Activated extracellular signal-regulated kinase correlates with cyst formation and transforming growth factor-beta expression in fetal obstructive uropathy

Human renal dysplasia is frequently associated with urinary tract obstruction and the abnormal expression of mitogen-activated protein kinase (MAPK). Here, we determined the renal responses and MAPK expression in developing kidneys that were obstructed in fetal lambs. Kidneys were harvested at various times after obstruction (gestation day 60) through normal term (day 145). Dilation of Bowman's capsule and proximal tubules was seen 2 days after obstruction and involved the whole cortex 18 days later, with numerous cysts present throughout the kidney at term. The proliferation marker Ki-67 and transforming growth factor-beta (TGF-beta) were detected 2 days after obstruction and progressively increased in tubules, cysts, and the interstitium. In control kidneys, p38 was expressed in tubules only during the fetal stage, whereas phosphorylated extracellular signal-regulated kinase (P-ERK) was limited to ureteric buds and collecting ducts at all stages examined. However, Jun-N-terminal kinase (JNK) was absent in the fetal kidney but present in tubules at term. In obstructed kidneys, cyst epithelia were positive for p38 and P-ERK but negative for JNK throughout all stages. These studies show that P-ERK correlated spatially and temporally with Ki-67 and TGF-beta expression, which suggests that ERK may contribute to cyst formation and fibrosis in the obstructed fetal kidney.     

Extracellular signal-regulated kinase inhibition slows disease progression in mice with polycystic kidney disease

The expression of mitogen-activated protein kinases (MAPK) in DBA/2-pcy/pcy (pcy) mice, a murine model of polycystic kidney disease was investigated. Proliferating cell nuclear antigen-positive cells were recognized in cyst epithelium from embryonic day 14.5 to 25 wk of age. Extracellular signal-regulated kinase (ERK) was expressed in the renal tubules of control and pcy mice, but stronger immunostaining was observed in cyst epithelium. Phosphorylated ERK was detected only in pcy mice and was localized predominantly in the cysts. p38 MAPK (p38) was no longer expressed after birth in controls but was detected in the cyst epithelium and in occasional tubular cells of pcy mice at all stages examined. c-Jun N-terminal kinase (JNK) was expressed in all tubular segments of controls after neonatal day 7, whereas in pcy kidneys, tubules became positive for JNK after 8 wk, and the cysts expressed little JNK. Administration of an oral MAP/ERK kinase inhibitor, PD184352, 400 mg/kg per d, to 10-wk-old pcy mice daily for the first week and then every third day for 6 additional weeks significantly decreased BP, kidney weight, serum creatinine level, and water intake and significantly increased urine osmolality. The cystic index and expression of phosphorylated ERK and ERK were significantly lower in PD184352-treated pcy mice. These results demonstrate that the expression of MAPK is dysregulated in cyst epithelium and that inhibition of ERK slowed the progression of renal disease in pcy mice.     

Expression of mitogen-activated protein kinase family in rat renal development

BACKGROUND: Among mitogen-activated protein kinase (MAPK) family members, extracellular signal-regulated kinase (ERK) promotes proliferation or differentiation, whereas c-Jun N-terminal kinase (JNK) and p38 MAPK (p38) are thought to inhibit cell growth and induce apoptosis. MAPK phosphatase-1 (MKP-1) inactivates and modulates MAPKs. During renal development, large scale proliferation and apoptosis occur. We investigated the temporal and spatial expression patterns of MAPKs and MKP-1 in rat kidney during development. METHODS: Western blot analysis and immunohistochemistry were performed in the developing and mature kidney of the rat. RESULTS: The expression of ERK, p38, and MKP-1 were high in developing kidney. On the other hand, JNK was abundantly expressed in adult kidney. Active forms of ERK, p38, and JNK correlated with the protein expression levels. Immunohistochemical studies revealed that ERK was strongly expressed by blastema cells, mesenchymal cells, and ureteric bud tips in nephrogenic zone of embryonic kidney. In neonatal kidney, ERK was more abundant in the deep cortex and the medulla corresponding to tubule maturation. p38 and MKP-1 were detected uniformly in mesenchymal cells, mesangial cells, and ureteric bud epithelia of fetal kidney without an obvious correlation with the occurrence of apoptosis. JNK was expressed by tubular cells and podocytes of adult kidney. CONCLUSIONS: ERK, p38, and MKP-1 are strongly expressed in developing kidney, and JNK is detected predominantly in adult kidney. Both the temporal and spatial expression of ERK coincides with the maturation of the kidney.     

Renal activation of extracellular signal-regulated kinase in rats with autosomal-dominant polycystic kidney disease

BACKGROUND: Abnormal proliferation of renal tubule epithelial cells is a central factor in the biogenesis and sustained expansion of cysts in autosomal-dominant polycystic kidney disease (ADPKD). Recent evidence from in vitro studies of human cyst wall epithelial cells has implicated a role for the mitogen-activated protein (MAP) kinase pathway in this aberrant proliferation. To determine the extent to which this signaling pathway is involved in cyst pathogenesis in vivo, we measured the expression of select components of the MAP kinase cascade in Han:SPRD rats with ADPKD at an early stage of the disease. METHODS: Kidneys of 8-week-old normal Han:SPRD rats (+/+) or rats heterozygous (Cy/+) for ADPKD were examined by Western blot analysis and immunohistochemistry to determine the expression of extracellular-regulated kinase (ERK), phosphorylated ERK (P-ERK), Raf-1 (MAPKKK), phosphorylated Raf-1 (P-Raf-1), B-Raf, Rap-1 and phosphorylated protein kinase A (P-PKA). RESULTS: P-ERK was expressed to a greater extent in Cy/+ kidneys (3.74 +/- 1.07 fold) than in normal kidneys, whereas ERK abundance was not different. P-Raf-1 levels were higher in Cy/+ than in +/+ kidneys (1.53 +/- 0.08 fold) consistent with upstream stimulation of receptor tyrosine kinase. B-Raf and Raf-1 abundances were greater in Cy/+ than in +/+ (1.74 +/- 0.25 and 1.27 +/- 0.08 fold, respectively). In Cy/+, immunohistochemistry showed increased P-ERK and B-Raf expression in the abnormal mural epithelial cells within cysts. These findings, together with the detection of P-PKA and the small G protein, Rap-1, in cyst epithelial cells, implicate a potential role for cyclic adenosine monophosphate (AMP) in the activation of ERK in ADPKD cells. CONCLUSIONS: We conclude that the MAP kinase pathway is activated to the level of ERK in the abnormal mural epithelial cells lining cysts in animals with a dominantly inherited type of polycystic kidney disease. We suggest that cAMP, acting through PKA, Rap-1 and B-Raf, may contribute to the activation of ERK in a way that complements receptor tyrosine kinase-mediated agonists in the promotion of cyst enlargement.     

Preconditioning with cyclosporine A or FK506 differentially regulates mitogen-activated protein kinase expression in rat kidneys with ischemia/reperfusion injury

BACKGROUND: The signaling pathways of mitogen-activated protein kinases (MAPKs) are important molecular components responsible for ischemia/reperfusion (I/R) injury in the kidneys. Preconditioning with cyclosporine A (CsA) or FK506 reduces subsequent I/R injury. We studied the effect of preconditioning with CsA or FK506 on MAPK expression in ischemic rat kidneys. METHODS: Two separate studies were performed using Sprague-Dawley rats. First, MAPK (extracellular signal-regulated kinase [ERK], jun N-terminal kinase [JNK], p38) expressions were observed at 0, 10, 20, 30, 60, 120, and 1,440 min after I/R injury. Second, the effects of preconditioning with CsA or FK506 on MAPK expressions were observed in rat kidneys with I/R injury. I/R injury was induced by clamping both renal arteries for 45 min. Rats were pretreated with intravenous (IV) CsA (3 mg/kg) or IV FK506 (0.3 mg/kg) 6 hr before I/R injury and killed 30 min later. Expression of MAPK was measured using immunoblot and immunohistochemistry. RESULTS: MAPK (ERK, JNK, p38) expressions were significantly increased in kidneys with I/R injury compared with sham-operated controls, and immunohistochemistry revealed increased MAPK immunoreactivity in renal tubules of the outer medulla. Kidneys preconditioned with low-dose CsA or FK506 showed significantly increased ERK expression compared with kidneys with I/R injury alone (CsA, 9.5- vs. 4.5-fold; FK506 10.4- vs. 4.5-fold: P<0.05) but showed decreased JNK (CsA, 3.8- vs. 5.3-fold; FK506, 3.4- vs. 5.3-fold: P<0.05) and p38 expression (CsA, 2.5- vs. 3.7-fold; FK506, 2.1- vs. 3.7-fold: P<0.05). CONCLUSIONS: Preconditioning with CsA or FK506 differentially regulates the expression of MAPK in rat kidneys with I/R injury, and this may explain the remarkable protective effects of these agents.     

A study of the native kidneys in patients with chronic renal failure. Report 2: Correlation between cystic changes in native kidneys and development of renal tumor

The factors which made acquired cysts develop to renal tumors in chronic hemodialysis patients was investigated from clinical and histological findings. Although three renal tumors were found among 151 patients with chronic renal failure, clinically, one case had acquired cystic disease of the kidneys (ACDK), one case had simple cysts and the other case did not have any cyst. However, the last two cases had multiple small cysts histologically. In ACDK, renal tubules were degenerated and dilated, fused to each other, forming more larger cysts. Furthermore, epithelium of acquired cysts showed columer and dysplastic change, and papillary adenomas were developed into the inner space of the cyst wall. And ACDK kidney without renal tumor also revealed the same findings in histological examinations. It was postulated that renal tumor occurred from the papillary projections of the dysplastic epithelium of cysts. Therefore cysts in uremic patients seemed to be different from the simple cyst in normally functioning kidneys.     

Aberrant epithelial cell growth in autosomal dominant polycystic kidney disease

Renal cyst enlargement in autosomal dominant polycystic kidney disease (ADPKD) is characterized by increased epithelial cell proliferation and fluid accumulation. Using monolayer epithelial cultures derived from individually microdissected human ADPKD cysts and immunolocalization studies in vivo, the roles of matrix and growth factors in aberrant ADPKD cell proliferation have been studied. Abnormal ADPKD basement membrane ultrastructure was associated with increased turnover of 35S-labeled heparan sulfate proteoglycans (HSPG) by comparison to normal renal tubule epithelia in vitro. Mitogenic assays demonstrated significant increase in 3H-thymidine incorporation into ADPKD epithelia grown on type I and type IV collagen by comparison to normal proximal straight tubules (PST), collecting ducts, and thick ascending limbs of Henle (TAL). Proliferation on laminin or fibronectin matrices was unchanged and immunolocalization of matrix proteins was polarized and restricted to basal membranes of both ADPKD cysts and renal tubule epithelia in vivo. ADPKD epithelia in vitro were hypersensitive to the mitogenic action of epidermal growth factor (EGF) and EGF immunoreactivity was detected in ADPKD cyst lining epithelia, in cyst fluid, and in conditioned media from confluent ADPKD cultures, suggesting an autocrine mechanism of growth regulation. In addition, inhibition of epithelial proliferation by transforming growth factor-beta (TGF-beta), which was 100% in normal renal tubule epithelia, was reduced to 41% in ADPKD epithelia.     

Evidence for JNK-dependent up-regulation of proteoglycan synthesis and for activation of JNK1 following cyclical mechanical stimulation in a human chondrocyte culture model

OBJECTIVE: To examine the expression of mitogen-activated protein kinases (MAPKs) in human chondrocytes, to investigate whether selective activation of MAPKs is involved in up-regulation of proteoglycan (PG) synthesis following cyclical mechanical stimulation (MS), and to examine whether MS is associated with integrin-dependent or independent activation of MAPKs. METHODS: The C-28/I2 and C-20/A4 human chondrocyte cell lines were mechanically stimulated in monolayer cell culture. PG synthesis was assessed by [(35)S]-sulphate incorporation in the presence and absence of the p38 inhibitor SB203580, and the extracellular-regulated kinase (ERK1/2) inhibitor PD98059. Kinase expression and activation were assessed by Western blotting using phosphorylation status-dependent and independent antibodies, and by kinase assays. The Jun N-terminal kinase (JNK) inhibitor SP600125 and the anti-beta(1) integrin (CD29) function-blocking antibody were used to assess JNK activation and integrin dependence, respectively. RESULTS: Increased PG synthesis following 3 h of cyclic MS was abolished by pretreatment with 10 microM SB203580, but was not affected by 50 microM PD98059. The kinases p38, ERK1/ERK2 and JNKs were expressed in both stimulated and unstimulated cells. Phosphorylated p38 was detected at various time points following 0.5, 1, 2 and 3 h MS in C-28/I2, but not detected in C-20/A4 cell lines. Phosphorylation of ERK1 and ERK2 was not significantly affected by MS. Phosphorylation of the 54 and 46 kDa JNKs increased following 0.5, 1, 2 and 3 h of MS, and following CO(2) deprivation. MS-induced JNK phosphorylation was inhibited by SB203580 at concentrations > or =5 microM and activation of JNK1 following MS was blocked by SP600125 and partially inhibited by anti-CD29. CONCLUSIONS: The data suggest JNK, rather than p38 or ERK dependent increases in PG synthesis, and selective, partially integrin-dependent, activation of JNK kinases in human chondrocyte cell lines following cyclical MS. JNK activation is also very sensitive to changes in CO(2)/pH in this chondrocyte culture model.     

Immunohistochemical analysis of the normal and cystic kidney using antibody against polycystin 2

A second gene responsible for polycystic kidney disease(PKD) has been identified recently, and an antisera(YCC2) against this gene's product, polycystin 2, has been generated. In the present study, we investigated the normal distribution of polycystin 2 in human adult kidneys and analyzed the expression of polycystin 2 in the cystic tubules of kidneys from patients with PKD and acquired cystic disease of the kidney(ACDK). The expression of polycystin 2 in normal regions of resected human kidneys, 4 cases of autosomal dominant polycystic kidney disease(ADPKD) and 4 cases of ACDK was examined by immunohistochemically staining the specimens with a polyclonal antibody specific to the C-terminal region of polycystin 2. This region is specific to polycystin 2 and does not crossreact with polycystin 1. In normal kidneys, prominent expression of polycystin 2 was observed in the distal tubules. A faint level of expression was detected in the proximal tubules, and the glomerulus and vessels were almost negative for expression. In the cystic kidneys of ADPKD patients, 68.7% of the cystic tubules stained positively for YCC2, although partial staining was seen in 41.2% of the positive cystic tubules. Although the genetic background of the samples is unknown, the co-existence of positive and negative cysts suggest that a "two-hit" hypothesis is feasible and that the mutations are likely to be missense or in frame changes. In ACDK cysts, YCC2-positive staining was prominent in small cysts (less than 0.5 mm in diameter), which were also positive for DBA, a marker for distal tubules. In contrast, larger cysts of more than 0.5 mm in diameter which stained positive for a proximal tubule marker, Lotus T, tended to be less positively stained for YCC2. Overall, 94.5% of the cysts stained positive for YCC2, which is a much higher rate than that of PKD cysts. These results suggest that ACDK cysts may be generated by a different mechanism from that of PKD cysts.     

Activation and cellular localization of the p38 and JNK MAPK pathways in rat crescentic glomerulonephritis

BACKGROUND: The p38 and c-Jun N-terminal kinase (JNK) mitogen-activated protein kinase (MAPK) are intracellular signal transduction pathways involved in the production of inflammatory mediators. Little, however, is known about the contribution of these pathways to renal inflammation, nor the cell types in which these pathways are activated within normal and inflamed kidneys. The aim of this study was therefore to delineate the pattern and cellular localization of p38 and JNK activation in normal rat kidney and rat acute and chronic inflammatory renal disease. METHODS: Normal male Sprague-Dawley rats and groups of rats given accelerated anti-glomerular basement membrane (GBM) disease were killed at 3 hours, day 1, day 7, or day 28 and examined for p38 and JNK pathway activation by Western blotting and immunolocalization of the phosphorylated p38 (p-p38) and JNK (p-JNK) kinases. RESULTS: In terms of glomerular MAPK activation, Western blotting identified the presence of both p-p38 and p-JNK in normal glomeruli, localized by immunohistochemistry to podocytes and epithelial cells of Bowman's capsule. In anti-GBM disease, Western blotting showed that p38 activation peaked at 3 hours and remained elevated above normal throughout the disease time course. JNK activation (via the 54 kD isoform) likewise increased at 3 hours of anti-GBM disease and remained elevated throughout disease. At 3 hours, p-p38, but not p-JNK, was localized to neutrophils and glomerular endothelial cells. p-JNK was localized to glomerular endothelial cells at day 7. Macrophages, lymphocytes, activated podocytes, and myofibroblasts were positive for both p-p38 and p-JNK. In terms of tubular MAPK activation, Western blotting identified p38 and JNK activation in tubules of normal kidney. Immunostaining showed that most cortical tubules contained some p-p38 and p-JNK stained cells. There was a significant increase in tubular p38 activation at 3 hours of anti-GBM disease, followed by increased JNK activation of the 54 kD isoform from day 7 onward, and the 46 kD isoform at day 28. Immunostaining of diseased tissue localized p-p38 and p-JNK to virtually all cortical tubular cells. CONCLUSION: The p38 and JNK MAPK pathways are activated in glomeruli and tubules of normal kidney. In acute anti-GBM disease, there was an increase in p38 activation within glomerular endothelial cells and within infiltrating neutrophils, suggesting an important role for p38 MAPK in acute inflammation. In progressive anti-GBM disease, p38 and JNK activation in podocytes, glomerular endothelial cells, infiltrating macrophages, T cells, and myofibroblasts suggests that both the p38 and JNK MAPK pathways are important in chronic inflammation and fibrosis. Blockade of these pathways may therefore be potentially therapeutic in the treatment of acute and chronic renal inflammation.     

MAPK信号通路在骨关节炎发病机制中的研究进展

丝裂原活化蛋白激酶（mitogen—activated proteinkinase,MAPK）真核细胞信号传递的重要途径之一,在调节控制细胞结构和功能活动中发挥关键作用。在真核生物中MAPK信号通路包括p38、ERK、JNK、ERK5等多个亚家族。随着研究的不断深入,发现p38、ERK、JNK信号转导途径的活化与骨关节炎（osteoarthritis,OA）软骨损伤密切相关,诱导软骨细胞产生基质金属蛋白酶,加速关节软骨病理性降解,并参与软骨细胞增殖、凋亡与分化等一系列反应,明确MAPK信号通路在OA中的发生发展机制已成为研究的新热点。     

Androgen receptor pathway in rats with autosomal dominant polycystic kidney disease

Androgens have been implicated in mediating disease escalation in autosomal dominant polycystic kidney disease (ADPKD). Dihydrotestosterone (DHT), an agonist, and flutamide (FLT), an antagonist, were administered to Han:SPRD rats with ADPKD, and the role of androgen receptor (AR) abundance and activation on the enlargement and function of cystic kidneys was evaluated. Renal AR abundance determined by immunoblots in 8- to 10-wk-old Cy/+ male rats was naturally increased four-fold above that of littermate +/+ controls. In male Cy/+, castration decreased AR abundance below control +/+ by -89.4%, and AR expression within cyst mural epithelial cells was strikingly decreased. Castration of Cy/+ male rats also reduced the usual increases in kidney weight by -49.7%, kidney cyst area by -34.0%, and serum urea nitrogen by -72.8%; these indices were restored to precastration levels by DHT. In Cy/+ male rats, FLT administration reduced the increase in kidney weight by -27.6% and serum urea nitrogen by -53.7% and decreased the increment in AR expression by -84.2% in comparison with untreated +/+ controls. There was no effect of FLT in female rats. Immunoblot expression of phospho-extracellular signal-regulated kinase 1/2 (P-ERK) and B-Raf, key intermediates in the mitogen-activated protein kinase pathway that are abnormally elevated in Cy/+, was unaffected by castration and/or administration of DHT or FLT. AR was not expressed in renal epithelial cell nuclei of androgen-deficient rats but was displayed in most tubule and mural cyst cell nuclei of androgen-replete rats. In androgen-deficient Cy/+, 80.6% of renal epithelial cells that had entered the cell cycle (proliferating cell nuclear antigen positive) also expressed P-ERK. In androgen-replete rats, proliferating cell nuclear antigen-positive cells co-expressed AR (12.7%), P-ERK (36.4%), and P-ERK + AR (45.0%); 5.9% were probably stimulated by other mitogenic mechanisms. It is concluded that androgens potentiate renal cell proliferation and cyst enlargement through ERK1/2-dependent and ERK1/2-independent signaling mechanisms in Han:SPRD. It is suggested that the basal rate of cell proliferation is determined by ERK1/2 signaling to a major extent and that androgens have additive effects.     

High expression of PKC-MAPK pathway mRNAs correlates with glomerular lesions in human diabetic nephropathy

BACKGROUND: Activation of protein kinase C (PKC) is a major signaling pathway for transforming growth factor (TGF)-beta to induce extracellular matrix (ECM) production in diabetic nephropathy (DN). PKC also activates mitogen-activated protein kinase (MAPK), which is called the PKC-MAPK pathway. The PKC-MAPK pathway is probably responsible for PKC-related abnormalities in diabetic glomeruli. To confirm the involvement of this pathway, we determined the localization and expression of mRNAs in glomeruli by in situ hybridization method. METHODS: In the present study, we examined expression of PKCbeta1, MAPK/ERK kinase (MEK) 1, MEK2, extracellular signal-regulated protein kinase (ERK) 1, ERK2, and TGF-beta1 mRNAs using renal tissue samples from kidneys affected by DN (N= 21) and from normal human kidney (NHK; N= 6). We also performed an immunohistochemical study using anti-phosphorylated MEK1/2 (P-MEK) and ERK1/2 (P-ERK) antibodies. The glomerular severity of DN was classified into three groups according to mesangial expansion: D1 (N= 4), D2 (N= 13), and D3 (N= 4). We analyzed differences and correlations between variables. RESULTS: In the glomeruli, the number of cells that stained for these mRNAs in DN was significantly higher than in NHK. The expression of PKC-MAPK pathway mRNAs tended to be inversely proportional to the degree of mesangial expansion. The P-MEK and P-ERK signal intensity were parallel to its mRNA expression pattern. Furthermore, there were significant correlations among the P-MEK, P-ERK signal intensity, PKCbeta1 mRNA expression. CONCLUSION: Our results suggest that high expression of PKC-MAPK pathway mRNAs plays an important role in the development and/or progression of early tissue damage in DN.     

Matrix metalloproteinase-2 in a murine model of infantile-type polycystic kidney disease

It was previously found that elevated levels of matrix metalloproteinase (MMP)-2 (gelatinase A) and -9 (gelatinase B) were synthesized and secreted into the medium by cultured kidney tubules derived from cystic C57BL/6J-cpk mice. To determine whether increased synthesis and secretion occur in vivo in this mouse model of polycystic kidney disease, kidney protein extracts, mRNA, and tissue sections were compared for expression and activity of MMP-2 and -9. Although both MMP were detected in tissue extracts, the differences in expression levels and activity in normal and cystic kidneys were far greater for MMP-2. High levels of MMP-2 seemed to result from increased expression by the cystic kidneys predominantly in the second and third postnatal weeks (a time when the kidneys are undergoing rapid cystic enlargement). Much of the increased MMP was present in the inactive zymogen form, although active enzyme was readily detected by sodium dodecyl sulfate-polyacrylamide gel zymography and in situ zymography. MMP-2 was abnormally localized to the interstitium and to foci between cysts, suggesting that MMP-2 may regulate collagen accumulation at those sites, thus allowing cyst enlargement and limiting the severity of interstitial fibrosis.     

烫伤大鼠心肌细胞丝裂素活化蛋白激酶的活化及胞内分布规律的研究

目的　观察大鼠严重烫伤后早期心肌细胞中丝裂素活化蛋白激酶 [MAPKs,包括 p38激酶、细胞外信号调节激酶 (ERKs)和应激活化蛋白激酶 (JNK) ]的活化及胞内分布规律 ,探讨其与心肌损伤的关系。　方法　制作严重烫伤大鼠模型 ,于伤后 1、3、6、12、2 4h取其全血及心肌组织标本 ,并取正常大鼠的相应标本为对照。常规检测各血清标本中肌酸激酶同工酶 MB(CK MB)的活力 ;采用Western印迹法 ,检测各心肌组织标本中MAPKs各成员的活化情况 ,并对其组织切片行免疫组化染色。　结果　伤后 p38激酶、ERK均发生活化并伴核转位 ,以 1、3、6h最明显 (P <0 .0 1) ;伤后 1～ 2 4hJNK均未见活化。血清CK MB含量于伤后 3h升高 ,12h达高峰 (P <0 .0 5～ 0 .0 1)。　结论　p38激酶和ERK信号通路可能在严重烧伤后早期心肌细胞发生的损伤性反应中起重要作用 ,而前者可能是烧伤引发心肌损伤的主要信号转导通路之一。     

白蛋白诱导的肾小管细胞凋亡与丝裂素激活蛋白激酶信号通路

目的 探讨白蛋白诱导肾小管上皮细胞凋亡以及诱导凋亡的信号传导机制&#65377; 方法 将培养的大鼠肾小管细胞NRK-52E分别与不同浓度(10&#65380; 20&#65380; 30 mg/ml)的去脂无内毒素牛血清白蛋白(BSA)共同孵育6&#65380; 12&#65380; 18和24 h&#65377;透射电镜&#65380;共聚焦激光显微镜和流式细胞仪检测细胞凋亡&#65377;BSA 20 mg/ml刺激NRK-52E细胞15&#65380; 30&#65380; 60和120 min后, Westen印迹测定p38&#65380;氨基末端激酶(JNK)和细胞外信号调节激酶(ERK)活性&#65377;将SB202190(20 μmol/L, p38抑制剂)&#65380;SP600125(10 μmol/L, JNK抑制剂)和PD98059(20 μmol/L, ERK抑制剂)分别与白蛋白和NRK-52E细胞共同孵育24 h后检测细胞凋亡&#65377;结果 白蛋白以时间和剂量依赖方式诱导肾小管细胞凋亡&#65377;白蛋白与NRK-52E细胞共孵育后,p38和JNK活性明显升高,ERK活性显著降低&#65377;SB202190和SP600125可分别抑制白蛋白诱导NRK-52E细胞凋亡,而PD98059促进白蛋白诱导的NRK-52E细胞凋亡&#65377;结论 白蛋白以时间和剂量依赖方式诱导肾小管细胞凋亡,而p38和JNK激活与ERK抑制介导了白蛋白诱导的肾小管细胞凋亡&#65377;     

Pathways of apoptosis in human autosomal recessive and autosomal dominant polycystic kidney diseases

Autosomal dominant polycystic kidney disease (ADPKD) is a major cause of end-stage renal disease in adults. Autosomal recessive (AR) PKD affects approximately 1:20,000 live-born children with high perinatal mortality. Both diseases have abnormalities in epithelial proliferation, secretion, and cell-matrix interactions, leading to progressive cystic expansion and associated interstitial fibrosis. Cell number in a kidney reflects the balance between proliferation and apoptosis. Apoptosis results from extrinsic (ligand-induced, expression of caspase-8) and intrinsic (mitochondrial damage, expression of caspase-9) triggers. Previous studies have suggested a role for apoptosis in PKD cyst formation and parenchymal destruction. Mechanisms underlying apoptosis in human ADPKD and ARPKD were examined by quantitative immunohistochemistry and Western immunoblot analyses of age-matched normal and PKD tissues. Caspase-8 expression was significantly greater in small cysts and normal-appearing tubules than in larger cysts in ADPKD kidneys. Caspase-8 also appeared early in the disease process of ADPKD. In ARPKD, expression of caspase-8 was most pronounced in later stages of the disease and was not confined to a specific cyst size. In conclusion, apoptosis in human ADPKD is an early event, occurring predominantly in normal-appearing tubules and small cysts, and is triggered by an extrinsic factor, but it occurs later in ARPKD.     

Immune suppression in polymicrobial sepsis: differential regulation of Th1 and Th2 responses by p38 MAPK

BACKGROUND: Studies have indicated that a shift from a Th1 to a Th2 response occurs that contributes to the late immunosuppression seen during sepsis. However, the mechanism by which this occurs is unknown. In this regard, mediators released in response to sepsis are thought to upregulate a family of stress-induced mitogen-activated protein kinases (MAPKs), such as JNK, ERK, and p38 MAPK, which may play a role in this process. MATERIALS AND METHODS: To determine the role of MAPK in immune suppression, we induced polymicrobial sepsis in C3H/HeN male mice using cecal ligation and puncture (CLP). Splenic lymphocytes were harvested 24 h post-CLP and stimulated with the T-cell mitogen concanavalin A, and the expression and activation of these MAPKs were assessed by Western analysis. To determine the extent to which these MAPKs may have an impact on splenic immune function, cells were pretreated with a 10 microM concentration of the p38 MAPK inhibitor SB203580 or the MEK inhibitor PD98059 or with DMSO vehicle. The cells were then stimulated with 2.5 microg/ml of the T-cell mitogen concanavalin A, and cytokine release was then determined (by ELISA). RESULTS: In the lymphocytes from CLP mice no JNK signal was detected, however, p38 expression and activation were markedly (P < 0.05, n = 6) increased. In contrast, the expression of activated ERK markedly decreased following septic challenge. The results indicate that p38 MAPK inhibition with SB203580 suppressed the sepsis-induced augmentation of interleukin-10 release while restoring the suppressed Th1 cytokine interleukin-2 release typically encountered following sepsis. Inhibition of ERK had no effect on cytokine release. Neither PD98059 nor SB203580 had an effect on interferon gamma release or on proliferative capacity. CONCLUSION: This would indicate that the induction of p38 MAPK activation in splenocytes contributes to the immunosuppression seen in late sepsis.