Up-regulation and functional effect of cardiac β3-adrenoreceptors in alcoholic monkeys

Increased CaMKII activation and contrast changes of cardiac β1-and β3-Adrenergic signaling pathways in a humanized angiotensinogen model of hypertension

Aims

Upregulation of Ca²⁺/calmodulin-dependent protein kinase II (CaMKII) contributes to the pathogenesis of cardiovascular disease, including hypertension. Transgenic rats expressing the human angiotensinogen gene [TGR (hAGT)L1623] are a new novel humanized model of hypertension that associates with declines in cardiac contractile function and β-adrenergic receptor (AR) reserve. The molecular mechanisms are unclear. We tested the hypothesis that in TGR (hAGT)L1623 rats, left ventricular (LV) myocyte CaMKIIδ and β₃-AR are upregulated, but β₁-AR is down-regulated, which are important causes of cardiac dysfunction and β-AR desensitization.

Main methods

We compared LV myocyte CaMKIIδ, CaMKIIδ phosphorylation (at Thr287) (pCaMKIIδ), and β₁-and β₃-AR expressions and determined myocyte functional and [Ca²⁺]_I transient ([Ca²⁺]_iT) responses to β-AR stimulation with and without pretreatment of myocytes using an inhibitor of CaMKII, KN-93 (10^-6 M, 30 min) in male Sprague Dawley (SD; N = 10) control and TGR (hAGT)L1623 (N = 10) adult rats.

Key findings

Hypertension in TGR (hAGT)L1623 rats was accompanied by significantly increased LV myocyte β₃-AR protein levels and reduced β₁-AR protein levels. CaMKIIδ phosphorylation (at Thr287), pCaMKIIδ was significantly increased by 35%. These changes were followed by significantly reduced basal cell contraction (dL/dt_max), relaxation (dR/dt_max), and [Ca²⁺]_iT. Isoproterenol (10^-8 M) produced significantly smaller increases in dL/dt_max, dR/dt_max, and [Ca²⁺]_iT. Moreover, only in TGR (hAGT)L1623 rats, pretreatment of LV myocytes with KN-93 (10^-6 M, 30 min) fully restored normal basal and isoproterenol-stimulated myocyte contraction, relaxation, and [Ca²⁺]_iT.

Significance

LV myocyte CaMKIIδ overactivation with associated contrast changes in β₃-AR and β₁-AR may be the key molecular mechanism for the abnormal contractile phenotype and β-AR desensitization in this humanized model of hypertension.

Chronic Ca2+/Calmodulin-Dependent Protein Kinase II Inhibition Rescues Advanced Heart Failure

Ca2+/calmodulin-dependent protein kinase II (CaMKII) is upregulated in congestive heart failure (CHF), contributing to electrical, structural, and functional remodeling. CaMKII inhibition is known to improve CHF, but its direct cardiac effects in CHF remain unclear. We hypothesized that CaMKII inhibition improves cardiomyocyte function, [Ca2+]i regulation, and β-adrenergic reserve, thus improving advanced CHF. In a 16-week study, we compared plasma neurohormonal levels and left ventricular (LV)- and myocyte-functional and calcium transient ([Ca2+]iT) responses in male Sprague-Dawley rats (10/group) with CHF induced by isoproterenol (170 mg/kg sq for 2 days). In rats with CHF, we studied the effects of the CaMKII inhibitor KN-93 or its inactive analog KN-92 (n = 4) (70 µg/kg per day, mini-pump) for 4 weeks. Compared with controls, isoproterenol-treated rats had severe CHF with 5-fold-increased plasma norepinephrine and about 50% decreases in ejection fraction (EF) and LV contractility [slope of LV end-systolic pressure-LV end-systolic volume relation (EES)] but increased time constant of LV relaxation (τ). They also showed significantly reduced myocyte contraction [maximum rate of myocyte shortening (dL/dtmax)], relaxation (dL/dtmax), and [Ca2+]iT Isoproterenol superfusion caused significantly fewer increases in dL/dtmax and [Ca2+]iT KN-93 treatment prevented plasma norepinephrine elevation, with increased basal and acute isoproterenol-stimulated increases in EF and EES and decreased τ in CHF. KN-93 treatment preserved normal myocyte contraction, relaxation, [Ca2+]iT, and β-adrenergic reserve, whereas KN-92 treatment failed to improve LV and myocyte function, and plasma norepinephrine remained high in CHF. Thus, chronic CaMKII inhibition prevented CHF-induced activation of the sympathetic nervous system, restoring normal LV and cardiomyocyte basal and β-adrenergic-stimulated contraction, relaxation, and [Ca2+]iT, thereby playing a rescue role in advanced CHF. SIGNIFICANCE STATEMENT: We investigated the therapeutic efficacy of late initiation of chronic Ca2+/calmodulin-dependent protein kinase II (CaMKII) inhibition on progression of advanced congestive heart failure (CHF). Chronic CaMKII inhibition prevented CHF-induced activation of the sympathetic nervous system and restored normal intrinsic cardiomyocyte basal and β-adrenergic receptor-stimulated relaxation, contraction, and [Ca2+]i regulation, leading to reversal of CHF progression. These data provide new evidence that CaMKII inhibition is able and sufficient to rescue a failing heart, and thus cardiac CaMKII inhibition is a promising target for improving CHF treatment.

Alcoholic Cardiomyopathy: Disrupted Protein Balance and Impaired Cardiomyocyte Contractility

Alcoholic cardiomyopathy (ACM) can develop after consumption of relatively large amounts of alcohol over time or from acute binge drinking. Of the many factors implicated in the etiology of ACM, chronic perturbation in protein balance has been strongly implicated. This review focused on recent contributions (since 2010) in the area of protein metabolism and cardiac function related to ACM. Data reviewed include that from in vitro and preclinical in vivo animal studies where alcohol or an oxidative metabolite was studied and outcome measures in either cardiomyocytes or whole heart pertaining to protein synthesis or degradation were reported. Additionally, studies on the contractile properties of cardiomyocytes were also included to link signal transduction with function. Methodological differences including the potential impact of sex, dosing, and duration/timing of alcohol administration are addressed. Acute and chronic alcohol consumption decreases cardiac protein synthesis and/or activation of proteins within the regulatory mammalian/mechanistic target of rapamycin complex pathway. Albeit limited, evidence suggests that myocardial protein degradation via the ubiquitin pathway is not altered, while autophagy may be enhanced in ACM. Alcohol impairs ex vivo cardiomyocyte contractility in relation to its metabolism and expression of proteins within the growth factor pathway. Dysregulation of protein metabolism, including the rate of protein synthesis and autophagy, may contribute to contractile deficits and is a hallmark feature of ACM meriting additional sex-inclusive, methodologically consistent studies.

Alcohol effects on cardiac function

The consumption of ethanol can have both beneficial and detrimental effects on the function of the heart and cardiovascular system, depending on the amount consumed. Low-to-moderate amounts of ethanol intake are associated with improvements in cardiac function and vascular health. On the other hand, ethanol chronically consumed in large amounts acts as a toxin to the heart and vasculature. The cardiac injury produced by chronic alcohol abuse can progress to heart failure and eventual death. Furthermore, alcohol abuse may exacerbate preexisting heart conditions, such as hypertension and cardiomyopathy. This article focuses on the molecular mechanisms and pathophysiology of both the beneficial and detrimental cardiac effects of alcohol.

Overexpression myocardial inducible nitric oxide synthase exacerbates cardiac dysfunction and beta-adrenergic desensitization in experimental hypothyroidism

BACKGROUND

Altered nitric oxide synthase (NOS) has been implicated in the pathophysiology of heart failure (HF). Recent evidence links hypothyroidism to the pathology of HF. However, the precise mechanisms are incompletely understood. The alterations and functional effects of cardiac NOS in hypothyroidism are unknown. We tested the hypothesis that hypothyroidism increases cardiomyocyte inducible NOS (iNOS) expression, which plays an important role in hypothyroidism-induced depression of cardiomyocyte contractile properties, [Ca(2+)]i transient ([Ca(2+)]iT), and β-adrenergic hyporesponsiveness.

METHODS AND RESULTS

We simultaneously evaluated LV functional performance and compared myocyte three NOS, β-adrenergic receptors (AR) and SERCA2a expressions and assessed cardiomyocyte contractile and [Ca(2+)]iT responses to β-AR stimulation with and without pretreatment of iNOS inhibitor (1400 W, 10(-5)mol/L) in 26 controls and 26 rats with hypothyroidism induced by methimazole (~30 mg/kg/day for 8 weeks in the drinking water). Compared with controls, in hypothyroidism, total serum T3 and T4 were significantly reduced followed by significantly decreased LV contractility (EES) with increased LV time constant of relaxation. These LV abnormalities were accompanied by concomitant significant decreases in myocyte contraction (dL/dtmax), relaxation (dR/dtmax), and [Ca(2+)]iT. In hypothyroidism, isoproterenol (10(-8)M) produced significantly smaller increases in dL/dtmax, dR/dtmax and [Ca(2+)]iT. These changes were associated with decreased β1-AR and SERCA2a, but significantly increased iNOS. Moreover, only in hypothyroidism, pretreatment with iNOS inhibitor significantly improved basal and isoproterenol-stimulated myocyte contraction, relaxation and [Ca(2+)]iT.

CONCLUSIONS

Hypothyroidism produces intrinsic defects of LV myocyte force-generating capacity and relaxation with β-AR desensitization. Up-regulation of cardiomyocyte iNOS may promote progressive cardiac dysfunction in hypothyroidism.

Chronic alcohol self-administration in monkeys shows long-term quantity/frequency categorical stability

BACKGROUND

The current criteria for alcohol use disorders (AUDs) do not include consumption (quantity/frequency) measures of alcohol intake, in part due to the difficulty of these measures in humans. Animal models of ethanol (EtOH) self-administration have been fundamental in advancing our understanding of the neurobiological basis of AUD and can address quantity/frequency measures with accurate measurements over prolonged periods of time. The nonhuman primate model of voluntary oral alcohol self-administration has documented both binge drinking and drinking to dependence and can be used to test the stability of consumption measures over time.

METHODS

Here, an extensive set of alcohol intakes (g/kg/d) was analyzed from a large multi-cohort population of Rhesus (Macaca mulatta) monkeys (n = 31). Daily EtOH intake was uniformly distributed over chronic (12 months) access for all animals.

RESULTS

Underlying this distribution of intakes were subpopulations of monkeys that exhibited distinctive clustering of drinking patterns, allowing us to categorically define very heavy drinking (VHD), heavy drinking (HD), binge drinking (BD), and low drinking (LD). These categories were stable across the 12 months assessed by the protocol, but exhibited fluctuations when examined at shorter intervals.

CONCLUSIONS

The establishment of persistent drinking categories based on quantity/frequency suggests that consumption variables can be used to track long-term changes in behavioral, molecular, or physiochemical mechanisms related to our understanding of diagnosis, prevention, intervention, and treatment efficacies.

Chronic alcohol abuse and HIV disease progression: studies with the non-human primate model

The populations at risk for HIV infection, as well as those living with HIV, overlap with populations that engage in heavy alcohol consumption. Alcohol use has been associated with high-risk sexual behavior and an increased likelihood of acquiring HIV, as well as poor outcome measures of disease such as increased viral loads and declines in CD4+ T lymphocytes among those living with HIV-infections. It is difficult to discern the biological mechanisms by which alcohol use affects the virus:host interaction in human populations due to the numerous variables introduced by human behavior. The rhesus macaque infected with simian immunodeficiency virus has served as an invaluable model for understanding HIV disease and transmission, and thus, provides an ideal model to evaluate the effects of chronic alcohol use on viral infection and disease progression in a controlled environment. In this review, we describe the different macaque models of chronic alcohol consumption and summarize the studies conducted with SIV and alcohol. Collectively, they have shown that chronic alcohol consumption results in higher levels of plasma virus and alterations in immune cell populations that potentiate SIV replication. They also demonstrate a significant impact of chronic alcohol use on SIV-disease progression and survival. These studies highlight the utility of the rhesus macaque in deciphering the biological effects of alcohol on HIV disease. Future studies with this well-established model will address the biological influence of alcohol use on susceptibility to HIV, as well as the efficacy of anti-retroviral therapy.

Alcoholic cardiomyopathy: pathophysiologic insights

Alcoholic cardiomyopathy (ACM) is a specific heart muscle disease found in individuals with a history of long-term heavy alcohol consumption. ACM is associated with a number of adverse histological, cellular, and structural changes within the myocardium. Several mechanisms are implicated in mediating the adverse effects of ethanol, including the generation of oxidative stress, apoptotic cell death, impaired mitochondrial bioenergetics/stress, derangements in fatty acid metabolism and transport, and accelerated protein catabolism. In this review, we discuss the evidence for such mechanisms and present the potential importance of drinking patterns, genetic susceptibility, nutritional factors, race, and sex. The purpose of this review is to provide a mechanistic paradigm for future research in the area of ACM.

Monkey alcohol tissue research resource: banking tissues for alcohol research

BACKGROUND

An estimated 18 million adults in the United States meet the clinical criteria for diagnosis of alcohol abuse or alcoholism, a disorder ranked as the third leading cause of preventable death. In addition to brain pathology, heavy alcohol consumption is comorbid with damage to major organs including heart, lungs, liver, pancreas, and kidneys. Much of what is known about risk for and consequences of heavy consumption derive from rodent or retrospective human studies. The neurobiological effects of chronic intake in rodent studies may not easily translate to humans due to key differences in brain structure and organization between species, including a lack of higher-order cognitive functions, and differences in underlying prefrontal cortical neural structures that characterize the primate brain. Further, rodents do not voluntarily consume large quantities of ethanol (EtOH) and they metabolize it more rapidly than primates.

METHODS

The basis of the Monkey Alcohol Tissue Research Resource (MATRR) is that nonhuman primates, specifically monkeys, show a range of drinking excessive amounts of alcohol (>3.0 g/kg or a 12 drink equivalent per day) over long periods of time (12 to 30 months) with concomitant pathological changes in endocrine, hepatic, and central nervous system (CNS) processes. The patterns and range of alcohol intake that monkeys voluntarily consume parallel what is observed in humans with alcohol use disorders and the longitudinal experimental design spans stages of drinking from the EtOH-naïve state to early exposure through chronic abuse. Age- and sex-matched control animals self-administer an isocaloric solution under identical operant procedures.

RESULTS

The MATRR is a unique postmortem tissue bank that provides CNS and peripheral tissues, and associated bioinformatics from monkeys that self-administer EtOH using a standardized experimental paradigm to the broader alcohol research community.

CONCLUSIONS

This resource provides a translational platform from which we can better understand the disease processes associated with alcoholism.

Monkeys that voluntarily and chronically drink alcohol damage their brains: a longitudinal MRI study

Neuroimaging has consistently documented reductions in the brain tissue of alcoholics. Inability to control comorbidity, environmental insult, and nutritional deficiency, however, confound the ability to assess whether ethanol itself is neurotoxic. Here we report monkey oral ethanol self-administration combined with MR imaging to characterize brain changes over 15 months in 18 well-nourished rhesus macaques. Significant brain volume shrinkage occurred in the cerebral cortices of monkeys drinking ≥ 3 g/kg ethanol/day (12 alcoholic drinks) at 6 months, and this persisted throughout the period of continuous access to ethanol. Correlation analyses revealed a cerebral cortical volumetric loss of ~0.11% of the intracranial vault for each daily drink (0.25 g/kg), and selective vulnerability of cortical and non-cortical brain regions. These results demonstrate for the first time a direct relation between oral ethanol intake and measures of decreased brain gray matter volume in vivo in primates. Notably, greater volume shrinkage occurred in monkeys with younger drinking onset that ultimately became heavier drinkers than monkeys with older drinking onset. The pattern of volumetric changes observed in nonhuman primates following 15 months of drinking suggests that cerebral cortical gray matter changes are the first macroscopic manifestation of chronic ethanol exposure in the brain.

Effect of β3 adrenoceptor activation in the basolateral amygdala on ethanol seeking behaviors

RATIONALE

The interaction between ethanol (EtOH) and anxiety plays an integral role in the development and maintenance of alcoholism. Many medications in pre-clinical or clinical trials for the treatment of alcoholism share anxiolytic properties. However, these drugs typically have untoward side effects, such as sedation or impairment of motor function that may limit their clinical use. We have recently demonstrated that BRL 37344 (BRL), a selective β3-adrenoceptor (AR) agonist, enhances a discrete population of GABAergic synapses in the basolateral amygdala (BLA) that mediates feed-forward inhibition from lateral paracapsular (LPC) GABAergic interneurons onto BLA pyramidal cells. Behavioral studies revealed that intra-BLA infusion of BRL significantly reduced measures of unconditioned anxiety-like behavior without locomotor depressant effects.

OBJECTIVES

The present studies tested the effect of BRL (0.1, 0.5, or 1.0 μg/side) on EtOH self-administration using an intermittent access home cage two-bottle choice procedure and limited access operant responding for EtOH or sucrose.

RESULTS

Intra-BLA infusion of BRL did not reduce home cage, intermittent EtOH self-administration. However, using an operant procedure that permits the discrete assessment of appetitive (seeking) and consummatory measures of EtOH self-administration, BRL reduced measures of EtOH and sucrose seeking, but selectively reduced operant responding for EtOH during extinction probe trials. BRL had no effect on consummatory behaviors for EtOH or sucrose.

CONCLUSIONS

Together, these data suggest that intra-BLA infusion of BRL significantly reduces motivation to seek EtOH and provide initial evidence that β3-ARs and LPC GABAergic synapses may represent promising targets for the development of novel pharmacotherapies for the treatment of alcoholism.

Standardized method for the harvest of nonhuman primate tissue optimized for multiple modes of analyses

Appropriate animal models are critical to conduct translational studies of human disorders without variables that can confound clinical studies. Such analytic methods as patch-clamp electrophysiological and voltammetric recordings of neurons in brain slices require living brain tissue. In order to obtain viable tissue from nonhuman primate brains, tissue collection methods must be designed to preserve cardiovascular and respiratory functions for as long as possible. This paper describes a method of necropsy that has been used in three species of monkeys that satisfies this requirement. At necropsy, animals were maintained under a deep surgical plane of anesthesia while a craniotomy was conducted to expose the brain. Following the craniotomy, animals were perfused with ice-cold, oxygenated artificial cerebrospinal fluid to displace blood and to reduce the temperature of the entire brain. The brain was removed within minutes of death and specific brain regions were immediately dissected for subsequent in vitro electrophysiology or voltammetry experiments. This necropsy method also provided for the collection of tissue blocks containing all brain regions that were immediately frozen and stored for subsequent genomic, proteomic, autoradiographic and histological studies. An added benefit from the design of this necropsy method is that all major peripheral tissues were also collected and are now being utilized in a wide range of genomic, biochemical and histological assays. This necropsy method has resulted in the establishment and growth of a nonhuman primate alcohol tissue bank designed to distribute central nervous system and peripheral tissues to the larger scientific community.

The effects of chronic ethanol self-administration on hippocampal serotonin transporter density in monkeys

Evidence for an interaction between alcohol consumption and the serotonin system has been observed repeatedly in both humans and animal models yet the specific relationship between the two remains unclear. Research has focused primarily on the serotonin transporter (SERT) due in part to its role in regulating extracellular levels of serotonin. The hippocampal formation is heavily innervated by ascending serotonin fibers and is a major component of the neurocircuitry involved in mediating the reinforcing effects of alcohol. The current study investigated the effects of chronic ethanol self-administration on hippocampal SERT in a layer and field specific manner using a monkey model of human alcohol consumption. [(3)H]Citalopram was used to measure hippocampal SERT density in male cynomolgus macaques that voluntarily self-administered ethanol for 18 months. Hippocampal [(3)H]citalopram binding was less dense in ethanol drinkers than in controls, with the greatest effect observed in the molecular layer of the dentate gyrus. SERT density was not correlated with measures of ethanol consumption or blood ethanol concentrations, suggesting the possibility that a threshold level of consumption had been met. The lower hippocampal SERT density observed suggests that chronic ethanol consumption is associated with altered serotonergic modulation of hippocampal neurotransmission.

Synaptic and morphological neuroadaptations in the putamen associated with long-term, relapsing alcohol drinking in primates

Alcoholism and alcohol use disorders are characterized by several months to decades of heavy and problematic drinking, interspersed with periods of abstinence and relapse to heavy drinking. This alcohol-drinking phenotype was modeled using macaque monkeys to explore neuronal adaptations in the striatum, a brain region controlling habitual behaviors. Prolonged drinking with repeated abstinence narrowed the variability in daily intake, increased the amount of ethanol consumed in bouts, and led to higher blood ethanol concentrations more than twice the legal intoxication limit. After the final abstinence period of this extensive drinking protocol, we found a selective increase in dendritic spine density and enhanced glutamatergic transmission in the putamen, but not in the caudate nucleus. Intrinsic excitability of medium-sized spiny neurons was also enhanced in the putamen of alcohol-drinking monkeys in comparison with non-drinkers, and GABAeric transmission was selectively suppressed in the putamen of heavy drinkers. These morphological and physiological changes indicate a shift in the balance of inhibitory/excitatory transmission that biases the circuit toward an enduring increase in synaptic activation of putamen output as a consequence of prolonged heavy drinking/relapse. The resultant potential for increased putamen activation may underlie an alcohol-drinking phenotype of regulated drinking and sustained intoxication.