Natural Sulfurs Inhibit LPS-Induced Inflammatory Responses through NF-κB Signaling in CCD-986Sk Skin Fibroblasts.

Nipin Sp,Kyoung-Jin Jang,Alexis Rugamba,Jin-Moo Lee,Jong-Chan Park,Dong Young Kang,Se Won Bae,Eun Seong Jo,Hyoung Do Kim

doi:10.3390/life11050427

Abstract

Lipopolysaccharide (LPS)-induced inflammatory response leads to serious damage, up to and including tumorigenesis. Natural mineral sulfur, non-toxic sulfur (NTS), and methylsulfonylmethane (MSM) have anti-inflammatory activity that may inhibit LPS-induced inflammation. We hypothesized that sulfur compounds could inhibit LPS-induced inflammatory responses in CCD-986Sk skin fibroblasts. We used Western blotting and real-time PCR to analyze molecular signaling in treated and untreated cultures. We also used flow cytometry for cell surface receptor analysis, comet assays to evaluate DNA damage, and ELISA-based cytokine detection. LPS induced TLR4 activation and NF-κB signaling via canonical and protein kinase C (PKC)-dependent pathways, while NTS and MSM downregulated that response. NTS and MSM also inhibited LPS-induced nuclear accumulation and binding of NF-κB to proinflammatory cytokines COX-2, IL-1β, and IL-6. Finally, the sulfur compounds suppressed LPS-induced ROS accumulation and DNA damage in CCD-986Sk cells. These results suggest that natural sulfur compounds could be used to treat inflammation and may be useful in the development of cosmetics.

Highlights

The skin is considered the largest organ of the human body, acting as a protective barrier against environmental harms, playing a vital role in pathogen defense, and maintaining homeostasis [1]
We found an increase in TLR4 and NF-κB with 10 ng/mL LPS, while higher concentrations of LPS reduced expression of TLR4 and NF-κB, perhaps being due to the induction of cell death (Figure 1A)
Flow cytometry showed an increase in TLR4 expression in response to LPS, which was reversed by 3 μg/mL non-toxic sulfur (NTS)

Summary

Introduction

The skin is considered the largest organ of the human body, acting as a protective barrier against environmental harms, playing a vital role in pathogen defense, and maintaining homeostasis [1]. A rupture in this system activates the immune response to maintain structural and functional integrity by inducing intercellular molecular signaling and matrix remodeling [2]. Human fibroblasts mediate the inflammatory immune response by producing soluble signals such as growth factors, cytokines, and lipid mediators, as well as producing insoluble regulatory signals such as extracellular matrix proteins [3]. Fibroblasts facilitate wound healing and structural rearrangement by producing soluble inflammatory mediators in the immune response to infections [4,5]. Lipopolysaccharide (LPS) initiates an inflammatory response in non-immune cells by stimulating the innate immune system through the pathogen-associated molecular pattern (PAMP) [7]. It neutralizes bacterial proinflammatory factors to limit the innate inflammatory response, which leads to TLR activation and is used as a treatment approach in bacterial infections of the skin [8]. Studies in RAW264.7 murine macrophage cells have showed that glucosamine, an amino sugar, provides anti-inflammatory activity, inhibiting cyclooxygenase-2 (COX-2) and inducible nitric oxide (iNOS), as well as p38MAP kinase and nuclear transcription factor NF-kappaB (NF-κB), upon stimulation with LPS [9,10]

Results

Discussion

Conclusion