activated protein kinase (MAPK). The loss of mitochondrial membrane potential (ΔΨm), increased Cytochrome c release, and activated Caspase-9 and Caspase-3, indicating that the mitochondrial pathway is involved in mechanical stress-induced chondrocyte apoptosis. Treatment with inhibitors of JNK (SP600125), p38 MAPK (SB203580), and ERK (PD98059) prior to mechanical stimulation reversed both the static load-induced chondrocyte apoptosis and the activation of JNK, p38 MAPK, and ERK. Taken together, the data presented in this study demonstrate that mechanical stress induces apoptosis in rat cervical endplate chondrocytes through the MAPK-mediated mitochondrial apoptotic pathway.  相似文献   

8.
The molecular mechanisms behind phenotypic modulation of smooth muscle cells (SMCs) remain unclear. In our recent paper, we reported the establishment of novel culture system of gizzard SMCs (Hayashi, K., H. Saga, Y. Chimori, K. Kimura, Y. Yamanaka, and K. Sobue. 1998. J. Biol. Chem. 273: 28860-28867), in which insulin-like growth factor-I (IGF-I) was the most potent for maintaining the differentiated SMC phenotype, and IGF-I triggered the phosphoinositide 3-kinase (PI3-K) and protein kinase B (PKB(Akt)) pathway. Here, we investigated the signaling pathways involved in de-differentiation of gizzard SMCs induced by PDGF-BB, bFGF, and EGF. In contrast to the IGF-I-triggered pathway, PDGF-BB, bFGF, and EGF coordinately activated ERK and p38MAPK pathways. Further, the forced expression of active forms of MEK1 and MKK6, which are the upstream kinases of ERK and p38MAPK, respectively, induced de-differentiation even when SMCs were stimulated with IGF-I. Among three growth factors, PDGF-BB only triggered the PI3-K/PKB(Akt) pathway in addition to the ERK and p38MAPK pathways. When the ERK and p38MAPK pathways were simultaneously blocked by their specific inhibitors or an active form of either PI3-K or PKB(Akt) was transfected, PDGF-BB in turn initiated to maintain the differentiated SMC phenotype. We applied these findings to vascular SMCs, and demonstrated the possibility that the same signaling pathways might be involved in regulating the vascular SMC phenotype. These results suggest that changes in the balance between the PI3-K/PKB(Akt) pathway and the ERK and p38MAPK pathways would determine phenotypes of visceral and vascular SMCs. We further reported that SMCs cotransfected with active forms of MEK1 and MKK6 secreted a nondialyzable, heat-labile protein factor(s) which induced de-differentiation of surrounding normal SMCs.  相似文献   

9.
Cannabinoids have been shown to inhibit the growth of a broad spectrum of tumour cells. However, the molecular mechanisms involved in that effect have not been completely elucidated. Here, we investigated the possible involvement of mitogen-activated protein kinases (MAPKs) in CB2 receptor-induced apoptosis of human leukaemia cells. Results show that stimulation of the CB2 receptor leads to p38 MAPK activation and that inhibition of this kinase attenuates CB2 receptor-induced caspase activation and apoptosis. These findings support a role for p38 MAPK in CB2 receptor-induced apoptosis of human leukaemia cells.  相似文献   

10.
It is widely accepted that physiological mechanical stimulation suppresses apoptosis and induces synthesis of extracellular matrix by osteoblasts; however, the effect of stress overloading on osteoblasts has not been fully illustrated. In the present study, we investigated the effect of cyclic compressive stress on rat osteoblasts apoptosis, using a novel liquid drop method to generate mechanical stress on osteoblast monolayers. After treatment with different levels of mechanical stress, apoptosis of osteoblasts and activations of mitogen-activated protein kinases (MAPKs) and PI3-kinase (PI3K)/Akt signaling pathways were investigated. Osteoblasts apoptosis was observed after treated with specific inhibitors prior to mechanical stimulation. Protein levels of Bax/Bcl-2/caspase-3 signaling were determined using western blot with or without inhibitors of PI3K/Akt and phosphorylation of c-jun N-terminal kinase (JNK) MAPK. Results showed that mechanical stimulation led to osteoblasts apoptosis in a dose-dependent manner and a remarkable activation of MAPKs and PI3K/Akt signaling pathways. Activation of PI3K/Akt protected against apoptosis, whereas JNK MAPK increased apoptosis via regulation of Bax/Bcl-2/caspase-3 activation. In summary, the PI3K/Akt and JNK MAPK signaling pathways played opposing roles in osteoblasts apoptosis, resulting in inhibition of apoptosis upon small-magnitude stress and increased apoptosis upon large-magnitude stress.  相似文献   

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