Dioscin

Dioscin,a natural steroidal saponin derived from Dioscorea nipponica Makino, exhibits diverse pharmacological effects, including anti-inflammatory, antioxidant, and anti-apoptotic properties. Recent research highlighted its protective role in cardiovascular and cerebrovascular systems. Dioscin has been shown to inhibit ischemia/reperfusion-induced cardiomyocyte apoptosis, enhance superoxide dismutase activity, and reduce intracellular reactive oxygen species. Resaerchers investigate Dioscin's potential in mitigating sepsis-induced cardiomyopathy (SIC) through the Toll-like receptor 4 (TLR4)/MyD88/p65 signaling pathway.

Figure 1: Depicts the Chemical structure of Dioscin

Dioscin Ameliorates Hemodynamic and Myocardial Damage in SIC Rat Model: Dioscin alleviated LPS-induced changes in SIC rats. Dioscin decreased heart rate (HR) and heart weight index (HWI), while increasing left ventricle ejection fraction (LVEF) and mean arterial blood pressure (MAP) . Additionally, Dioscin improved myocardial tissue damage, characterized by reduced inflammatory cell infiltration and myocardial fiber rupture , and decreased 4-HNE levels , following LPS induction. These findings indicate Dioscin's protective effects on cardiovascular function and myocardial tissue in SIC rats.

Figure 2: Dioscin decreased heart rate (HR) and heart weight index (HWI), increased left ventricle ejection fraction (LVEF) and mean arterial blood pressure (MAP), improved the myocardial tissue damage, and reduced 4‐hydroxy‐2‐nonenal (4‐HNE) level in myocardial tissues of sepsis‐induced cardiomyopathy (SIC) rat model. (A) The chemical structure of Dioscin. (B–E) The SIC rat model was established by intravenous injection of LPS. HR (B), LVEF (C), and MAP (D) of rats were evaluated using the Vevo 2100 imaging system, and then the HWI (E) was detected using the electronic analytical balance. (F–H) Rat myocardial tissues were observed by hematoxylin and eosin staining (F) (under ×100 magnification, scale bar = 100 μm), and the 4‐HNE level in myocardial tissue was detected by immunohistochemistry (G) (under ×40 magnification, scale bar = 100 μm); (H) the quantitative analysis of the 4‐HNE level in myocardial tissue .

Dioscin Modulates Oxidative Stress, Apoptosis, and TLR4 Expression in SIC Rat Model: Dioscin countered LPS-induced changes in SOD, CAT, and GSH activities, and Bcl-2 and Bax levels in SIC rats. Dioscin increased SOD, CAT, and GSH activities  and elevated Bcl-2 levels while decreasing Bax levels , indicating reduced oxidative stress and apoptosis. Additionally, Dioscin mitigated LPS-induced TLR4 upregulation in myocardial tissues , suggesting a link between TLR4 expression and myocardial injury in SIC rats.

Figure: 3. Dioscin reversed the effects of lipopolysaccharide on decreasing superoxide dismutase (SOD), catalase (CAT), and glutathione (GSH) activities and B‐cell lymphoma‐2 (Bcl‐2) level, and increasing Bax and oll‐like receptor 4 (TLR4) levels in sepsis‐induced cardiomyopathy (SIC) rat model. (A–C) The serum samples of SIC rat model were collected, and then the activities of SOD (A), CAT (B), and GSH (C) were assessed using colorimetric assay. (D–G) The levels of Bax and Bcl‐2 (D, E), and TLR4 expression (F, G) in myocardial tissues were determined by Western blot, and glyceraldehyde 3‐phosphate dehydrogenase (GAPDH) was used as an internal control .

Dioscin's Protective Effects on H9c2 Cells Are Attenuated by TLR4 Overexpression: Dioscin reduced TLR4 levels and ROS production, and promoted viability in LPS-induced H9c2 cells. However, overexpressing TLR4 reversed Dioscin's effects on TLR4 expression , cell viability , and ROS production . Specifically, Dioscin decreased TLR4 levels  and increased cell viability in LPS-treated H9c2 cells. Dioscin also reduced ROS production, as evidenced by DHE staining . These findings suggest that Dioscin's protective effects against oxidative stress and cell damage in H9c2 cells are mediated by TLR4 regulation . .Dioscin + NC; n = 3, one‐way analysis of variance was utilized to compare difference among multiple groups, followed by Tukey post hoc test, repeated measures analysis of variance was utilized for multiple measurements of the same group at different conditions as in the figure below.

Figure: 4. Overexpressed toll‐like receptor 4 (TLR4) offset the role of Dioscin in reducing levels of TLR4 and reactive oxygen species (ROS), and enhancing viability of lipopolysaccharide (LPS)‐induced H9c2 cells. (A–F) The H9c2 cells were transfected with overexpressing TLR4 plasmids or its negative control (NC), and the cells were treated with LPS and/or Dioscin for 24 h. TLR4 level was measured by Western blot (A, B) and quantitative real‐time polymerase chain reaction (C), and GAPDH was used as an internal control. The viability of the treated H9c2 cells was tested using MTT assay (D), and the production of ROS was evaluated in treated H9c2 cells by dihydroethidium staining assay (E‐F) (under ×200 magnification.

Overexpressed TLR4 attenuated the roles of Dioscin in elevating SOD, CAT, and GSH activities and Bcl‐2 level, and diminishing the levels of Bax, MyD88, and P‐p65/p65 in LPS‐treated H9c2 cells

Through in vitro assays, researchers proved that LPS obviously inhibited SOD, CAT, and GSH activities in H9c2 cells , while Dioscin enhanced SOD, CAT, and GSH activities in LPS‐induced H9c2 cells .However, overexpressed TLR4 partially counteracted this promoting effect of Dioscin on the activities of SOD, CAT, and GSH . Afterwards, we also examined the expressions of apoptosis‐related factors Bax and Bcl‐2 in LPS‐treated H9c2 cells, and the results of Western blot exhibited that after LPS treatment, the Bax level was notably raised yet Bcl‐2 level was lessened in H9c2 cells ; however, Dioscin reversed the influence of LPS through repressing Bax expression, and boosting Bcl‐2 expression in H9c2 cells. Besides, transfection with plasmids overexpressing TLR4 was demonstrated to mitigate the effects of Dioscin on Bax and Bcl‐2 levels in LPS‐induced H9c2 cells . Meanwhile, researchers  found that LPS overtly elevated MyD88 level and p‐p65/p65 value , whilst Dioscin reversed the promotive effects of LPS on MyD88 expression and p‐p65/p65 value . Importantly, overexpressed TLR4 weakened the influences of Dioscin via promoting MyD88 expression and p‐p65/p65 value in LPS‐induced H9c2 cells). These data hinted that Dioscin was implicated in the oxidative stress of LPS‐induced H9c2 cells by mediating TLR4/MyD88/p65 pathway.

Figure: 5. Overexpressed toll‐like receptor 4 (TLR4) attenuated the impacts of Dioscin upon increasing superoxide dismutase (SOD), catalase (CAT), and glutathione (GSH) activities and B‐cell lymphoma‐2 (Bcl‐2) level, and decreasing Bax, MyD88, and phosphorylated‐p65 (p‐p65)/p65 levels in lipopolysaccharide (LPS)‐induced H9c2 cells. (A–C) The activities of SOD (A), CAT (B), and GSH (C) in the treated H9c2 cells were measured using colorimetric assay. (D, E) The expressions of Bcl‐2 and Bax in treated H9c2 cells were detected by Western blot, and glyceraldehyde 3‐phosphate dehydrogenase (GAPDH) was used as an internal control. (F–H) The expressions of MyD88, p‐p65, and p65 in treated H9c2 cells were quantified by Western blot. GAPDH was used as an internal control, and the p‐p65/p65 value was calculated .

In short, these research studies  demonstrates that Dioscin exerts protective effects against sepsis-induced cardiac injury (SIC) through the TLR4/MyD88/p65 signaling pathway. Dioscin attenuates oxidative stress, inflammation, and cardiomyocyte apoptosis in LPS-induced SIC rat models and H9c2 cells. Specifically, Dioscin reverses LPS-induced changes in hemodynamic parameters, reduces myocardial tissue damage and 4-HNE levels, enhances antioxidant defenses (SOD, CAT, GSH), regulates apoptosis-related factors (Bax, Bcl-2) and Inhibits TLR4 expression and downstream MyD88/p65 signaling. Overall, our reserach provides new insights into Dioscin's protective effects against SIC and highlights its potential as a novel therapeutic agent for treating this complex disease.