Melatonin attenuates glandular cystitis via modulation of THBS1 and TLR4/p38 MAPK/STAT3 signaling

Melatonin (MEL) is a natural hormone widely found in animals and humans. A multitude of studies have illustrated MEL exerts anti-inflammatory impacts on diverse organs. However, it remains unclear how MEL plays a role in glandular cystitis (GC) at present. We investigated how MEL affected GC through thrombospondin-1 (THBS1). MEL was employed to treat human bladder epithelial cells (SV-HUC-1) subsequent to their stimulation by lipopolysaccharide (LPS). Subsequently, the expression levels of inflammatory factors in human bladder epithelial cells under different treatment methods were measured. We perfused LPS into the bladders of rats once every three days for eight consecutive weeks. The rats belonging to the treatment group underwent a four-week treatment regimen with MEL (10 mg/kg). Ultimately, we meticulously detected the expression levels of Toll-like receptor 4 (TLR4), Nuclear Factor κB p65 Subunit (NF-κB p65), p38 Mitogen-Activated Protein Kinase (p38 MAPK) as well as Signal Transducer and Activator of Transcription 3 (STAT3). Additionally, to gain deeper insights, further proteomic analysis was conducted, which was expected to disclose more detailed molecular mechanisms. In vitro, we found that LPS had a remarkable effect on human bladder epithelial cells, significantly augmenting the expression levels of several key inflammatory factors. Specifically, the expressions of interleukin 1β (IL-1β), interleukin 6 (IL-6), interleukin 10 (IL-10), and tumor necrosis factor alpha (TNF-α) were noticeably enhanced after LPS stimulation. Meanwhile, the expression of key molecules in related signaling pathways—including TLR4, NF-κB p65, p38 MAPK, p-p38, STAT3 and p-STAT3—also increase significantly. Similar results were observed in a rat model of GC as well. After treatment with MEL, the expressions of the inflammatory factors decreased, and the expressions of various signaling pathways also decreased accordingly. According to our proteomics analysis, THBS1 might be an important protein involved in the progression of GC. MEL is able to reduce the expression of THBS1, leading to the alleviation of the inflammation of GC. MEL reduces the inflammatory response in GC by regulating the TLR4/p38 MAPK/STAT3 axis. THBS1 plays a critical role in promoting the progression of GC, and this finding provides a new perspective for understanding the molecular mechanisms of GC or identifying potential therapeutic targets for GC.