ABSTRACT
Previously, we discovered that cells contain a 5-hydroxytryptamine (5-HT) degradation system (5DS), which includes 5-HT2A receptor (5-HT2AR), 5-HT synthase, and monoamine oxidase A (MAO-A). Among these, 5-HT2AR has the ability to regulate the expression of 5-HT synthase and MAO-A, and activation of 5DS causes upregulation of these proteins at the same time, resulting in the production of reactive oxygen species (ROS) in the mitochondria. In this study, we investigated the relationship between interstitial pneumonia (IP) and 5DS activation, as well as the therapeutic effect of inhibiting 5DS on IP. Animal models of bleomycin (BLM)-induced IP in mice and radiation (Rad)-induced IP in rats were established, and the models were treated with the 5-HT2AR antagonist sarpogrelate hydrochloride (SH), 5-HT synthesis inhibitor carbidopa (CDP), and their combination (SH∶CDP = 2∶1). The animal experiments were carried out in accordance with the regulations of the Animal Ethics Committee of China Pharmaceutical University. In the two IP models, immunohistochemistry staining and Western blot analysis showed that the expression of 5-HT synthase was significantly upregulated in all cells of lung tissue, while the expression of 5-HT2AR and MAO-A was most significantly upregulated in the macrophages. Treatment with SH or CDP significantly reduced pulmonary interstitial thickening, alveolar atrophy with collapse, massive macrophage infiltration and interstitial fibrosis in the two IP models, as measured by HE and Masson staining, and a combination of both almost eliminated the lung tissue lesions. Moreover, treatment with the combination of SH and CDP almost completely eliminated increased ROS and malondialdehyde levels, decreased superoxide dismutase activity, increased tumor necrosis factor-α and interleukin-1β levels, and upregulated nuclear factor-κB phosphorylation and α-smooth muscle actin, matrix metalloproteinase-2, and collagen expression. SH and CDP worked together to create a synergistic effect. The findings suggested that the activation of 5DS, as evidenced by increased 5-HT synthesis in all cells of lung tissue and increased 5-HT synthesis and degradation in macrophages, is probably related to the occurrence of IP and that inhibition of 5DS can effectively treat IP.
ABSTRACT
Hyperglycemic kidney injury (HKI) is a common complication of diabetic patients. We examined the relationship between HKI and the abnormal expression of 5-hydroxytryptamine (5-HT) system induced by hyperglycemia in type 2 diabetes mellitus (T2DM). In animal experiments, a T2DM model was established in mice by feeding a high-fat diet with intraperitoneal injection of streptozotocin. The mice were treated with the 5-HT2A receptor (5-HT2AR) antagonist sarpogrelate hydrochloride (SH) and 5-HT synthesis inhibitor carbidopa (CDP) (respectively or in combination). In cell culture experiments, human glomerular mesangial cells (HMC) were stimulated with D-glucose (D-Glu), and 5-HT2AR, 5-HT synthesis, and 5-HT degradation were inhibited by SH, CDP, or monoamine oxidase A (MAO-A) inhibitor clorgyline. Periodic acid-Schiff (PAS) staining and Masson staining, immunohistochemistry and Western blot, fluorescent probe, and enzyme linked immunosorbent assay (ELISA) and enzyme reagent were respectively used to detect histopathology, protein expression, intracellular reactive oxygen species (ROS), and biochemical indexes. The animal experiments were in accordance with the regulations of the Animal Ethics Committee of China Pharmaceutical University. The results showed that 5-HT2AR, 5-HT synthases, and MAO-A were expressed in glomerular basement membrane and kidney tubular epithelial cells of mouse kidney and HMC. The expression of these proteins was significantly up-regulated in T2DM mice or when HMC cells were exposed to high concentration of D-Glu. HKI, characterized by abnormal renal function, glomerular swelling, and glomerular basement membrane thickening and fibrosis, is closely associated with an increase in kidney 5-HT2AR, 5-HT synthesis, and 5-HT degradation. Among them, 5-HT2AR can mediate the expression of 5-HT synthases and MAO-A; MAO-A can catalyze the degradation of 5-HT to increase the production of mitochondrial ROS, leading to the phosphorylation of nuclear factor kappa B (NF-κB) with the production of inflammatory cytokines, and the up-regulation of matrix metalloproteinase-2 (MMP-2) and α-smooth muscle actin (α-SMA) with the production of collagens. SH and CDP can effectively treat HKI, and the combination of SH and CDP has a clear synergistic effect.
ABSTRACT
Fatigue is a common complication of type 2 diabetes mellitus (T2DM). We examined the relationship between T2DM fatigue and the skeletal muscle 5-hydroxytryptamine (5-HT) system. In animal experiments, a T2DM model was established in mice by feeding a high-fat diet with intraperitoneal injection of streptozotocin. The mice were treated with the 5-HT2A receptor antagonist sarpogrelate hydrochloride (SH) and the 5-HT synthesis inhibitor carbidopa (CDP) (separately and in combination). In cell culture experiments, C2C12 cells were stimulated with D-glucose, palmitic acid or 5-HT. 5-HT2AR, 5-HT synthesis and 5-HT degradation were inhibited by SH, CDP, or monoamine oxidase A (MAO-A) inhibitor. The animal experiments were in accordance with the regulations of the Animal Ethics Committee of China Pharmaceutical University. The results showed that 5-HT2AR, 5-HT synthase and MAO-A were expressed in mouse skeletal muscle and C2C12 cells. The expression of these proteins was significantly up-regulated in T2DM mice or when C2C12 cells were exposed to palmitic acid and D-glucose; palmitic acid was a stronger stimulant of their expression than D-glucose. Rotating rod experiments and biochemical index tests have shown that T2DM fatigue is associated with an increase in skeletal muscle 5-HT2AR, 5-HT synthesis and 5-HT degradation. 5-HT2AR mediates the expression of MAO-A and the synthesis of 5-HT, which indirectly regulates the degradation of 5-HT. MAO-A regulates cell inflammation, mitochondrial ROS production and membrane potential depolarization by mediating 5-HT degradation. MAO-A also inhibits the expression of peroxisome proliferator-activated receptor γ coactivator-1 (PGC-1), carnitine palmitoyltransferase-1 (CPT1) and ATP synthase-6 (ATP6), thus inhibiting mitochondrial functions such as fatty acid β oxidation and ATP synthesis. SH and CDP can effectively treat T2DM fatigue, and can also reduce blood glucose and blood lipid, and the combination of SH and CDP has a clear synergistic effect.