Pericytes improve locomotor recovery after spinal cord injury in male and female neonatal rats.

Objective: It is not known how activation of the hypoxia-inducible factor (HIF) pathway in pericytes, cells of the microvascular wall, influences new capillary growth. We tested the hypothesis that HIF-activated pericytes promote angiogenesis in a neonatal model of spinal cord injury (SCI).

Methods: Human placental pericytes stimulated with cobalt chloride and naïve pericytes were injected into the site of a thoracic hemi-section of the spinal cord in rat pups on postnatal day three (P3).

The connexin 43/ZO-1 complex regulates cerebral endothelial F-actin architecture and migration.

Endothelial cell migration is a fundamental process during angiogenesis and, therefore, a point of intervention for therapeutic strategies aimed at controlling pathologies involving blood vessel growth. We sought to determine the role of the gap junction protein connexin 43 (Cx43) in key features of angiogenesis in the central nervous system. We used an in vitro model to test the hypothesis that a complex of interacting proteins, including Cx43 and zonula occludens-1 (ZO-1), regulates the migratory behavior of cerebral endothelium.

Driving the Hypoxia-Inducible Pathway in Human Pericytes Promotes Vascular Density in an Exosome-Dependent Manner.

Objectives: The mechanisms involved in activating pericytes, cells that ensheath capillaries, to engage in the formation of new capillaries, angiogenesis, remain unknown. In this study, the hypothesis was tested that pericytes could be stimulated to promote angiogenesis by driving the HIF pathway.

Methods: Pericytes were stimulated with CoCl2 to activate the HIF pathway.

Tyrosine phosphorylation of HSC70 and its interaction with RFC mediates methotrexate resistance in murine L1210 leukemia cells.

We previously identified and characterized a 66-68 kDa membrane-associated, tyrosine phosphorylated protein in murine leukemia L1210 cells as HSC70 which is a methotrexate (MTX)-binding protein. In order to further characterize the functional role of HSC70 in regulating MTX resistance in L1210 cells, we first showed that HSC70 colocalizes and interacts with reduced folate carrier (RFC) in L1210 cells by confocal laser scanning microscopy and Duolink in situ proximity ligation assay. The tyrosine phosphorylation status of HSC70 found in the membrane fraction was different from the parental L1210/0 and cisplatin (CDDP)-MTX cross resistant L1210/DDP cells.

Alterations of retinal vasculature in cystathionine-β-synthase heterozygous mice: a model of mild to moderate hyperhomocysteinemia.

Mild to moderate hyperhomocysteinemia is prevalent in humans and is implicated in neurovascular diseases, including recently in certain retinal diseases. Herein, we used hyperhomocysteinemic mice deficient in the Cbs gene encoding cystathionine-β-synthase (Cbs(+/-)) to evaluate retinal vascular integrity. The Cbs(+/+) (wild type) and Cbs(+/-) (heterozygous) mice (aged 16 to 52 weeks) were subjected to fluorescein angiography and optical coherence tomography to assess vasculature in vivo.

Homocysteine disrupts outgrowth of microvascular endothelium by an iNOS-dependent mechanism.

Objective: To test the hypothesis that Hcy impairs angiogenic outgrowth through an iNOS-dependent mechanism.

Methods: Adult C57Bl/6 mouse choroid explants were used in angiogenic outgrowth assays. Mouse microvascular endothelial cells were studied in culture during scrape-induced migration and dispersed cell locomotion experiments.

Opening of the blood-brain barrier before cerebral pathology in mild hyperhomocysteinemia.

Hyperhomocysteinemia (HHcy) is a risk factor for cognitive impairment. The purpose of this study was to determine the temporal pattern of cerebral pathology in a mouse model of mild HHcy, because understanding this time course provides the basis for understanding the mechanisms involved. C57Bl/6 mice with heterozygous deletion cystathionine β-synthase (cbs (+/-); Het) were used as a model of mild HHcy along with their wild-type littermates (cbs (+/+); WT).

Hyperhomocysteinemic mice show cognitive impairment without features of Alzheimer's disease phenotype.

Hyperhomocysteinemia (HHcy) is associated with cognitive impairment and Alzheimer's disease. Whether this association is mechanistic remains unclear. Here, we used a mouse model to test the hypothesis that HHcy increases levels of amyloid-β (Aβ) transporters in microvessels that form the blood-brain barrier, elevates Aβ content (Aβ40 and Aβ42) in the brain, and impairs cognitive performance.

Metabotropic glutamate receptor 5 mediates phosphorylation of vascular endothelial cadherin and nuclear localization of β-catenin in response to homocysteine.

Elevated plasma homocysteine (Hcy) is an independent risk factor for vascular disease and stroke in part by causing generalized endothelial dysfunction. A receptor that is sensitive to Hcy and its intracellular signaling systems has not been identified. β-catenin is a pleiotropic regulator of transcription and cell function.

Homocysteine impairs endothelial wound healing by activating metabotropic glutamate receptor 5.

Objective: Hcy is an independent risk factor for cerebrovascular disease and cognitive impairment. The purpose of this study was to elucidate the role of mGluR5 in Hcy-mediated impairment of cerebral endothelial wound repair.

Methods: Mouse CMVECs (bEnd.

Nitrative stress in cerebral endothelium is mediated by mGluR5 in hyperhomocysteinemia.

Hyperhomocysteinemia (HHcy) disrupts nitric oxide (NO) signaling and increases nitrative stress in cerebral microvascular endothelial cells (CMVECs). This is mediated, in part, by protein nitrotyrosinylation (3-nitrotyrosine; 3-NT) though the mechanisms by which extracellular homocysteine (Hcy) generates intracellular 3-NT are unknown. Using a murine model of mild HHcy (cbs(+/-) mouse), we show that 3-NT is significantly elevated in cerebral microvessels with concomitant reductions in serum NO bioavailability as compared with wild-type littermate controls (cbs(+/+)).

Hyperhomocysteinemia increases permeability of the blood-brain barrier by NMDA receptor-dependent regulation of adherens and tight junctions.

Hyperhomocysteinemia (HHcy) increases permeability of the blood-brain barrier, but the mechanisms are undetermined. Homocysteine (Hcy) is an agonist of the neuronal N-methyl-D-aspartate receptor (NMDAr). We tested the hypothesis that HHcy disrupts the blood-brain barrier by an NMDAr-dependent mechanism in endothelium.

Vascular complications of cystathionine β-synthase deficiency: future directions for homocysteine-to-hydrogen sulfide research.

Homocysteine (Hcy), a cardiovascular and neurovascular disease risk factor, is converted to hydrogen sulfide (H(2)S) through the transsulfuration pathway. H(2)S has attracted considerable attention in recent years for many positive effects on vascular health and homeostasis. Cystathionine β-synthase (CBS) is the first, and rate-limiting, enzyme in the transsulfuration pathway.

Extracellular transsulfuration generates hydrogen sulfide from homocysteine and protects endothelium from redox stress.

Homocysteine, a cardiovascular and neurocognitive disease risk factor, is converted to hydrogen sulfide, a cardiovascular and neuronal protectant, through the transsulfuration pathway. Given the damaging effects of free homocysteine in the blood and the importance of blood homocysteine concentration as a prognosticator of disease, we tested the hypotheses that the blood itself regulates homocysteine-hydrogen sulfide metabolism through transsulfuration and that transsulfuration capacity and hydrogen sulfide availability protect the endothelium from redox stress. Here we show that the transsulfuration enzymes, cystathionine β-synthase and cystathionine γ-lyase, are secreted by microvascular endothelial cells and hepatocytes, circulate as members of the plasma proteome, and actively produce hydrogen sulfide from homocysteine in human blood.

Regional activation of rapid onset vasodilatation in mouse skeletal muscle: regulation through α-adrenoreceptors.

Exercise onset entails motor unit recruitment and the initiation of vasodilatation. Dilatation can ascend the arteriolar network to encompass proximal feed arteries but is opposed by sympathetic nerve activity, which promotes vasoconstriction and inhibits ascending vasodilatation through activating α-adrenoreceptors. Whereas contractile activity can antagonize sympathetic vasoconstriction, more subtle aspects of this interaction remain to be defined.

Hypoxic pulmonary vasodilation: a paradigm shift with a hydrogen sulfide mechanism.

Hypoxic pulmonary vasoconstriction (HVC), an intrinsic and assumed ubiquitous response of mammalian pulmonary blood vessels, matches regional ventilation to perfusion via an unknown O(2)-sensing mechanism. Global pulmonary hypoxia experienced by individuals suffering from chronic obstructive pulmonary disease or numerous hypoventilation syndromes, including sleep apnea, often produces maladaptive pulmonary hypertension, but pulmonary hypertension is not observed in diving mammals, where profound hypoxia is routine. Here we examined the response of cow and sea lion pulmonary arteries (PA) to hypoxia and observed the expected HVC in the former and a unique hypoxic vasodilation in resistance vessels in the latter.

A simple and valid method to determine thermoregulatory sweating threshold and sensitivity.

Sweating threshold temperature and sweating sensitivity responses are measured to evaluate thermoregulatory control. However, analytic approaches vary, and no standardized methodology has been validated. This study validated a simple and standardized method, segmented linear regression (SReg), for determination of sweating threshold temperature and sensitivity.

Chronic diet-induced hyperhomocysteinemia impairs eNOS regulation in mouse mesenteric arteries.

Hyperhomocysteinemia (HHcy) impairs endothelium-dependent vasodilation by increasing reactive oxygen species, thereby reducing nitric oxide (NO.) bioavailability. It is unclear whether reduced expression or function of the enzyme that produces NO.

Age-related changes in conducted vasodilation: effects of exercise training and role in functional hyperemia.

Conducted vasodilation may coordinate blood flow in microvascular networks during skeletal muscle contraction. We tested the hypotheses that 1) exercise training enhances conducted vasodilation and 2) age-related changes in the capacity for conduction affect muscle perfusion during contractions. To address hypothesis 1, young (4-5 mo), adult (12-14 mo), and old (19-21 mo) C57BL6 male mice were sedentary or given access to running wheels for 8 wk.

Advancing age produces sex differences in vasomotor kinetics during and after skeletal muscle contraction.

Little is known of the vasomotor responses of skeletal muscle arterioles during and following muscle contraction. We hypothesized that aging leads to impaired arteriolar responses to muscle contraction and recovery. Nitric oxide (NO) availability, which is age dependent, has been implicated in components of these kinetics.

Effect of aging on the structure and function of skeletal muscle microvascular networks.

Humans are active creatures, yet physical activity and activity tolerance decline over the life span. One prevailing theme in the literature to account for a portion of the reduced activity tolerance with aging is the observation that the capacity to augment blood flow to skeletal muscle may be impaired with advancing age. This dysfunction may be due to adaptations in the structure or function of their microvascular networks, which collectively determine blood flow resistance.

The microcirculation of skeletal muscle in aging.

Microvascular structure and function are key aspects of tissue and organ health. At approximately 40% of total body mass, skeletal muscle contains more microvessels than any other organ system in the body. Moreover, skeletal muscle is the most dynamic tissue in the body with the capacity to increase blood flow and metabolic rate 30- to 50- fold.

Neurovascular alignment in adult mouse skeletal muscles.

Objective: Muscle blood flow increases with motor unit recruitment. The physical relationships between somatic motor nerves, which control muscle fiber contraction, and arterioles, which control microvascular perfusion, are unexplored. The authors tested the hypothesis that motor axons align with arterioles in adult skeletal muscle.