Pentraxin 3 deficiency exacerbates lipopolysaccharide-induced inflammation in adipose tissue

Pentraxin 3 (PTX3) has been characterized as a soluble and multifunctional pattern recognition protein in the regulation of innate immune response. However, little is known about its role in adipose tissue inflammation and obesity. Herein, we investigated the role of PTX3 in the regulation of lipopolysaccharide (LPS)-induced inflammation in adipocytes and adipose tissue, as well as high-fat diet (HFD)-induced metabolic inflammation in obesity.

Ptx3 knockdown 3T3-L1 Cells were generated using shRNA for Ptx3 gene and treated with different inflammatory stimuli. For the in vivo studies, Ptx3 knockout mice were treated with 0.3 mg/kg of LPS for 6 h. Adipose tissues were collected for gene and protein expression by qPCR and western blotting, respectively. Ptx3 knockout mice were fed with HFD for 12 week since 6 week of age.

We observed that the expression of PTX3 in adipose tissue and serum PTX3 were markedly increased in response to LPS administration. Knocking down Ptx3 in 3T3-L1 cells reduced adipogenesis and caused a more profound and sustained upregulation of proinflammatory gene expression and signaling pathway activation during LPS-stimulated inflammation in 3T3-L1 adipocytes. In vivo studies showed that PTX3 deficiency significantly exacerbated the LPS-induced upregulation of inflammatory genes and downregulation of adipogeneic genes in visceral and subcutaneous adipose tissue of mice. Accordingly, LPS stimulation elicited increased activation of nuclear factor-κB (NF-κB) and p44/42 MAPK (Erk1/2) signaling pathways in visceral and subcutaneous adipose tissue. The expression of PTX3 in adipose tissue was also induced by HFD, and PTX3 deficiency led to the upregulation of proinflammatory genes in visceral adipose tissue of HFD-induced obese mice.

Our results suggest a protective role of PTX3 in LPS- and HFD-induced sustained inflammation in adipose tissue.