Perinatal cocaine exposure impairs myocardial beta-adrenoceptor signaling in the neonatal rat

Longitudinal Effects of Embryonic Exposure to Cocaine on Morphology, Cardiovascular Physiology, and Behavior in Zebrafish

A sizeable portion of the societal drain from cocaine abuse results from the complications of in utero drug exposure. Because of challenges in using humans and mammalian model organisms as test subjects, much debate remains about the impact of in utero cocaine exposure. Zebrafish offer a number of advantages as a model in longitudinal toxicology studies and are quite sensitive physiologically and behaviorally to cocaine. In this study, we have used zebrafish to model the effects of embryonic pre-exposure to cocaine on development and on subsequent cardiovascular physiology and cocaine-induced conditioned place preference (CPP) in longitudinal adults. Larval fish showed a progressive decrease in telencephalic size with increased doses of cocaine. These treated larvae also showed a dose dependent response in heart rate that persisted 24 h after drug cessation. Embryonic cocaine exposure had little effect on overall health of longitudinal adults, but subtle changes in cardiovascular physiology were seen including decreased sensitivity to isoproterenol and increased sensitivity to cocaine. These longitudinal adult fish also showed an embryonic dose-dependent change in CPP behavior, suggesting an increased sensitivity. These studies clearly show that pre-exposure during embryonic development affects subsequent cocaine sensitivity in longitudinal adults.

Prenatal cocaine exposure differentially causes vascular dysfunction in adult offspring

Epidemiological studies have shown a clear association of adverse intrauterine environment and an increased risk of cardiovascular diseases and hypertension in adult life. The present study tested the hypothesis that prenatal cocaine exposure causes reprogramming of vascular reactivity, leading to an increased risk of hypertension in adult offspring. Pregnant rats received cocaine (30 mg kg(-1) day(-1)) or saline from days 15 to 21 of gestational age, and experiments were conducted in 3-month-old offspring. Cocaine had no effect on the baseline blood pressure but significantly increased norepinephrine-stimulated blood pressure and decreased the baroreflex sensitivity in male but not female offspring. The cocaine treatment significantly increased norepinephrine-induced contractions in pressurized resistance-sized mesenteric arteries but not in aortas, which was primarily because of a loss of endothelial NO synthase-mediated inhibition and an enhanced Ca(2+) sensitivity in mesenteric arteries. In addition, the cocaine treatment significantly attenuated the endothelium-dependent relaxation in mesenteric arteries in male but not female offspring. Endothelial NO synthase protein levels in aortas but not mesenteric arteries were significantly increased in the cocaine-treated animals. However, cocaine significantly decreased phosphorylation levels of endothelial NO synthase in both aortas and mesenteric arteries. The results suggest that prenatal cocaine exposure programs vascular contractility via changes in endothelial NO synthase-regulated Ca(2+) sensitivity of myofilaments in the sex- and tissue-dependent manners in resistance arteries leading to an increased risk of hypertension in male offspring.

Short- and long-term adverse effects of cocaine abuse during pregnancy on the heart development

The effect of cocaine on the developing fetus is a topic of considerable interest and debate. One of the potential effects of fetal cocaine exposure is damage to the developing heart. This review provides an overview of the current understanding of the short- and long-term effects of fetal cocaine exposure on the heart in both humans and animal models. Human studies are still preliminary but have suggested that fetal cocaine exposure impacts on the developing heart. Studies in animal models provide strong evidence for a programming effect resulting in detrimental long-term changes to the heart induced by fetal cocaine exposure. In the rat model, fetal cocaine results in apoptosis in the term heart, left ventricular remodeling and myocyte hypertrophy, as well as increased sensitivity to ischemia/reperfusion injury in the adult male offspring. The rat model has also shown evidence of epigenetic modifications in response to intrauterine cocaine. Increased DNA methylation of promoter regions leads to a long-term decrease in the expression of the cardioprotective gene, PKCepsilon. The current data shows fetal cocaine exposure has significant immediate and long-term cardiac consequences in animal models and while human studies are still incomplete they suggest this phenomenon may also be significant in humans exposed to cocaine during development.

Chronic cocaine-induced cardiac oxidative stress and mitogen-activated protein kinase activation: the role of Nox2 oxidase

Chronic cocaine exposure is associated with severe cardiac complications, but the mechanisms of cocaine cardiotoxicity remain unclear, and current therapies are unsatisfactory. We investigated the hypothesis of oxidative stress-mediated cardiotoxicity and the role of NADPH oxidase in this process in a mouse model of chronic escalating "binge" cocaine administration (milligrams per kilogram): days 1 to 4 at 3 x 15 mg, days 5 to 8 at 3 x 20 mg, days 9 to 12 at 3 x 25 mg, and days 13 to 14 at 3 x 30 mg. Compared with vehicle controls, chronic binge cocaine administration significantly increased the cardiac NADPH-dependent O(2)(.) production (1.96- +/- 0.4-fold) as detected by tiron (an O(2)(.) scavenger)-inhibitable lucigenin chemiluminescence and dihydroethidium fluorescence. Cocaine-induced reactive oxygen species (ROS) production was associated with significant increases ( approximately 2-fold) in the protein expressions of Nox2 (an isoform of NADPH oxidase) and its regulatory subunits: p22(phox), p67(phox), p47(phox), p40(phox), and Rac1, and in p47(phox) phosphorylation as detected by immunoblotting (all p < 0.03). Increased Nox2 activity was accompanied by the activation of extracellular signal-regulated kinase 1/2, p38 mitogen-activated protein kinase (MAPK), and c-Jun NH(2)-terminal kinase, notably in the cardiomyocytes. Cell culture experiments revealed that cocaine-induced ROS production was primarily a direct action of cocaine on cardiac myocytes, which caused severe oxidative damage to myocytes and cell death as detected by terminal deoxynucleotidyl transferase dUTP nick-end labeling assay. These could be inhibited by inhibitors to protein kinase C (bisindolymaleimide) or by depletion of Nox2 using small interfering RNA. In conclusion, chronic cocaine administration directly causes severe myocardial oxidative stress through the activation of Nox2 oxidase. Increased ROS production contributes to MAPK activation and the subsequent myocyte damage. Inhibitors to NADPH oxidase or antioxidants may have therapeutic potential in the treatment of cocaine cardiotoxicity.

The housekeeping gene (GA3PDH) and the long interspersed nuclear element (LINE) in the blood and organs of rats treated with cocaine

Housekeeping genes are necessary for maintenance of the vital activity of the cells of any phylum of organisms. Transposons or mobile genetic elements are eurysynusic in nature. Thus, the role of these and other genes in the pathogenesis of many diseases and of drug addiction in particular is being investigated. The goal of the work is to determine the influence of cocaine on the activity of GA3PDH and on a representative of the LINE family (L1Rn) in plasma, and in a pellet of blood cells, and in the organs of rats. Gene expression was evaluated by RT-PCR. The GA3PDH (452-bp fragment) was predictably found in plasma, in a pellet of blood cells, and in organs. Its quantity in plasma was greater in the experimental groups than in the control. In a pellet of blood cells and in organs, the GA3PDH activity between the different groups of animals essentially did not differ. The L1Rn fragment (319 bp) in plasma was not found. The expression of L1Rn was much higher in a pellet of blood cells and in organs of experimental animals. These experiments have shown the presence of GA3PDH in the plasma of the controls and an increase in quantity in the plasma of experimental animals. The activation of LINE in a pellet of blood cells of rats and in organs under the influence of cocaine has been demonstrated. Apparently, a recruitment phenomenon of housekeeping genes and transposons is possible in the pathogenesis of drug addiction.

Prenatal exposure to cocaine decreases adenylyl cyclase activity in embryonic mouse striatum

Adenylyl cyclase activity was measured in the striatum of naive mice as a function of age and in mice exposed in utero to cocaine. In naive Swiss-Webster mice, basal and forskolin-stimulated adenylyl cyclase activity increased gradually from embryonic day 13 (E13) until 2-3 weeks of age when activity peaked before decreasing slightly to adult levels. The ability of the dopamine D1 receptor agonist, SKF 82958, to stimulate adenylyl cyclase activity also increased in magnitude until P15. In a separate study, pregnant Swiss-Webster mice were injected twice daily with cocaine (15 mg/kg, s.c.) or an equal volume of saline from E10 to E17. Adenylyl cyclase activity was measured in the striatum of E18 embryos. Basal adenylyl cyclase activity was significantly reduced following prenatal exposure to cocaine. Likewise, the ability of forskolin or SKF 82958 to stimulate adenylyl cyclase was attenuated following cocaine exposure. DeltaFosB was not induced, contrary to what is seen in adult mice. These results demonstrate a functional change in a critical signal transduction pathway following chronic in utero exposure to cocaine that might have profound effects of the development of the brain. Alterations in the cAMP system may underlie some of the deficits seen in humans exposed in utero to cocaine.

The effect of maternal cocaine exposure on neonatal rat cardiac function

Fetal cocaine exposure has been associated with a variety of cardiovascular dysfunctions in humans. We treated pregnant rats with either saline or cocaine at 60 mg/kg by gastric lavage for the entire gestational period and for 14 days after parturition. We then performed high-frequency transthoracic echocardiography to determine whether cocaine exposure affected neonatal cardiac contractile function in vivo in 7- and 14-day-old neonatal rats. All studies were performed in the unsedated, conscious state. Heart rate (HR) and systolic function, expressed as fractional area of change at the midpapillary muscle level, were calculated from two-dimensional images. Resting HR was faster in the cocaine-exposed group at both ages, but baseline contractile function was not different between control (CTL) and cocaine-exposed (COC) neonatal rats. Dobutamine induced a significant increase in HR in all groups at only the largest dose tested (Day 7 CTL HR increased from 438 +/- 3 bpm to 462 +/- 10 bpm; Day 7 COC HR increased from 466 +/- 3 bpm to 493 +/- 7 bpm; Day 14 CTL HR increased from 443 +/- 4 bpm to 487 +/- 4 bpm; Day 14 COC HR increased from 477 +/- 4 bpm to 501 +/- 5 bpm). Dobutamine elicited a significant increase in contractile response at both Day 7 (from 76.6% +/- 0.6% to 81.5% +/- 0.7%) and Day 14 in CTL (from 78.2% +/- 0.7% to 81.9% +/- 0.7%), but not in COC, animals (from 76.7% +/- 0.8% to 78.9% +/- 0.8% at Day 7 and from 76.8% +/- 1.1% to 79.3% +/- 0.8% at Day 14). Epinephrine induced a significant increase in contractile response in CTL, but not in COC, rats at Day 7 and had no effect on fractional area of change at 14 days of age in either CTL or COC animals. Our results indicate that perinatal cocaine exposure does not modify resting contractile function but attenuates the contractile response to beta-adrenoceptor stimulation in the neonatal rat. These results suggest that perinatal cocaine exposure may lead to decreased responsiveness to inotropic drugs during the early neonatal period.

Perinatal cocaine exposure stimulates the expression and activation of CREB in the neonatal rat heart

cAMP response binding protein (CREB) is a transcriptional factor known to regulate gene expression. Phosphorylation of CREB at serine 133 is necessary for CREB activation, and quantification of phospho-CREB (p-CREB) expression is an index of CREB activation. Because CREB expression and activation in specific brain regions are modified after chronic cocaine administration, we sought to determine whether chronic perinatal cocaine exposure affects the expression of CREB and p-CREB in the postnatal rat heart. Pregnant rats were treated daily with saline (control) or cocaine at 20 mg/kg (C20) or 60 mg/kg (C60) by intragastric administration throughout gestation. The expression of total CREB and p-CREB was quantified in nuclear extracts isolated from 1- and 7-d-old neonatal rat hearts. Cardiac nuclear p-CREB was increased in the C20 and C60 groups on d 1 and 7 of age compared with their respective age-matched control groups. The increase in p-CREB expression corresponded to an increase in cAMP response element binding activity. We also assayed nuclear protein kinase A activity, which was up-regulated in d 1 animals with prenatal cocaine exposure, but was comparable in all groups at d 7. Our results suggest that perinatal cocaine exposure stimulates CREB activation in the neonatal heart, and it may be mediated by different mechanisms at d 1 and d 7. The changes in myocardial CREB activation induced by perinatal cocaine exposure are likely to result in modified gene expression in the neonatal heart that may account for the cardiac dysfunction reported in human neonates born to cocaine-abusing mothers.

Postcardiac surgery complications: association of acute renal dysfunction and atrial fibrillation

Postoperative creatinine increase is associated with adverse outcome after cardiac surgery. Although postoperative stroke and renal dysfunction are associated after cardiac surgery, suggesting a common systemic insult, a similar assessment of atrial fibrillation and renal dysfunction has not been performed. Therefore, we tested the hypothesis that patients with new-onset atrial fibrillation complicating coronary bypass surgery have a greater postoperative creatinine increase. Data were obtained for 453 elective coronary bypass surgery patients with no history of atrial fibrillation. Multivariate regression analyses of factors associated with peak fractional change in creatinine demonstrated a two-way interaction between age and atrial fibrillation (variable estimate, -1.1; P = 0.002). Similar results were obtained in a secondary multivariate model analyzing factors associated with peak postoperative creatinine (variable estimate, -0.01; P = 0.04). We confirmed our hypothesis that patients with new-onset atrial fibrillation are more likely to have acute renal dysfunction after cardiac surgery. The association of atrial fibrillation and creatinine increase diminishes with advancing age. These data are consistent with a common pathophysiology that contributes in an age-dependent fashion to the etiology of both acute renal dysfunction and atrial fibrillation after coronary bypass surgery.

IMPLICATIONS

We found an independent association between new-onset atrial fibrillation and postoperative creatinine increase that is influenced by age. The degree to which atrial fibrillation is associated with postoperative creatinine increase diminishes with advancing age. This interaction suggests that a common etiology for these two complications may be more important in younger patients.

Consequences of maternal cocaine on cerebral microvascular functions in piglets

Maternal cocaine abuse is associated with fetal and neonatal neurological abnormalities. Prolonged exposure to cocaine can induce blood flow disorders, growth restriction, and hypoxia in the newborn. We investigated the impact of chronic fetal cocaine exposure on cerebral microvascular reactivity and autonomic function in the piglets. Pregnant pigs received cocaine (1 mg/kg i.v.; twice weekly) or saline throughout the last trimester. Prenatal exposure to cocaine did not have any significant effect on the birth weight of the piglets as compared to the control. Following delivery, effects of recurrent prenatal cocaine exposure on cerebral microvascular functions were examined in piglets (3-6 days old). Pial arteriolar responses to applications of 5-hydroxytryptamine (5-HT), endothelin-1 (ET-1), and clonidine were examined using closed cranial windows. Functional effects of prenatal cocaine exposure on changes in mean arterial pressure (MAP) and pial arteriolar diameter induced by intracisternal injection (i.c.) of clonidine (1 microg/kg) were also determined. Topical applications of 5-HT, ET-1, and clonidine dose-dependently decreased pial arteriolar diameter in the control and these constrictions were significantly enhanced in the in utero cocaine-exposed piglets. Prenatal cocaine exposure did not have any significant effects on the resting MAP and heart rate as there were no differences between the groups. IC clonidine caused sustained decrease in MAP in both groups but the decrease was more pronounced in the cocaine than the control group. IC clonidine causes cerebral microvascular dilation coincident with the development of hypotension. Such dilation was severely attenuated in the cocaine group, even though the hypotension was much more pronounced than in the control. In conclusion, prenatal cocaine exposure resulted in attenuated autoregulatory vasodilation and potentiated responses to vasoconstrictor agents. The mechanisms behind the effects of in utero cocaine exposure on alteration of newborn cerebral functions need further investigation. Such actions may be important in development of cerebral pathologies associated with recurrent prenatal cocaine exposure.

Cocaine: effects of in utero exposure on the fetus and neonate

In North America, an increasing number of babies are prenatally exposed to cocaine, yet the implications of cocaine use during pregnancy are not fully understood. The effects of cocaine are exerted primarily by its influence on aminergic receptors in the central and peripheral nervous systems. Developmental, physiological, and behavioral problems in infants and children are likely outcomes of maternal cocaine abuse, but these findings are confounded by concomitant use of other drugs such as marijuana and cocaine and by factors such as time, dosage, and route of cocaine intake. Different screening options exist for cocaine and its metabolites, including sampling of neonatal urine, hair and meconium need to be considered, as do the sensitivity and the ethical implications of such testing. Clinical management of cocaine-exposed infants requires attention to several issues, including: central nervous system irritation, cardiac anomalies, apnea, and feeding difficulties, as well as infant safety and follow-up postdischarge. Early detection and intervention remain the primary objectives of caring for cocaine-exposed infants.