Piragliatin

Efferocytosis is a process whereby macrophages remove apoptotic cells, such as neutrophils, that have accumulated in tissues, which is required for resolution of inflammation. Efferocytosis is impaired in individuals with increasing age and in those with various systemic diseases. Recently, efferocytosis has been reported to be related to the pathogenesis and progression of periodontitis, and enhancement of efferocytosis, especially in the subjects with impaired efferocytosis, was suggested to lead to periodontitis prevention and care. Various anti‐inflammatory ingredients are used in oral care products, but their effect on efferocytosis is unclear. Here, we aimed to identify ingredients contained in oral care products that are effective for efferocytosis regulation.

The ability of dead cells to induce inflammation in human gingival fibroblast (HGF) cells were evaluated by measuring IL‐6 secretion. Six ingredients in oral care products used as anti‐inflammatory agents were evaluated for their effect on efferocytosis using flow cytometry. The expression of various efferocytosis‐related molecules, such as MERTK and LRP1 involved in recognition, and LXRα and ABCA1 that function in metabolism, were measured in RAW264.7 cells with or without ingredient treatment. Rac1 activity, which is related to the uptake of dead cells, was measured using the G‐LISA kit.

Dead cells elicited IL‐6 secretion in HGF cells. Among the six ingredients, GK2 and hinokitiol enhanced efferocytosis activity. GK2 and hinokitiol significantly increased the expression of MERTK and LRP1, and also enhanced LXRα and ABCA1 expression after efferocytosis. Furthermore, they increased Rac1 activity in the presence of dead cells.

Among the six ingredients tested, GK2 and hinokitiol promoted efferocytosis by regulating apoptotic cell recognition, uptake, and metabolism‐related molecules. Efferocytosis upregulation may be one of the mechanisms of GK2 and hinokitiol in the treatment of inflammatory diseases, such as periodontitis.

The effect of low-molecular-weight mimetics of NGF and BDNF (GK-2 and GSB-214 in a dose 0.5 mg/kg, respectively) on malondialdehyde content and activity of an antioxidant defense enzyme glutathione peroxidase was studied in experiments on C57BL/6 mice with streptozotocin-induced diabetes. An increase in the malondialdehyde content indicating enhanced formation of peroxidation products and a decrease of glutathione peroxidase activity in the blood plasma of untreated diabetic animals were revealed. Both studied mimetics were shown to attenuate the severity of these disorders. Since the ability of these compounds to activate the PI3K/Akt signaling pathway was previously demonstrated in vitro on HT-22 cell culture, we studied the effect of LY294002, an inhibitor of this pathway, on the above parameters. It was found that LY294002 attenuates the normalizing effect of GK-2 and GSB-214 only in relation to glutathione peroxidase activity, but not malondialdehyde level.