Diosgenin Protects Against Kidney Injury and Mitochondrial Apoptosis Induced by 3-MCPD Through the Regulation of ER Stress, Ca2+ Homeostasis, and Bcl2 Expression

Calcium signaling crosstalk between the endoplasmic reticulum and mitochondria, a new drug development strategies of kidney diseases

Calcium (Ca2+) acts as a second messenger and constitutes a complex and large information exchange system between the endoplasmic reticulum (ER) and mitochondria; this process is involved in various life activities, such as energy metabolism, cell proliferation and apoptosis. Increasing evidence has suggested that alterations in Ca2+ crosstalk between the ER and mitochondria, including alterations in ER and mitochondrial Ca2+ channels and related Ca2+ regulatory proteins, such as sarco/endoplasmic reticulum Ca2+-ATPase (SERCA), inositol 1,4,5-trisphosphate receptor (IP3R), and calnexin (CNX), are closely associated with the development of kidney disease. Therapies targeting intracellular Ca2+ signaling have emerged as an emerging field in the treatment of renal diseases. In this review, we focused on recent advances in Ca2+ signaling, ER and mitochondrial Ca2+ monitoring methods and Ca2+ homeostasis in the development of renal diseases and sought to identify new targets and insights for the treatment of renal diseases by targeting Ca2+ channels or related Ca2+ regulatory proteins.

Diosgenin Targets CaMKK2 to Alleviate Type II Diabetic Nephropathy through Improving Autophagy, Mitophagy and Mitochondrial Dynamics

Diabetic nephropathy (DN) is a worldwide health problem with increasing incidence. Diosgenin (DIO) is a natural active ingredient extracted from Chinese yams (Rhizoma dioscoreae) with potential antioxidant, anti-inflammatory, and antidiabetic effects. However, the protective effect of DIO on DN is still unclear. The present study explored the mitigating effects and underlying mechanisms of DIO on DN in vivo and in vitro. In the current study, the DN rats were induced by a high-fat diet and streptozotocin and then treated with DIO and metformin (Mef, a positive control) for 8 weeks. The high-glucose (HG)-induced HK-2 cells were treated with DIO for 24 h. The results showed that DIO decreased blood glucose, biomarkers of renal damage, and renal pathological changes with an effect comparable to that of Mef, indicating that DIO is potential active substance to relieve DN. Thus, the protective mechanism of DIO on DN was further explored. Mechanistically, DIO improved autophagy and mitophagy via the regulation of the AMPK-mTOR and PINK1-MFN2-Parkin pathways, respectively. Knockdown of CaMKK2 abolished AMPK-mTOR and PINK1-MFN2-Parkin pathways-mediated autophagy and mitophagy. Mitophagy and mitochondrial dynamics are closely linked physiological processes. DIO also improved mitochondrial dynamics through inhibiting fission-associated proteins (DRP1 and p-DRP1) and increasing fusion proteins (MFN1/2 and OPA1). The effects were abolished by CaMKK2 and PINK1 knockdown. In conclusion, DIO ameliorated DN by enhancing autophagy and mitophagy and by improving mitochondrial dynamics in a CaMKK2-dependent manner. PINK1 and MFN2 are proteins that concurrently regulated mitophagy and mitochondrial dynamics.

Endoplasmic reticulum stress in diabetic kidney disease: adaptation and apoptosis after three UPR pathways

Diabetes kidney disease (DKD) is one of the common chronic microvascular complications of diabetes, which has become the most important cause of modern chronic kidney disease beyond chronic glomerulonephritis. The endoplasmic reticulum is one of the largest organelles, and endoplasmic reticulum stress (ERS) is the basic mechanism of metabolic disorder in all organs and tissues. Under the stimulation of stress-induced factors, the endoplasmic reticulum, as a trophic receptor, regulates adaptive and apoptotic ERS through molecular chaperones and three unfolded protein reaction (UPR) pathways, thereby regulating diabetic renal damage. Therefore, three pathway factors have different expressions in different sections of renal tissues. This study deeply discussed the specific reagents, animals, cells, and clinical models related to ERS in DKD, and reviewed ERS-related three pathways on DKD with glomerular filtration membrane, renal tubular reabsorption, and other pathological lesions of different renal tissues, as well as the molecular biological mechanisms related to the balance of adaption and apoptosis by searching and sorting out MeSH subject words from PubMed database.

Research progress of diosgenin extraction from Dioscorea zingiberensis C. H. Wright: Inspiration of novel method with environmental protection and efficient characteristics

Diosgenin was the starting materials to synthesize various hormone drugs and mainly generated from Dioscorea zingiberensis C. H. Wright by acidolysis, enzymolysis, microbiological fermentation, and integrated manner. Only acidic hydrolysis with strong acid such as hydrochloric acid or sulfuric acid was used in practice in diosgenin enterprises due to their feasibility and simplicity, nevertheless finally resulting in a great deal of unmanageable wastewater and severely polluted the surrounding environment. Aiming to provide a comprehensive and up-to date information of researches on diosgenin production from this plant, 151 cases were collected from scientific databases including Web of Science, Pubmed, Science Direct, Wiley, Springer, and China Knowledge Resource Integrated (CNKI). Their advantages and disadvantages with different production methods were analyzed based on these available data in this review paper. Considering the fact that nearly all of diosgenin enterprises were closed for the environmental protection and the life health of the people, this review paper was beneficial for providing useful guidelines to develop novel technologies with environmentally-friendly and cleaner features for diosgenin production or facilitate the transformation of other methods like enzymolysis, microbiological fermentation, or integrated methods from laboratory scale to industry scale.

Anticancer Activity of Diosgenin and Its Molecular Mechanism

Diosgenin, a steroidal sapogenin, obtained from Trigonella foenum-graecum, Dioscorea, and Rhizoma polgonati, has shown high potential and interest in the treatment of various cancers such as oral squamous cell carcinoma, laryngeal cancer, esophageal cancer, liver cancer, gastric cancer, lung cancer, cervical cancer, prostate cancer, glioma, and leukemia. This article aims to provide an overview of the in vivo, in vitro, and clinical studies reporting the diosgenin's anticancer effects. Preclinical studies have shown promising effects of diosgenin on inhibiting tumor cell proliferation and growth, promoting apoptosis, inducing differentiation and autophagy, inhibiting tumor cell metastasis and invasion, blocking cell cycle, regulating immunity and improving gut microbiome. Clinical investigations have revealed clinical dosage and safety property of diosgenin. Furthermore, in order to improve the biological activity and bioavailability of diosgenin, this review focuses on the development of diosgenin nano drug carriers, combined drugs and the diosgenin derivatives. However, further designed trials are needed to unravel the diosgenin's deficiencies in clinical application.

3-MCPD exposure enhances ovarian fibrosis and reduces oocyte quality in mice

3-monochloro-1,2-propanediol (3-MCPD) is a food contaminant believed to be harmful to human health. Previous studies showed that 3-MCPD exerts toxic effects in multiple tissues, but whether 3-MCPD affects female reproductive function remained unknown. Here, using mouse gastric lavage models, we report that 3-MCPD exposure for four weeks affected body growth, decreased the ovary/body weight ratio, and increased atretic follicle numbers. Expression levels of follicular development-related factors decreased. Further studies found that ovaries from 3-MCPD exposed mice had activated the Transforming Growth Factor-β (TGF-β) signaling pathway and promoted ovarian fibrosis. Increased TNF-α, IL-1 and NF-κB expression also indicated the occurrence of ovarian inflammation. Exposure to 3-MCPD stimulated the caspase pathway and enhanced granulosa cell apoptosis. Consistent with disrupted ovarian homeostasis, 3-MCPD exposure interfered with mitochondrial function, generated more reactive oxygen species, increased ferrous ion and lipid peroxidation levels, and resulted in decreased oocyte development potential. Collectively, these findings indicated that 3-MCPD exposure induced ovarian inflammation and fibrosis, and caused disorders of mitochondrial function and ferrous ion homeostasis in oocytes, which consequently disturbed follicle maturation and reduced oocyte quality.

GRP75 Modulates Endoplasmic Reticulum-Mitochondria Coupling and Accelerates Ca2+-Dependent Endothelial Cell Apoptosis in Diabetic Retinopathy

Endoplasmic reticulum (ER) and mitochondrial dysfunction play fundamental roles in the pathogenesis of diabetic retinopathy (DR). However, the interrelationship between the ER and mitochondria are poorly understood in DR. Here, we established high glucose (HG) or advanced glycosylation end products (AGE)-induced human retinal vascular endothelial cell (RMEC) models in vitro, as well as a streptozotocin (STZ)-induced DR rat model in vivo. Our data demonstrated that there was increased ER-mitochondria coupling in the RMECs, which was accompanied by elevated mitochondrial calcium ions (Ca²⁺) and mitochondrial dysfunction under HG or AGE incubation. Mechanistically, ER-mitochondria coupling was increased through activation of the IP3R1-GRP75-VDAC1 axis, which transferred Ca²⁺ from the ER to the mitochondria. Elevated mitochondrial Ca²⁺ led to an increase in mitochondrial ROS and a decline in mitochondrial membrane potential. These events resulted in the elevation of mitochondrial permeability and induced the release of cytochrome c from the mitochondria into the cytoplasm, which further activated caspase-3 and promoted apoptosis. The above phenomenon was also observed in tunicamycin (TUN, ER stress inducer)-treated cells. Meanwhile, BAPTA-AM (calcium chelator) rescued mitochondrial dysfunction and apoptosis in DR, which further confirmed of our suspicions. In addition, 4-phenylbutyric acid (4-PBA), an ER stress inhibitor, was shown to reverse retinal dysfunction in STZ-induced DR rats in vivo. Taken together, our findings demonstrated that DR fueled the formation of ER-mitochondria coupling via the IP3R1-GRP75-VDAC1 axis and accelerated Ca²⁺-dependent cell apoptosis. Our results demonstrated that inhibition of ER-mitochondrial coupling, including inhibition of GRP75 or Ca²⁺ overload, may be a potential therapeutic target in DR.

Diosgenin protects against podocyte injury in early phase of diabetic nephropathy through regulating SIRT6

BACKGROUND

Diabetic nephropathy (DN) is a serious complication of diabetes mellitus. DN is the main cause of end-stage renal disease (ESRD). SIRT6 becomes the important target of DN. Diosgenin (a monomer from Chinese herbs) is probable to bind to SIRT6.

PURPOSE

Based on studies presented in the literature on kidney injuries plus screening for the binding effects of the drug to Sirt6, we aimed to carry out the study to assess the effects of diosgenin involved in improving podocyte damage in the early phase of DN..

METHODS

DN model was established in spontaneous diabetic db/db mice. Animal experiment was in two parts. The first part includes four groups consisting of control (Con) group, model (Mod) group, low dose of diosgenin (DL) group and high dose of diosgenin (DH) group. The second part includes four groups consisting of control group, model group, DH+OSS_128167 (OSS, inhibitor of SIRT6) group, MDL800 (agonist of SIRT6) group. MPC5 cell line was selected in cell experiment, which was mainly composed of six groups including Con group, palmitic acid (PA) group, PA+DL group, PA+DH group, PA+DH+OSS group, PA+MDL800 group. Some procedures such as transcriptomics, RT-qPCR and so on were used in the study to explore and verify the mechanism.

RESULTS

The abnormal changes of mesangial matrix expansion, glomerular basement membrane (GBM) thickness, foot process (FP) width, urine albumin/creatinine (UACR), DESMIN, ADRP, NEPHRIN, PODOCIN, SIRT6 in Mod group were alleviated in DH group rather than DL group in the first part of animal experiment. The effect in DH group could be reversed in DH+OSS group and the same effect was observed in MDL800 group in the second part of animal experiment. The same results were also found in cell experiment. Protein level and mRNA expression of pyruvate dehydrogenase kinase 4 (PDK4) and Angiopoietin-like-4 (ANGPTL4) were increased in PA group, which could be alleviated in DH group, MDL800 group rather than DH+OSS group.

CONCLUSIONS

Diosgenin could protect against podocyte injury in early phase of diabetic nephropathy by regulating SIRT6.

Diosgenin exerts an antihypertensive effect in spontaneously hypertensive rats via gut-brain communication

Gut microbiota is well-established to regulate host blood pressure. Diosgenin is a natural steroid sapogenin with documented anti-inflammatory, antioxidant and antihypertensive properties. We aimed to investigate whether the antihypertensive effects of diosgenin are mediated by the microbiota-gut-brain axis in spontaneously hypertensive rats (SHR). 15-Week-old male Wistar Kyoto rats (WKY) and age-matched SHR were randomly distributed into three groups: WKY, SHR treated with a vehicle, and SHR treated with diosgenin (100 mg kg^-1). Our results showed that diosgenin prevented elevated systolic blood pressure (SBP) and ameliorated cardiac hypertrophy in SHR. Moreover, the gut microbiota composition and intestinal integrity were improved. Furthermore, increased butyrate-producing bacteria and plasma butyrate and decreased plasma lipopolysaccharides were observed in SHR treated with diosgenin. These findings were associated with reduced microglial activation and neuroinflammation in the paraventricular nucleus. Our findings suggest that diosgenin attenuates hypertension by reshaping the gut microbiota and improving the gut-brain axis.

Nephrotoxicity evaluation of 3-monochloropropane-1,2-diol exposure in Sprague-Dawley rats using data-independent acquisition-based quantitative proteomics analysis

3-Monochloropropane-1,2-diol (3-MCPD), as a heat-induced food process contaminant, possesses strongly toxic effect on kidney. The present study focuses on characterizing the proteome and clarifying the underlying molecular regulatory mechanisms in a model of kidney injury in rats treated with 3-MCPD. Data-independent acquisition (DIA)-mass spectrometry (MS) based proteomics was used to identify dysregulated proteins in kidney tissues of Sprague-Dawley (SD) rats treated with 30 mg/kg/day 3-MCPD by gavage for 28 days. It was found that a total of 975 proteins were deregulated after 3-MCPD treatment. Bioinformatic analyses revealed that several enzymes related to the metabolisms of amino acid, lipid and carbohydrate in endogenous metabolism were altered in response to 3-MCPD treatment. Moreover, some proteins involved in these pathways were also changed, mainly including oxidative stress, oxidative phosphorylation, apoptosis and autophagy. Our study unravels the vital roles of loss of mitochondrial homeostasis and function and cell death pathways in the development of renal damage induced by 3-MCPD, which provides further valuable insights into the initiation and resolution of 3-MCPD nephrotoxicity. The proposed DIA-MS workflow not only provides a choice for proteomic analysis in toxicological research, but also provides a more comprehensive understanding of the molecular mechanisms of nephrotoxicity induced by toxins.

Calcium Signaling Mediates Cell Death and Crosstalk with Autophagy in Kidney Disease

The kidney is an important organ for the maintenance of Ca²⁺ homeostasis in the body. However, disruption of Ca²⁺ homeostasis will cause a series of kidney diseases, such as acute kidney injury (AKI), chronic kidney disease (CKD), renal ischemia/reperfusion (I/R) injury, autosomal dominant polycystic kidney disease (ADPKD), podocytopathy, and diabetic nephropathy. During the progression of kidney disease, Ca²⁺ signaling plays key roles in various cell activities such as necrosis, apoptosis, eryptosis and autophagy. Importantly, there are complex Ca²⁺ flux networks between the endoplasmic reticulum (ER), mitochondria and lysosomes which regulate intracellular Ca²⁺ signaling in renal cells and contribute to kidney disease. In addition, Ca²⁺ signaling also links the crosstalk between various cell deaths and autophagy under the stress of heavy metals or high glucose. In this regard, we present a review of Ca²⁺ signaling in cell death and crosstalk with autophagy and its potential as a therapeutic target for the development of new and efficient drugs against kidney diseases.