Impact of a long-term high-glucose environment on pro-inflammatory responses in macrophages stimulated with lipopolysaccharide

• Published in: Naunyn-Schmiedeberg's archives of pharmacology 2021-10, Vol.394 (10), p.2129-2139
• Main Authors: Suzuki, Tokiko, Yamashita, Shigeyuki, Hattori, Kohshi, Matsuda, Naoyuki, Hattori, Yuichi
• Format: Article
• Language: English
• Subjects: Acetylcysteine; Animals; Antioxidants; Biomedical and Life Sciences; Biomedicine; Cytokines - metabolism; Diabetes mellitus (non-insulin dependent); Glucose; Glucose - pharmacology; Heme Oxygenase-1 - metabolism; Hyperglycemia; Hyperglycemia - chemically induced; Hyperglycemia - metabolism; Inflammation; Inflammation - chemically induced; Inflammation - metabolism; Insulin; Interleukin 6; Lipopolysaccharides; Lipopolysaccharides - pharmacology; Macrophages; Membrane Proteins - metabolism; Mice; Neurosciences; NF-E2-Related Factor 2 - metabolism; NF-kappa B - metabolism; NF-κB protein; Nitric oxide; Nitric Oxide - metabolism; Nitric Oxide Synthase Type II - metabolism; Nitric-oxide synthase; Original Article; Pharmacology/Toxicology; RAW 264.7 Cells; Reactive oxygen species; Reactive Oxygen Species - metabolism
• ISSN: 0028-1298; 1432-1912
• DOI: 10.1007/s00210-021-02137-8

Cumulative evidence has established that macrophages orchestrate inflammatory responses that crucially contribute to the pathogenesis of insulin-resistant obesity and type 2 diabetes. In the present study, we examined the impact of hyperglycemia on macrophage pro-inflammatory responses under an inflammatory stimulus. To conduct this study, RAW264.7 macrophages were cultured under normal- (5.5 mM) or high-glucose (22 or 40 mM) conditions for 7 days and stimulated with lipopolysaccharide (LPS). Long-term exposure to high glucose significantly enhanced the increase in the production of pro-inflammatory cytokines, including tumor necrosis-α, interleukin (IL)-1β, and IL-6, when macrophages were stimulated with LPS. The LPS-induced increases in inducible nitric oxide (NO) synthase (iNOS) expression and NO production were also significantly enhanced by long-term exposure of macrophages to high glucose. Treatment with N -acetyl- l -cysteine, a widely used thiol-containing antioxidant, blunted the enhancement of the LPS-induced upregulation of pro-inflammatory cytokine production, iNOS expression, and NO production in macrophages. When intracellular reactive oxygen species (ROS) were visualized using the fluorescence dye 5-(and-6)-chloromethyl-2′,7′-dichlorofluorescein diacetate, acetyl ester, a significant increase in ROS generation was found after stimulation of macrophages with LPS, and this increased ROS generation was exacerbated under long-term high-glucose conditions. LPS-induced translocation of phosphorylated nuclear factor-κB (NF-κB), a transcription factor regulating many pro-inflammatory genes, into the nucleus was promoted under long-term high-glucose conditions. Altogether, the present results indicate that a long-term high-glucose environment can enhance activation of NF-κB in LPS-stimulated macrophages possibly due to excessive ROS production, thereby leading to increased macrophage pro-inflammatory responses.