Blocking the LncRNA MALAT1/miR-224-5p/NLRP3 Axis Inhibits the Hippocampal Inflammatory Response in T2DM With OSA.

Ping Du,Yelei Han,Jing Feng,Jiahui Wang

doi:10.3389/fncel.2020.00097

Abstract

Studies have shown that diabetes can cause cognitive dysfunction, and cognitive dysfunction in patients with diabetes combined with obstructive sleep apnea (OSA) is more severe. LncRNAs are known to be associated with type 2 diabetes mellitus (T2DM) with OSA. This study aimed to investigate the role and underlying mechanism of the lncRNA MALAT1/miR-224-5p/NLRP3 axis in T2DM with OSA. qRT-PCR was used to quantify the expression of MALAT1, miR-224-5p, and NLRP3 in brain tissues. NLRP3 expression was assessed by immunohistochemistry (IHC) and immunofluorescent labeling. The interaction involving MALAT1, miR-224-5p, and NLRP3 was evaluated by transfection. Western blotting was utilized to evaluate the expression levels of the pathway-related proteins NLRP3, caspase 1, tumor necrosis factor-α (TNF-α) and interleukin-1 β (IL-1β) both in vitro and in vivo. qRT-PCR was used to assess the mRNA expression levels of NLRP3, caspase 1, TNF-α and IL-1β both in vitro and in vivo. In brain tissues of T2DM with OSA, MALAT1 and NLRP3 were overexpressed, while miR-224-5p was downregulated, which was consistent with subsequent cell experiments. We screened the miRNAs that could bind to MALAT1 and NLRP3 by the StarBase database and the TargetScanMouse7.2 website. Our research showed that among these miRNAs, the level of miR-224-5p was most significantly negatively correlated with the levels of MALAT1 and NLRP3. Also, a firefly luciferase assay showed that miR-224-5p, which is a target of MALAT1, directly reduced the expression of the downstream protein NLRP3. Overexpression of miR-224-5p significantly inhibited the expression levels of NLRP3, caspase 1, TNF-α and IL-1β in vitro. MALAT1 promoted NLRP3 expression by acting as a competing endogenous RNA and sponging miR-224-5p. MiR-224-5p reduces microglial inflammation activation through the regulation of NLRP3 expression, which ultimately affected the NLRP3/IL-1β pathway in the hippocampus. This suggests that miR-224-5p may serve as a potential target for T2DM and OSA therapy.

Highlights

Obstructive sleep apnea (OSA) is a common disease that is characterized by recurrent upper airway obstruction during sleep, resulting in intermittent hypoxia (IH; Franklin and Lindberg, 2015)
The results showed that tumor necrosis factor-α (TNF-α) and interleukin-1 β (IL-1β) both increased in the C57+IH group and the KK group compared to the C57 control group
To reveal the roles of MALAT1, NLRP3 and miR-224-5p and their relationship in the type 2 diabetes mellitus (T2DM) with the OSA model, the expression of MALAT1 and miR-224-5p in normal C57 mice, C57 mice exposed to IH, KKAy mice and KKAy mice exposed to IH was analyzed by qRT-PCR

Summary

Introduction

Obstructive sleep apnea (OSA) is a common disease that is characterized by recurrent upper airway obstruction during sleep, resulting in intermittent hypoxia (IH; Franklin and Lindberg, 2015). OSA patients are considered to be a potential risk for developing metabolic syndrome (Basta and Vgontzas, 2007). Studies have shown that diabetes can cause cognitive dysfunction in the brain, and cognitive dysfunction in patients with diabetes and OSA is more severe. The main cause of cognitive dysfunction is the irreversible damage to neurons in the hippocampus of the brain (Hicks et al, 1993). Our team studied the activation of glial cells in the hippocampus and released HMGB1 to act on neuronal cells, causing neuronal damage and resulting in learning and cognitive dysfunction (Shi et al, 2018).

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