Endothelial Nitric Oxide Mediates Caffeine Antagonism of Alcohol-Induced Cerebral Artery Constriction

Cerebrovascular Effects of Alcohol Combined with Tetrahydrocannabinol

Introduction: Alcohol (ethanol) and cannabis are among the most widely used recreational drugs in the world. With increased efforts toward legalization of cannabis, there is an alarming trend toward the concomitant (including simultaneous) use of cannabis products with alcohol for recreational purpose. While each drug possesses a distinct effect on cerebral circulation, the consequences of their simultaneous use on cerebral artery diameter have never been studied. Thus, we set to address the effect of simultaneous application of alcohol and (-)-trans-Δ-9-tetrahydrocannabinol (THC) on cerebral artery diameter. Materials and Methods: We used Sprague-Dawley rats because rat cerebral circulation closely mimics morphology, ultrastructure, and function of cerebral circulation of humans. We focused on the middle cerebral artery (MCA) because it supplies blood to the largest brain territory when compared to any other cerebral artery stemming from the circle of Willis. Experiments were performed on pressurized MCA ex vivo, and in cranial windows in vivo. Ethanol and THC were probed at physiologically relevant concentrations. Researchers were "blind" to experimental group identity during data analysis to avoid bias. Results: In males, ethanol mixed with THC resulted in greater constriction of ex vivo pressurized MCA when compared to the effects exerted by separate application of each drug. In females, THC, ethanol, or their mixture failed to elicit measurable effect. Vasoconstriction by ethanol/THC mixture was ablated by either endothelium removal or pharmacological block of calcium- and voltage-gated potassium channels of large conductance (BK type) and cannabinoid receptors. Block of prostaglandin production and of endothelin receptors also blunted constriction by ethanol/THC. In males, the in vivo constriction of MCA by ethanol/THC did not differ from ethanol alone. In females, the in vivo constriction of this artery by ethanol was significantly smaller than in males. However, artery constriction by ethanol/THC did not differ from the constriction in males. Conclusions: Our data point at the complex nature of the cerebrovascular effects elicited by simultaneous use of ethanol and THC. These effects include both local and systemic components.

Interspecies and regional variability of alcohol action on large cerebral arteries: regulation by KCNMB1 proteins

Alcohol intake leading to blood ethanol concentrations (BEC) ≥ legal intoxication modifies brain blood flow with increases in some regions and decreases in others. Brain regions receive blood from the Willis' circle branches: anterior, middle (MCA) and posterior cerebral (PCA), and basilar (BA) arteries. Rats and mice have been used to identify the targets mediating ethanol-induced effects on cerebral arteries, with conclusions being freely interchanged, albeit data were obtained in different species/arterial branches. We tested whether ethanol action on cerebral arteries differed between male rat and mouse and/or across different brain regions and identified the targets of alcohol action. In both species and all Willis' circle branches, ethanol evoked reversible and concentration-dependent constriction (EC50s ≈ 37-86 mM; below lethal BEC in alcohol-naïve humans). Although showing similar constriction to depolarization, both species displayed differential responses to ethanol: in mice, MCA constriction was highly sensitive to the presence/absence of the endothelium, whereas in rat PCA was significantly more sensitive to ethanol than its mouse counterpart. In the rat, but not the mouse, BA was more ethanol sensitive than other branches. Both interspecies and regional variability were ameliorated by endothelium. Selective large conductance (BK) channel block in de-endothelialized vessels demonstrated that these channels were the effectors of alcohol-induced cerebral artery constriction across regions and species. Variabilities in alcohol actions did not fully matched KCNMB1 expression across vessels. However, immunofluorescence data from KCNMB1-/- mouse arteries electroporated with KCNMB1-coding cDNA demonstrate that KCNMB1 proteins, which regulate smooth muscle (SM) BK channel function and vasodilation, regulate interspecies and regional variability of brain artery responses to alcohol.

Alcohol Use Disorders and Their Harmful Effects on the Contractility of Skeletal, Cardiac and Smooth Muscles

Alcohol misuse has deleterious effects on personal health, family, societal units, and global economies. Moreover, alcohol misuse usually leads to several diseases and conditions, including alcoholism, which is a chronic condition and a form of addiction. Alcohol misuse, whether as acute intoxication or alcoholism, adversely affects skeletal, cardiac and/or smooth muscle contraction. Ethanol (ethyl alcohol) is the main effector of alcohol-induced dysregulation of muscle contractility, regardless of alcoholic beverage type or the ethanol metabolite (with acetaldehyde being a notable exception). Ethanol, however, is a simple and "promiscuous" ligand that affects many targets to mediate a single biological effect. In this review, we firstly summarize the processes of excitation-contraction coupling and calcium homeostasis which are critical for the regulation of contractility in all muscle types. Secondly, we present the effects of acute and chronic alcohol exposure on the contractility of skeletal, cardiac, and vascular/ nonvascular smooth muscles. Distinctions are made between in vivo and in vitro experiments, intoxicating vs. sub-intoxicating ethanol levels, and human subjects vs. animal models. The differential effects of alcohol on biological sexes are also examined. Lastly, we show that alcohol-mediated disruption of muscle contractility, involves a wide variety of molecular players, including contractile proteins, their regulatory factors, membrane ion channels and pumps, and several signaling molecules. Clear identification of these molecular players constitutes a first step for a rationale design of pharmacotherapeutics to prevent, ameliorate and/or reverse the negative effects of alcohol on muscle contractility.

Effects of Consumption of Alcohol on Intraocular Pressure: Korea National Health and Nutrition Examination Survey 2010 to 2011

This study researched the association between alcohol consumption, intraocular pressure (IOP), and risk of open-angle glaucoma (OAG) using nationwide population-based cross-sectional data from the Korean population based survey. Information on alcohol intake was obtained by questionnaire and comprehensive ophthalmic examinations were performed. Among a total of 6057 participants, the prevalence of OAG was 4.4% (6.0% for men and 3.0% for women). Multivariate adjusted models showed that alcohol consumption showed significant relationship with changes in IOP. In sex-stratified analyses, alcohol consumption more than 2 times per week was associated with increased IOP in men without OAG, while in women with OAG drinking alcohol more than 4 times per week was associated with increased IOP. This study showed significant differences between men and women without glaucoma who consumed alcohol more than four times per week (p-value: 0.03). Our results suggest that alcohol consumption is associated with risk of elevated IOP depending on sex and presence of glaucoma in Koreans. Therefore, patients who need to control IOP should consider the effects of alcohol consumption.

Extra-endothelial TRPV1 channels participate in alcohol and caffeine actions on cerebral artery diameter

Alcohol (ethyl alcohol; ethanol) and caffeine are the two most widely used psychoactive substances in the world. Caffeine and ethanol have both been reported to constrict cerebral arteries in several species, including humans. We have recently shown that application of 10-μM caffeine mixed with 50 mM ethanol to in vitro pressurized cerebral arteries of rats reduced ethanol-induced constriction. This effect was dependent on the presence of nitric oxide (NO^•) and could be observed in de-endothelialized arteries supplied with the NO donor sodium nitroprusside (SNP). The molecular target(s) of ethanol-caffeine interaction in cerebral arteries has remained unknown. In the present work, we used rat and mouse middle cerebral arteries (MCA) to identify the extra-endothelial effectors of NO-mediated, caffeine-induced protection against ethanol-evoked arterial constriction. Constriction of intact MCA of rat by either 50 mM ethanol or 10 μM caffeine was ablated in the presence of a selective TRPV1 pharmacological blocker. TRPV1 pharmacological block, but not block of TRPA1, PKG, or BK channels, removed caffeine-induced protection against ethanol-evoked rat MCA constriction, whether evaluated in arteries with intact endothelium or in SNP-supplemented, de-endothelialized arteries. In mouse arteries, caffeine-induced protection against ethanol-induced MCA constriction was significantly amplified, resulting in actual vasodilation, upon pharmacological block of TRPV1, and in TRPV1 knock-out arteries. Despite some species-specific differences, our study unequivocally demonstrates the presence of functional, extra-endothelial TRPV1 that participates in both endothelium-independent MCA constriction by separate exposure to ethanol or caffeine and caffeine-induced protection against ethanol-evoked MCA constriction.

Tyrosine 450 in the Voltage- and Calcium-Gated Potassium Channel of Large Conductance Channel Pore-Forming (slo1) Subunit Mediates Cholesterol Protection against Alcohol-Induced Constriction of Cerebral Arteries

Alcohol (ethanol) at physiologically relevant concentrations (<100 mM) constricts cerebral arteries via inhibition of voltage- and calcium-gated potassium channels of large conductance (BK) located in vascular smooth muscle (VSM). These channels consist of channel-forming slo1 (cbv1, KCNMA1) and accessory beta1 (KCNMB1) subunits. An increase in VSM cholesterol (CLR) via either dietary CLR intake or in vitro CLR enrichment was shown to protect against endothelium-independent, alcohol-induced constriction of cerebral arteries. The molecular mechanism(s) of this protection remains unknown. Here, we demonstrate that CLR enrichment of de-endothelialized middle cerebral arteries (MCAs) of rat increased CLR content in the VSM in a concentration-dependent manner. CLR enrichment blunted MCA constriction evoked by 18-75 mM but not by 100 mM alcohol. MCA enrichment with coprostanol (COPR) also blunted vasoconstriction by 50 mM alcohol, despite the fact that COPR and CLR differ in their ability to modify several major physical properties of the bilayer. CLR protection against 50 but not 100 mM alcohol was also observed in C57BL/6 and KCNMB1 knockout (KO) mice. Permeabilization of KCNMA1 KO MCAs with Y450Fcbv1 totally ablated CLR, but not COPR protection against vasoconstriction by 50 mM alcohol. Thus, CLR and alcohol interact at the level of the BK channel slo1 subunit, with Y450 being critical for CLR protection against alcohol-induced vasoconstriction. We document for the first time a functional competition between CLR and alcohol in regulating cerebral artery diameter and a critical role of a single amino acid within the BK channel pore-forming subunit in controlling CLR-alcohol interaction at the organ level.

Statin therapy exacerbates alcohol-induced constriction of cerebral arteries via modulation of ethanol-induced BK channel inhibition in vascular smooth muscle

Statins constitute the most commonly prescribed drugs to decrease cholesterol (CLR). CLR is an important modulator of alcohol-induced cerebral artery constriction (AICAC). Using rats on a high CLR diet (2% CLR) we set to determine whether atorvastatin administration (10mg/kg daily for 18-23weeks) modified AICAC. Middle cerebral arteries were pressurized in vitro at 60mmHg and AICAC was evoked by 50mM ethanol, that is within the range of blood alcohol detected in humans following moderate-to-heavy drinking. AICAC was evident in high CLR+atorvastatin group but not in high CLR diet+placebo. Statin exacerbation of AICAC persisted in de-endothelialized arteries, and was blunted by CLR enrichment in vitro. Fluorescence imaging of filipin-stained arteries showed that atorvastatin decreased vascular smooth muscle (VSM) CLR when compared to placebo, this difference being reduced by CLR enrichment in vitro. Voltage- and calcium-gated potassium channels of large conductance (BK) are known VSM targets of ethanol, with their beta1 subunit being necessary for ethanol-induced channel inhibition and resulting AICAC. Ethanol-induced BK inhibition in excised membrane patches from freshly isolated myocytes was exacerbated in the high CLR diet+atorvastatin group when compared to high CLR diet+placebo. Unexpectedly, atorvastatin decreased the amount and function of BK beta1 subunit as documented by immunofluorescence imaging and functional patch-clamp studies. Atorvastatin exacerbation of ethanol-induced BK inhibition disappeared upon artery CLR enrichment in vitro. Our study demonstrates for the first time statin's ability to exacerbate the vascular effect of a widely consumed drug of abuse, this exacerbation being driven by statin modulation of ethanol-induced BK channel inhibition in the VSM via CLR-mediated mechanism.

Differential distribution and functional impact of BK channel beta1 subunits across mesenteric, coronary, and different cerebral arteries of the rat

Large conductance, Ca²⁺_i- and voltage-gated K⁺ (BK) channels regulate myogenic tone and, thus, arterial diameter. In smooth muscle (SM), BK channels include channel-forming α and auxiliary β1 subunits. BK β1 increases the channel's Ca²⁺ sensitivity, allowing BK channels to negatively feedback on depolarization-induced Ca²⁺ entry, oppose SM contraction and favor vasodilation. Thus, endothelial-independent vasodilation can be evoked though targeting of SM BK β1 by endogenous ligands, including lithocholate (LCA). Here, we investigated the expression of BK β1 across arteries of the cerebral and peripheral circulations, and the contribution of such expression to channel function and BK β1-mediated vasodilation. Data demonstrate that endothelium-independent, BK β1-mediated vasodilation by LCA is larger in coronary (CA) and basilar (BA) arteries than in anterior cerebral (ACA), middle cerebral (MCA), posterior cerebral (PCA), and mesenteric (MA) arteries, all arterial segments having a similar diameter. Thus, differential dilation occurs in extracranial arteries which are subjected to similar vascular pressure (CA vs. MA) and in arteries that irrigate different brain regions (BA vs. ACA, MCA, and PCA). SM BK channels from BA and CA displayed increased basal activity and LCA responses, indicating increased BK β1 functional presence. Indeed, in the absence of detectable changes in BK α, BA and CA myocytes showed an increased location of BK β1 in the plasmalemma/subplasmalemma. Moreover, these myocytes distinctly showed increased BK β1 messenger RNA (mRNA) levels. Supporting a major role of enhanced BK β1 transcripts in artery dilation, LCA-induced dilation of MCA transfected with BK β1 complementary DNA (cDNA) was as high as LCA-induced dilation of untransfected BA or CA.