Chronic hypoxia alters fetal cerebrovascular responses to endothelin-1.

In utero hypoxia influences the structure and function of most fetal arteries, including those of the developing cerebral circulation. Whereas the signals that initiate this hypoxic remodeling remain uncertain, these appear to be distinct from the mechanisms that maintain the remodeled vascular state. The present study explores the hypothesis that chronic hypoxia elicits sustained changes in fetal cerebrovascular reactivity to endothelin-1 (ET-1), a potent vascular contractant and mitogen. In fetal lambs, chronic hypoxia (3,820-m altitude for the last 110 days of gestation) had no significant effect on plasma ET-1 levels or ETA receptor density in cerebral arteries but enhanced contractile responses to ET-1 in an ETA-dependent manner. In organ culture (24 h), 10 nM ET-1 increased medial thicknesses less in hypoxic than in normoxic arteries, and these increases were ablated by inhibition of PKC (chelerythrine) in both normoxic and hypoxic arteries but were attenuated by inhibition of CaMKII (KN93) and p38 (SB203580) in normoxic but not hypoxic arteries. As indicated by Ki-67 immunostaining, ET-1 increased medial thicknesses via hypertrophy. Measurements of colocalization between MLCK and SMαA revealed that organ culture with ET-1 also promoted contractile dedifferentiation in normoxic, but not hypoxic, arteries through mechanisms attenuated by inhibitors of PKC, CaMKII, and p38. These results support the hypothesis that chronic hypoxia elicits sustained changes in fetal cerebrovascular reactivity to ET-1 through pathways dependent upon PKC, CaMKII, and p38 that cause increased ET-1-mediated contractility, decreased ET-1-mediated smooth muscle hypertrophy, and a depressed ability of ET-1 to promote contractile dedifferentiation.

Role of the sympathetic autonomic nervous system in hypoxic remodeling of the fetal cerebral vasculature.

Fetal hypoxia triggers compensatory angiogenesis and remodeling through mechanisms not fully elucidated. In response to hypoxia, hypoxia-inducible factor drives expression of cytokines that exert multiple effects on cerebral structures. Among these, the artery wall is composed of a heterogeneous cell mix and exhibits distinct patterns of cellular differentiation and reactivity. Governing these patterns are the vascular endothelium, smooth muscle (SM), adventitia, sympathetic perivascular nerves (SPN), and the parenchyma. Although an extensive literature details effects of nonneuronal factors on cerebral arteries, the trophic role of perivascular nerves remains unclear. Hypoxia increases sympathetic innervation with subsequent release of norepinephrine (NE), neuropeptide-Y (NPY), and adenosine triphosphate, which exert motor and trophic effects on cerebral arteries and influence dynamic transitions among SM phenotypes. Our data also suggest that the cerebrovasculature reacts very differently to hypoxia in fetuses and adults, and we hypothesize that these differences arise from age-related differences in arterial SM phenotype reactivity and proximity to trophic factors, particularly of neural origin. We provide an integration of recent literature focused on mechanisms by which SPN mediate hypoxic remodeling. Our recent findings suggest that trophic effects of SPN on cerebral arteries accelerate functional maturation through shifts in SM phenotype in an age-dependent manner.

Contribution of increased VEGF receptors to hypoxic changes in fetal ovine carotid artery contractile proteins.

Recent studies suggest that vascular endothelial growth factor (VEGF) can modulate smooth muscle phenotype and, consequently, the composition and function of arteries upstream from the microcirculation, where angiogenesis occurs. Given that hypoxia potently induces VEGF, the present study explores the hypothesis that, in fetal arteries, VEGF contributes to hypoxic vascular remodeling through changes in abundance, organization, and function of contractile proteins. Pregnant ewes were acclimatized at sea level or at altitude (3,820 m) for the final 110 days of gestation. Endothelium-denuded carotid arteries from full-term fetuses were used fresh or after 24 h of organ culture in a physiological concentration (3 ng/ml) of VEGF. After 110 days, hypoxia had no effect on VEGF abundance but markedly increased abundance of the Flk-1 (171%) and Flt-1 (786%) VEGF receptors. Hypoxia had no effect on smooth muscle α-actin (SMαA), decreased myosin light chain (MLC) kinase (MLCK), and increased 20-kDa regulatory MLC (MLC(20)) abundances. Hypoxia also increased MLCK-SMαA, MLC(20)-SMαA, and MLCK-MLC(20) colocalization. Compared with hypoxia, organ culture with VEGF produced the same pattern of changes in contractile protein abundance and colocalization. Effects of VEGF on colocalization were blocked by the VEGF receptor antagonists vatalanib (240 nM) and dasatinib (6.3 nM). Thus, through increases in VEGF receptor density, hypoxia can recruit VEGF to help mediate remodeling of fetal arteries upstream from the microcirculation. The results support the hypothesis that VEGF contributes to hypoxic vascular remodeling through changes in abundance, organization, and function of contractile proteins.

Methodological rigor and reporting quality of clinical practice guidelines for adults hospitalized with bacterial pneumonia: a scoping review protocol.

OBJECTIVE: This scoping review will present a profile of methodological rigor and reporting quality of clinical practice guidelines for adults hospitalized with bacterial pneumonia. INTRODUCTION: An ideal clinical practice guideline is evidence-based and the product of a rigorous and robust literature-vetted process, yet reports show that rigor is not being achieved. Moreover, a new vulnerable population has been identified due to COVID-19, increasing the need for high quality clinical practice guidelines. Preliminary searches yielded no scoping or systematic reviews on methodological rigor and reporting quality of clinical practice guidelines used for managing bacterial pneumonia in hospitalized adults. INCLUSION CRITERIA: This review will consider current national and international clinical practice guidelines for management of hospitalized adult patients with either suspected or confirmed primary bacterial pneumonia. The review will include adult patients with multiple diagnoses if there is a clearly delineated clinical practice guideline for pneumonia. METHODS: A 3-step search strategy will be conducted using JBI methodology for scoping reviews. After an initial MEDLINE search for keywords, a broad search of 7 databases, 1 simultaneous platform, gray literature, specialty organizations, and international guideline groups will be conducted from 2017 to the present, in any language. Reference lists will be screened for additional sources. A 2-step screening process will be used to identify eligible clinical practice guidelines. Three reviewers will independently extract data using a standardized form. Domain scores will be analyzed and presented as percentages, and the results will be interpreted as map trends. DETAILS OF THIS REVIEW PROJECT ARE AVAILABLE AT: Open Science Framework https://osf.io/eucqy/.

Chronic hypoxia and VEGF differentially modulate abundance and organization of myosin heavy chain isoforms in fetal and adult ovine arteries.

Chronic hypoxia increases vascular endothelial growth factor (VEGF) and thereby promotes angiogenesis. The present study explores the hypothesis that hypoxic increases in VEGF also remodel artery wall structure and contractility through phenotypic transformation of smooth muscle. Pregnant and nonpregnant ewes were maintained at sea level (normoxia) or 3,820 m (hypoxia) for the final 110 days of gestation. Common carotid arteries harvested from term fetal lambs and nonpregnant adults were denuded of endothelium and studied in vitro. Stretch-dependent contractile stresses were 32 and 77% of normoxic values in hypoxic fetal and adult arteries. Hypoxic hypocontractility was coupled with increased abundance of nonmuscle myosin heavy chain (NM-MHC) in fetal (+37%) and adult (+119%) arteries. Conversely, hypoxia decreased smooth muscle MHC (SM-MHC) abundance by 40% in fetal arteries but increased it 123% in adult arteries. Hypoxia decreased colocalization of NM-MHC with smooth muscle α-actin (SM-αA) in fetal arteries and decreased colocalization of SM-MHC with SM-αA in adult arteries. Organ culture with physiological concentrations (3 ng/ml) of VEGF-A(165) similarly depressed stretch-dependent stresses to 37 and 49% of control fetal and adult values. The VEGF receptor antagonist vatalanib ablated VEGF's effects in adult but not fetal arteries, suggesting age-dependent VEGF receptor signaling. VEGF replicated hypoxic decreases in colocalization of NM-MHC with SM-αA in fetal arteries and decreases in colocalization of SM-MHC with SM-αA in adult arteries. These results suggest that hypoxic increases in VEGF not only promote angiogenesis but may also help mediate hypoxic arterial remodeling through age-dependent changes in smooth muscle phenotype and contractility.

VEGF receptors mediate hypoxic remodeling of adult ovine carotid arteries.

Recent studies suggest that VEGF contributes to hypoxic remodeling of arterial smooth muscle, although hypoxia produces only transient increases in VEGF that return to normoxic levels despite sustained changes in arterial structure and function. To explore how VEGF might contribute to long-term hypoxic vascular remodeling, this study explores the hypothesis that chronic hypoxia produces sustained increases in smooth muscle VEGF receptor density that mediate long-term vascular effects of hypoxia. Carotid arteries from adult sheep maintained at sea level or altitude (3,820 m) for 110 days were harvested and denuded of endothelium. VEGF levels were similar in chronically hypoxic and normoxic arteries, as determined by immunoblotting. In contrast, VEGF receptor levels were significantly increased by 107% (VEGF-R1) and 156% (VEGF-R2) in hypoxic compared with normoxic arteries. In arteries that were organ cultured 24 h with 3 nM VEGF, VEGF replicated effects of hypoxia on abundances of smooth muscle α actin (SMαA), myosin light chain kinase (MLCK), and MLC20 and the effects of hypoxia on colocalization of MLC20 with SMαA, as measured via confocal microscopy. VEGF did not replicate the effects of chronic hypoxia on colocalization of MLCK with SMαA or MLCK with MLC20, suggesting that VEGF's role in hypoxic remodeling is highly protein specific, particularly for contractile protein organization. VEGF effects in organ culture were inhibited by VEGF receptor blockers vatalinib (240 nM) and dasatinib (6.3 nM). These findings support the hypothesis that long-term upregulation of VEGF receptors help mediate sustained effects of hypoxia on the abundance and colocalization of contractile proteins in arterial smooth muscle.