Angiotensin II (Ang II) evokes a variety of hypertrophic responses such as activation of protein kinases, reprogramming of gene expressions and an increase in protein synthesis in cardiac myocytes. In this study, we examined the role of Rho family small GTP binding proteins (G proteins) in Ang II-induced cardiac hypertrophy. Ang II strongly activated extracellular signal-regulated protein kinases (ERKs) in cardiac myocytes of neonatal rats. Although Ang II-induced activation of ERKs was completely suppressed by an Ang II type 1 receptor antagonist, CV-11974, this activation was not inhibited by the pretreatment with C3 exoenzyme, which abrogates Rho functions. Overexpression of Rho GDP dissociation inhibitor (Rho-GDI), dominant negative mutants of Rac1 (D.N.Rac1), or D.N.Cdc42 had no effects on Ang II-induced activation of transfected ERK2. The promoter activity of skeletal alpha-actin and c-fos genes was increased by Ang II, and the increase was partly inhibited by overexpression of Rho-GDI and the pretreatment with C3 exoenzyme. Ang II increased phenylalanine incorporation into cardiac myocytes by approximately 1.4 fold as compared with control, and this increase was also significantly suppressed by the pretreatment with C3 exoenzyme. These results suggest that the Rho family small G proteins play important roles in Ang II-induced hypertrophic responses in cardiac myocytes.

Actins↗

PubMed2000

[PL granule-induced pneumonia requiring mechanical ventilation].

PL granule is one of the most common forms of composite medicine for colds in Japan, including acetaminophen. We report a case of PL granule-induced pneumonia that required mechanical ventilation. A 72-year old man who had been prescribed amiodarone for more than one year before for arrhythmogenic right ventricular dystrophy, repeatedly took PL granules at one-week intervals because of sneezing and fever. He then underwent acute respiratory failure. He needed mechanical ventilation for severe hypoxemia, but recovered with glucocorticoid pulse therapy. Because the blastoid transformation test using his peripheral blood lymphocytes was positive on stimulation with PL granules, but negative on amiodarone stimulation, he was diagnosed as having drug (PL granule)-induced pneumonia. Only one case of PL granule-induced pneumonia and seven of acetaminophen-induced pneumonia have been reported. None of these patients needed mechanical ventilation. PL granule-induced pneumonia should be treated cautiously because of possible acute exacerbation.

Aged↗

PubMed2000

Pulmonary nocardiosis during immunosuppressive therapy for idiopathic pulmonary fibrosis.

Nocardiosis is a subacute or chronic suppurative infection caused by Nocardia species. Although it is more common in immunocompromised hosts, idiopathic pulmonary fibrosis (IPF) has not been recognized as a predisposing factor for nocardial infection. We report a case of IPF, in which pulmonary nocardiosis developed during treatment with prednisolone and cyclophosphamide. The risk of pulmonary nocardiosis may be increased in cases of IPF on immunosuppressive therapy. Since IPF often accompanies lung carcinoma, it is important to correctly differentiate nocardiosis from carcinoma.

Aged↗

PubMed2000

Na+/H+ exchange inhibitor reduces vascular injury caused by ischemia-reperfusion in the rat hind limb.

This study was designed to evaluate the effects of an Na+/H+ exchange inhibitor, SM-20550, on ischemia-reperfusion injury in the skeletal muscle. Male Sprague-Dawley rats were exposed to ischemia and reperfusion by clamping and releasing clamps both at the abdominal aorta and the bilateral femoral arteries. Rats were divided into three groups; the sham, the SM-20550 treated (SM), and the untreated control (Control) groups. In the SM and control groups, rats were exposed to 5-hr ischemia and 5-hr reperfusion. In the sham group, vessel isolation only was performed. SM-20550 (2.8 mg/kg/hr) in the SM group or vehicle in the sham and control group was continuously administered during ischemia and reperfusion periods. The wall thickness of the vessels were significantly (p<0.01) decreased in the control group than any other group. The internal diameter was significantly (p<0.01) higher in the control and SM group than in the sham group. The wall thickness/internal diameter ratio was significantly (p<0.05) lower in the control group than in the SM group. Thus, an Na+/H+ exchange inhibitor, SM-20550, ameliorated the morphological change due to ischemia reperfusion. These findings provide a clue into the mechanism of ischemia reperfusion injury.

Animals↗

PubMed1999

Calcineurin plays a critical role in pressure overload-induced cardiac hypertrophy.

BACKGROUND: Cardiac hypertrophy is a fundamental adaptive response to hemodynamic overload; how mechanical load induces cardiac hypertrophy, however, remains elusive. It was recently reported that activation of a calcium-dependent phosphatase, calcineurin, induces cardiac hypertrophy. In the present study, we examined whether calcineurin plays a critical role in pressure overload-induced cardiac hypertrophy. METHODS AND RESULTS: Pressure overload produced by constriction of the abdominal aorta increased the activity of calcineurin in the rat heart and induced cardiac hypertrophy, including reprogramming of gene expression. Treatment of rats with a calcineurin inhibitor, FK506, inhibited the activation of calcineurin and prevented the pressure overload-induced cardiac hypertrophy and fibrosis without change of hemodynamic parameters. Load-induced expression of immediate-early-response genes and fetal genes was also suppressed by the FK506 treatment. CONCLUSIONS: The present results suggest that the calcineurin signaling pathway plays a pivotal role in load-induced cardiac hypertrophy and may pave the way for a novel pharmacological approach to prevent cardiac hypertrophy.

Animals↗

PubMed1999

Increased leukotriene A(4) hydrolase expression in the heart of angiotensin II-induced hypertensive rat.

Leukotriene A(4) (LTA(4)) hydrolase is essential for the conversion of LTA(4) to LTB(4), an inflammatory lipid mediator. We investigated whether LTA(4) hydrolase was regulated in the heart by angiotensin II (ang II) infusion. Continuous ang II infusion via an osmotic minipump for up to 7 days upregulated mRNA and protein levels of LTA(4) hydrolase ( approximately 3.5-fold of control) in the heart in a pressor-dependent manner. Immunohistochemistry demonstrated intense LTA(4) hydrolase staining in the myofibroblast as well as migrated monocytes/macrophages. These data suggest that the cardiac LTA(4) hydrolase-LTB(4) system plays a positive role in the promotion of cardiac inflammation in hypertension.

Angiotensin II↗

PubMed1999

A crucial role of sterol regulatory element-binding protein-1 in the regulation of lipogenic gene expression by polyunsaturated fatty acids.

Dietary polyunsaturated fatty acids (PUFA) are negative regulators of hepatic lipogenesis that exert their effects primarily at the level of transcription. Sterol regulatory element-binding proteins (SREBPs) are transcription factors responsible for the regulation of cholesterol, fatty acid, and triglyceride synthesis. In particular, SREBP-1 is known to play a crucial role in the regulation of lipogenic gene expression in the liver. To explore the possible involvement of SREBP-1 in the suppression of hepatic lipogenesis by PUFA, we challenged wild-type mice and transgenic mice overexpressing a mature form of SREBP-1 in the liver with dietary PUFA. In the liver of wild-type mice, dietary PUFA drastically decreased the mature, cleaved form of SREBP-1 protein in the nucleus, whereas the precursor, uncleaved form in the membranes was not suppressed. The decreases in mature SREBP-1 paralleled those in mRNAs for lipogenic enzymes such as fatty acid synthase and acetyl-CoA carboxylase. In the transgenic mice, dietary PUFA did not reduce the amount of transgenic SREBP-1 protein, excluding the possibility that PUFA accelerated the degradation of mature SREBP-1. The resulting sustained expression of mature SREBP-1 almost completely canceled the suppression of lipogenic gene expression by PUFA in the SREBP-1 transgenic mice. These results demonstrate that the suppressive effect of PUFA on lipogenic enzyme genes in the liver is caused by a decrease in the mature form of SREBP-1 protein, which is presumably due to the reduced cleavage of SREBP-1 precursor protein.

Animal Feed↗

PubMed1999

Sphingosylphosphorylcholine induces a hypertrophic growth response through the mitogen-activated protein kinase signaling cascade in rat neonatal cardiac myocytes.

The sphingolipid metabolites, sphingosine (SPH), SPH 1-phosphate (S1P), and sphingosylphosphorylcholine (SPC), can act as intracellular as well as extracellular signaling molecules. These compounds have been implicated in the regulation of cell growth, differentiation, and programmed cell death in nonmyocytes, but the effects of sphingolipid metabolites in cardiac myocytes are not known. Cultured neonatal rat cardiac myocytes were stimulated with SPH (1 to 10 micromol/L), S1P (1 to 10 micromol/L), or SPC (0.1 to 10 micromol/L) for 24 hours to determine the effects of sphingolipid metabolites on the rates of protein synthesis and degradation. Stimulation with SPC led to an increase in the total amount of protein, an accelerated rate of total protein synthesis, and a decrease in protein degradation in a dose-dependent manner. However, S1P had little effect and SPH had no effect on total protein synthesis. In addition, stimulation with SPC led to a 1.4-fold increase in myocardial cell size and enhanced atrial natriuretic factor gene expression. Pretreatment of the cardiac myocytes with pertussis toxin or PD98059 attenuated the SPC-induced hypertrophic growth response. Further, stimulation with SPC increased phosphorylation of mitogen-activated protein kinase (MAPK) and stimulated MAPK enzyme activity. Finally, endothelin-1 stimulated the generation of SPC in cardiac myocytes. The observation that SPC induces a hypertrophic growth response in cardiac myocytes suggests that SPC may play a critical role in the development of cardiac hypertrophy. The effects of SPC could be mediated, in part, by activation of a G protein-coupled receptor and a MAPK signaling cascade.

Adrenergic beta-Agonists↗

PubMed1999

MAPK superfamily plays an important role in daunomycin-induced apoptosis of cardiac myocytes.

BACKGROUND: Although anthracyclines, such as daunomycin (DM) and adriamycin, are potent chemotherapeutic agents, they have serious adverse effects, including cardiac toxicity. In the present study, we investigated the molecular mechanisms of DM-induced cardiomyocyte impairment. METHODS AND RESULTS: When cultured cardiac myocytes of neonatal rats were exposed to 1 micromol/L DM for 24 hours, many cells became positive for TUNEL staining, with morphological changes characteristic of apoptosis. Fragmentation of DNA into oligonucleosome-size fragments was recognized by agarose gel electrophoresis in DM-treated myocytes. DM activated 3 members of the mitogen-activated protein kinase (MAPK) family dose-dependently, such as extracellular signal-regulated protein kinases (ERKs), c-Jun NH(2)-terminal kinases, and p38 MAPK in cardiac myocytes. Oxyradical scavengers or Ca(2+) chelators inhibited DM-induced activation of ERKs and p38 MAPK. DM-induced activation of ERKs was also inhibited by overexpression of dominant negative mutants of Ras (D.N.Ras), and the p38 MAPK activation was attenuated by D.N.Rho. The number of DM-induced apoptotic cells was markedly increased when the ERK signaling pathway was selectively blocked by a specific MAPK/ERK kinase inhibitor, PD98059, whereas pretreatment with a specific inhibitor of p38 MAPK, SB203580, significantly reduced the amount of apoptosis. CONCLUSIONS: These results suggest that DM activates MAPKs through reactive oxygen species and Ca(2+) and that the MAPK family plays important roles in DM-induced apoptosis in cardiac myocytes. ERKs protect cardiomyocytes from apoptosis, whereas p38 MAPK is involved in the induction of cardiomyocyte apoptosis.

Animals↗

PubMed1999

Transcriptional activation of the zinc finger transcription factor BTEB2 gene by Egr-1 through mitogen-activated protein kinase pathways in vascular smooth muscle cells.

We have recently demonstrated that a developmentally regulated zinc finger protein, basic transcription regulatory element binding protein 2 (BTEB2), is induced in neointimal smooth muscle in response to vascular injury. In this study, we investigated the molecular mechanisms regulating BTEB2 expression in vascular smooth muscle cells (SMCs) in vitro. BTEB2 mRNA expression is rapidly and persistently induced in SMCs by phorbol 12-myristate 13-acetate (PMA) and basic fibroblast growth factor. We have isolated and characterized the promoter region of the human BTEB2 gene to determine the regulatory network controlling expression of this gene in vascular SMCs. Functional studies on the BTEB2 promoter coupled to a luciferase reporter gene demonstrated activation of the promoter by PMA and basic fibroblast growth factor. Both characterization of DNA-protein complexes in vitro and site-specific mutation analysis of the BTEB2 promoter have defined a 9-bp sequence, 5'-CGCCCGCGC-3', located at -25, as the Egr-1 binding site mediating an induction of the BTEB2 promoter activity by PMA. In addition, we show that this site mediates inducible expression through the mitogen-activated protein kinase pathways. These results indicate that BTEB2 is a target of the early-response gene Egr-1, and mitogen-activated protein kinase pathways directly or indirectly activate BTEB2 expression. Given a rapid induction of Egr-1 on stimulation with growth factors or injury, these findings may represent at least one of the molecular mechanisms underlying phenotypic modulation of smooth muscles after vascular injury.

Animals↗