Dendritic morphology of developing hippocampal neurons in Cyp11a1 null mice.

INTRODUCTION: Neurosteroids have a variety of neurological functions, such as neurite growth, neuroprotection, myelination, and neurogenesis. P450scc, encoded by CYP11A1 gene, is the cholesterol side chain cleavage enzyme that catalyzes the first and rate limiting step in the steroidogenesis. In this study, we examine the dendritic morphology in developing hippocampal neurons of Cyp11a1 null mice at P15, a critical period for synapse formation and maturation. METHODS: Knockout mice were maintained until P15 with hormone administration. The Golgi-Cox method stained CA1 and CA3 pyramidal neurons in the hippocampus to reveal dendritic morphology. RESULTS: We demonstrated that Cyp11a1 null mice usually die within 7 days after birth and thus collected brain samples at postnatal day 5 (P5) for examination. There were significant shrinkage of dendrite size and diminishment of dendritic branching in CA1 and CA3 pyramidal neurons in the hippocampus of Cyp11a1 null mice, suggesting a developmental delay. We wonder if this delay may catch up later in life. Since the age of P15 is a critical period for synapse formation and maturation, the Cyp11a1 null mice were rescued by receiving hormone administration until P15 that the dendritic morphology in the developing hippocampal neurons could be examined. The results indicated that the total dendritic length, number of dendritic branches, as well as dendritic arborization in the CA1 and CA3 pyramidal neurons are significantly decreased in P15 knockout mice when compared to the wild type. The spine densities were also significantly decreased. In addition, the western blot analysis revealed decrease PSD-95 expression levels in the knockout mice compared to the wild type at P15. CONCLUSION: These results suggested that Cyp11a1 deficiency impairs the dendritic structures in the developing hippocampal pyramidal neurons.

Propranolol Alleviates Cardiac Injury After Acute Catecholamine Infusion Through p38-MAPK Pathways.

ABSTRACT: Hypercatecholaminergic conditions are known to cause heart failure and cardiac fibrosis when severe. Although previous investigations have studied the effects of beta-blockade in experimental models of catecholaminergic states, the detailed benefits of beta-blockade in more realistic models of hyper-adrenergic states were less clear. In this study, we examined acute cardiac changes in rats with hyperacute catecholamine-induced heart failure with and without propranolol treatment. Male Sprague-Dawley rats (n = 12) underwent a 6-hour infusion of epinephrine and norepinephrine alone, with an additional propranolol bolus (1 mg/kg) at hour 1 (n = 6). Cardiac tissues were examined after 6 hours. Cardiac immunohistochemistry revealed significantly decreased expression of phosphorylated p-38 (left ventricle, P = 0.021; right ventricle, P = 0.021), with upregulation of reactive oxidative species and other profibrosis proteins, after catecholamine infusion alone. After 1 propranolol 1 mg/kg bolus, the levels of phosphorylated-p38 returned to levels comparable with sham (left ventricle, P = 0.021; right ventricle, P = 0.043), with additional findings including downregulation of the apoptotic pathway and profibrotic proteins. We conclude that catecholamine-induced heart failure exerts damage through the p-38 mitogen-activated protein kinase pathway and demonstrates profibrotic changes mediated by matrix metalloproteinase 9, alpha-smooth muscle actin, and fibroblast growth factor 23. Changes in these pathways attenuated acute catecholamine-induced heart failure after propranolol bolus 1 mg/kg. We conclude that propranolol bolus at 1 mg/kg is able to mediate the effects of catecholamine excess through the p-38 mitogen-activated protein kinase pathway, profibrosis, and extrinsic apoptosis pathway.

Hypoxia-Induced Kidney Injury in Newborn Rats.

Exposure to hypoxia during the early postnatal period can have adverse effects on vital organs. Neonatal Sprague-Dawley rats housed in a hypoxic chamber were compared to those in a normoxic chamber from postnatal days 0 to 7. Arterial blood was collected to evaluate renal function and hypoxia. Kidney morphology and fibrosis were evaluated using staining methods and immunoblotting. In the kidneys of the hypoxic group, protein expressions of hypoxia-inducible factor-1 were higher than those in the normoxic group. Hypoxic rats had higher levels of hematocrit, serum creatinine, and lactate than normoxic rats. Body weight was reduced, and protein loss of kidney tissue was observed in hypoxic rats compared to normoxic rats. Histologically, hypoxic rats showed glomerular atrophy and tubular injury. Renal fibrosis with collagen fiber deposition was observed in the hypoxic group. The expression of nicotinamide adenine dinucleotide phosphate oxidases was enhanced in the kidneys of hypoxic rats. Proteins involved in apoptosis were upregulated in the kidneys of hypoxic rats. An increase in the expression of pro-inflammatory cytokines was also observed in the kidneys of hypoxic rats. Hypoxic kidney injury in neonatal rats was associated with oxidative stress, inflammation, apoptosis, and fibrosis.

Low-Dose Propranolol Prevents Functional Decline in Catecholamine-Induced Acute Heart Failure in Rats.

Severe hyper-catecholaminergic states likely cause heart failure and cardiac fibrosis. While previous studies demonstrated the effects of beta-blockade in experimental models of single-catecholamine excess states, the detailed benefits of beta-blockade in more realistic models of hyper-adrenergic states are less clearly understood. In this study, we examined different therapeutic dosages and the effects of propranolol in rats with hyper-acute catecholamine-induced heart failure, and subsequent cardiopulmonary changes. Rats (n = 41) underwent a 6 h infusion of epinephrine and norepinephrine alone, with additional low-dose (1 mg/kg) or high-dose propranolol (10 mg/kg) at hour 1. Cardiac and pulmonary tissues were examined after 6 h. Catecholamine-only groups had the lowest survival rate. Higher doses of propranolol (15 mg/kg) caused similarly low survival rates and were not further analyzed. All low-dose propranolol rats survived, with a modest survival improvement in the high-dose propranolol groups. Left ventricular (LV) systolic pressure and LV end-diastolic pressure improved maximally with low-dose propranolol. Cardiac immunohistochemistry revealed an LV upregulation of FGF-23 in the catecholamine groups, and this improved in low-dose propranolol groups. These results suggest catecholamine-induced heart failure initiates early pre-fibrotic pathways through FGF-23 upregulation. Low-dose propranolol exerted cardio-preventative effects through FGF-23 downregulation and hemodynamic-parameter improvement in our model of hyper-acute catecholamine-induced heart failure.

Norepinephrine Leads to More Cardiopulmonary Toxicities than Epinephrine by Catecholamine Overdose in Rats.

While catecholamines like epinephrine (E) and norepinephrine (NE) are commonly used in emergency medicine, limited studies have discussed the harm of exogenously induced catecholamine overdose. We investigated the possible toxic effects of excessive catecholamine administration on cardiopulmonary function and structure via continuous 6 h intravenous injection of E and/or NE in rats. Heart rate, echocardiography, and ventricular pressure were measured throughout administration. Cardiopulmonary structure was also assessed by examining heart and lung tissue. Consecutive catecholamine injections induced severe tachycardia. Echocardiography results showed NE caused worse dysfunction than E. Simultaneously, both E and NE led to higher expression of Troponin T and connexin43 in the whole ventricles, which increased further with E+NE administration. The NE and E+NE groups showed severe pulmonary edema while all catecholamine-administering groups demonstrated reduced expression of receptor for advanced glycation end products and increased connexin43 levels in lung tissue. The right ventricle was more vulnerable to catecholamine overdose than the left. Rats injected with NE had a lower survival rate than those injected with E within 6 h. Catecholamine overdose induces acute lung injuries and ventricular cardiomyopathy, and E+NE is associated with a more severe outcome. The similarities of the results between the NE and E+NE groups may indicate a predominant role of NE in determining the overall cardiopulmonary damage. The results provide important clinical insights into the pathogenesis of catecholamine storm.