A Pacific Oyster-Derived Antioxidant, DHMBA, Protects Renal Tubular HK-2 Cells against Oxidative Stress via Reduction of Mitochondrial ROS Production and Fragmentation

Assessing the toxic dose of the potent antioxidant 3,5-dihydroxy-4-methoxybenzyl alcohol in rats

3,5-dihydroxy-4-methoxybenzyl alcohol (DHMBA), identified from the Pacific oyster Crassostrea gigas, has dual properties to block oxidative stress as a radical scavenger and a potential cell function regulator. DHMBA has been shown to suppress adipogenesis, inflammatory activated macrophages, osteoclastogenesis, osteoblastic bone formation, and anti-cancer activity in vitro, suggesting its role in preventing and treating several diseases. The toxicological effects of DHMBA may be important for the development of its pharmacological application. However, the toxicity of DHMBA has not been determined. To evaluate the no-observed-adverse-effect level of synthetic DHMBA, this study was conducted in male and female rats at a single oral dose of DHMBA 500, 1000, or 2000 mg/kg body weight, for 14 days at 30, 100, 300, and 1000 mg/kg/day, and for 91 days at the DHMBA 1, 5, and 25 mg/kg/day dose in male and female rats. The toxicological effects of DHMBA were evaluated by analyzing the changes in general condition, including body weight, behavior, body temperature, abnormal gait, decreased mobility, decreased alternate, slowed approach response, slowed touch response, slowed auditory response, abnormal righting reflex in air, and decreased abdominal muscle tone, blood biochemistry test, macroscopic pathological examination, organ weight, histopathological examination, inflammatory changes, or obvious abnormalities in the hematopoietic system. As a result, this study demonstrated that the no-observed-adverse-effect level of synthetic DHMBA in male and female rats was 25 mg/kg/day when administered for 91 days. This result may provide important toxicological information in the use of the DHMBA as a pharmacological tool.

Modified Tou Nong Powder obstructs ulcerative colitis by regulating autophagy and mitochondrial function

ETHNOPHARMACOLOGICAL RELEVANCE

Modified Tou Nong Powder (MTNP) is a traditional Chinese medicine formula widely used for treating body surface ulcers. Since colonic ulcers share similar pathological characteristics, MTNP has shown promising results in alleviating ulcerative colitis (UC) and has been safely used in clinical practice.

AIM OF THE STUDY

This study aims to investigate how MTNP alleviates experimental colitis by inducing autophagy through the regulation of the AMP-activated protein kinase (AMPK)/Peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α) signaling pathway.

MATERIALS AND METHODS

In this study, UC rat models were created using 2,4,6-Trinitrobenzenesulfonic acid (TNBS). The therapeutic effects of MTNP on TNBS-induced colitis were evaluated through various methods such as disease activity index, visual examination, and histological examination of the colon. An inflammation model was also established in Caco-2 cells using H2O2. Western blot analysis was used to assess the expression of autophagy-related proteins, while immunofluorescence detection was employed for protein localization. Furthermore, quantitative real-time polymerase chain reaction (qPCR) was performed to analyze the expression of autophagy-related genes, confirming the role of MTNP in modulating the AMPK/PGC-1α signaling pathway.

RESULTS

In vivo, oral administration of MTNP led to a remarkable reduction in colonic injury, inhibition of inflammatory infiltration, and improvement in the abnormal expression of inflammatory factors in colonic tissues. Furthermore, MTNP stimulated autophagy by activating the AMPK/PGC-1α signaling pathway, thereby mitigating mitochondrial dysfunction. In vitro, exposure to MTNP drug-containing serum (MTNP-DS) resulted in a reduction of reactive oxygen species levels, improvement in mitochondrial membrane potential, and activation of the AMPK/PGC-1α pathway, leading to the promotion of mitochondrial autophagy.

CONCLUSION

The results indicate that MTNP triggers autophagy and enhances mitochondrial function, leading to the alleviation of UC in both in vitro and in vivo. These benefits are strongly linked to the activation of the AMPK/PGC-1α signaling pathway.

The novel marine factor 3,5-dihydroxy-4-methoxybenzyl alcohol exhibits anticancer activity by regulating multiple signaling pathways in human glioblastoma cells: Blocking EGF signaling

Glioblastoma is the most common adult malignant brain tumor. This tumor is aggressive and the most lethal. Trials to improve the outcome of patients with this tumor remain critical. There are no effective therapies for malignant glioma. Glioblastoma is characterized by ligand-independent overexpression of epidermal growth factor (EGF) receptors. EGF receptor signaling can promote tumorigenesis by increasing cell proliferation and tissue invasion and by inhibiting apoptosis of cancer cells. The marine factor 3,5-dihydroxy-4-methoxybenzyl alcohol (DHMBA) has been shown to block oxidative stress by scavenging free radicals in various cell types. This study investigates the effects of DHMBA on human glioblastoma cells in vitro. Glioblastoma cells were cultured in DMEM-low glucose containing 10 % fetal bovine serum (FBS) in the presence of DHMBA (0.1-250 μM). Culturing with DHMBA significantly suppressed cell proliferation in the presence of FBS or EGF. Mechanistically, DHMBA treatment significantly decreased the levels of PI3-kinase 100α, Akt, MAPK, phosphor-MAPK, and mTOR, which are promoters of cell growth, and increased the levels of tumor suppressors p53, p21, and Rb, leading to the reduction of cancer cell growth. DHMBA treatment significantly stimulated the death of glioblastoma cells by increasing the levels of caspase-3 and cleaved caspase-3. In addition, culture with DHMBA significantly inhibited metastatic activity, including adhesion and migration of cancer cells. Thus, DHMBA may have inhibitory effects on the activity of human glioblastoma cells in vitro. This study may provide a new strategy for the treatment of glioblastoma tumors.

3,5-Dihydroxy-4-methoxybenzyl alcohol, a novel antioxidant isolated from oyster meat, inhibits the hypothalamus-pituitary-adrenal axis to regulate the stress response

BACKGROUND

Antioxidants that can scavenge reactive oxygen in the brain and inhibit hyperactivity of the HPA axis are desirable.

AIMS

We investigated the cerebral translocation of the antioxidant 3,5-dihydroxy-4-methoxybenzyl alcohol (DHMBA) and the effects of DHMBA administration on the hypothalamus-pituitary-adrenal (HPA) axis in stress-loaded rats.

METHODS

Experiment 1: Plasma and brain DHMBA concentrations were measured over time after oral DHMBA administration to male B6 mice. Experiment 2: Female Wistar Imamichi rats were used. The normal group was not subjected to stress. The stress, DHMBA, and vitamin E groups were subjected to individual and overcrowding stress. Brain and hippocampal 8-hydroxy-2'-deoxyguanosine levels, hippocampal glucocorticoid receptor-α levels, plasma corticosterone levels and RNA levels of glutathione peroxidase 4, catalase, and glutathione reductase in the hippocampus were measured.

RESULTS

In Experiment 1, DHMBA was not detected in the plasma or brain before DHMBA administration but was detected in both after administration. In Experiment 2, brain and hippocampal 8-hydroxy-2'-deoxyguanosine levels and plasma corticosterone levels were significantly lower in the DHMBA than in the stress group. Glucocorticoid receptor-α levels were higher in the DHMBA than in the stress group. DHMBA increased RNA levels of antioxidant enzymes in the hippocampus.

CONCLUSION

DHMBA was translocated to the brain after administration. DHMBA administration decreased 8-hydroxy-2'-deoxyguanosine levels in the brain and hippocampus, increased hippocampal glucocorticoid receptor-α levels, and decreased the plasma corticosterone concentration, suggesting that DHMBA inhibits hyperactivity of the HPA axis. Nrf2 pathway activity induced by DHMBA resulted in increased antioxidant enzyme levels in the hippocampus.

Peanut Shell Extract Improves Mitochondrial Function in db/db Mice via Suppression of Oxidative Stress and Inflammation

Accumulating evidence shows a strong correlation between type 2 diabetes mellitus, mitochondrial dysfunction, and oxidative stress. We evaluated the effects of dietary peanut shell extract (PSE) supplementation on mitochondrial function and antioxidative stress/inflammation markers in diabetic mice. Fourteen db/db mice were randomly assigned to a diabetic group (DM in AIN-93G diet) and a PSE group (1% wt/wt PSE in AIN-93G diet) for 5 weeks. Six C57BL/6J mice were fed with an AIN-93G diet for 5 weeks (control group). Gene and protein expression in the liver, brain, and white adipose tissue (WAT) were determined using qRT-PCR and Immunoblot, respectively. Compared to the control group, the DM group had (i) increased gene and protein expression levels of DRP1 (fission), PINK1 (mitophagy), and TNFα (inflammation) and (ii) decreased gene and protein expression levels of MFN1, MFN2, OPA1 (fusion), TFAM, PGC-1α (biogenesis), NRF2 (antioxidative stress) and IBA1 (microglial activation) in the liver, brain, and WAT of db/db mice. Supplementation of PSE into the diet restored the DM-induced changes in the gene and protein expression of DRP1, PINK1, TNFα, MFN1, MFN2, OPA1, TFAM, PGC-1α, NRF2, and IBA1 in the liver, brain, and WAT of db/db mice. This study demonstrates that PSE supplementation improved mitochondrial function in the brain, liver, and WAT of db/db mice, in part due to suppression of oxidative stress and inflammation.

Aberrant expression of NEDD4L disrupts mitochondrial homeostasis by downregulating CaMKKβ in diabetic kidney disease

Disturbance in mitochondrial homeostasis within proximal tubules is a critical characteristic associated with diabetic kidney disease (DKD). CaMKKβ/AMPK signaling plays an important role in regulating mitochondrial homeostasis. Despite the downregulation of CaMKKβ in DKD pathology, the underlying mechanism remains elusive. The expression of NEDD4L, which is primarily localized to renal proximal tubules, is significantly upregulated in the renal tubules of mice with DKD. Coimmunoprecipitation (Co-IP) assays revealed a physical interaction between NEDD4L and CaMKKβ. Moreover, deletion of NEDD4L under high glucose conditions prevented rapid CaMKKβ protein degradation. In vitro studies revealed that the aberrant expression of NEDD4L negatively influences the protein stability of CaMKKβ. This study also explored the role of NEDD4L in DKD by using AAV-shNedd4L in db/db mice. These findings confirmed that NEDD4L inhibition leads to a decrease in urine protein excretion, tubulointerstitial fibrosis, and oxidative stress, and mitochondrial dysfunction. Further in vitro studies demonstrated that si-Nedd4L suppressed mitochondrial fission and reactive oxygen species (ROS) production, effects antagonized by si-CaMKKβ. In summary, the findings provided herein provide strong evidence that dysregulated NEDD4L disturbs mitochondrial homeostasis by negatively modulating CaMKKβ in the context of DKD. This evidence underscores the potential of therapeutic interventions targeting NEDD4L and CaMKKβ to safeguard renal tubular function in the management of DKD.

The potential of therapeutic strategies targeting mitochondrial biogenesis for the treatment of insulin resistance and type 2 diabetes mellitus

Type 2 diabetes mellitus (T2DM) is a persistent metabolic disorder marked by deficiencies in insulin secretion and/or function, affecting various tissues and organs and leading to numerous complications. Mitochondrial biogenesis, the process by which cells generate new mitochondria utilizing existing ones plays a crucial role in energy homeostasis, glucose metabolism, and lipid handling. Recent evidence suggests that promoting mitochondrial biogenesis can alleviate insulin resistance in the liver, adipose tissue, and skeletal muscle while improving pancreatic β-cell function. Moreover, enhanced mitochondrial biogenesis has been shown to ameliorate T2DM symptoms and may contribute to therapeutic effects for the treatment of diabetic nephropathy, cardiomyopathy, retinopathy, and neuropathy. This review summarizes the intricate connection between mitochondrial biogenesis and T2DM, highlighting the potential of novel therapeutic strategies targeting mitochondrial biogenesis for T2DM treatment and its associated complications. It also discusses several natural products that exhibit beneficial effects on T2DM by promoting mitochondrial biogenesis.

Oxidative stress-initiated one-carbon metabolism drives the generation of interleukin-10-producing B cells to resolve pneumonia

The metabolic reprogramming underlying the generation of regulatory B cells during infectious diseases remains unknown. Using a Pseudomonas aeruginosa-induced pneumonia model, we reported that IL-10-producing B cells (IL-10+ B cells) play a key role in spontaneously resolving infection-mediated inflammation. Accumulated cytosolic reactive oxygen species (ROS) during inflammation were shown to drive IL-10+ B-cell generation by remodeling one-carbon metabolism. Depletion of the enzyme serine hydroxymethyltransferase 1 (Shmt1) led to inadequate one-carbon metabolism and decreased IL-10+ B-cell production. Furthermore, increased one-carbon flux elevated the levels of the methyl donor S-adenosylmethionine (SAM), altering histone H3 lysine 4 methylation (H3K4me) at the Il10 gene to promote chromatin accessibility and upregulate Il10 expression in B cells. Therefore, the one-carbon metabolism-associated compound ethacrynic acid (EA) was screened and found to potentially treat infectious pneumonia by boosting IL-10+ B-cell generation. Overall, these findings reveal that ROS serve as modulators to resolve inflammation by reprogramming one-carbon metabolism pathways in B cells.