Protective effect of didymin against 2, 3, 7, 8-tetrachlorodibenzo-p-dioxin-induced reproductive toxicity in male rats

PURPOSE

2, 3, 7, 8-Tetrachlorodibenzo-p-dioxin (TCDD) is one of the most potent environmental toxicants, which causes oxidative stress and adversely affects the male reproductive system. The current study aimed to evaluate the ameliorative role of didymin (DDM) against TCDD-induced testicular toxicity.

METHODS

Forty-eight male Sprague-Dawley rats were divided into four equal groups (n=12). (i) Control group, (ii) TCDD-induced group was provided with 10 μg/kg/day of TCDD, (iii) TCDD + DDM group received 10 μg/kg/day of TCDD and 2 mg/kg/day of DDM, and (iv) DDM-treated group was administered with 2 mg/kg/day of DDM. After 56 days of treatment, biochemical, steroidogenic, hormonal, spermatogenic, apoptotic, and histopathological parameters were estimated.

RESULTS

TCDD affected the biochemical profile by reducing the activities of antioxidant enzymes, while increasing the levels of malondialdehyde (MDA) and reactive oxygen species (ROS). Furthermore, it decreased the expressions of steroidogenic enzymes, 3β-hydroxysteroid dehydrogenase (HSD), 17β-HSD, steroidogenic acute regulatory protein (StAR), cholesterol side-chain cleavage enzyme (CYP11A1), and 17α-hydroxylase/17, 20-lyase (CYP17A1), as well as reduced the levels of follicle-stimulating hormone (FSH), luteinizing hormone (LH), and plasma testosterone. Besides, epididymal sperm count, viability, and motility were decreased, while sperm morphological anomalies were increased. Moreover, TCDD altered the apoptotic profile by up-regulating the expressions of Bax and caspase-3, while downregulated the Bcl-2 expression. Additionally, histopathological damages were prompted due to TCDD administration. However, DDM restored all the TCDD-induced damages owing to its antioxidant, anti-apoptotic, and androgenic potential.

CONCLUSION

Our data suggested that DDM might play its role as a therapeutic agent against TCDD-prompted testicular toxicity.

Didymin protects pancreatic beta cells by enhancing mitochondrial function in high-fat diet-induced impaired glucose tolerance

PURPOSE

Prolonged exposure to plasma free fatty acids (FFAs) leads to impaired glucose tolerance (IGT) which can progress to type 2 diabetes (T2D) in the absence of timely and effective interventions. High-fat diet (HFD) leads to chronic inflammation and oxidative stress, impairing pancreatic beta cell (PBC) function. While Didymin, a flavonoid glycoside derived from citrus fruits, has beneficial effects on inflammation dysfunction, its specific role in HFD-induced IGT remains yet to be elucidated. Hence, this study aims to investigate the protective effects of Didymin on PBCs.

METHODS

HFD-induced IGT mice and INS-1 cells were used to explore the effect and mechanism of Didymin in alleviating IGT. Serum glucose and insulin levels were measured during the glucose tolerance and insulin tolerance tests to evaluate PBC function and insulin resistance. Next, RNA-seq analysis was performed to identify the pathways potentially influenced by Didymin in PBCs. Furthermore, we validated the effects of Didymin both in vitro and in vivo. Mitochondrial electron transport inhibitor (Rotenone) was used to further confirm that Didymin exerts its ameliorative effect by enhancing mitochondria function.

RESULTS

Didymin reduces postprandial glycemia and enhances 30-minute postprandial insulin levels in IGT mice. Moreover, Didymin was found to enhance mitochondria biogenesis and function, regulate insulin secretion, and alleviate inflammation and apoptosis. However, these effects were abrogated with the treatment of Rotenone, indicating that Didymin exerts its ameliorative effect by enhancing mitochondria function.

CONCLUSIONS

Didymin exhibits therapeutic potential in the treatment of HFD-induced IGT. This beneficial effect is attributed to the amelioration of PBC dysfunction through improved mitochondrial function.

Didymin alleviates metabolic dysfunction-associated fatty liver disease (MAFLD) via the stimulation of Sirt1-mediated lipophagy and mitochondrial biogenesis

BACKGROUND

Metabolic dysfunction-associated fatty liver disease (MAFLD) is one of the most prevalent metabolic syndromes worldwide. However, no approved pharmacological treatments are available for MAFLD. Chenpi, one kind of dried peel of citrus fruits, has traditionally been utilized as a medicinal herb for liver diseases. Didymin is a newly identified oral bioactive dietary flavonoid glycoside derived from Chenpi. In this study, we investigated the therapeutic potential of Didymin as an anti-MAFLD drug and elucidated its underlying mechanisms.

METHODS

High-fat diet (HFD)-induced MAFLD mice and alpha mouse liver 12 (AML12) cells were utilized to evaluate the effects and mechanisms of Didymin in the treatment of MAFLD. Liver weight, serum biochemical parameters, and liver morphology were examined to demonstrate the therapeutic efficacy of Didymin in MAFLD treatment. RNA-seq analysis was performed to identify potential pathways that could be affected by Didymin. The impact of Didymin on Sirt1 was corroborated through western blot, molecular docking analysis, microscale thermophoresis (MST), and deacetylase activity assay. Then, a Sirt1 inhibitor (EX-527) was utilized to confirm that Didymin alleviates MAFLD via Sirt1. Western blot and additional assays were used to investigate the underlying mechanisms.

RESULTS

Our results suggested that Didymin may possess therapeutic potential against MAFLD in vitro and in vivo. By promoting Sirt1 expression as well as directly binding to and activating Sirt1, Didymin triggers downstream pathways that enhance mitochondrial biogenesis and function while reducing apoptosis and enhancing lipophagy.

CONCLUSIONS

These suggest that Didymin could be a promising medication for MAFLD treatment. Furthermore, its therapeutic effects are mediated by Sirt1.

Didymin Suppresses Microglia Pyroptosis and Neuroinflammation Through the Asc/Caspase-1/GSDMD Pathway Following Experimental Intracerebral Hemorrhage

Neuroinflammation has been proven to exert an important effect on brain injury after intracerebral hemorrhage (ICH). Previous studies reported that Didymin possessed anti-inflammatory properties after acute hepatic injury, hyperglycemia-induced endothelial dysfunction, and death. However, the role of Didymin in microglial pyroptosis and neuroinflammation after ICH is unclear. The current study aimed to investigate the effect of Didymin on neuroinflammation mediated by microglial pyroptosis in mouse models of ICH and shed some light on the underlying mechanisms. In this study, we observed that Didymin treatment remarkably improved neurobehavioral performance and decreased BBB disruption and brain water content. Microglial activation and neutrophil infiltration in the peri-hematoma tissue after ICH were strikingly mitigated by Didymin as well. At the molecular level, administration of Didymin significantly unregulated the expression of Rkip and downregulated the expression of pyroptotic molecules and inflammatory cytokines such as Nlrp3 inflammasome, GSDMD, caspase-1, and mature IL-1β, TNF-α, and MPO after ICH. Besides, Didymin treatment decreased the number of Caspase-1-positive microglia and GSDMD-positive microglia after ICH. Inversely, Locostatin, an Rkip-specific inhibitor, significantly abolished the anti-pyroptosis and anti-neuroinflammation effects of Didymin. Moreover, Rkip binding with Asc could interrupt the activation and assembly of the inflammasome. Mechanistically, inhibition of Caspase-1 by VX-765 attenuated brain injury and suppressed microglial pyroptosis and neuroinflammation by downregulation of GSDMD, mature IL-1β, TNF-α, and MPO based on Locostatin-treated ICH. Taken together, Didymin alleviated microglial pyroptosis and neuroinflammation, at least in part through the Asc/Caspase-1/GSDMD pathway via upregulating Rkip expression after ICH. Therefore, Didymin may be a potential agent to attenuate neuroinflammation via its anti-pyroptosis effect after ICH.

Didymin switches M1-like toward M2-like macrophage to ameliorate ulcerative colitis via fatty acid oxidation

Inflammatory response by different polarized macrophages has a critical role in a variety of immunological pathophysiology, such as ulcerative colitis (UC). Herein, targeting the paradigm of macrophage phenotypes by small molecular modulators may influence the disease status. In the present study, we firstly demonstrated that didymin, one of the most abundant flavonoid constituents present in the citrus fruits such as oranges and lemons, remarkably attenuated the clinical symptoms of acute and chronic colitis in mice. Mechanistic studies showed that didymin converted pro-inflammatory M1-like to anti-inflammatory M2-like macrophage phenotype, but did not alter the polarization of M2-like macrophages. Metabolic tracing studies revealed that didymin strengthened fatty acid oxidation rather than glycolysis by inducing Hadhb expression. More importantly, in vivo studies verified that promotion of Hadhb expression resulted in the conversion of M1- toward M2-like macrophages and eventually alleviated colitis. Our data highlights the potential of macrophage paradigm in UC inflammation and put forth the stage for considering didymin as a metabolism regulator in reprogramming macrophage polarization, which may serve as a promising therapeutic approach for treatment of inflammation-associated disorders.

In vitro and in vivo evaluation of didymin cyclodextrin inclusion complexes: characterization and chemosensitization activity

Didymin is a dietary flavonoid that first found in citrus fruits, and possesses antioxidant properties. Our preliminary experiments first discovered that didymin was able to sensitize the resistant cancer cells against chemotherapeutics and combat multidrug resistance. However, its poor aqueous solubility and resultant low bioavailability limit its potentials as an adjuvant phytochemical drug for chemotherapy. Thus, this study prepared the inclusion complex of didymin with β-cyclodextrin and 2-hydroxypropyl-β-cyclodextrin to improve its bioavailability and then evaluate their chemosensitization effects. The didymin inclusion complexes formulation was prepared and their host-guest structure was characterized by FT-IR, PXRD, DSC, and SEM techniques. In vitro/in vivo results demonstrated that didymin inclusion complex enhanced its water solubility and orally bioavailability. Furthermore, didymin inclusion complex exerted considerable chemosensitivity potency, and improve the anti-tumor effects of chemotherapeutics in vivo. Therefore, didymin inclusion complex could provide a safe, effective, economical, and adjuvant drug for future treatment of chemoresistant cancers.

Didymin, a dietary citrus flavonoid exhibits anti-diabetic complications and promotes glucose uptake through the activation of PI3K/Akt signaling pathway in insulin-resistant HepG2 cells

Didymin is a naturally occurring orally active flavonoid glycoside (isosakuranetin 7-O-rutinoside) found in various citrus fruits, which has been previously reported to possess a wide variety of pharmacological activities including anticancer, antioxidant, antinociceptive, neuroprotective, hepatoprotective, inflammatory, and cardiovascular. However, there have not been any reports concerning its anti-diabetic potential until now. Therefore, we evaluated the anti-diabetic potential of didymin via inhibition of α-glucosidase, protein tyrosine phosphatase 1B (PTP1B), rat lens aldose reductase (RLAR), human recombinant AR (HRAR), and advanced glycation end-product (AGE) formation inhibitory assays. Didymin strongly inhibited PTP1B, α-glucosidase, HRAR, RLAR, and AGE in the corresponding assays. Kinetic study revealed that didymin exhibited a mixed type inhibition against α-glucosidase and HRAR, while it competitively inhibited PTP1B and RLAR. Docking simulations of didymin demonstrated negative binding energies and close proximity to residues in the binding pocket of HRAR, RLAR, PTP1B and α-glucosidase, indicating that didymin have high affinity and tight binding capacity towards the active site of these enzymes. Furthermore, we also examined the molecular mechanisms underlying the anti-diabetic effects of didymin in insulin-resistant HepG2 cells which significantly increased glucose uptake and decreased the expression of PTP1B in insulin-resistant HepG2 cells. In addition, didymin activated insulin receptor substrate (IRS)-1 by increasing phosphorylation at tyrosine 895 and enhanced the phosphorylations of phosphoinositide 3-kinase (PI3K), Akt, and glycogen synthasekinase-3(GSK-3). Interestingly, didymin reduced the expression of phosphoenolpyruvate carboxykinase and glucose 6-phosphatase, two key enzymes involved in the gluconeogenesis and leading to a diminished glucose production. The results of the present study clearly demonstrated that didymin will be useful for developing multiple target-oriented therapeutic modalities for treatment of diabetes, and diabetes-associated complications.

elegans

Didymin, a type of flavono-o-glycoside compound naturally present in citrus fruits, has been reported to be an effective anticancer agent. However, its effects on stress resistance are unclear. In this study, we treated Caenorhabditis elegans with didymin at several concentrations. We found that didymin reduced the effects of UV stressor on nematodes by decreasing reactive oxygen species levels and increasing superoxide dismutase (SOD) activity. Furthermore, we found that specific didymin-treated mutant nematodes daf-16(mu86) & daf-2(e1370), daf-16(mu86), akt-1(ok525), akt-2(ok393), and age-1(hx546) were susceptible to UV irradiation, whereas daf-2(e1371) was resistant to UV irradiation. In addition, we found that didymin not only promoted DAF-16 to transfer from cytoplasm to nucleus, but also increased both protein and mRNA expression levels of SOD-3 and HSP-16.2 after UV irradiation. Our results show that didymin affects UV irradiation resistance and it may act on daf-2 to regulate downstream genes through the insulin/IGF-1-like signaling pathway.

Didymin by suppressing NF-κB activation prevents VEGF-induced angiogenesis in vitro and in vivo

Although didymin, a dietary flavonoid glycoside from citrus fruits, known to be a potent antioxidant with anti-cancer activities, its role in angiogenesis is not known. In this study, we examined the effect of didymin on VEGF-induced angiogenesis in vitro and in vivo models. Our results suggest that treatment of human umbilical vein endothelial cell (HUVECs) with didymin significantly prevented the VEGF-induced cell proliferation, migration, and invasion. Further, didymin significantly prevented the VEGF-induced endothelial tube formation in culture. Didymin also attenuated the VEGF-induced generation of ROS, activation of NF-κB and the expression of adhesion molecules such as VCAM-1, ICAM-1, and E-selectin in HUVECs. Further, didymin also prevented the VEGF-induced microvessel sprouting in ex vivo mouse aortic rings. Most importantly, didymin significantly prevented the invasion of endothelial cells and formation of blood capillary-like structures in Matrigel plug model of angiogenesis in mice. Thus, our results suggest a novel antiangiogenic efficacy of didymin in addition to its reported anti-cancer properties, which warrant further development of this agent for cancer therapy.

Didymin prevents hyperglycemia-induced human umbilical endothelial cells dysfunction and death

Although didymin, a flavonoid-O-glycosides compound naturally found in the citrus fruits, has been reported to be a potent anticancer agent in the prevention of various cancers, its role in the prevention of cardiovascular complications is unclear. Most importantly, its effect in the prevention of endothelial dysfunction, a pathological process involved in the atherogenesis, is unknown. We have examined the efficacy of didymin in preventing the high glucose (HG; 25 mM)-induced human umbilical vein endothelial cells (HUVECs) dysfunction. Our results indicate that incubation of HUVECs with HG resulted in the loss of cell viability, and pre-incubation of didymin prevented it. Further, didymin prevented the HG-induced generation of reactive oxygen species (ROS) as well as lipid peroxidation product, malondialdehyde. Pretreatment of HUVECs with didymin also prevented the HG-induced decrease in eNOS and increase in iNOS expressions. Further, didymin prevented the HG-induced monocytes cell adhesion to endothelial cells, expressions of ICAM-1 and VCAM-1 and activation of NF-κB. Didymin also prevented the release of various inflammatory cytokines and chemokines in HG-treated HUVECs. In conclusion, our results demonstrate that didymin with its anti-oxidative and anti-inflammatory actions prevents hyperglycemia-induced endothelial dysfunction and death. Thus, it could be developed as a potential natural therapeutic agent for the prevention of cardiovascular complications in diabetes.

Didymin ameliorates hepatic injury through inhibition of MAPK and NF-κB pathways by up-regulating RKIP expression

A flavone was isolated from Origanum vulgare and identified as didymin (O. vulgare didymin, OVD). The protective effect and mechanism of OVD on acute liver injury was then assessed in vivo and in vitro. Our results showed that OVD significantly alleviated CCl₄-induced liver injury in mice and markedly decreased serum ALT and AST activities. OVD treatment significantly reduced CYP2E1 activity, lipid peroxidation level, ROS generation, NO production and pro-inflammatory cytokines (such as TNF-α, IL-6 and IL-1β) in liver tissues and RAW 264.7 cells, but enhanced the hepatic antioxidative enzymes activities. Further study showed that OVD significantly inhibited the NF-κB and MAPK pathways. Interestingly, OVD notably enhanced Raf kinase inhibitor protein (RKIP) expression, and the effects of OVD on histological changes, oxidative stress and inflammation was largely abolished by the RKIP specific inhibitor locostatin. Our findings indicate that OVD can ameliorate CCl₄-induced liver injury, which may be ascribed to its radical scavenging action, antioxidant activity, and modulation of MAPK and NF-κB signaling pathways.