. Effect of maternal chronic hypoxic exposure during gestation on apoptosis in fetal rat heart. Am J Physiol Heart Circ Physiol 285: H983-H990, 2003. First published May 15, 2003 10.1152/ajpheart.00005.2003Chronic hypoxia during pregnancy is one of the most common insults to fetal development. We tested the hypothesis that maternal hypoxia induced apoptosis in the hearts of nearterm fetal rats. Pregnant rats were divided into two groups, normoxic control and continuous hypoxic exposure (10.5% O 2) from day 15 to 21 of gestation. Hearts were isolated from fetal rats of 21-day gestational age. Maternal hypoxia increased hypoxia-inducible factor-1␣ protein in fetal hearts. Chronic hypoxia significantly increased the percentage and size of binucleated myocytes and increased apoptotic cells from 1.4 Ϯ 0.14% to 2.7 Ϯ 0.3% in the fetal heart. In addition, the active cleaved form of caspase 3 was significantly increased in the hypoxic heart, which was associated with an increase in caspase 3 activity. There was a significant increase in Fas protein levels in the hypoxic heart. Chronic hypoxia did not change Bax protein levels but significantly decreased Bcl-2 proteins. In addition, chronic hypoxia significantly suppressed expression of heat shock protein 70. However, chronic hypoxia significantly increased expression of the anti-apoptotic protein 14-3-3 , among other 14-3-3 isoforms. Chronic hypoxia differentially regulated ␤-adrenoreceptor (␤-AR) subtypes with an increase in ␤1-AR levels but no changes in ␤2-AR. The results demonstrate that maternal hypoxia increases apoptosis in fetal rat heart, which may be mediated by an increase in Fas and a decrease in Bcl-2 proteins. Chronic hypoxia-mediated increase in ␤1-AR and decrease in heat shock proteins may also play an important role in apoptosis in the fetal heart. fetus PROGRAMMED CELL DEATH (apoptosis) plays an important role in heart development as well as in several cardiovascular diseases (9, 10, 13). Inappropriate prenatal loss of cardiomyocytes through apoptosis has been suggested to play a role in a variety of cardiac dysfunctions in infants and adults. Chronic hypoxia during the course of pregnancy is one of the most common insults to the fetal development and is thought to be associated with fetal intrauterine growth retardation (26). It has been demonstrated that prenatal hypoxia produces cardiac congenital defects in the rat (5). In fetal sheep, chronic hypoxia suppressed cardiac function and contractility (3), increased lactate dehydrogenase and citrate synthase in fetal myocardium (31), and resulted in cardiac hypertrophy (25, 27). Studies in cultured neonatal rat cardiomyocytes demonstrated that hypoxia caused apoptosis in these cells (24,41). However, it is unknown whether in vivo maternal chronic hypoxic exposure during pregnancy induces apoptotic cell death in the fetal heart. Apoptosis is a highly selective process controlled and regulated by intracellular signal transduction that involves the activation of cysteine proteases known as caspases, resul...

Prenatal chronic hypoxia increases the susceptibility of adult heart to I-R injury. Several possible mechanisms may be involved, including an increase in beta(2)-adrenoreceptor and the G(s)alpha/G(i)alpha ratio, and a decrease in heat shock protein 70 and endothelial nitric oxide synthase in the left ventricle.

We have previously demonstrated that cocaine induces apoptosis in primary cultures of fetal rat cardiomyocytes. The current study was designed to determine whether cocaine administered to the mother during pregnancy induced apoptosis in fetal rat heart. Pregnant rats were treated with cocaine subcutaneously (30 and 60 mg/kg per day) starting at day 15 of gestation and were terminated at day 21. Cocaine produced a dose-dependent increase in apoptotic cell death in the fetal heart by 1.3-fold (30 mg/kg per day) and 2.4-fold (60 mg/kg per day) of the control level (1.99+/-0.15%). Cocaine-induced DNA fragmentation in the fetal heart showed characteristic apoptotic ladder. In accordance, cocaine dose-dependently increased activities of caspase-3, caspase-8, and caspase-9 in the fetal heart by 0.5-, 0.6-, and 0.6-fold, respectively, at 30 mg/kg per day, and by 3.3-, 2.9-, and 2.3-fold, respectively, at 60 mg/kg per day. In contrast, cocaine showed no effect on caspase activities in the maternal heart. Bcl-2 and Bax proteins were detected in fetal rat heart, with 2.2-fold higher expression of Bcl-2 than Bax. Cocaine significantly increased Bax protein levels and decreased Bcl-2 protein levels, leading to a 7.5-fold increase in the Bax-to-Bcl-2 ratio in fetal rat heart. We conclude that cocaine causes apoptosis in fetal rat heart in vivo by upregulating the Bax-to-Bcl-2 ratio and increasing caspase activities, which is likely to play an important role in the adverse effects of cocaine on heart development.

Cocaine induces apoptosis in fetal rat myocardial cells (FRMCs). However, the mechanisms are not clear. The present study examined the role of p38 mitogen-activated protein kinase (MAPK) and cytochrome c release in the cocaine-induced apoptosis in primary culture of FRMCs prepared from the fetal heart of gestational age of 21 days. Cocaine induced timedependent, concurrent increases in cytochrome c release and activities of caspase-9 and caspase-3, which preceded apoptosis. Caspase-8 was not activated. In accordance, cyclosporin A and the inhibitors of caspase-9 and caspase-3 inhibited cocaineinduced caspase activation and apoptosis. Cocaine stimulated a transient increase in the p38 MAPK activity at a time point of 15 min but reduced the extracellular signal-regulated kinase (ERK) activity at 5 and 15 min in FRMCs. The p38␣ MAPK inhibitor SB203580 [4-(4-fluorophenyl)-2-(4-methylsulfinylphenyl)-5-(4-pyridyl)1H-imidazole] inhibited cocaine-induced activation of caspases and apoptosis. In contrast, the p38␤ MAPK and mitogen-activated protein kinase kinase/ERK inhibitors SB 202190 [4-(4-fluorophenyl)-2-(4-hydroxyphenyl)-5-(4-pyridyl)-1H-imidazole] and PD98059 (2Ј-amino-3Ј-methoxyflavone), respectively, increased apoptosis in the absence of cocaine and potentiated cocaine-induced apoptosis. Consistent with its inhibition of apoptosis, SB203580 inhibited cocaine-induced cytochrome c release and activation of caspase-9 and caspase-3. In addition, cocaine induced a decrease in Bcl-2 protein levels, with no effect on Bax levels. The cocaine-mediated reduction of Bcl-2 levels was not affected with SB203580 and the caspase inhibitors. The results suggest that in FRMCs, p38␣ MAPK plays an important role in the cocaine-induced apoptosis by promoting cytochrome c release, downstream or independent of Bcl-2 protein-mediated regulation. In contrast, p38␤ MAPK and ERK protect fetal myocardial cells against apoptosis.Cocaine abuse among women of childbearing age is prevalent in the United States. A number of developmental disorders in human infants have been attributed to cocaine exposure in utero. These include decreased birth weight and head circumference, sudden infant death syndrome, systemic hypertension, and tachycardia (Handler et al., 1991;Silvestri et al., 1991). Cocaine can cross the placenta and accumulate in the fetus (Schenker et al., 1993). Our recent studies have demonstrated that maternal cocaine administration during pregnancy induces apoptosis in the fetal heart . Cocaine also directly induces an increase in apoptotic cell death in fetal rat myocardial cells (FRMCs) . However, the cellular and molecular mechanisms responsible for cocaine-induced cardiac myocyte apoptosis are presently not clear.Apoptotic cell death is characterized by the activation of a unique class of aspartate-specific proteases, i.e., caspases. Sequential activation of caspases results in cleavage of substrate proteins and breakdown of DNA molecules. It has been well documented that the caspase cascade involved in apoptosis includes...

The circadian clock enables organisms to rapidly adapt to the ever-changing environmental conditions that are caused by daily light/dark cycles. Circadian clock genes universally affect key agricultural traits, particularly flowering time. Here, we show that OsPRR37, a circadian clock gene, delays rice flowering time in an expression level-dependent manner. Using high-throughput mRNA sequencing on an OsPRR37 overexpressing transgenic line (OsPRR37-OE5) and the recipient parent Guangluai4 that contains the loss-of-function Osprr37, we identify 14,992 genes that display diurnal rhythms, which account for 52.9% of the transcriptome. Overexpressing OsPRR37 weakens the transcriptomic rhythms and alters the phases of rhythmic genes. In total, 3,210 differentially expressed genes (DEGs) are identified, among which 1,863 rhythmic DEGs show a correlation between the change of absolute amplitudes and the mean expression levels. We further reveal that OsPRR37 functions as a transcriptional repressor to repress the expression levels and amplitudes of day-phased clock genes. More importantly, OsPRR37 confers expanded regulation on the evening-phased rhythmic DEGs by repressing the morning-phased rhythmic DEGs. Further study shows that OsPRR37 expands its regulation on flowering pathways by repressing Ehd1. Thus, our results demonstrate an expanded regulation mechanism of the circadian clock on the diurnal rhythms of the transcriptome.