Let-7 Regulation of Macrophage Differentiation and Inflammatory Response in Normal and Hyperglycaemic Conditions

UoM administered thesis: Phd

  • Authors:
  • Israa Salman

Abstract

Macrophages orchestrate the transition between the key stages of wound healing through their ability to functionally differentiate or polarise towards different phenotypes, mainly pro- lnflammatory (M1) and pro-healing (M2) subtypes. Chronic wounds are characterised by an over- abundance of M1 macrophages that fail to polarise towards an M2 phenotype, particularly in chronic diabetic wounds. The let-7 family of microRNAs have been shown to modulate aspects of macrophage differentiation and behaviour in many biological processes. This project aims to understand the roles of specific let-7 family members in macrophage polarisation, and how differences in their expression and function in a hyperglycaemic or diabetic environment may be involved in the associated changes macrophage polarisation. In two macrophage models, bone marrow-derived macrophages (BMDM) and RAW.264.7 cells, let-7b is found to be the most significantly down-regulated let-7 in M1 macrophages cultured in high glucose media. Our functional studies on Let-7b revealed that its over expression is sufficient to drive macrophages towards an M2 phenotype as indicated by increased M2 and lowered M1 biomarker expression. Let-7b is shown to be involved in controlling aspects of TLR4/NF-kB signalling, the main pathway mediating M1 polarisation. Let-7b is shown to control TLR4, NF- kB (P65), and IL-6 at mRNA and protein levels. Let-7b was also found to be involved in TLR4 endocytosis, NF-kB phosphorylation and nuclear translocation, and direct targeting of Il-6 m- RNA. Moreover, let-7b is found to be involved in modulating a number of M1 behavioural characteristics, such as inhibiting autophagy and promoting phagocytosis. More specifically let-7b can mitigate the effects of hyperglycaemia on M1 inflammatory response and behaviour. This establishes let-7 as a potential therapeutic target for treating prolonged inflammatory conditions like chronic diabetic wounds.

Details

Original languageEnglish
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Award date1 Aug 2021