Cocaine Constrictor Mechanisms of the Cerebral Vasculature

Evidence of cortical vascular impairments in early stage of Alzheimer's transgenic mice: Optical imaging

Alzheimer's disease (AD), a neurodegenerative disorder with progressive cognitive decline, remains clinically challenging with limited understanding of etiology and interventions. Clinical studies have reported vascular defects prior to other pathological manifestations of AD, leading to the "Vascular Hypothesis" for the disorder. However, in vivo assessments of cerebral vasculature in AD rodent models have been constrained by limited spatiotemporal resolution or field of view of conventional imaging. We herein employed two in vivo imaging technologies, Dual-Wavelength Imaging and Optical Coherence Doppler Tomography, to evaluate cerebrovascular reactivity (CVR) to vasoconstrictive cocaine and vasodilatory hypercapnia challenges and to detect resting 3D cerebral blood flow (CBF) in living transgenic AD mice at capillary resolution. Results showed that CVR to cocaine and hypercapnia was significantly attenuated in 7-10 months old AD mice vs controls, indicating reduced vascular flexibility and reactivity. Additionally, in the AD mice, arterial CBF velocities were slower and the microvascular density in cortex was decreased compared to controls. These results reveal significant vascular impairments including reduced CVR and resting CBF in early-staged AD mice. Hence, this cutting-edge in vivo optical imaging offers an innovative venue for detecting early neurovascular dysfunction in AD brain with translational potential.

MicroRNA-423-5p Mediates Cocaine-Induced Smooth Muscle Cell Contraction by Targeting Cacna2d2

Cocaine abuse increases the risk of atherosclerotic cardiovascular disease (CVD) and causes acute coronary syndromes (ACS) and hypertension (HTN). Significant research has explored the role of the sympathetic nervous system mediating the cocaine effects on the cardiovascular (CV) system. However, the response of the sympathetic nervous system alone is insufficient to completely account for the CV consequences seen in cocaine users. In this study, we examined the role of microRNAs (miRNAs) in mediating the effect of cocaine on the CV system. MiRNAs regulate many important biological processes and have been associated with both response to cocaine and CV disease development. Multiple miRNAs have altered expression in the CV system (CVS) upon cocaine exposure. To understand the molecular mechanisms underlying the cocaine response in the CV system, we studied the role of miRNA-423-5p and its target Cacna2d2 in the regulation of intracellular calcium concentration and SMC contractility, a critical factor in the modulation of blood pressure (BP). We used in vivo models to evaluate BP and aortic stiffness. In vitro, cocaine treatment decreased miR-423-5p expression and increased Cacna2d2 expression, which led to elevated intracellular calcium concentrations and increased SMC contractility. Overexpression of miR-423-5p, silencing of its target Cacna2d2, and treatment with a calcium channel blocker reversed the elevated SMC contractility caused by cocaine. In contrast, suppression of miR-423-5p increased the intracellular calcium concentration and SMC contractibility. In vivo, smooth muscle-specific overexpression of miR-423-5p ameliorated the increase in BP and aortic stiffness associated with cocaine use. Thus, miR-423-5p regulates SMC contraction by modulating Cacna2d2 expression increasing intracellular calcium concentrations. Modulation of the miR-423-5p-Cacna2d2-Calcium transport pathway may represent a novel therapeutic strategy to improve cocaine-induced HTN and aortic stiffness.

Cocaine's cerebrovascular vasoconstriction is associated with astrocytic Ca2+ increase in mice

Human and animal studies have reported widespread reductions in cerebral blood flow associated with chronic cocaine exposures. However, the molecular and cellular mechanisms underlying cerebral blood flow reductions are not well understood. Here, by combining a multimodal imaging platform with a genetically encoded calcium indicator, we simultaneously measured the effects of acute cocaine on neuronal and astrocytic activity, tissue oxygenation, hemodynamics and vascular diameter changes in the mouse cerebral cortex. Our results showed that cocaine constricted blood vessels (measured by vessel diameter Φ changes), decreasing cerebral total blood volume (HbT) and temporally reducing tissue oxygenation. Cellular imaging showed that the mean astrocytic Ca2+ dependent fluorescence [Formula: see text] increase in response to cocaine was weaker but longer lasting than the mean neuronal Ca2+ dependent fluorescence [Formula: see text] changes. Interestingly, while cocaine-induced [Formula: see text] increase was temporally correlated with tissue oxygenation change, the [Formula: see text] elevation after cocaine was in temporal correspondence with the long-lasting decrease in arterial blood volumes. To determine whether the temporal association between astrocytic activation and cocaine induced vasoconstriction reflected a causal association we inhibited astrocytic Ca2+ using GFAP-DREADD(Gi). Inhibition of astrocytes attenuated the vasoconstriction resulting from cocaine, providing evidence that astrocytes play a critical role in cocaine's vasoconstrictive effects in the brain. These results indicate that neurons and astrocytes play different roles in mediating neurovascular coupling in response to cocaine. Our findings implicate neuronal activation as the main driver of the short-lasting reduction in tissue oxygenation and astrocyte long-lasting activation as the driver of the persistent vasoconstriction with cocaine. Understanding the cellular and vascular interaction induced by cocaine will be helpful for future putative treatments to reduce cerebrovascular pathology from cocaine use.

Cocaine nephropathy: A rare cause of abnormal nephrograms

Cocaine use is associated with a variety of renal injuries. Although rhabdomyolysis is the most common cause of cocaine-induced nephropathy, cocaine can also cause renal vasculitis, acute interstitial nephritis, acute tubular necrosis, thrombotic microangiopathy, and renal infarction. We present a rare case of cocaine-induced nephropathy in a 30-year-old male who presented with acute kidney injury and abnormal nephrograms at contrast-enhanced computed tomography. Mechanisms of cocaine-induced renal injury and differential causes of abnormal nephrograms encountered at imaging are discussed. Cocaine-induced nephropathy is a rare but important cause of abnormal nephrograms and should be considered in the differential diagnosis when clinically appropriate.

Cocaine addicted rats show reduced neural activity as revealed by manganese-enhanced MRI

Cocaine addiction develops as a continuum from recreational to habitual and ultimately compulsive drug use. Cocaine addicts show reduced brain activity. However, it is not clear if this condition results from individual predisposing traits or is the result of chronic cocaine intake. A translational neuroimaging approach with an animal model distinguishing non-addict-like vs. addict-like animals may help overcome the limitations of clinical research by comparing controlled experimental conditions that are impossible to obtain in humans. Here we aimed to evaluate neuronal activity in freely moving rats by manganese enhanced magnetic resonance imaging in the 0/3crit model of cocaine addiction. We show that addict-like rats exhibit reduced neuronal activity compared to cocaine-naïve controls during the first week of abstinence. In contrast, cocaine-experienced non-addict-like rats maintained their brain activity at a level comparable to cocaine-naïve controls. We also evaluated brain activity during cocaine bingeing, finding a general reduction of brain activity in cocaine experienced rats independent of an addiction-like phenotype. These findings indicate that brain hypoactivity in cocaine addiction is associated with the development of compulsive use rather than the amount of cocaine consumed, and may be used as a potential biomarker for addiction that clearly distinguishes non-addict-like vs addict-like cocaine use.

Pituitary Dysfunction in Pediatric Patients with Optic Nerve Hypoplasia: A Retrospective Cohort Study (1975-2014)

BACKGROUND/AIMS

The risk factors for pituitary hormone dysfunction (PHD) in children with optic nerve hypoplasia (ONH) are not well understood. This study identified the type, timing, and predictors of PHD in children with ONH.

METHODS

ONH patient charts were reviewed retrospectively. The incidence rate of PHD was calculated assuming a Poisson distribution. Predictors of PHD were identified through a multivariable Cox proportional hazards model.

RESULTS

Among 144 subjects with ONH, 49.3% (n = 71) developed PHD over 614.7 person-years of follow-up. The incidence was 11.55 (95% confidence interval [CI]: 9.02-14.57/100 person-years). The median time to first PHD was 2.88 (interquartile range: 0.02-18.72) months. Eighty-two percent developed their first PHD by their 5th and 90% by their 10th birthday, and 89% within 5 years of ONH diagnosis. Prematurity (adjusted hazard ratio [aHR]: 0.33; 95% CI: 0.1-1.07), blindness (aHR: 1.72; 95% CI: 1.03-2.86), maternal substance abuse (aHR: 1.51; 95% CI: 0.91-2.48), abnormal posterior pituitary (aHR: 3.8; 95% CI: 2.01-7.18), and hypoplastic/absent anterior pituitary (aHR: 2.52; 95% CI: 1.29-4.91) were significant predictors of PHD.

CONCLUSIONS

The clinical predictors of PHD included blindness, pituitary gland abnormalities, and maternal substance abuse. These predictors help clinical decision-making related to the need for and frequency of hormone testing in pediatric patients with ONH.