Browsing by Author "Appiah, Cephas"
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Item Assessment of Neuroinflammation in Cognitive and Motor Brain Regions in Female Rats Exposed to Chronic Intermittent Hypoxia(2024-03-21) Appiah, Cephas; Little, Joel; Kunwar, Kishor; Cunningham, TomSleep apnea increases the risk of neurodegenerative disorders in postmenopausal women. In this study, we tested whether chronic intermittent hypoxia (CIH), a preclinical model of sleep apnea-associated cyclical hypoxia, can be used to identify early changes in the brain that might contribute to impair neurological function in intact (INT) and ovariectomized (OVX) female rats. To test this hypothesis, we conducted immunohistochemistry studies using markers for glial activation and neuroinflammation. We hypothesize that CIH will increase glial activation in ovariectomized (OVX) relative to intact (INT) female rats. Adult female Sprague Dawley INT (n=4) or OVX (n=4) rats that were part of a larger study and underwent 7 days of CIH (10% O2 and 21% O2 cycle, every 6 mins, 8h/day during the light phase) or continuous normoxia (CON) were euthanized on day 8, and their brains were collected. Brains were processed for microglia (IBA1) and astrocytes (GFAP) activation markers in (CA1) hippocampus, medial prefrontal cortex (mPFC), and caudate putamen (CP) striatum. Confocal images from each region are being used to optimize a fractal analysis protocol to test for changes in glial morphology. Raw images will be linearly processed in Huygens Essentials software to limit noise and optimize quality for further analysis in ImageJ. Skeletal and fractal analyses will be performed on randomly selected cells in the photomicrographs to determine cell ramification (branching, junctions, endpoint voxels, branch lengths) and complexity (fractal dimension, cell span ratio, density) to complement cell counts of immunohistochemical markers of activation. Our preliminary analysis has allowed us to determine the appropriate parameters needed for image capture and subsequent analysis. We have observed some possible qualitative changes indicative of increased activation in the CA1, CP, and mPFC regions following CIH in OVX rats relative to intact rats. The results of this study aim to contribute to our understanding of the potential impact of CIH in female rats of differing ovarian function, providing insights into sleep apnea-associated CNS dysfunction in women.Item Sex differences in the activation of central autonomic control regions and neuroinflammation in chronic intermittent hypoxia(2023) Appiah, Cephas; Little, Joel; Mabry, Steve; Cunningham, Rebecca L.; Cunningham, J. ThomasPurpose: Obstructive sleep apnea (OSA) is an independent risk factor for hypertension. Chronic interment hypoxia (CIH), which models episodic hypoxemia of OSA, produces daytime hypertension, oxidative stress, and activation of central autonomic regions that regulate mean arterial pressure (MAP) in male Sprague Dawley (SD) rats. Unlike gonadally intact females, gonadectomized females and males develop CIH hypertension. Lesioning of median preoptic nucleus (MnPO) in males prevents CIH hypertension. We hypothesize that the sex difference observed in CIH hypertension is due sex differences in neuroinflammation and activation of central autonomic regions that support MAP in CIH. Methods: Gonadally intact adult male and female SD rats (250-300g) were continuously exposed to normoxia (CON) or CIH (10% O2 every 3mins cycling 21% O2 every 3mins, 8h/day) for 7 days. Radiotelemetry transmitters were implanted in rats to record MAP and heart rate (HR). After one week of baseline recording, the rats were exposed to either continuous normoxia or CIH and were euthanized (inactin 100 mg/kg ip) on the 8th day for immunohistochemistry and blood analysis. All forebrain sections were stained for FosB/ΔFosB and either neuronal nitric oxide synthase (NOS1) or IBA1 to identify active microglia. Results: CIH males exhibited significantly increased hematocrit indicating erythropoiesis compared to control males (CON 42.1% ± 0.6, n=10; CIH 44.6% ± 0.7, n = 10. P = 0.0173). CIH males exhibited an increase in the average number of FosB positive neurons (CON male 20 ± 2 cells/section, CIH male 35 ± 3; CON female 11 ± 1, CIH female 12 ± 2,) and colocalization of FosB and NOS1 (CON male 10 ± 1 cells/section, CIH male 18 ± 4; CON female 5 ± 1, CIH female 6 ± 1) in the MnPO. CIH females showed a trend for an increase in the average number of IBA1 immunoreactive microglial cells in MnPO (CON 187 ± 16, n = 2; CIH 218 ± 18, n = 4). Conclusion: CIH is associated with increased FosB staining in the MnPO of male rats as opposed to female rats which is consistent with our working hypothesis. In addition, FosB positive MnPO neurons also contained NOS1. In female rats, CIH is associated with a trend for an increase in the numbers of IBA1 positive microglia, indicating increased neuroinflammation in females that is independent of hypertension. CIH was associated with increased FosB staining in NOS1 positive MnPO neurons suggesting that they may be contributing to the sustained hypertension reported in male rats. The research is funded by NIH grant RO1 HL155977.