Platelet-derived growth factor-BB phosphorylates heat shock protein 27 in cardiac myocytes

Activation of spinal PDGFRβ in microglia promotes neuronal autophagy via p38 MAPK pathway in morphine-tolerant rats

The adverse side effects of opioids, especially antinociceptive tolerance, limit their clinical application. A recent study reported that platelet-derived growth factor receptor β (PDGFRβ) blockage selectively inhibited morphine tolerance. Autophagy has been reported to contribute to the cellular and behavioral responses to morphine. However, little is known about the relationship between PDGFRβ and autophagy in the mechanisms of morphine tolerance. In this study, rats were intrathecally administered with morphine twice daily for 7 days to induce antinociceptive tolerance, which was evaluated using a tail-flick latency test. By administration autophagy inhibitor 3-Methyladenine, PDGFRβ inhibitor imatinib, p38 mitogen-activated protein kinase (MAPK) inhibitor SB203580 hydrochloride and minocycline hydrochloride, western blot, immunofluorescence, and transmission electron microscopy techniques were used to elucidate the roles of PDGFRβ, autophagy, and related signaling pathways in morphine tolerance. This study demonstrated for the first time that spinal PDGFRβ in microglia promotes autophagy in gamma-aminobutyric acid (GABA) interneurons through activating p38 MAPK pathway during the development of morphine tolerance, which suggest a potential strategy for preventing the development of morphine tolerance clinically, thereby improving the use of opioids in pain management.

Platelet-Derived Growth Factor in Heart Failure

Defective vascular and cardiomyocyte function are implicated in the development and progression of both heart failure with reduced and preserved ejection fraction. Any treatment option that augments these myocardial processes may therefore be of significant value. The platelet-derived growth factor (PDGF) family is involved in a wide range of growth processes and plays a key role in both regulating angiogenesis and mesenchymal cell development. Thus, PDGF may serve as a potent therapy for heart failure. While numerous animal studies have demonstrated beneficial cardiovascular effects of growth factor therapy, promising laboratory data has not yet translated to effective therapies. In this review, we outline the biological role of PDGF and summarize previous studies that have focused on the cardiovascular effects of normal PDGF signaling, administration of PDGF, and the effects of PDGF on stem cell therapy.

Impaired p38 MAPK/HSP27 signaling underlies aging-related failure in opioid-mediated cardioprotection

Cardioprotection and preconditioning mediated via G-protein-coupled receptors may be lost or impaired with advancing age, limiting ischemic tolerance and the ability to pharmacologically protect older hearts from ischemic injury. Our preliminary findings indicated a loss of delta-opioid receptor-mediated protection in aged vs. young mouse hearts, which may involve alterations in protective kinase signaling. In the present study, we tested the hypothesis that aging-related loss of opioid-triggered cardioprotection involves failure to activate p38 MAPK and its distal signaling targets. Langendorff-perfused hearts from young (10-14 weeks) or aged (24-26 months) C57 mice underwent 25-min ischemia and 45-min reperfusion in the presence or absence of 1 micromol/l DPDPE (delta-opioid agonist) or 1 micromol/l anisomycin (activator of p38 MAPK), and functional recovery and protein activation/phosphorylation were assessed. Contractile recovery was similar in untreated young and aged hearts (50+/-2% and 53+/-5%, respectively), and was enhanced by DPDPE in young hearts only (67+/-3%). Immunoblot analysis revealed that DPDPE comparably activated or phosphorylated GRK2, Akt, ERK1/2 and p70S6 kinase in young and aged hearts, whereas aging abrogated the stimulatory effects of DPDPE on p38 MAPK and HSP27. Treatment with anisomycin elicited comparable activation of p38 MAPK and HSP27 in both young and aged hearts, coupled with a pronounced and equivalent cardioprotection in the two groups (73+/-3% and 77+/-2%, respectively), an effect abolished by the p38 MAPK inhibitor, SB203580. These data indicate that aging-related loss of delta-opioid-mediated cardioprotection involves failure to activate p38 MAPK and HSP27. Direct targeting of this pathway elicits comparable protection in both age groups.

Heat shock protein 27: its potential role in vascular disease

Heat shock proteins are molecular chaperones that have an ability to protect proteins from damage induced by environmental factors such as free radicals, heat, ischaemia and toxins, allowing denatured proteins to adopt their native configuration. Heat shock protein-27 (Hsp27) is a member of the small Hsp (sHsp) family of proteins, and has a molecular weight of approximately 27 KDa. In addition to its role as a chaperone, it has also been reported to have many additional functions. These include effects on the apoptotic pathway, cell movement and embryogenesis. In this review, we have focused on its possible role in vascular disease.

Peptide growth factors signal differentially through protein kinase C to extracellular signal-regulated kinases in neonatal cardiomyocytes

The extracellular signal-regulated kinases 1/2 (ERK1/2) are activated in cardiomyocytes by Gq protein-coupled receptors and are associated with induction of hypertrophy. Here, we demonstrate that, in primary cardiomyocyte cultures, ERK1/2 were also significantly activated by platelet-derived growth factor (PDGF), epidermal growth factor (EGF) or fibroblast growth factor (FGF), but insulin, insulin-like growth factor 1 (IGF-1) and nerve growth factor (NGF) had relatively minor effects. PDGF, EGF or FGF increased cardiomyocyte size via ERK1/2, whereas insulin, IGF-1 or NGF had no effect suggesting minimum thresholds/durations of ERK1/2 signaling are required for the morphological changes associated with hypertrophy. Peptide growth factors are widely accepted to activate phospholipase C gamma1 (PLCgamma1) and protein kinase C (PKC). In cardiomyocytes, only PDGF stimulated tyrosine phosphorylation of PLCgamma1 and nPKCdelta. Furthermore, activation of ERK1/2 by PDGF, but not EGF, required PKC activity. In contrast, EGF substantially increased Ras.GTP with rapid activation of c-Raf, whereas stimulation of Ras.GTP loading by PDGF was minimal and activation of c-Raf was delayed. Our data provide clear evidence for differential coupling of PDGF and EGF receptors to the ERK1/2 cascade, and indicate that a minimum threshold/duration of ERK1/2 signaling is required for the development of cardiomyocyte hypertrophy.

alphaB-crystallin is phosphorylated during myocardial infarction: involvement of platelet-derived growth factor-BB

alphaB-crystallin is the most abundant low-molecular-weight heat shock protein in heart and recent studies have demonstrated that it plays a cardioprotective role during myocardial infarction both in vivo and in vitro. On the other hand, platelet-derived growth factor (PDGF), a potent serum mitogen, has been reported to improve cardiac function after myocardial infarction. In the present study, using a mouse myocardial infarction model, we investigated whether alphaB-crystallin is phosphorylated during myocardial infarction and the implication of PDGF-BB. Phosphorylation of alphaB-crystallin at Ser-59 was time dependently induced and plasma PDGF-BB levels were concomitantly increased. Moreover, PDGF-BB-stimulated phosphorylation of alphaB-crystallin was suppressed by SB203580, a specific inhibitor of p38 mitogen-activated protein (MAP) kinase, in primary cultured cardiac myocytes. Our results indicate that PDGF-BB induces phosphorylation of alphaB-crystallin via p38 MAP kinase during myocardial infarction.

Midazolam suppresses thrombin-induced heat shock protein 27 phosphorylation through inhibition of p38 mitogen-activated protein kinase in cardiac myocytes

It has been shown that anesthetics have effects of cardiac preconditioning. Heat shock proteins (HSPs) function as molecular chaperone. Among them, HSP27, a low-molecular-weight HSP, abundantly exist in heart. However, the relationship between anesthetics and HSP27 in heart is not yet clarified. We investigated whether thrombin induces or phosphorylates HSP27 in primary cultured mouse myocytes and the effect of midazolam on the thrombin-stimulated HSP27 phosphorylation and the mechanism behind it. Thrombin time dependently phosphorylated HSP27 at Ser-15 and Ser-85 while having no effect on the levels of HSP27. Midazolam markedly suppressed the thrombin-induced phosphorylation of HSP27 at both Ser-15 and Ser-85. Thrombin induced the phosphorylation of p44/p42 MAP kinase and p38 MAP kinase without affecting stress-activated protein kinase/c-Jun N-terminal kinase. In addition, midazolam attenuated the phosphorylation of thrombin-induced p38 MAP kinase but not that of p44/p42 MAP kinase. SB203580 and PD169316, inhibitors of p38 MAP kinase, suppressed the thrombin-induced phosphorylation of HSP27 at both Ser-15 and Ser-85. These results strongly suggest that thrombin induces the HSP27 phosphorylation at least through the p38 MAP kinase activation in cardiac myocytes and that midazolam inhibits the thrombin-induced HSP27 phosphorylation via suppression of p38 MAP kinase activation.