Vascular transcriptional alterations produced by juvenile obesity in Ossabaw swine.

We adopted a transcriptome-wide microarray analysis approach to determine the extent to which vascular gene expression is altered as a result of juvenile obesity and identify obesity-responsive mRNAs. We examined transcriptional profiles in the left anterior descending coronary artery (LAD), perivascular fat adjacent to the LAD, and descending thoracic aorta between obese (n = 5) and lean (n = 6) juvenile Ossabaw pigs (age = 22 wk). Obesity was experimentally induced by feeding the animals a high-fat/high-fructose corn syrup/high-cholesterol diet for 16 wk. We found that expression of 189 vascular cell genes in the LAD and expression of 165 genes in the thoracic aorta were altered with juvenile obesity (false discovery rate ≤ 10%) with an overlap of only 28 genes between both arteries. Notably, a number of genes found to be markedly upregulated in the LAD of obese pigs are implicated in atherosclerosis, including ACP5, LYZ, CXCL14, APOE, PLA2G7, LGALS3, SPP1, ITGB2, CYBB, and P2RY12. Furthermore, pathway analysis revealed the induction of proinflammatory and pro-oxidant pathways with obesity primarily in the LAD. Gene expression in the LAD perivascular fat was minimally altered with juvenile obesity. Together, we provide new evidence that obesity produces artery-specific changes in pretranslational regulation with a clear upregulation of proatherogenic genes in the LAD. Our data may offer potential viable drug targets and mechanistic insights regarding the molecular precursors involved in the origins of overnutrition and obesity-associated vascular disease. In particular, our results suggest that the oxidized LDL/LOX-1/NF-κB signaling axis may be involved in the early initiation of a juvenile obesity-induced proatherogenic coronary artery phenotype.

The role of α-adrenergic receptors in mediating beat-by-beat sympathetic vascular transduction in the forearm of resting man.

Sympathetic vascular transduction is commonly understood to act as a basic relay mechanism, but under basal conditions, competing dilatory signals may interact with and alter the ability of sympathetic activity to decrease vascular conductance. Thus, we determined the extent to which spontaneous bursts of muscle sympathetic nerve activity (MSNA) mediate decreases in forearm vascular conductance (FVC) and the contribution of local α-adrenergic receptor-mediated pathways to the observed FVC responses. In 19 young men, MSNA (microneurography), arterial blood pressure and brachial artery blood flow (duplex Doppler ultrasound) were continuously measured during supine rest. These measures were also recorded in seven men during intra-arterial infusions of normal saline, phentolamine (PHEN) and PHEN with angiotensin II (PHEN+ANG). The latter was used to control for increases in resting blood flow with α-adrenergic blockade. Spike-triggered averaging was used to characterize beat-by-beat changes in FVC for 15 cardiac cycles following each MSNA burst and a peak response was calculated. Following MSNA bursts, FVC initially increased by +3.3 ± 0.3% (P = 0.016) and then robustly decreased to a nadir of -5.8 ± 1.6% (P < 0.001). The magnitude of vasoconstriction appeared graded with the number of consecutive MSNA bursts; while individual burst size only had a mild influence. Neither PHEN nor PHEN+ANG infusions affected the initial rise in FVC, but both infusions significantly attenuated the subsequent decrease in FVC (-2.1 ± 0.7% and -0.7 ± 0.8%, respectively; P < 0.001 vs. normal saline). These findings indicate that spontaneous MSNA bursts evoke robust beat-by-beat decreases in FVC that are exclusively mediated via α-adrenergic receptors.

Antecedent hydrogen sulfide elicits an anti-inflammatory phenotype in postischemic murine small intestine: role of heme oxygenase-1.

We recently demonstrated that preconditioning with an exogenous hydrogen sulfide donor (NaHS-PC) 24 h before ischemia and reperfusion (I/R) causes postcapillary venules to shift to an anti-inflammatory phenotype in C57BL/6J wild-type (WT) mice such that these vessels fail to support increases in postischemic leukocyte rolling (LR) and leukocyte adhesion (LA). The objective of the present study was to determine whether heme oxygenase-1 (HO-1) is a mediator of these anti-inflammatory effects noted during I/R in mice preconditioned with NaHS. Intravital fluorescence microscopy was used to visualize LR and LA in single postcapillary venules of the murine small intestine. I/R induced marked increases in LR and LA, effects that were prevented by NaHS-PC. Treatment with the HO inhibitor tin protoporphyrin IX, but not the inactive protoporphyrin CuPPIX, just before reperfusion prevented the anti-inflammatory effects of antecedent NaHS. The anti-inflammatory effects of NaHS-PC were mimicked by preconditioning with hemin, an agent that induces HO-1 expression. We then evaluated the effect of NaHS as a preconditioning stimulus in mice that were genetically deficient in HO-1 (HO-1(-/-) on an H129 background with appropriate WT strain controls). NaHS-PC was ineffective in HO-1(-/-) mice. Our work indicates that HO-1 serves as an effector of the anti-inflammatory effects of NaHS-PC during I/R 24 h later.

Antecedent hydrogen sulfide elicits an anti-inflammatory phenotype in postischemic murine small intestine: role of BK channels.

The objectives of this study were to determine the role of calcium-activated, small (SK), intermediate (IK), and large (BK) conductance potassium channels in initiating the development of an anti-inflammatory phenotype elicited by preconditioning with an exogenous hydrogen sulfide (H(2)S) donor, sodium hydrosulfide (NaHS). Intravital microscopy was used to visualize rolling and firmly adherent leukocytes in vessels of the small intestine of mice preconditioned with NaHS (in the absence and presence of SK, IK, and BK channel inhibitors, apamin, TRAM-34, and paxilline, respectively) or SK/IK (NS-309) or BK channel activators (NS-1619) 24 h before ischemia-reperfusion (I/R). I/R induced marked increases in leukocyte rolling and adhesion, effects that were largely abolished by preconditioning with NaHS, NS-309, or NS-1619. The postischemic anti-inflammatory effects of NaHS-induced preconditioning were mitigated by BKB channel inhibitor treatment coincident with NaHS, but not by apamin or TRAM-34, 24 h before I/R. Confocal imaging and immunohistochemistry were used to demonstrate the presence of BKα subunit staining in both endothelial and vascular smooth muscle cells of isolated, pressurized mesenteric venules. Using patch-clamp techniques, we found that BK channels in cultured endothelial cells were activated after exposure to NaHS. Bath application of the same concentration of NaHS used in preconditioning protocols led to a rapid increase in a whole cell K(+) current; specifically, the component of K(+) current blocked by the selective BK channel antagonist iberiotoxin. The activation of BK current by NaHS could also be demonstrated in single channel recording mode where it was independent of a change in intracellular Ca(+) concentration. Our data are consistent with the concept that H(2)S induces the development of an anti-adhesive state in I/R in part mediated by a BK channel-dependent mechanism.

Intravital microscopic methods to evaluate anti-inflammatory effects and signaling mechanisms evoked by hydrogen sulfide.

Hydrogen sulfide (H2S) is an endogenous gaseous signaling molecule with potent anti-inflammatory properties. Exogenous application of H2S donors, administered either acutely during an inflammatory response or as an antecedent preconditioning intervention that invokes the activation of anti-inflammatory cell survival programs, effectively limits leukocyte rolling, adhesion and emigration, generation of reactive oxygen species, chemokine and cell adhesion molecule expression, endothelial barrier disruption, capillary perfusion deficits, and parenchymal cell dysfunction and injury. This chapter focuses on intravital microscopic methods that can be used to assess the anti-inflammatory effects exerted by H2S, as well as to explore the cellular signaling mechanisms by which this gaseous molecule limits the aforementioned inflammatory responses. Recent advances include use of intravital multiphoton microscopy and optical biosensor technology to explore signaling mechanisms in vivo.

Myocardial Stunning with Hemodialysis: Clinical Challenges of the Cardiorenal Patient.

We discuss the current state of knowledge related to the pathogenesis of myocardial stunning as well as the potential mechanisms responsible for the clinical presentation of myocardial stunning in hemodialysis patients. We suggest future research areas for this critical and clinically important condition in this high-risk patient population. In consideration of acute and chronic changes secondary to dialysis, especially in patients with risk for coronary artery disease, the prevalence of myocardial stunning and its role in the natural history of these patients' disease progression is considered. We propose a paradigm: that the majority of the pathophysiologic mechanisms by which hemodialysis may induce myocardial stunning falls into two categories with (1) vascular and/or (2) metabolic contributions. In order to prevent eventual myocardial hibernation, myocardial remodeling, scarring, and loss of contractile function with aberrant electrical conductivity that could lead to sudden death, it is imperative to identify the risk factors associated with myocardial stunning during hemodialysis. Further understanding of these mechanisms may lead to novel clinical interventions and pharmacologic therapeutic agents.

Ischemia/reperfusion injury: The role of immune cells.

Ischemia/reperfusion (I/R) injury is an inflammatory condition that is characterized by innate immunity and an adaptive immune response. This review is focused on the acute inflammatory response in I/R injury, and also the adaptive immunological mechanisms in chronic ischemic disease that lead to increased vulnerability during acute events, in relation to the cell types that have been shown to mediate innate immunity to an adaptive immune response in I/R, specifically myocardial infarction. Novel aspects are also highlighted in respect to the mechanisms within the cardiovascular system and cardiovascular risk factors that may be involved in the inflammatory response accompanying myocardial infarction. Experimental myocardial I/R has suggested that immune cells may mediate reperfusion injury. Specifically, monocytes, macrophages, T-cells, mast cells, platelets and endothelial cells are discussed with reference to the complement cascade, toll-like receptors, cytokines, oxidative stress, renin-angiotensin system, and in reference to the microvascular system in the signaling mechanisms of I/R. Finally, the findings of the data summarized in this review are most important for possible translation into clinical cardiology practice and possible avenues for drug development.