The temporal relationship between p38 MAPK and HSP27 activation in ischaemic and pharmacological preconditioning

An ischaemic preconditioning protocol and subsequent sustained ischaemia were characterized by activation and attenuation of p38 MAPK phosphorylation, respectively. However, the significance of events downstream of p38 MAPK needs investigation. Therefore the temporal relationship between phosphorylation of p38 MAPK and its downstream substrate HSP27 was studied during either an ischaemic or –adrenergic preconditioning protocol and during sustained ischaemia.Isolated rat hearts were preconditioned (with or without a p38 MAPK inhibitor, SB203580) with 1 × 5 min or 3 × 5 min global ischaemia or 5 min –adrenergic stimulation (10^–7 M isoproterenol), followed by 25 min sustained ischaemia and 30 min reperfusion. Hearts were freeze–clamped at different time intervals and fractionated to determine p38 MAPK and HSP27 phosphorylation, via Western blotting.Significant phosphorylation of cytosolic p38 MAPK and membrane (myo–fibrillar) HSP27 occurred at the end of the first preconditioning episode. However, p38 MAPK phosphorylation disappeared during subsequent preconditioning episodes, while HSP27 phosphorylation was maintained for the duration of the protocol. Similar changes in p38 MAPK and HSP27 occurred with 5 min –adrenergic preconditioning. After 25 min ischaemia, significant phosphorylation of cytosolic and membrane HSP27 was observed, while p38 MAPK phosphorylation was attenuated in ischaemic and –adrenergic preconditioned compared to non–preconditioned hearts. SB203580–induced abolishment of p38 MAPK and HSP27 phosphorylation during the triggering phase of both preconditioning protocols reversed the changes in these parameters seen after sustained ischaemia.The results suggest that p38 MAPK activation triggers HSP27 phosphorylation during both the preconditioning protocols and during sustained ischaemia. Protection of preconditioned hearts during sustained ischaemia was characterized by phosphorylation of both cytosolic and myofibrillar HSP27.     

Stimulation of p38 MAPK by hormal preconditioning with atrial natriuretic peptide

AIM: Stress-activated signaling pathways responsiblefor hepatic ischemia reperfusion injury and theirmodulation by protective interventions are widelyunknown. Preconditioning of rat livers with AtrialNatriuretic Peptide (ANP) attenuates ischemiareperfusion injury (Gerbes et al. Hepatology 1998, 28:1309-1317). Since ANP has recently been shown to bea regulator of the p38 MAPK pathway in endothelialcells (Kiemer et al. Circ Res 2002, 90:874-881), aim ofthis study was to investigate activities of MAPK duringischemia and reperfusion and effects of ANP on MAPK.METHODS: Rat livers were perfused with KH-buffer inthe presence or absence of ANP for 20 min, kept in coldUW solution for 24 h, and reperfused for up to 120 min.Activities of p38 MAPK and JNK was determined by invitro phosphorylation assays using MBP and c-jun assubstrates. After SDS/PAGE electrophoresis, gels werequantified by phosphorimaging.RESULTS: Activity of p38 MAPK in control organsdecreased in the course of ischemia and reperfusionby 85%, whereas ANP increased p38 activity by up to30-fold. JNK activation of control livers increased in thecourse of ischemia and reperfusion by up to three-fold.This increase in JNK activity was slightly elevated inANP preconditioned organs.CONCLUSION: This work represents a systematicinvestigation of MAPK activation during liver ischemiaand reperfusion. Employing ANP, for the first time apharmacological approach to modulate these centralsignal transduction molecules is presented.     

Stimulation of p38 MAPK by hormonal preconditioning with atrial natriuretic peptide

AIM：Stress-activated signaling pathways responsible for hepatic ischemia reperfusion injury and their modulation by protective interventions are widely unknown.Preconditioning of rat livers with Atrial Natriuretic Peptide(ANP)attenuates ischemia reperfusion injury(Gerbes et al.Hepatology1998,18:1309-1317),SinANP has recently been shown to be a regulator of the p38MAPKpathway in endothelial cells(Kiemer et al.CircRes2002,90:874-881).aim of this thudy was to investigate activities of MAPK during ischemia and reperfusion and effects of ANP on MAPK.METHODS:Rat livers were perfused with KH-buffer in the presence or absence of ANP for 20min,kept in cold UWsloution for 24h,and reperfused forupto120min,Activities of p38MAPKand JNKwas determined by in vitro phosphorylation assays using MBP and c-jun as substrates.After SDS/PAGE electrophoresis,gels were quantified by phosphorimaging.RESULTS:Activity of p38MAPKin control organs decreased in the course of ischemia and reperfusion by85%,whereas ANPincreased p38 activity by up to 30-fold.JNKactivation of control livers increased in the course of ischemia and reperfusion by up to three-fold.This increase in JNK activrity was slightly elevated in ANP preconditioned organs.CONCLUSION:This work represents a systematic investigation of MAPK activation during liver ischemia and reperfusion.Employing ANP,for the first time a pharmacological approach to modulate these central signal transduction molecules is presented.     

p38 MAPK activity is not increased early during sustained coronary artery occlusion in preconditioned versus control rabbit heart

Our aim was to test the hypothesis that cardioprotection achieved with ischemic preconditioning (PC) involves increased activity of p38 mitogen-activated protein kinase (MAPK) early during sustained coronary artery occlusion. Using the isolated buffer-perfused rabbit heart model of regional ischemia, we quantified p38 MAPK activity (pmol/min/mg protein: by biochemical assay) at 5 and 10 min into coronary occlusion in hearts that first received PC ischemia or no intervention (controls), and in non-ischemic shams. Control hearts exhibited significant increases in p38 MAPK activity, averaging 883+/-142 and 1135+/-179 at 5 and 10 min of occlusion, v 144+/-49 in shams (P<0.05 and P<0.01). p38 MAPK activity was not, however, augmented with PC; rather, at 5 min into occlusion, activity was attenuated, averaging 432+/-72 (P=N.S. v sham). This early, modest reduction in p38 MAPK activity may be physiologically relevant: in additional hearts subjected to 30 min of sustained coronary occlusion and 2 h of reperfusion, infarct size (by tetrazolium staining: expressed as a % of the risk region) was 54+/-5% in hearts treated with SB 203580 (confirmed in our study to inhibit p38 MAPK activity at 5 min into occlusion) v 70+/-5% in vehicle controls (P<0.05). Thus, cardioprotection achieved with ischemic preconditioning in rabbit heart does not involve augmentation of p38 MAPK activity early during sustained coronary occlusion.     

The p38 MAPK inhibitor, SB203580, abrogates ischaemic preconditioning in rat heart but timing of administration is critical

There is debate concerning the involvement of p38 mitogen activated protein kinase (MAPK) in the mediation of ischaemic preconditioning. Pharmacological inhibition of p38 MAPK with SB203580 has been reported to block preconditioning in some studies but not in others. We hypothesised that this divergence could be due to differences in the timing of inhibitor administration. Isolated rat hearts were perfused in the Langendorff mode and subjected to 35 min regional ischaemia followed by 120 min reperfusion. Hearts were then double stained with Evans' blue and triphenyltetrazolium chloride to determine risk (R) and infarct zones (I), expressed as I/R% ratios. Preconditioned hearts were subjected to 2 times 5 min global ischaemia with 10 min intervening reperfusion. SB203580 10 μ M was perfused either during the preconditioning protocol (PC+SB-early), just prior to and during the first 15 min of the lethal ischaemia (PC+SB-late) or prior to regional ischaemia in the absence of preconditioning. Ischaemic preconditioning significantly limited infarct size (I/R 38.9 ± 3.0% in control vs 13.4 ± 2.4%, P < 0.01). In the PC+SB-early group, preconditioning was still fully protective (I/R% 14.6 ± 1.0). However, in the PC+SB-late group, SB203580 completely blocked the protection afforded by preconditioning (I/R% 33.6 ± 4.4%, P < 0.01 vs 13.4 ± 2.4% in preconditioned hearts, p < 0.05). SB203580 alone did not affect infarct size when given prior to and during regional ischaemia (I/R 36.2 ± 2.7%). These histological data are corroborated by a significant increase in p38 MAPK activation in the preconditioned hearts during sustained ischaemia in comparison with the controls. In conclusion the activation of p38 MAPK during lethal ischaemia, but not during the ischaemic preconditioning protocol, is essential for the mediation of protection and may resolve some of the earlier controversy surrounding the use of SB203580 in preconditioning studies. Received: 28 June 2000, Returned for revision: 21 July 2000, Revision received: 9 August 2000, Accepted: 13 September 2000     

Hypertensive target organ damage is attenuated by a p38 MAPK inhibitor: role of systemic blood pressure and endothelial protection

OBJECTIVE: Evidence suggests important relationships among chronic inflammatory processes, endothelial dysfunction, hypertension and target organ damage. The present study examined the effects of chronic treatment with an anti-inflammatory p38 mitogen-activated protein kinase (MAPK) inhibitor (SB-239063AN) in the N(omega)-nitro-l-arginine methyl ester-treated spontaneously hypertensive rat (SHR+l-NAME) model of severe hypertension and accelerated target organ damage. Methods: SHRs were divided into control (n=16), l-NAME (n=26) and l-NAME+SB-239063AN (n=24) groups. l-NAME was delivered by the drinking water ad lib (50 mg/L) and SB-239063AN was administered by the diet (1200 ppm) for 4 weeks. Arterial blood pressure (telemetry) and target organ damage (kidney, heart, and vasculature) were examined. Results: The introduction of l-NAME to the drinking water elicited a severe/sustained increase in blood pressure and significant morbidity and mortality. Chronic treatment with SB-239063AN had no effect on the initial blood pressure response (7 days) to l-NAME but attenuated subsequent increases in diastolic blood pressure and significantly reduced morbidity/mortality (42% vs. 5%, p<0.002). Renal dysfunction characterized by increased total protein and albumin excretion was apparent within 2 weeks in the SHR+l-NAME groups. Treatment with SB-239063AN delayed the onset of proteinuria and albuminuria. SB-239063AN treatment also significantly reduced l-NAME-induced interstitial fibrosis in the kidney and restrictive concentric hypertrophy in the left ventricle (end-diastolic volume 0.24+/-0.05 vs. 0.41+/-0.05 ml; p<0.05). Endothelial dysfunction was also not altered by SB-239063AN treatment (Rmax 49+/-6% vs. 45+/-9%). CONCLUSIONS: The results demonstrate that morbidity/mortality and accelerated target organ damage induced by inhibition of nitric oxide synthase in SHR was attenuated by treatment with a selective p38 MAPK inhibitor, SB-239063AN. The organ protection observed in the heart and kidney was not associated with preservation of endothelial function.     

Activation of p38 MAPK is a key step in tumor necrosis factor-mediated inflammatory bone destruction

OBJECTIVE: To investigate whether activation of p38 MAPK is a crucial signaling factor in inflammatory bone destruction mediated by tumor necrosis factor (TNF). Mice overexpressing TNF were treated with 2 different inhibitors of p38 MAPK, and the effect of this treatment on joint inflammation and structural damage was assessed. METHODS: Human TNF-transgenic mice received systemic treatment with 2 different p38 MAPK inhibitors (RO4399247 and AVE8677). Treatment was started at the time of symptom onset and lasted for 6 weeks. Mice were assessed for clinical signs of arthritis, bone erosion, and cartilage damage. In addition, the effect of these inhibitors on osteoclast generation in vitro and in vivo was assessed. RESULTS: Both p38 MAPK inhibitors significantly reduced clinical signs of TNF-mediated arthritis. This was attributable to reducing synovial inflammation by 50% without affecting the cellular composition of the infiltrate. Synovial expression of interleukin-1 and RANKL was reduced upon p38 MAPK blockade, and activation of the molecular target MAPK-activated protein kinase 2 (MAPKAP-2) was also inhibited. Proteoglycan loss of articular cartilage was reduced by 50%, although p38 MAPK inhibition did not change matrix molecule synthesis by cultivated chondrocytes. Importantly, bone loss was almost completely prevented by p38 MAPK inhibition. The numbers of synovial osteoclasts and precursors were dramatically reduced, and both p38 MAPK inhibitors also inhibited in vitro osteoclastogenesis at micromolar concentrations and blocked activation of MAPKAP-2 as well as differentiation markers in cultured osteoclast precursors. CONCLUSION: These results suggest the major importance of p38 MAPK for TNF-mediated inflammatory bone destruction in arthritis and suggest that inhibition of p38 MAPK might be an important tool for reducing structural damage in rheumatoid arthritis.     

丝裂素活化蛋白激酶参与去甲肾上腺素预处理的保护作用

目的:探讨丝裂素活化蛋白激酶(P38MAPK,P38)是否参与去甲肾上腺素预处理的延迟保护作用。方法:18只大鼠随机分成三组:(1)缺血／再灌注(I／R)组;(2)NE预处理组;(3)SB203580(P38的特异性抑制剂)+NE预处理组。于预处理后24 h对心脏进行较长时间缺血再灌注,观察其心肌梗塞范围、LDH释放。结果:与未预处理组的心肌组织比较,于NE预处理后24 h I／R所致的心梗范围缩小,血浆LDH活性降低(P均<0.01)。用SB203580抑制P38磷酸化时,则消除了预处理后的延迟保护作用,上述心肌损伤指标接近单纯缺血／再灌注组(P>0.05)。结论:去甲肾上腺素预处理有使心肌减少缺血／再灌注损伤的延迟保护作用,P38参与了这种保护作用。     

P38MAPK磷酸化对HepG2细胞耐药的影响及其意义

目的 探讨p38MAPK磷酸化对HepG2细胞耐药的影响及其意义.方法 采用浓度递增法,建立动态HepG2/顺铂(CDDP)耐药模型,Western blot检测磷酸化p38的表达;予以p38MAPK特异性抑制剂SB203580分别处理24、48、72 h后,流式细胞仪动态分析HepG2/CDDP耐药细胞周期、四甲基偶氮唑盐法检测顺铂对HepG2/CDDP耐药细胞的半数药物抑制浓度(IC50)、Western blot检测HepG2/CDDP耐药细胞凋亡分子Bcl-2、Bax及P-gp蛋白的表达.动态耐药模型磷酸化P38的检测行单因素方差分析; SB203580处理后计量资料行3×3析因设计方差分析,率的比较采用x2检验.结果 成功建立HepG2/CDDP耐药细胞株,其对CDDP的IG50值与对照HepG2细胞差异具有统计学意义(t=99.30,P<0.01);随着HepG2/CDDP耐药细胞株耐药表型的增强,P38MAPK活化水平逐渐增强(F=69.39,P<0.01).P38MAPK特异性抑制剂SB203580可逐渐降低HepG2/CDDP对顺铂的IC50值(F=2350,P<0.01)、G0/Gl期细胞比例(x2=520,P<0.01)、Bcl-2/Bax表达比值(F=83.8,P<0.01)及细胞膜药物转运相关蛋白P-gP的表达(F=107,P<0.01).结论 P38活化水平随着肝癌耐药细胞株耐药表型的增强而逐渐升高;抑制P38的活化可有效逆转肝癌HepG2/CDDP耐药细胞株的耐药性.     

p38-MAPK induced dephosphorylation of alpha-tropomyosin is associated with depression of myocardial sarcomeric tension and ATPase activity

Our objective in work presented here was to understand the mechanisms by which activated p38alpha MAPK depresses myocardial contractility. To test the hypothesis that activation of p38 MAPK directly influences sarcomeric function, we used transgenic mouse models with hearts in which p38 MAPK was constitutively turned on by an upstream activator (MKK6bE). These hearts demonstrated a significant depression in ejection fraction after induction of the transgene. We also studied hearts of mice expressing a dominant negative p38alpha MAPK. Simultaneous determination of tension and ATPase activity of detergent-skinned fiber bundles from left ventricular papillary muscle demonstrated a significant inhibition of both maximum tension and ATPase activity in the transgenic-MKK6bE hearts. Fibers from hearts expressing dominant negative p38alpha MAPK demonstrated no significant change in tension or ATPase activity. There were no significant changes in phosphorylation level of troponin-T3 and troponin-T4, or myosin light chain 2. However, compared with controls, there was a significant depression in levels of phosphorylation of alpha-tropomyosin and troponin I in fiber bundles from transgenic-MKK6bE hearts, but not from dominant negative p38alpha MAPK hearts. Our experiments also showed that p38alpha MAPK colocalizes with alpha-actinin at the Z-disc and complexes with protein phosphatases (PP2alpha, PP2beta). These data are the first to indicate that chronic activation of p38alpha MAPK directly depresses sarcomeric function in association with decreased phosphorylation of alpha-tropomyosin.     

Phosphorylation state of hsp27 and p38 MAPK during preconditioning and protein phosphatase inhibitor protection of rabbit cardiomyocytes

Small heat shock proteins (hsp) have been implicated in mediation of classic preconditioning in the rabbit, Hsp27 is a terminal substrate of the p38 MAPK cascade. One and 2D gel electrophoresis and immunoblotting of cell fractions was used to determine p38 MAPK and hsp27 phosphorylation levels, respectively, during in vitro ischemia in control, calyculin A (Cal A)-treated (protein phosphatase inhibitor), SB203580-treated (p38MAPK inhibitor) and preconditioned (IPC) isolated adult rabbit cardiomyocytes. The dual phosphorylation of p38 MAPK was increased by early ischemia (30-60 min), after which there was a loss of total cytosolic p38 MAPK. The ischemic increase of p38 MAPK dual phosphorylation was enhanced by IPC. Cal A strongly activated dual phosphorylation of p38 MAPK in oxygenated cells and this was maintained into early ischemia, SB203580 inhibited the dual phosphorylation of p38 MAPK and attenuated the loss of total cytosolic p38 MAPK. In each protocol, ischemia translocated hsp27 from the cytosolic fraction to the cytoskeletal fraction at similar rates and extents, Hsp27 phosphorylation was quantitated as the fraction of diphosphorylated hsp27, based on IEF mobility shifts of hsp27 phosphorylation isoforms. In oxygenated control cells, cytosolic and cytoskeletal hsp27 was highly phosphorylated. After 90 min ischemia, cytoskeletal hsp27 was markedly dephosphorylated. Cal A slightly increased control cytoskeletal hsp27 phosphorylation. During ischemic incubation, Cal A blocked ischemic dephosphorylation, SB203580 accelerated ischemic hsp27 dephosphorylation and injury, IPC insignificantly decreased the initial rate of ischemic dephosphorylation of hsp27, but not the extent of dephosphorylation in later ischemia. Phosphorylation is regulated by both kinase and phosphatase activities. IPC protection was not correlated with a significant increase in cytosolic or cytoskeletal hsp27 phosphorylation levels during prolonged (> 60-90 min) ischemia.     

p38 MAPK信号转导通路参与NO诱导兔关节软骨细胞凋亡

目的探讨p38 MAPK信号转导通路在软骨细胞凋亡中的作用。方法体外培养兔关节软骨细胞,一氧化氮(NO)供体NOC-18和p38 MAPK抑制剂SB203580作用于细胞24 h,用AnnexinV-FITC/PI流式细胞术检测软骨细胞凋亡率,W estern b lot测定p38、磷酸化p38蛋白的表达水平。结果与对照组比较,SB203580显著降低了NOC-18诱导的软骨细胞凋亡率(P<0.05);NOC-18以浓度依赖的方式促进p38 MAPK的磷酸化,而SB203580能抑制其磷酸化(P<0.05)。结论p38 MAPK通路参与了NO诱导的兔关节软骨细胞凋亡的信号转导。     

p38 MAP kinase is a mediator of ischemic preconditioning in pigs

OBJECTIVE: The role of p38MAPK in ischemic preconditioning (IP) is still equivocal, insofar as the p38MAPK-inhibitor SB203580 abolished IP in rats, rabbits and dogs, but not in pigs. Blockade of p38MAPK prior to the sustained ischemia also generated contradictory findings, insofar as p38MAPK acted as trigger in dogs but as mediator in rats. We have now tested whether the two structurally unrelated p38MAPK-inhibitors, BIX-645 and SB203580, abolished infarct size (IS) reduction by IP in pigs and whether their effects depended on the time of administration. METHODS: Sixty-five enflurane-anesthetized pigs underwent 90 min low-flow ischemia and 120 min reperfusion without or with one preceding cycle of 10 min preconditioning ischemia and 15 min reperfusion. Pigs received BIX-645 (1 mg/kg, i.v.) or SB203580 (10 microM, i.c.) prior to either IP or the sustained ischemia. RESULTS: IS (% TTC-staining) was reduced by IP [4.8+/-3.1(S.E.M.), P<0.05] compared to placebo (25.8+/-5.5). BIX-645 or SB203580 per se had no effect on IS (23.5+/-5.2 and 21.8+/-4.4, respectively). IS reduction by IP was abolished by BIX-645 (26.2+/-6.4 or 25.5+/-4.7) and SB203580 (19.9+/-4.3 or 16.7+/-4.7), given either prior to IP or the sustained ischemia, respectively. The supernatant of homogenized myocardial biopsies taken during the sustained ischemia from preconditioned pigs receiving either BIX-645 or SB203580 inhibited the anisomycin-stimulated ATF-2 phosphorylation in cultured Rat1 fibroblasts. This in vitro inhibition of ATF-2 phosphorylation correlated to the actual IS. CONCLUSION: The attenuation of the IS-reducing effect of IP depends on the effectiveness of blockade of p38MAPK activity. p38MAPK is a mediator of IP in pigs.     

Activation of p38 MAPK is a key step in tumor necrosis factor–mediated inflammatory bone destruction

Objective

To investigate whether activation of p38 MAPK is a crucial signaling factor in inflammatory bone destruction mediated by tumor necrosis factor (TNF). Mice overexpressing TNF were treated with 2 different inhibitors of p38 MAPK, and the effect of this treatment on joint inflammation and structural damage was assessed.

Methods

Human TNF‐transgenic mice received systemic treatment with 2 different p38 MAPK inhibitors (RO4399247 and AVE8677). Treatment was started at the time of symptom onset and lasted for 6 weeks. Mice were assessed for clinical signs of arthritis, bone erosion, and cartilage damage. In addition, the effect of these inhibitors on osteoclast generation in vitro and in vivo was assessed.

Results

Both p38 MAPK inhibitors significantly reduced clinical signs of TNF‐mediated arthritis. This was attributable to reducing synovial inflammation by 50% without affecting the cellular composition of the infiltrate. Synovial expression of interleukin‐1 and RANKL was reduced upon p38 MAPK blockade, and activation of the molecular target MAPK‐activated protein kinase 2 (MAPKAP‐2) was also inhibited. Proteoglycan loss of articular cartilage was reduced by 50%, although p38 MAPK inhibition did not change matrix molecule synthesis by cultivated chondrocytes. Importantly, bone loss was almost completely prevented by p38 MAPK inhibition. The numbers of synovial osteoclasts and precursors were dramatically reduced, and both p38 MAPK inhibitors also inhibited in vitro osteoclastogenesis at micromolar concentrations and blocked activation of MAPKAP‐2 as well as differentiation markers in cultured osteoclast precursors.

Conclusion

These results suggest the major importance of p38 MAPK for TNF‐mediated inflammatory bone destruction in arthritis and suggest that inhibition of p38 MAPK might be an important tool for reducing structural damage in rheumatoid arthritis.

     

Circadian rhythmicity mediated by temporal regulation of the activity of p38 MAPK

Circadian clocks are composed of central oscillators, input pathways that transduce external information to the oscillators, and output pathways that allow the oscillators to temporally regulate cellular processes. Little is known about the output pathways. In this study, we show that the Neurospora crassa osmosensing MAPK pathway, essential for osmotic stress responses, is a circadian output pathway that regulates daily rhythms in the expression of downstream genes. Rhythmic activation of the highly conserved stress-activated p38-type MAPK [Osmotically Sensitive-2 (OS-2)] by the N. crassa circadian clock allows anticipation and preparation for hyperosmotic stress and desiccation that begin at sunrise. These results suggest a conserved role for MAPK pathways in circadian rhythmicity.     

Modulation of neutrophil activity by nitric oxide during acute myocardial ischaemia and reperfusion

Summary Nitric oxide (NO) exerts an inhibitory effect on polymorphonuclear neutrophil (PMN) function, via a cyclic GMP-mediated mechanism, while PMNs are known to play an important role in myocardial ischaemia-reperfusion injury (MI-R). Since the major source of NO, vascular endothelium, becomes functionally impaired during MI-R, it is attractive to hypothesize that it is this loss of endothelial nitric oxide production that allows PMN adherence and activation. The studies reviewed here add substance to this hypothesis. Authentic NO, administered during MI-R both reduces myocardial necrosis and PMN accumulation, while basal NO release, as estimated by coronary artery ring responses to L-NAME, an NO synthase inhibitor, declines during reperfusion with a time-course mirrored by PMN adherence in the same preparation. Reduction in infarct size and decreased PMN accumulation can also be demonstrated with L-arginine and NO donors. Since endothelial dysfunction leads to PMN adherence and PMNs have been shown to contribute to endothelial dysfunction, it seems probable that a positive feedback loop is generated during MI-R, leading to the amplification of PMN activity and subsequent myocardial damage.     

周期性机械牵拉诱导A549细胞p38MAPK的表达

目的 探讨p38蛋白激酶(p38 MAPK)是否参与周期性机械牵拉刺激在人肺泡Ⅱ型上皮A549细胞的信号转导过程.方法 实验分对照组(刺激前)、机械牵拉(刺激后)5、15、30、60 min共5组,每组3皿细胞.建立离体的A549细胞机械牵拉模型:以大小为1000 μstrain的牵拉力刺激细胞,在刺激前和刺激后5、15、30、60 min时间点进行观察.结果 A549细胞经机械牵拉刺激后,磷酸化p38蛋白水平增加,以30 min时间点最为明显.随着机械牵拉时间的延长,在60 min时间点磷酸化p38蛋白水平下降至约基线水平.结论 机械牵拉刺激信号可激活A549细胞p38 MAPK,从而引起继发细胞信号转导及功能改变.     

Activation of vascular p38MAPK by mechanical stretch is independent of c-Src and NADPH oxidase: influence of hypertension and angiotensin II

Little is known about vascular MAPK regulation in response to mechanical strain. Whether mechanically-sensitive pathways are altered in hypertension is unclear. We examined effects of stretch and Ang II on activation of p38MAPK in vascular smooth muscle cells (VSMC) from WKY and SHR. The role of c-Src and redox-sensitive pathways in stretch-induced effects were examined. VSMC from mesenteric arteries were plated onto flexible silastic plates and exposed to acute or chronic cyclic stretch (10%, 1 Hz) with or without Ang II (0.1 uM). Acute stretch stimulated p38MAPK activation in WKY and SHR, independently of c-Src and reactive oxygen species (ROS), since PP2 (c-Src inhibitor) and apocynin (NADPH oxidase inhibitor), failed to alter stretch-mediated p38MAPK. Chronic stretch blunted p38MAPK phosphorylation in WKY and increased phosphorylation in SHR. Stretch, in the presence of Ang II, induced an increase in procollagen-1 expression. This was blocked by SB203580 (p38MAPK inhibitor). Accordingly, vascular p38MAPK is a mechano-sensitive MAPK, differentially regulated by acute and chronic stretch in WKY and SHR. Functionally, stretch and Ang II, amplify profibrotic responses in a p38MAPK-dependent manner, responses that are perturbed in SHR. Such molecular process may influence vascular fibrosis in hypertension and appear to be independent of c-Src and ROS.