Articulating Hip Spacers with a Constrained Acetabular Liner: Effect of Acetabular Bone Loss and Cementation Quality.

Articulating hip spacers for periprosthetic joint infection (PJI) offer numerous advantages over static spacers such as improved patient mobilization, hip functionality, and soft tissue tension. Our study aimed to determine complication rates of a functional articulating spacer using a constrained liner to determine the role of acetabular cementation mantle and bone loss on the need for second-stage surgery. A retrospective review of 103 patients was performed and demographic information, spacer components and longevity, spacer-related complications, reinfection rates, and grade of bone loss and acetabular cement mantle quality were determined. There was no significant difference in spacer-related complications or reinfection rate between PJI and native hip infections. 33 of 103 patients (32.0%) elected to retain their spacers. Between patients who retained their initial spacer and those who underwent reimplantation surgery, there was not a significant difference in cement mantle grade (p = 0.52) or degree of bone loss (p = 0.78). Functional articulating antibiotic spacers with cemented constrained acetabular liners demonstrate promising early results in the treatment of periprosthetic and native hip infections. The rate of dislocation events was low. Further efforts to improve cement fixation may help decrease the need for second-stage reimplantation surgery.

Back to Play Considerations in a Patient With Bell's Palsy: A Case Report and Review.

Bell's palsy is an acute, ipsilateral facial paralysis secondary to inflammation of cranial nerve VII. This condition is classically caused by herpes simplex virus (HSV); however, many providers will make a diagnosis in the setting of other underlying conditions that are known to cause similar symptoms. The annual incidence of Bell's palsy is 11.5-53.3 per 100,000 persons, with a small subset of individuals being contact sport athletes. A unique challenge to treating Bell's palsy in collegiate athletes is finding a way for these players to return to their sport in a timely fashion, while also avoiding traumatic ocular injuries. Athletic goggles may provide a potential alternative option for athletes to return to the play of their respective sport prior to the physical symptoms subsiding. Due to the prolonged duration of most Bell's palsy symptoms, athletic goggles have the ability to save up to a full season of eligibility for a player. Aside from ocular injuries, a further challenge which encompasses all cases of Bell's palsy is the negative psychosocial effects which accompany the physical symptoms of this condition. Both the patient's physical and psychosocial health considerations must be taken into consideration. In this case report, we review the utility of ocular protection in helping collegiate athletes with unilateral facial paralysis return to play prior to the resolution of symptoms.

Mirizzi Syndrome: A Case Report.

Mirizzi syndrome (MS) describes a rare complication of cholelithiasis resulting from extrinsic compression of the common hepatic duct by impacted gallstones in the cystic duct or Hartmann's pouch. MS is most commonly seen in adults and is more prevalent in the female population. Due to the pathophysiology of MS being similar to other causes of cholecystitis and biliary obstruction, the symptomatology is rather nonspecific. While ultrasound and magnetic resonance cholangiopancreatography are commonly used for diagnosis, treatment of this condition typically involves cholecystectomy. Identifying MS versus other more common causes of obstructive jaundice is paramount in limiting complications. In this report, we describe a case of MS diagnosed in a 32-year-old male who presented with nonspecific abdominal pain and other signs of obstructive jaundice. The goal of this study is to show how identifying a rare underlying cause of a common presentation can lead to improved patient outcomes.

Investing in the Frontlines: Why Trusting and Supporting Communities of Color Will Help Address Gun Violence.

This article proposes potential strategies to address gun violence in communities of color while identifying the harms associated with a policing-centered, criminal legal approach. In addition to highlighting the dangers associated with the United States' current criminal legal tactics to reduce gun violence in these communities, the authors advocate for community-endorsed strategies that give those impacted by this issue the resources to take on gun violence in their own communities. Specifically, they identify, describe, and endorse a series of violence prevention programs that rely on community relations to detect and prevent incidents of gun violence and that view gun violence as a public health rather than criminal legal issue.

Transient receptor potential canonical type 3 channels: Interactions, role and relevance - A vascular focus.

Transient receptor potential canonical type 3 channels (TRPC3) are expressed in neural, cardiac, respiratory and vascular tissues, with both similarities and differences between human and animal models for the same cell types. In common with all members of the six subfamilies of TRP channels, TRPC3 are non-voltage gated, non-selective cation channels that are mainly permeated by Ca2+, and have distinct molecular, biophysical, anatomical and functional properties. TRP channels are present in excitable and non-excitable cells where they sense and respond to a wide variety of physical and chemical stimuli. TRPC3 are expressed in the endothelium and/or smooth muscle of specific intact arteries, such as mesenteric, cerebral and myometrial, where they are critical for the control of vascular tone, and show altered activity in development and disease. In artery endothelium, TRPC3 contributes to endothelium-derived hyperpolarization and nitric oxide-mediated vasodilation. In artery smooth muscle, TRPC3 contributes to constrictor mechanisms. In both endothelium and smooth muscle, TRPC3 contributes to function via caveolae-caveolin dependent and independent mechanisms. In different cell types and states, like other TRP channels, TRPC3 can form complexes with other TRP proteins and associated channels and accessory proteins, including those associated with endo(sarco)plasmic reticulum (ER/SR), thereby facilitating Ca2+ channel activation and/or refilling ER/SR Ca2+ stores. The diversity of TRPC3 interactions with other vascular signaling components is a potential target for artery specific control mechanisms. This brief perspective highlights recent advances in understanding the functional diversity of TRPC3, with an emphasis on vascular health and disease.

TRPV3 expression and vasodilator function in isolated uterine radial arteries from non-pregnant and pregnant rats.

This study investigated the expression and function of transient receptor potential vanilloid type-3 ion channels (TRPV3) in uterine radial arteries isolated from non-pregnant and twenty-day pregnant rats. Immunohistochemistry (IHC) suggested TRPV3 is primarily localized to the smooth muscle in arteries from both non-pregnant and pregnant rats. IHC using C' targeted antibody, and qPCR of TRPV3 mRNA, suggested pregnancy increased arterial TRPV3 expression. The TRPV3 activator carvacrol caused endothelium-independent dilation of phenylephrine-constricted radial arteries, with no difference between vessels from non-pregnant and pregnant animals. Carvacrol-induced dilation was reduced by the TRPV3-blockers isopentenyl pyrophosphate and ruthenium red, but not by the TRPA1 or TRPV4 inhibitors HC-030031 or HC-067047, respectively. In radial arteries from non-pregnant rats only, inhibition of NOS and sGC, or PKG, enhanced carvacrol-mediated vasodilation. Carvacrol-induced dilation of arteries from both non-pregnant and pregnant rats was prevented by the IKCa blocker TRAM-34. TRPV3 caused an endothelium-independent, IKCa-mediated dilation of the uterine radial artery. NO-PKG-mediated modulation of TRPV3 activity is lost in pregnancy, but this did not alter the response to carvacrol.

Mushroom hunting by using bioinformatics: application of a predictive framework facilitates the selective identification of sesquiterpene synthases in basidiomycota.

The Basidiomycota fungi represent a diverse source of natural products, particularly the sesquiterpenoids. Recently, genome sequencing, genome mining, and the subsequent discovery of a suite of sesquiterpene synthases in Omphalotus olearius was described. A predictive framework was developed to facilitate the discovery of sesquiterpene synthases in Basidiomycota. Phylogenetic analyses indicated a conservation of both sequence and initial cyclization mechanisms used. Here, the first robust application of this predictive framework is reported. It was used to selectively identify sesquiterpene synthases that follow 1,6-, 1,10-, and 1,11-cyclization mechanisms in the crust fungus Stereum hirsutum. The successful identification and characterization of a 1,6- and a 1,10-cyclizing sesquiterpene synthase, as well as three 1,11-cyclizing Δ(6) -protoilludene synthases, is described. This study verifies the accuracy and utility of the predictive framework as a roadmap for the discovery of specific sesquiterpene synthases from Basidiomycota, and thus represents an important step forward in natural product discovery.

Pregnancy-induced remodelling and enhanced endothelium-derived hyperpolarization-type vasodilator activity in rat uterine radial artery: transient receptor potential vanilloid type 4 channels, caveolae and myoendothelial gap junctions.

In pregnancy, the vasculature of the uterus undergoes rapid remodelling to increase blood flow and maintain perfusion to the fetus. The present study determines the distribution and density of caveolae, transient receptor potential vanilloid type 4 channels (TRPV4) and myoendothelial gap junctions, and the relative contribution of related endothelium-dependent vasodilator components in uterine radial arteries of control virgin non-pregnant and 20-day late-pregnant rats. The hypothesis examined is that specific components of endothelium-dependent vasodilator mechanisms are altered in pregnancy-related uterine radial artery remodelling. Conventional and serial section electron microscopy were used to determine the morphological characteristics of uterine radial arteries from control and pregnant rats. TRPV4 distribution and expression was examined using conventional confocal immunohistochemistry, and the contribution of endothelial TRPV4, nitric oxide (NO) and endothelium-derived hyperpolarization (EDH)-type activity determined using pressure myography with pharmacological intervention. Data show outward hypertrophic remodelling occurs in uterine radial arteries in pregnancy. Further, caveolae density in radial artery endothelium and smooth muscle from pregnant rats was significantly increased by ~94% and ~31%, respectively, compared with control, whereas caveolae density did not differ in endothelium compared with smooth muscle from control. Caveolae density was significantly higher by ~59% on the abluminal compared with the luminal surface of the endothelium in uterine radial artery of pregnant rats but did not differ at those surfaces in control. TRPV4 was present in endothelium and smooth muscle, but not associated with internal elastic lamina hole sites in radial arteries. TRPV4 fluorescence intensity was significantly increased in the endothelium and smooth muscle of radial artery of pregnant compared with control rats by ~2.6- and 5.5-fold, respectively. The TRPV4 signal was significantly higher in the endothelium compared with the smooth muscle in radial artery of both control and pregnant rats, by ~5.7- and 2.7-fold, respectively. Myoendothelial gap junction density was significantly decreased by ~37% in radial artery from pregnant compared with control rats. Pressure myography with pharmacological intervention showed that NO contributes ~80% and ~30%, and the EDH-type component ~20% and ~70% of the total endothelium-dependent vasodilator response in radial arteries of control and pregnant rats, respectively. TRPV4 plays a functional role in radial arteries, with a greater contribution in those from pregnant rats. The correlative association of increased TRPV4 and caveolae density and role of EDH-type activity in uterine radial artery of pregnant rats is suggestive of their causal relationship. The decreased myoendothelial gap junction density and lack of TRPV4 density at such sites is consistent with their having an integral, albeit complex, interactive role in uterine vascular signalling and remodelling in pregnancy.

Enhanced contractility in pregnancy is associated with augmented TRPC3, L-type, and T-type voltage-dependent calcium channel function in rat uterine radial artery.

In pregnancy, α-adrenoceptor-mediated vasoconstriction is augmented in uterine radial arteries and is accompanied by underlying changes in smooth muscle (SM) Ca(2+) activity. This study aims to determine the Ca(2+) entry channels associated with altered vasoconstriction in pregnancy, with the hypothesis that augmented vasoconstriction involves transient receptor potential canonical type-3 (TRPC3) and L- and T-type voltage-dependent Ca(2+) channels. Immunohistochemistry showed TRPC3, L-type Cav1.2 (as the α1C subunit), T-type Cav3.1 (α1G), and Cav3.2 (α1H) localization to the uterine radial artery SM. Fluorescence intensity of TRPC3, Cav1.2, and Cav3.2 was increased, and Cav3.1 decreased in radial artery SM from pregnant rats. Western blot analysis confirmed increased TRPC3 protein expression in the radial artery from pregnant rats. Pressure myography incorporating pharmacological intervention to examine the role of these channels in uterine radial arteries showed an attenuation of phenylephrine (PE)-induced constriction with Pyr3 {1-[4-[(2,3,3-trichloro-1-oxo-2-propen-1-yl)amino]phenyl]-5-(trifluoromethyl)-1H-pyrazole-4-carboxylic acid}-mediated TRPC3 inhibition or with nifedipine-mediated L-type channel block alone in vessels from pregnant rats; both effects of which were diminished in radial arteries from nonpregnant rats. Combined TRPC3 and L-type inhibition attenuated PE-induced constriction in radial arteries, and the residual vasoconstriction was reduced and abolished with T-type channel block with NNC 55-0396 in arteries from nonpregnant and pregnant rats, respectively. With SM Ca(2+) stores depleted and in the presence of PE, nifedipine, and NNC 55-0396, blockade of TRPC3 reversed PE-induced constriction. These data suggest that TRPC3 channels act synergistically with L- and T-type channels to modulate radial artery vasoconstriction, with the mechanism being augmented in pregnancy.

Polymorphism in endothelial connexin40 enhances sensitivity to intraluminal pressure and increases arterial stiffness.

OBJECTIVE: To determine whether impairment of endothelial connexin40 (Cx40), an effect that can occur in hypertension and aging, contributes to the arterial dysfunction and stiffening in these conditions. APPROACH AND RESULTS: A new transgenic mouse strain, expressing a mutant Cx40, (Cx40T202S), specifically in the vascular endothelium, has been developed and characterized. This mutation produces nonfunctional hemichannels, whereas gap junctions containing the mutant are electrically, but not chemically, patent. Mesenteric resistance arteries from Cx40T202S mice showed increased sensitivity of the myogenic response to intraluminal pressure in vitro, compared with wild-type mice, whereas transgenic mice overexpressing native Cx40 (Cx40Tg) showed reduced sensitivity. In control and Cx40Tg mice, the sensitivity to pressure of myogenic constriction was modulated by both NO and endothelium-derived hyperpolarization; however, the endothelium-derived hyperpolarization component was absent in Cx40T202S arteries. Analysis of passive mechanical properties revealed that arterial stiffness was enhanced in vessels from Cx40T202S mice, but not in wild-type or Cx40Tg mice. CONCLUSIONS: Introduction of a mutant form of Cx40 in the endogenous endothelial Cx40 population prevents endothelium-derived hyperpolarization activation during myogenic constriction, enhancing sensitivity to intraluminal pressure and increasing arterial stiffness. We conclude that genetic polymorphisms in endothelial Cx40 can contribute to the pathogenesis of arterial disease.

Increased caveolae density and caveolin-1 expression accompany impaired NO-mediated vasorelaxation in diet-induced obesity.

Diet-induced obesity induces changes in mechanisms that are essential for the regulation of normal artery function, and in particular the function of the vascular endothelium. Using a rodent model that reflects the characteristics of human dietary obesity, in the rat saphenous artery we have previously demonstrated that endothelium-dependent vasodilation shifts from an entirely nitric oxide (NO)-mediated mechanism to one involving upregulation of myoendothelial gap junctions and intermediate conductance calcium-activated potassium channel activity and expression. This study investigates the changes in NO-mediated mechanisms that accompany this shift. In saphenous arteries from controls fed a normal chow diet, acetylcholine-mediated endothelium-dependent vasodilation was blocked by NO synthase and soluble guanylyl cyclase inhibitors, but in equivalent arteries from obese animals sensitivity to these agents was reduced. The expression of endothelial NO synthase (eNOS) and caveolin-3 in rat saphenous arteries was unaffected by obesity, whilst that of caveolin-1 monomer and large oligomeric complexes of caveolins-1 and -2 were increased in membrane-enriched samples. The density of caveolae was increased at the membrane and cytoplasm of endothelial and smooth muscle cells of saphenous arteries from obese rats. Dissociation of eNOS from caveolin-1, as a prerequisite for activation of the enzyme, may be compromised and thereby impair NO-mediated vasodilation in the saphenous artery from diet-induced obese rats. Such altered signaling mechanisms in obesity-related vascular disease represent significant potential targets for therapeutic intervention.

Discovery and characterization of terpenoid biosynthetic pathways of fungi.

Fungi produce a myriad of terpenoids with a broad range of biological activities, many of which can be adapted to human use. This requires knowledge of the enzymes responsible for the biosynthesis of these compounds. Herein, we describe strategies for identification and characterization of putative biosynthetic genes, structural examination of important pathway enzymes with a focus on altering activity, and identification of biosynthetic clusters, and genome mining for yet-to-be-discovered pathways. Fungi are a particularly attractive class of organism for terpenoid pathway discovery, as they often cluster their biosynthetic genes. The affordability of genome sequencing and the relatively small size of fungal genomes further simplify this process. While only a select few fungal strains are genetically tractable, many terpenoid biosynthetic genes are functional in Escherichia coli and Saccharomyces cerevisiae, allowing easy characterization. Identification of new terpenoid biosynthetic pathways has the potential to uncover new pharmaceutical compounds and establish new strategies for metabolic engineering.

Draft genome of Omphalotus olearius provides a predictive framework for sesquiterpenoid natural product biosynthesis in Basidiomycota.

The secondary metabolome of Basidiomycota represents a largely uncharacterized source of pharmaceutically relevant natural products. Terpenoids are the primary class of bioactive compounds isolated from mushrooms. The Jack O'Lantern mushroom Omphalotus olearius was identified 50 years ago as a prolific producer of anticancer illudin sesquiterpenoids; however, to date there have been exceptionally few studies into the biosynthesis of these important compounds. Here, we report the draft genome sequence of O. olearius, which reveals a diverse network of sesquiterpene synthases and two metabolic gene clusters associated with illudin biosynthesis. Characterization of the sesquiterpene synthases enabled a comprehensive survey of all currently available Basidiomycota genomes, thereby creating a predictive resource for terpenoid natural product biosynthesis in these organisms. Our results will facilitate discovery and biosynthetic production of unique pharmaceutically relevant bioactive compounds from Basidiomycota.

Transient receptor potential canonical type 3 channels facilitate endothelium-derived hyperpolarization-mediated resistance artery vasodilator activity.

AIMS: Microdomain signalling mechanisms underlie key aspects of artery function and the modulation of intracellular calcium, with transient receptor potential (TRP) channels playing an integral role. This study determines the distribution and role of TRP canonical type 3 (C3) channels in the control of endothelium-derived hyperpolarization (EDH)-mediated vasodilator tone in rat mesenteric artery. METHODS AND RESULTS: TRPC3 antibody specificity was verified using rat tissue, human embryonic kidney (HEK)-293 cells stably transfected with mouse TRPC3 cDNA, and TRPC3 knock-out (KO) mouse tissue using western blotting and confocal and ultrastructural immunohistochemistry. TRPC3-Pyr3 (ethyl-1-(4-(2,3,3-trichloroacrylamide)phenyl)-5-(trifluoromethyl)-1H-pyrazole-4-carboxylate) specificity was verified using patch clamp of mouse mesenteric artery endothelial and TRPC3-transfected HEK cells, and TRPC3 KO and wild-type mouse aortic endothelial cell calcium imaging and mesenteric artery pressure myography. TRPC3 distribution, expression, and role in EDH-mediated function were examined in rat mesenteric artery using immunohistochemistry and western blotting, and pressure myography and endothelial cell membrane potential recordings. In rat mesenteric artery, TRPC3 was diffusely distributed in the endothelium, with approximately five-fold higher expression at potential myoendothelial microdomain contact sites, and immunoelectron microscopy confirmed TRPC3 at these sites. Western blotting and endothelial damage confirmed primary endothelial TRPC3 expression. In rat mesenteric artery endothelial cells, Pyr3 inhibited hyperpolarization generation, and with individual SK(Ca) (apamin) or IK(Ca) (TRAM-34) block, Pyr3 abolished the residual respective IK(Ca)- and SK(Ca)-dependent EDH-mediated vasodilation. CONCLUSION: The spatial localization of TRPC3 and associated channels, receptors, and calcium stores are integral for myoendothelial microdomain function. TRPC3 facilitates endothelial SK(Ca) and IK(Ca) activation, as key components of EDH-mediated vasodilator activity and for regulating mesenteric artery tone.

Dietary obesity increases NO and inhibits BKCa-mediated, endothelium-dependent dilation in rat cremaster muscle artery: association with caveolins and caveolae.

Obesity is a risk factor for hypertension and other vascular disease. The aim of this study was to examine the effect of diet-induced obesity on endothelium-dependent dilation of rat cremaster muscle arterioles. Male Sprague-Dawley rats (213 ± 1 g) were fed a cafeteria-style high-fat or control diet for 16-20 wk. Control rats weighed 558 ± 7 g compared with obese rats 762 ± 12 g (n = 52-56; P < 0.05). Diet-induced obesity had no effect on acetylcholine (ACh)-induced dilation of isolated, pressurized (70 mmHg) arterioles, but sodium nitroprusside (SNP)-induced vasodilation was enhanced. ACh-induced dilation of arterioles from control rats was abolished by a combination of the K(Ca) blockers apamin, 1-[(2-chlorophenyl)diphenylmethyl]-1H-pyrazole (TRAM-34), and iberiotoxin (IBTX; all 0.1 µmol/l), with no apparent role for nitric oxide (NO). In arterioles from obese rats, however, IBTX had no effect on responses to ACh while the NO synthase (NOS)/guanylate cyclase inhibitors N(ω)-nitro-L-arginine methyl ester (L-NAME; 100 µmol/l)/1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ; 10 µmol/l) partially inhibited ACh-induced dilation. Furthermore, NOS activity (but not endothelial NOS expression) was increased in arteries from obese rats. L-NAME/ODQ alone or removal of the endothelium constricted arterioles from obese but not control rats. Expression of caveolin-1 and -2 oligomers (but not monomers or caveolin-3) was increased in arterioles from obese rats. The number of caveolae was reduced in the endothelium of arteries, and caveolae density was increased at the ends of smooth muscle cells from obese rats. Diet-induced obesity abolished the contribution of large-conductance Ca(2+)-activated K(+) channel to ACh-mediated endothelium-dependent dilation of rat cremaster muscle arterioles, while increasing NOS activity and inducing an NO-dependent component.

Calcium and endothelium-mediated vasodilator signaling.

Vascular tone refers to the balance between arterial constrictor and dilator activity. The mechanisms that underlie tone are critical for the control of haemodynamics and matching circulatory needs with metabolism, and thus alterations in tone are a primary factor for vascular disease etiology. The dynamic spatiotemporal control of intracellular Ca(2+) levels in arterial endothelial and smooth muscle cells facilitates the modulation of multiple vascular signaling pathways. Thus, control of Ca(2+) levels in these cells is integral for the maintenance of tone and blood flow, and intimately associated with both physiological and pathophysiological states. Hence, understanding the mechanisms that underlie the modulation of vascular Ca(2+) activity is critical for both fundamental knowledge of artery function, and for the development of targeted therapies. This brief review highlights the role of Ca(2+) signaling in vascular endothelial function, with a focus on contact-mediated vasodilator mechanisms associated with endothelium-derived hyperpolarization and the longitudinal conduction of responses over distance.

Optimized compatible set of BioBrick™ vectors for metabolic pathway engineering.

The BioBrick™ paradigm for the assembly of enzymatic pathways is being adopted and becoming a standard practice in microbial engineering. We present a strategy to adapt the BioBrick™ paradigm to allow the quick assembly of multi-gene pathways into a number of vectors as well as for the quick mobilization of any cloned gene into vectors with different features for gene expression and protein purification. A primary BioBrick™ (BB-eGFP) was developed where the promoter/RBS, multiple cloning sites, optional protein purification affinity tags and reporter gene were all separated into discrete regions by additional restriction enzymes. This primary BB-eGFP then served as the template for additional BioBrick™ vectors with different origins of replication, antibiotic resistances, inducible promoters (arabinose, IPTG or anhydrotetracycline), N- or C-terminal Histidine tags with thrombin cleavage, a LacZα reporter gene and an additional origin of mobility (oriT). All developed BioBricks™ and BioBrick™ compatible vectors were shown to be functional by measuring reporter gene expression. Lastly, a C(30) carotenoid pathway was assembled as a model enzymatic pathway to demonstrate in vivo functionality and compatibility of this engineered vector system.

Differential effects of diet-induced obesity on BKCa {beta}1-subunit expression and function in rat skeletal muscle arterioles and small cerebral arteries.

Mechanisms underlying obesity-related vascular dysfunction are unclear. This study examined the effect of diet-induced obesity on expression and function of large conductance Ca(2+)-activated potassium channel (BK(Ca)) in rat pressurized small resistance vessels with myogenic tone. Male Sprague-Dawley rats fed a cafeteria-style high fat diet (HFD; ∼30% energy from fat) for 16-20 wk were ∼30% heavier than controls fed standard chow (∼13% fat). Obesity did not alter BK(Ca) α-subunit function or α-subunit protein or mRNA expression in vessels isolated from the cremaster muscle or middle-cerebral circulations. In contrast, BK(Ca) ß(1)-subunit protein expression and function were significantly reduced in cremaster muscle arterioles but increased in middle-cerebral arteries from obese animals. Immunohistochemistry showed α- and ß(1)-subunits were present exclusively in the smooth muscle of both vessels. Cremaster muscle arterioles from obese animals showed significantly increased medial thickness, and media-to-lumen ratio and pressurized arterioles showed increased myogenic tone at 30 mmHg, but not at 50-120 mmHg. Myogenic tone was not affected by obesity in middle-cerebral arteries. The BK(Ca) antagonist iberiotoxin constricted both cremaster muscle and middle-cerebral arterioles from control rats; this effect of iberiotoxin was abolished in cremaster muscle arteries only from obese rats. Diet-induced obesity has contrasting effects on BK(Ca) function in different vascular beds, through differential effects on ß(1)-subunit expression. However, these alterations in BK(Ca) function had little effect on overall myogenic tone, suggesting that the mechanisms controlling myogenic tone can be altered and compensate for altered BK(Ca) expression and function.

Diet-induced obesity impairs endothelium-derived hyperpolarization via altered potassium channel signaling mechanisms.

BACKGROUND: The vascular endothelium plays a critical role in the control of blood flow. Altered endothelium-mediated vasodilator and vasoconstrictor mechanisms underlie key aspects of cardiovascular disease, including those in obesity. Whilst the mechanism of nitric oxide (NO)-mediated vasodilation has been extensively studied in obesity, little is known about the impact of obesity on vasodilation to the endothelium-derived hyperpolarization (EDH) mechanism; which predominates in smaller resistance vessels and is characterized in this study. METHODOLOGY/PRINCIPAL FINDINGS: Membrane potential, vessel diameter and luminal pressure were recorded in 4(th) order mesenteric arteries with pressure-induced myogenic tone, in control and diet-induced obese rats. Obesity, reflecting that of human dietary etiology, was induced with a cafeteria-style diet (∼30 kJ, fat) over 16-20 weeks. Age and sexed matched controls received standard chow (∼12 kJ, fat). Channel protein distribution, expression and vessel morphology were determined using immunohistochemistry, Western blotting and ultrastructural techniques. In control and obese rat vessels, acetylcholine-mediated EDH was abolished by small and intermediate conductance calcium-activated potassium channel (SK(Ca)/IK(Ca)) inhibition; with such activity being impaired in obesity. SK(Ca)-IK(Ca) activation with cyclohexyl-[2-(3,5-dimethyl-pyrazol-1-yl)-6-methyl-pyrimidin-4-yl]-amine (CyPPA) and 1-ethyl-2-benzimidazolinone (1-EBIO), respectively, hyperpolarized and relaxed vessels from control and obese rats. IK(Ca)-mediated EDH contribution was increased in obesity, and associated with altered IK(Ca) distribution and elevated expression. In contrast, the SK(Ca)-dependent-EDH component was reduced in obesity. Inward-rectifying potassium channel (K(ir)) and Na(+)/K(+)-ATPase inhibition by barium/ouabain, respectively, attenuated and abolished EDH in arteries from control and obese rats, respectively; reflecting differential K(ir) expression and distribution. Although changes in medial properties occurred, obesity had no effect on myoendothelial gap junction density. CONCLUSION/SIGNIFICANCE: In obese rats, vasodilation to EDH is impaired due to changes in the underlying potassium channel signaling mechanisms. Whilst myoendothelial gap junction density is unchanged in arteries of obese compared to control, increased IK(Ca) and Na(+)/K(+)-ATPase, and decreased K(ir) underlie changes in the EDH mechanism.