Ovarian leptin signalling regulates NLRP3 inflammasome activation and macrophage infiltration in a cell specific manner
Background: Obesity is associated with increased ovarian inflammation and the establishment of local leptin resistance. We presently investigated the role of leptin signalling on Nod-Like Receptor Protein 3 (NLPR3) inflammasome and macrophage prevalence in the pathophysiology of ovarian failure of obese mice. Methods: We collected ovaries from: (i) diet induced obese (DIO) mice fed chow diet (CD) or high-fat diet (HFD) for 4 or 16 weeks (wk); (ii) mice lacking the long-isoform of leptin receptor (ObRb; db/db); (iii) mice lacking leptin (ob/ob); and (iv) pharmacologically hyperleptinemic (LEPT) mice for protein and mRNA expression analysis. Next, granulosa cells (GCs) from antral follicles isolated from db/db and ob/ob mice were subjected to transcriptome analysis. Results: We observed no changes in the mRNA and protein levels of NLRP3 inflammasome components in the ovaries of db/db mice, as well as in markers of M1 and M2 macrophage infiltration. This contrasted with the downregulation of NLRP3 inflammasome components and M1 markers in ob/ob -/- and 16 wk HFD mice. Transcriptional analysis revealed opposing profiles between genetic models, with genes associated with steroid metabolism and prostaglandin action in db/db mice and genes controlling extracellular matrix in ob/ob mice being downregulated, despite both processes being crucial for follicular development and ovulation. Conclusions: Leptin signalling regulated NLRP3 inflammasome activation and expression of M1 markers in ovaries of obese mice, in an ObRb-dependent and -independent manner. Absence of changes in the expression of leptin signalling and proinflammatory mediators in GCs from db/db and ob/ob mice was associated with impaired folliculogenesis. Overall design: Comparative gene expression  analysis of RNA-seq data for db/db  and ob/ob from granulosa cells: cells were collected from antral follicles after mechanical disruption, and libraries performed by pooling approximately 50 cells together. Wild type (WT) and mutants (MUT) from either leptin receptor b deficient mouse (db) and  leptin deficient mouse (ob) formed the groups: db WT; db MUT; ob WT and ob MUT