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Biomedical subjects

J L Martin

Publications and source records attributed to J L Martin.

At least 73 records · Page 4Linked to original sources
PubMed2000

Opposite regulation of calbindin and calretinin expression by brain-derived neurotrophic factor in cortical neurons.

Regulation of calbindin and calretinin expression by brain-derived neurotrophic factor (BDNF) was examined in primary cultures of cortical neurons using immunocytochemistry and northern blot analysis. Here we report that regulation of calretinin expression by BDNF is in marked contrast to that of calbindin. Indeed, chronic exposure of cultured cortical neurons for 5 days to increasing concentrations of BDNF (0.1-10 ng/ml) resulted in a concentration-dependent decrease in the number of calretinin-positive neurons and a concentration-dependent increase in the number of calbindin-immunoreactive neurons. Consistent with the immunocytochemical analysis, BDNF reduced calretinin mRNA levels and up-regulated calbindin mRNA expression, providing evidence that modifications in gene expression accounted for the changes in the number of calretinin- and calbindin-containing neurons. Among other members of the neurotrophin family, neurotrophin-4 (NT-4), which also acts by activating tyrosine kinase TrkB receptors, exerted effects comparable to those of BDNF, whereas nerve growth factor (NGF) was ineffective. As for BDNF and NT-4, incubation of cortical neurons with neurotrophin-3 (NT-3) also led to a decrease in calretinin expression. However, in contrast to BDNF and NT-4, NT-3 did not affect calbindin expression. Double-labeling experiments evidenced that calretinin- and calbindin-containing neurons belong to distinct neuronal subpopulations, suggesting that BDNF and NT-4 exert opposite effects according to the neurochemical phenotype of the target cell.

Animals↗
PubMed2000

Characterization of an amino-terminal fragment of insulin-like growth factor binding protein-3 and its effects in MCF-7 breast cancer cells.

This study describes the purification, characterization and actions of a peptide derived from proteolysis of IGFBP-3 by an enzyme secreted by MCF-7 breast cancer cells. One millilitre of cell-conditioned medium at pH 5.5 fully proteolysed 10 microg plasma-derived IGFBP-3, yielding an immunoreactive fragment of apparent molecular mass 21 kDa by SDS-PAGE. After purification to homogeneity by IGF-I affinity chromatography and reverse-phase HPLC, sequence analysis revealed the amino-terminus of IGFBP-3, and mass spectrometry indicated a molecular mass of 12 295 Da. Analysis of the corresponding fragment generated by proteolysis of a non-glycosylated IGFBP-3 mutant indicated a molecular mass of 9855 Da, consistent with cleavage after Arg97. This suggests that the fragment derived from glycosylated IGFBP-3 contains approximately 2.5 kDa carbohydrate on Asn89. IGFBP-3[1-97] formed binary complexes with IGFs, but with reduced efficiency compared with intact IGFBP-3. IGFBP-3[1-97] at 11 nM inhibited IGF-I-stimulated DNA synthesis by 50-60% in MCF-7 breast cancer cells, similar to the inhibition observed with the intact protein. In the absence of IGF-I, DNA synthesis was inhibited by IGFBP-3[1-97], but not intact IGFBP-3. This suggests that the IGFBP-3 protease in MCF-7 cell medium can generate an inhibitor of IGF-dependent and independent breast cancer cell growth.

Blotting, Western↗
PubMed2000

The role of differential activation of p38-mitogen-activated protein kinase in preconditioned ventricular myocytes.

Activation of protein kinase C (PKC) and more recently mitogen-activated protein kinases (MAPKs) have been associated with the cardioprotective effect of ischemic preconditioning. We examined the interplay between these kinases in a characterized model of ischemic preconditioning in cultured rat neonatal ventricular cardiocytes where ectopic expression of active PKC-delta results in protection. Two members of the MAPK family, p38 and p42/44, were activated transiently during preconditioning by brief simulated ischemia/reoxygenation. Overexpression of active PKC-delta, rather than augmenting, completely abolished this activation. We therefore determined whether a similar process occurred during lethal prolonged simulated ischemia. In contrast to ischemia, brief, lethal-simulated ischemia activated only p38 (2.8+/-0.45 vs. basal, P<0.01), which was attenuated by expression of active PKC-delta or by preconditioning (0.48+/-0.1 vs. ischemia, P<0.01). To determine whether reduced p38 activation was the cause or an effect of protection, we used SB203580, a p38 inhibitor. SB203580 reduced ischemic injury (CK release 38.0+/-3.1%, LDH release 77.3+/-4.0%, and MTT bioreduction 127.1+/-4.8% of control, n=20, P<0.05). To determine whether p38 activation was isoform selective, myocytes were infected with adenoviruses encoding wild-type p38alpha or p38beta. Transfected p38alpha and beta show differential activation (P<0.001) during sustained simulated ischemia, with p38alpha remaining activated (1.48+/-0.36 vs. basal) but p38beta deactivated (0.36+/-0.1 vs. basal, P<0.01). Prior preconditioning prevented the activation of p38alpha (0.65+/-0.11 vs. ischemia, P<0.05). Moreover, cells expressing a dominant negative p38alpha, which prevented ischemic p38 activation, were resistant to lethal simulated ischemia (CK release 82.9+/-3.9% and MTT bioreduction 130.2+/-6.5% of control, n=8, P<0.05). Thus, inhibition of p38alpha activation during ischemia reduces injury and may contribute to preconditioning-induced cardioprotection in this model.

Animals↗
PubMed2000

Comparison between the role of the neuronal and inducible nitric oxide synthase in methamphetamine-induced neurotoxicity and sensitization.

The involvement of the neuronal and inducible nitric oxide synthase (nNOS and iNOS, respectively) in methamphetamine (METH)-induced dopaminergic neurotoxicity and behavioral sensitization was investigated. To determine METH-induced neurotoxicity, mice deficient in the nNOS and iNOS genes, nNOS(-/-) and iNOS(-/-) mice, and wild-type controls received either saline or METH (5 mg/kg x 3). After 72 h the level of striatal dopaminergic markers were measured. Administration of METH to nNOS(-/-) mice had no significant effect on the level of striatal dopamine, 3,4-dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA), or dopamine transporter (DAT) binding sites. However, METH caused 25-40% depletion of dopaminergic markers in iNOS(-/-) mice and 63-69% depletion in the wild-type mice. METH-induced locomotor activity was measured following the administration of a low dose (1 mg/kg) on day 1. Subsequently animals received the high dose of METH (5 mg/kg x 3). On day 4, after a 68-72 h drug free period, animals were challenged with 1 mg/kg METH, and locomotor activity was recorded. The intensity of METH-induced locomotion in nNOS(-/-) mice on day 1 and 4 was similar, suggesting that locomotor sensitization did not develop. However, the intensity of METH-induced locomotion in the iNOS(-/-) and wild-type mice on day 4 was doubled compared to day 1, suggesting the development of sensitization. The present findings indicate that nNOS(-/-) mice are more resistant to METH-induced neurotoxicity and behavioral sensitization than iNOS(-/-) mice. These results suggest a major role for nNOS rather than iNOS in the effects of METH.

Analysis of Variance↗
PubMed2000

The effect of phosphorylation by casein kinase 2 on the activity of insulin-like growth factor-binding protein-3.

Insulin-like growth factor (IGF)-binding protein-3 (IGFBP-3) is known to be secreted as a phosphoprotein, constitutively phosphorylated at casein kinase 2 (CK2) sites. To examine the effect of phosphorylation by CK2 on the properties of glycosylated human IGFBP-3, we phosphorylated plasma-derived IGFBP-3, containing less than 1 mol/mol phosphoserine, in vitro. As judged by incorporated 32P, enzymatic deglycosylation did not decrease the phosphate content of phospho-IGFBP-3. Phosphorylation had no effect on IGF-I or IGF-II binding, but was inhibitory to acid-labile subunit binding in the presence of either IGF. Determined in simian virus 40-transformed human fibroblasts, cell association by phospho-IGFBP-3 was inhibited approximately 50% compared with that of the nonphosphorylated preparation. Phospho-IGFBP-3 showed significant resistance to proteolysis by plasmin and a cysteine protease secreted by MCF-7 cells. However, no difference was seen between the two preparations in their inhibition of IGF-I-stimulated DNA synthesis when coincubated with IGF-I in neonatal skin fibroblasts or MCF-7 breast cancer cells, and little difference was found in their ability to potentiate IGF-I-stimulated DNA synthesis when preincubated with fibroblasts. These results indicate that IGFBP-3 interaction with acid-labile subunit and with the cell surface, both of which involve basic carboxyl-terminal residues, may be modulated by phosphorylation. Relative resistance to proteolysis and poor binding to cells suggest that CK2-phospho-IGFBP-3 may be a significant inhibitor of IGF activity in the extracellular environment.

Casein Kinase II↗
PubMed2000

Insulin-like growth factor binding protein-3 is regulated by dihydrotestosterone and stimulates deoxyribonucleic acid synthesis and cell proliferation in LNCaP prostate carcinoma cells.

We have investigated the production and actions of a growth regulatory protein, insulin-like growth factor binding protein (IGFBP)-3, in the androgen-responsive prostate carcinoma cell line LNCaP. Confluent monolayers of cells secreted approximately 0.7 ng/ml IGFBP-3 over 24 h. Dihydrotestosterone (DHT, 10 nM) and 1,25-dihydroxyvitamin D3 (vitamin D, 10 nM) increased IGFBP-3 in media to 149 +/- 15% and 206 +/- 18% of control, respectively, when added separately, and to 453 +/- 28% of control when used in combination. IGFBP-2, secreted at approximately 25-fold higher concentrations than IGFBP-3, was increased 50% by 10 nM DHT, but there was no effect of vitamin D on IGFBP-2 production in the absence or presence of DHT. Cell-associated IGFBP-3, and immunoreactive IGFBP-3 species of 20 kDa and 30 kDa were also increased in response to vitamin D plus DHT. A combination of vitamin D and DHT increased DNA synthesis in LNCaP cells 3-fold, and this was at least partly mediated by endogenous IGFBP-3 because anti-IGFBP-3 IgG, but not nonimmune serum IgG, reduced the stimulatory effect of vitamin D and DHT from 293 +/- 11.6% to 161 +/- 30.7% of control levels (P < 0.0001). Basal and DHT plus vitamin D-stimulated thymidine incorporation was significantly increased by 50 ng/ml human plasma-derived purified IGFBP-3. After 4 days treatment with vitamin D plus DHT, or pure IGFBP-3, LNCaP cell numbers were increased relative to control. These results indicate a role for IGFBP-3 in the proliferation of androgen-responsive prostate carcinoma cells.

Cell Division↗
PubMed2000

Differential regulation of insulin-like growth factor-binding protein-3 protease activity in MCF-7 breast cancer cells by estrogen and transforming growth factor-beta1.

We have examined the regulation of an insulin-like growth factor-binding protein-3 (IGFBP-3) protease secreted by MCF-7 human breast cancer cells using a ligand-binding assay that relies on the decrease in affinity for des(1-3)IGF-I that occurs when IGFBP-3 becomes proteolyzed. IGFBP-3 protease activity was not altered by treatment of MCF-7 cells with all-trans-retinoic acid, vitamin D, epidermal growth factor, platelet-derived growth factor, insulin, or forskolin. However, estradiol was a potent stimulator of IGFBP-3 protease activity, with a significant and maximal effect at 1 nM. This was prevented by cotreatment with tamoxifen, which had no significant effect in the absence of estradiol. By contrast, TGFbeta1 dose dependently inhibited the amount of protease activity secreted by MCF-7 cells, with complete reversal of IGFBP-3 degradation apparent in response to 10 ng/ml TGFbeta1. This study has demonstrated that estrogens and TGFbeta1, factors that are stimulatory and inhibitory, respectively, for MCF-7 cell growth, also stimulate and inhibit the production of an enzyme capable of proteolyzing the growth inhibitory protein IGFBP-3.

Blotting, Western↗
PubMed2000

Caseous lymphadenitis caused by Corynebacterium ulcerans in the dromedary camel.

Caseous lymphadenitis that affected the dorsal and ventral superficial lymph nodes in the left cervicothoracic region of a young dromedary camel is described. The agent isolated was Corynebacterium ulcerans. To our knowledge, this is the first description of purulent lymphadenitis caused by C. ulcerans in a species belonging to the Camelidae.

Animals↗
PubMed2000

Histopathologic changes in the brain, heart, and skeletal muscle of rhesus macaques, ten days after exposure to soman (an organophosphorus nerve agent).

BACKGROUND AND PURPOSE: Soman, an organophosphorus, anticholinergic, chemical warfare nerve agent, is studied at few research facilities, and there have been few pathologic studies of soman-exposed primates. We describe the brain, heart, and skeletal muscle lesions, review lesions described in literature, and discuss possible pharmacologic mechanisms for soman-induced neuron necrosis. METHODS: In this retrospective, histopathologic study, records were obtained for 36 rhesus macaques (Macaca mulatta) that were euthanized 10 days after soman exposure, from a larger group of 103 monkeys that were exposed to soman and used for pharmacologic and lethality studies. RESULTS: Brain lesions were seen in 9 of 15 animals that convulsed and in only 1 of 21 that did not convulse. The brain lesions in our primates were limited to the hippocampus, amygdala, and thalamus (of one animal), and consisted of neuron necrosis and dropout, spongiosis, gliosis, astrocytosis, and vascularization. Heart lesions consisted of myocardial degeneration and necrosis. Three animals had brain and heart lesions, 7 had brain lesions only, and 3 had heart lesions only. Skeletal muscle lesions, although minimal to mild, were in most of the animals, whether they had convulsed, but most had muscular tremors. These lesions were in the biceps brachii (11 of 22 monkeys), anterior tibialis (8/22), biceps femoris (7/22), flexor carpi radialis (5/22), gastrocnemius (3/22), and diaphragm (1/22). The limited literature on soman lesions in primate brain and heart, and the limited information on skeletal muscle lesions, is reviewed. CONCLUSIONS: Brain lesions were not as wide-spread as reported in other studies of primates and rodents, and were significantly associated with convulsions. Unlike other studies using rodents, we observed poor correlation between heart and brain lesions; thus, a single hypothesis to explain the pathogenesis for the brain and heart lesions may be difficult to establish.

Animals↗
PubMed1999

Methamphetamine- and 1-methyl-4-phenyl- 1,2,3, 6-tetrahydropyridine-induced dopaminergic neurotoxicity in inducible nitric oxide synthase-deficient mice.

Previous studies have suggested a role for the retrograde messenger, nitric oxide (NO), in methamphetamine (METH)- and 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)- induced dopaminergic neurotoxicity. Since evidence supported the involvement of the neuronal nitric oxide synthase (nNOS) isoform in the dopaminergic neurotoxicity, the present study was undertaken to investigate whether the inducible nitric oxide synthase (iNOS) isoform is also associated with METH- and MPTP-induced neurotoxicity. The administration of METH (5mg/kg x 3) to iNOS deficient mice [homozygote iNOS(-/-)] and wild type mice (C57BL/6) resulted in significantly smaller depletion of striatal dopaminergic markers in the iNOS(-/-) mice compared with the wild-type mice. METH-induced hyperthermia was also significantly lower in the iNOS(-/-) mice than in wild-type mice. In contrast to the outcome of METH administration, MPTP injections (20 mg/kg x 3) resulted in a similar decrease in striatal dopaminergic markers in iNOS(-/-) and wild-type mice. In the set of behavioral experiments, METH-induced locomotor sensitization was investigated. The acute administration of METH (1.0 mg/kg) resulted in the same intensity of locomotor activity in iNOS(-/-) and wild-type mice. Moreover, 68 to 72 h after the exposure to the high-dose METH regimen (5 mg/kg x 3), a marked sensitized response to a challenge injection of METH (1.0 mg/kg) was observed in both the iNOS(-/-) and wild-type mice. The finding that iNOS(-/-) mice were unprotected from MPTP-induced neurotoxicity suggests that the partial protection against METH-induced neurotoxicity observed was primarily associated with the diminished hyperthermic effect of METH seen in the iNOS(-/-) mice. Moreover, in contrast to nNOS deficiency, iNOS deficiency did not affect METH-induced behavioral sensitization.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1999

Crystal structure of human catecholamine sulfotransferase.

Sulfonation, like phosphorylation, can modify the activity of a variety of biological molecules. The sulfotransferase enzymes sulfonate neurotransmitters, drugs, steroid hormones, dietary carcinogens and proteins. SULT1A3 specifically sulfonates catecholamines such as dopamine, adrenaline and noradrenaline. The crystal structure of SULT1A3 with a sulfate bound at the active site, has been determined at 2.4 A resolution. Although the core alpha/beta fold is like that of estrogen and heparan sulfotransferases, major differences occur in and around the active site. Most notably, several regions surrounding the active site, including a section of 40 residues, are disordered in SULT1A3. Regions that are topologically equivalent to the disordered parts of SULT1A3 are involved in substrate and cofactor binding in estrogen and heparan sulfotransferase. Flexibility in these regions suggests that ligand binding elicits a disorder-order transition in and around the active site of sulfotransferases and might contribute to the broad substrate specificity of these enzymes.

Amino Acid Sequence↗
PubMed1999

Insulin-like growth factor binding protein-3 is secreted as a phosphoprotein by human breast cancer cells.

The growth regulatory activity of the insulin-like growth factor binding proteins (IGFBPs) may be modulated by post-translational modifications such as glycosylation, limited proteolysis and phosphorylation. In this study, we have examined phosphorylation of IGFBP-3 in two breast cancer cell lines: the estrogen receptor negative (ER-ve) Hs578T cell line in which IGFBP-3 is normally expressed, and ER+ve T47D breast cancer cells transfected with IGFBP-3 cDNA (T47D(BP-3)) and therefore expressing IGFBP-3 constitutively. Metabolic labelling with [32P] orthophosphate revealed that both cell lines secreted phosphorylated IGFBP-3 similar in size to plasma IGFBP-3 phosphorylated in vitro with casein kinase II, and that IGFBP-3 phosphorylation was differentially modulated in the two cell lines. In Hs578T cells, retinoic acid (10-100 nM) increased IGFBP-3 phosphorylation to a maximum of 150% of control. IGF-I, but not [LR3]IGF-I, reduced the proportion of phosphorylated IGFBP-3 in Hs578T conditioned medium, consistent with increased release of non-phosphorylated, cell-associated IGFBP-3. By contrast, IGFBP-3 phosphorylation in T47D(BP-3) cells was not affected by retinoic acid or IGF-I, but appeared slightly increased by estradiol. Together these data indicate that phosphorylation of IGFBP-3 in breast cancer cells may be regulated by agents known to affect breast cancer cell proliferation.

Biological Transport↗
PubMed1999

A role for HSP27 in sensory neuron survival.

Peripheral nerve injury in neonatal rats results in the death of the majority of the axotomized sensory neurons by 7 d after injury. In adult animals, however, all sensory neurons survive for at least 4 months after axotomy. How sensory neurons acquire the capacity to survive axonal injury is not known. Here we describe how the expression of the small heat shock protein 27 (HSP27) is correlated with neuronal survival after axotomy in vivo and after NGF withdrawal in vitro. The number of HSP27-immunoreactive neurons in the L4 DRG is low at birth and does not change significantly for 21 d after postnatal day 0 (P0) sciatic nerve axotomy. In contrast, in the adult all axotomized neurons begin to express HSP27. One week after P0 sciatic nerve section the total number of neurons in the L4 DRG is dramatically reduced, but all surviving axotomized neurons, as identified by c-jun immunoreactivity, are immunoreactive for HSP27. In addition, terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling reveals that very few HSP27-expressing neurons are dying 48 hr after neonatal axotomy. In vitro, a similar correlation exists between HSP27 expression and survival; in P0 DRG cultures, neurons that express HSP27 preferentially survive NGF withdrawal. Finally, overexpression of human HSP27 in neonatal rat sensory and sympathetic neurons significantly increases survival after NGF withdrawal, with nearly twice as many neurons surviving at 48 hr. Together these results suggest that HSP27 in sensory neurons plays a role in promoting survival after axotomy or neurotrophin withdrawal.

Aging↗
PubMed1999

Coherent reaction dynamics in a bacterial cytochrome c oxidase.

Biological reactions in protein complexes involve structural dynamics spanning many orders of magnitude in time. In standard descriptions of catalysis by enzymes, the transition state between reactant and product is reached by thermal, stochastic motion. In the ultrashort time domain, however, the protein moiety and cofactor motions leading to altered conformations can be coherent rather than stochastic in nature. Such coherent motions may play a key role in controlling the accessibility of the transition state and explain the high efficiency of the reaction. Here we present evidence for coherent population transfer to the product state during an ultrafast reaction catalysed by a key enzyme in aerobic organisms. Using the enzyme cytochrome c oxidase aa3 from the bacterium Paracoccus denitrificans, we have studied haem dynamics during the photo-initiated ultrafast transfer of carbon monoxide from haem a3 to CuB by femtosecond spectroscopy. The ground state of the unliganded a3 species is populated in a stepwise manner in time, indicating that the reaction is mainly governed by coherent vibrations (47cm(-1)). The reaction coordinate involves conformational relaxation of the haem group and we suggest that ligand transfer also contributes.

Carbon Monoxide↗
PubMed1999

Effects of mutant and antisense RNA of phospholamban on SR Ca(2+)-ATPase activity and cardiac myocyte contractility.

BACKGROUND: The delayed cardiac relaxation in failing hearts has been attributed to a reduced activity of sarcoplasmic reticulum Ca(2+)-ATPase (SERCA2). Phospholamban (PLB) inhibits SERCA2 activity and is therefore a potential target to improve the cardiac performance in heart failure. METHODS AND RESULTS: Mutants of PLB (Adv/mPLB) or antisense RNA of PLB (Adv/asPLB) was expressed in cardiac myocytes by recombinant adenovirus, and their effects on SERCA2 activity and myocyte contractility were studied. One mPLB, K3E/R14E, pentamerized with endogenous PLB in neonatal myocytes and resulted in a 45% increase in the affinity of SERCA2 for Ca(2+) and 27% faster diastolic Ca(2+) decline as determined by SR (45)Ca uptake assays and by indo 1-facilitated Ca(2+) transient measurement, respectively. Edge-detection analysis of adult myocyte contractility showed a 74% increase in fractional shortening, accompanied by 115% increase in velocity of relengthening and 25% decrease in time to half-maximal relengthening. In parallel, infection of neonatal cardiac myocytes by Adv/asPLB decreased the endogenous PLB level by 54%, which was associated with a 35% increase in Ca(2+) affinity of SERCA2 and 21% faster diastolic Ca(2+) decline. However, in adult cardiac myocytes, Adv/asPLB failed to significantly alter the endogenous PLB level, the SERCA2 activity, or most of the contractile parameters. CONCLUSIONS: K3E/R14E is a dominant negative mutant of PLB that disrupts the structural integrity and function of the endogenous PLB and consequently enhances SERCA2 activity and myocyte contractility. In neonatal myocytes, the decrease in steady-state abundance of PLB by asPLB also leads to increased SERCA2 activity.

Adenoviridae↗
PubMed1999

Geminate recombination of nitric oxide to endothelial nitric-oxide synthase and mechanistic implications.

The nitric-oxide synthase (NOS) catalyzes the oxidation of L-arginine to L-citrulline and NO through consumption of oxygen bound to the heme. Because NO is produced close to the heme and may bind to it, its subsequent role in a regulatory mechanism should be scrutinized. We therefore examined the kinetics of NO rebinding after photodissociation in the heme pocket of human endothelial NOS by means of time-resolved absorption spectroscopy. We show that geminate recombination of NO indeed occurs and that this process is strongly modulated by L-Arg. This NO rebinding occurs in a multiphasic fashion and spans over 3 orders of magnitude. In both ferric and ferrous states of the heme, a fast nonexponential picosecond geminate rebinding first takes place followed by a slower nanosecond phase. The rates of both phases decreased, whereas their relative amplitudes are changed by the presence of L-Arg; the overall effect is a slow down of NO rebinding. For the isolated oxygenase domain, the picosecond rate is unchanged, but the relative amplitude of the nanosecond binding decreased. We assigned the nanosecond kinetic component to the rebinding of NO that is still located in the protein core but not in the heme pocket. The implications for a mechanism of regulation involving NO binding are discussed.

Arginine↗
PubMed1999

A role for p38(MAPK)/HSP27 pathway in smooth muscle cell migration.

Smooth muscle cells are exposed to growth factors and cytokines that contribute to pathological states including airway hyperresponsiveness, atherosclerosis, angiogenesis, smooth muscle hypertrophy, and hyperplasia. A common feature of several of these conditions is migration of smooth muscle beyond the initial boundary of the organ. Signal transduction pathways activated by extracellular signals that instigate migration are mostly undefined in smooth muscles. We measured migration of cultured tracheal myocytes in response to platelet-derived growth factor, interleukin-1beta, and transforming growth factor-beta. Cellular migration was blocked by SB203580, an inhibitor of p38(MAPK). Time course experiments demonstrated increased phosphorylation of p38(MAPK). Activation of p38(MAPK) resulted in the phosphorylation of HSP27 (heat shock protein 27), which may modulate F-actin polymerization. Inhibition of p38(MAPK) activity inhibited phosphorylation of HSP27. Adenovirus-mediated expression of activated mutant MAPK kinase 6b(E), an upstream activator for p38(MAPK), increased cell migration, whereas overexpression of p38alpha MAPK dominant negative mutant and an HSP27 phosphorylation mutant blocked cell migration completely. The results indicate that activation of the p38(MAPK) pathway by growth factors and proinflammatory cytokines regulates smooth muscle cell migration and may contribute to pathological states involving smooth muscle dysfunction.

Adenoviridae↗