Abstract 016: Remodeling of perineuronal nets and astrocyte activation in the mediobasal hypothalamus in obesity-related hypertension

In the brain, astrocytes play a crucial role in maintaining synaptic plasticity. Recent studies have shown that perineuronal nets (PNNs) are essential for astrocyte function by supporting the integrity of the tripartite synapse in the mediobasal hypothalamus (MBH), a key brain region regulating metabolic physiology. However, it remains unclear whether MBH PNNs are dysregulated in the context of long-term high-fat diet (HFD) exposure and whether astrogliosis contributes to altered PNN formation, particularly in obesity-related hypertension. We hypothesized that long-term HFD induces PNN remodeling in association with astrogliosis. To test this, C57BL/6J mice were fed a high-fat (60% kcal from fat, n=3) or control diet (n=4) for 40 weeks. Continuous blood pressure was monitored in week 40 using telemetry probes. Immunofluorescent labeling of glial fibrillary acidic protein (GFAP), a marker of astrogliosis, and Wisteria floribunda agglutinin conjugated to fluorescein isothiocyanate (WFA-FITC), a marker of PNNs, was performed in the arcuate nucleus (ARC) and the ventromedial hypothalamus (VMH), two key regions in the MBH. In HFD mice, mean arterial pressure (115.09 ± 1.95 mmHg vs. 102.06 ± 1.84 mmHg; p <0.05) and heart rate (633.00 ± 4.84 BPM vs. 583.78 ± 9.44 BPM; p <0.05) were significantly elevated. Notably, HFD mice exhibited lower heart rate variability (8.84 ± 0.9 ms vs. 12.9 ± 0.51 ms; p <0.05), suggesting heightened sympathetic and/or reduced parasympathetic activity. Immunofluorescence analyses revealed a significant reduction in the mean fluorescence intensity (MFI) of PNNs (ARC; 5.53 ± 1.46 vs. 24.64 ± 2.83; p <0.0001, VMH; 13.76 ± 3.12 vs. 39.36 ± 5.81; p =0.0008) in HFD mice. In contrast, GFAP intensity was significantly increased (ARC; 43.06 ± 4.34 vs. 19.75 ± 3.59; p =0.0007, VMH; 10.64 ± 2.02 vs 2.86± 1.36; p =0.02) in HFD mice. Astrogliosis upregulates proteolytic enzymes responsible for PNN degradation. Further correlation analyses demonstrated a significant inverse relationship in GFAP and PNN intensity, ARC ( p =0.003) and VMH ( p =0.05), highlighting a potential role of astrogliosis in PNN remodeling within the MBH. In summary, Obesity-related hypertension is associated with reduced PNN integrity and increased astrogliosis in the MBH, and both phenomena are inversely correlated. These results suggest that the astrocyte-PNN interactions may represent a novel pathway for neurogenic hypertension.