Chronic Intermittent Hypoxia Regulates CaMKII-Dependent MAPK Signaling to Promote the Initiation of Abdominal Aortic Aneurysm

Tanshinone IIA inhibited intermittent hypoxia induced neuronal injury through promoting autophagy via AMPK-mTOR signaling pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Chronic intermittent hypoxia (CIH) is the primary pathophysiological process of obstructive sleep apnea (OSA) and is closely linked to neurocognitive dysfunction. Tanshinone IIA (Tan IIA) is extracted from Salvia miltiorrhiza Bunge and used in Traditional Chinese Medicine (TCM) to improve cognitive impairment. Studies have shown that Tan IIA has anti-inflammatory, anti-oxidant, and anti-apoptotic properties and provides protection in intermittent hypoxia (IH) conditions. However, the specific mechanism is still unclear.

AIM OF THE STUDY

To assess the protective effect and mechanism of Tan IIA treatment on neuronal injury in HT22 cells exposed to IH.

MATERIALS AND METHODS

The study established an HT22 cell model exposed to IH (0.1% O₂ 3 min/21% O₂ 7 min for six cycles/h). Cell viability was determined using the Cell Counting Kit-8, and cell injury was determined using the LDH release assay. Mitochondrial damage and cell apoptosis were observed using the Mitochondrial Membrane Potential and Apoptosis Detection Kit. Oxidative stress was assessed using DCFH-DA staining and flow cytometry. The level of autophagy was assessed using the Cell Autophagy Staining Test Kit and transmission electron microscopy (TEM). Western blot was used to detect the expressions of the AMPK-mTOR pathway, LC3, P62, Beclin-1, Nrf2, HO-1, SOD2, NOX2, Bcl-2/Bax, and caspase-3.

RESULTS

The study showed that Tan IIA significantly improved HT22 cell viability under IH conditions. Tan IIA treatment improved mitochondrial membrane potential, decreased cell apoptosis, inhibited oxidative stress, and increased autophagy levels in HT22 cells under IH conditions. Furthermore, Tan IIA increased AMPK phosphorylation and LC3II/I, Beclin-1, Nrf2, HO-1, SOD2, and Bcl-2/Bax expressions, while decreasing mTOR phosphorylation and NOX2 and cleaved caspase-3/caspase-3 expressions.

CONCLUSION

The study suggested that Tan IIA significantly ameliorated neuronal injury in HT22 cells exposed to IH. The neuroprotective mechanism of Tan IIA may mainly be related to inhibiting oxidative stress and neuronal apoptosis by activating the AMPK/mTOR autophagy pathway under IH conditions.

Identification of Novel Biomarkers for Abdominal Aortic Aneurysm Promoted by Obstructive Sleep Apnea

BACKGROUND

We sought to find new biomarkers for abdominal aortic aneurysms (AAA) caused by chronic intermittent hypoxia (CIH).

METHODS

The AAA mice model was created using Ang II. The mice were divided into normoxic and CIH groups. The structure of AAA was observed using abdominal ultrasonography, Elastica van Gieson (EVG), and hematoxylin and eosin (HE) staining. The expression of ɑ-SMA was investigated using immunohistochemistry. The novel biomarkers were screened using bioinformatics analysis. Quantitative real-time polymerase chain reaction (qRT-PCR) was employed to verify the expression of novel genes in both normal oxygen and CIH.

RESULTS

CIH appears to cause greater aortic dilation, higher AAA incidence, lower survival rate, thicker vessel wall, and more brittle elastic lamellae when compared to controls. The immunohistochemistry results showed that the expression of ɑ-SMA in the CIH group was reduced significantly. Four novel genes, including Homer2, Robo2, Ehf, and Asic1, were found to be differentially expressed between normal oxygen and CIH using qRT-PCR, indicating the same trend as bioinformatics analysis.

CONCLUSIONS

We discovered that CIH could hasten the occurrence and progression of AAA. Four genes (Homer2, Robo2, Ehf, and Asic1) may be novel biomarkers for AAA, which could aid in the search for new therapies for patients with AAA caused by CIH.

Protective effect of Astragaloside IV on chronic intermittent hypoxia-induced vascular endothelial dysfunction through the calpain-1/SIRT1/AMPK signaling pathway

Vascular endothelial dysfunction (VED) is linked with the pathogenesis of obstructive sleep apnea (OSA) comorbidities, such as cardiovascular disease. Astragaloside IV (As-IV) has exhibited significant improvement for endothelial dysfunction. Nonetheless, the protective mechanism is not clear. Therefore, the present study investigated the potential mechanism of As-IV on VED. Calpain-1 knockout and wild-type C57BL/6 mice exposed to chronic intermittent hypoxia (CIH) were established and treated with As-IV (40, 80 mg/kg) for 4 weeks. Human coronary artery endothelial cells (HCAECs) subjected to CIH exposure were pretreated with As-IV, MDL-28170 (calpain-1 inhibitor) and SRT1720 (SIRT1 activator) for 48 h in vitro. The endothelial function, inflammation, oxidative stress and mitochondrial function were measured to evaluate VED. Our data revealed that As-IV treatment ameliorated CIH-induced endothelial-dependent vasomotion and augmented nitric oxide (NO) production. As-IV administration suppressed the secretion of inflammation, oxidative stress and mitochondrial dysfunction. As-IV treatment reduced the expression of calpain-1 and restored the downregulated expression of SIRT1 and Thr¹⁷² AMPK and Ser¹¹⁷⁷ eNOS phosphorylation. The effects of calpain-1 knockout and SRT1720 were similar to the effect of As-IV on VED. These findings demonstrated that As-IV ameliorated VED induced by chronic intermittent hypoxia via the calpain-1/SIRT1/AMPK signaling pathway.

Impact of obstructive sleep apnea on aortic disease occurrence: a meta-analysis

Objective

Aortic diseases, mainly including aortic dilatation, aortic aneurysm (AA) and aortic dissection (AD), have high morbidity and mortality. Many studies have suggested that obstructive sleep apnea (OSA) acts as a candidate risk factor for aortic diseases. Thus, we performed a meta-analysis to explore comprehensively the effect of OSA on the risk of aortic disease occurrence.

Methods

We searched PubMed, Embase and Cochrane Library databases from inception to February 2022 to identify studies investigating the association between OSA and aortic diameter dilatation, the prevalence of OSA in individuals with or without AA/AD and the incidence of AA/AD in individuals with or without OSA. The Newcastle-Ottawa Scale (NOS) and the Agency for Healthcare Research and Quality (AHRQ) were respectively used to evaluate the quality of the included cohort and cross-sectional studies. A random or fixed effect model was used to generate pooled effects according to interstudy heterogeneity. Sensitivity analyses were performed to test the robustness of the results.

Results

We identified 10 observational publications with 214,127 participants in this meta-analysis. OSA was significantly associated with increased aortic diameter (WMD = 1.46, 95% CI, 1.10–1.83, p < 0.001). OSA prevalence was higher in patients with AA/AD compared to their counterparts without AA/AD (OR = 1.90, 95% CI, 1.30–2.76, p = 0.001). No significant difference in the incidence of AA/AD was observed in individuals with or without OSA (RR = 0.85, 95% CI, 0.62–1.16, p = 0.307). Sensitivity analyses did not modify these results.

Conclusions

This meta-analysis suggests that OSA is associated with aortic diameter dilatation but does not affect AA/AD occurrence.

Severe Intermittent Hypoxia Modulates the Macrophage Phenotype and Impairs Wound Healing Through Downregulation of HIF-2α

BACKGROUND

Obstructive sleep apnea is prevalent in patients with diabetic foot ulcers, while the effect of intermittent hypoxia on wound healing is unclear. The objective of this study was to investigate the effect of severe intermittent hypoxia on wound healing.

METHODS

C57BL/6 mice were exposed to 5 weeks of severe intermittent hypoxia or normoxia. The wound healing rate were assessed. The gene expression of CD206 and HIF-2α was tested in vivo and in vitro. Inflammatory factors in RAW264.7 macrophages were measured to investigate the effect of intermittent hypoxia on macrophage polarization. The proliferation of HUVECs and HaCaT cells was also assessed after exposure to intermittent hypoxia.

RESULTS

Severe intermittent hypoxia decreased wound healing at day 3. The expression of CD206 and HIF-2α was significantly decreased after exposure to severe intermittent hypoxia. In vitro, severe intermittent hypoxia significantly promoted M1 phenotype polarization of RAW264.7 macrophages and increased the expression of proinflammatory factors (IL-1β and TNF-α). Severe intermittent hypoxia also decreased the proliferation of HUVECs cultured in endothelial cell medium and HaCaT cells cultured in high glucose DMEM.

CONCLUSION

Severe intermittent hypoxia could lead to M1 but not M2 macrophage polarization through downregulation of HIF-2α, and then lead to impaired wound healing.