SMTP-44D improves diabetic neuropathy symptoms in mice through its antioxidant and anti-inflammatory activities

Antioxidant and anti-inflammatory effects of SMTP-44D in a streptozotocin-induced diabetic neuropathy mouse model

BACKGROUND

Diabetic neuropathy (DN) is a debilitating complication of diabetes, driven by oxidative stress, inflammation, and advanced glycation end products (AGE) signaling through its receptor (RAGE). Soluble epoxide hydrolase (sEH) metabolizes anti-inflammatory epoxyeicosatrienoic acids (EETs) into pro-inflammatory dihydroxyeicosatrienoic acids (DHETs), exacerbating DN pathology. SMTP-44D, an sEH inhibitor, has demonstrated antioxidant and anti-inflammatory effects in vitro; however, its in vivo efficacy remains unclear.

AIM

To investigate the antioxidant and anti-inflammatory activities of SMTP-44D in relation to sEH inhibition and AGE/RAGE signaling in a streptozotocin (STZ)-induced DN mouse model.

METHODOLOGY

STZ-induced diabetic mice were treated with SMTP-44D (30 mg/kg) from days 8 to 28 post STZ injection (200 mg/kg). Oxidative stress markers, inflammatory factors, AGE in the sciatic nerve, and RAGE in serum were assessed via ELISA. DHET levels in serum were measured using LC-MS/MS, and apoptosis in the sciatic nerve was assessed via TUNEL staining and fluorescent immunohistochemistry for cleaved caspase-3.

RESULTS

Our findings indicated that SMTP-44D inhibited sEH, reducing DHET levels and sustaining anti-inflammatory effects. It attenuated the migration of nuclear factor-kappa B, decreased AGE and RAGE levels, and suppressed oxidative stress and inflammatory markers in the sciatic nerve. Moreover, SMTP-44D inhibited apoptosis, potentially mitigating the axonal damage associated with DN.

CONCLUSION

Our findings suggest that SMTP-44D is a promising therapeutic agent for DN, acting through sEH inhibition and reducing AGE/RAGE levels.

Guizhi Fuling capsules can alleviate bortezomib-induced peripheral neuropathy by decreasing Interleukin-6 levels to regulate mTOR pathway-induced autophagy

OBJECTIVE

To investigate the therapeutic effect and underlying mechanism of Guizhi Fuling capsule (GZFL) on bortezomib-induced peripheral neuropathy (BiPN).

MATERIALS AND METHODS

Interleukin-6 (IL-6) levels in the plasma of Multiple myeloma (MM) patients were measured by ELISA, and correlation analysis between IL-6 and clinical features of BiPNs was performed. Then, we assess the clinical therapeutic effects of GZFL on MM patients by detecting IL-6 level, PN grade, FACT score, VAS score, MVC and SCV before and after the treatment. A combination of LC/MS and network pharmacology analysis was used to investigate the components and targets of GZFL. Then, bioinformatics was carried out. After PC12 cells were treated with GZFL, a BiPN cell model was constructed to evaluate cell autophagy function by cell viability, IL-6 levels, ROS levels, immunofluorescence staining of LC3 puncta, electron transmission electron microscopy (TEM), and Western blotting (WB). C57BL/6 mice were administered bortezomib by intraperitoneal injection to establish a model of BiPN. Nerve injury in BiPN mice was observed by measuring ethology, motor nerve conduction velocity, and IL-6. ROS, HE staining. TEM, western blotting and IHC were used to detect the expression of autophagy-related indexes.

RESULTS

In BiPN patients, IL-6 levels were positively correlated with the PN and FACT, VAS scores. Collectively, GZFL can alleviate BiPN by reducing the level of IL-6, which is mainly manifested in the decline of PN grade, FACT, VAS score and the improvement of MVC and SCV. Thirty-four components and 107 targets of GZFL for BiPN were obtained. IL-6, mTOR, and AKT1 showed high degree values, and the significantly enriched signaling pathways were closely related to inflammatory factors and autophagy pathways, such as TNF and the mTOR signaling pathway. GZFL significantly decreased IL-6 levels in cell and animal models of BiPN. For the autophagy test, GZFL increased PC12 cell ability and the numbers of LC3 puncta and autophagic vesicles after bortezomib treatment. In vivo experiments showed that GZFL effectively improved the behavior of mice with BiPN and alleviated sciatic nerve injury. WB and IHC showed that GZFL enhanced autophagy, as indicated by the alteration of autophagy-related protein levels in PC12 cells and sciatic nerve tissue.

CONCLUSION

The present study confirmed that GZFL significantly ameliorates peripheral neuropathy by regulating autophagy levels via alleviating high levels of IL-6 .

TRIAL REGISTRATION

The link to the registration: Chinese Clinical Trial Registry (https://www.chictr.org.cn/bin/project/edit?pid=214832). The name of the trial register is "The role of mitochondrial autophagy in multiple myeloma peripheral neuropathy and the application of traditional Chinese medicine for warming Yang and removing blood stasis". The clinical trial registration number is ChiCTR2400088065.

Ameliorating Effect of Red Fruit (Pandanus conoides Lamk) Oil in Streptozotosin-Induced Diabetic Peripheral Neuropathy Rat Model: role of oxidative and neuroinflammatory pathways

Objectives

Diabetic peripheral neuropathy (DPN) is the most common cause of neuropathy worldwide, with oxidative and inflammatory being the pathways involved in the disease pathology. Red fruit (Pandanus conoides Lamk) oil (RFO) is known to have potent antioxidants and anti-inflammatory activities. To investigate the effects of RFO in a rat model of streptozotocin-induced DPN.

Methods

Male Wistar rats were induced with 55 mg/kg streptozotocin (STZ) intraperitoneally. Rats with fasting blood glucose ≥ 200 mg/dL were assigned into groups treated with vehicle, pregabalin 30 mg/kg, and 0.3, 0.6, or 1.2 mL/kg RFO, respectively. The treatments were given for 3 weeks, six weeks after STZ induction. Neuropathic pain was evaluated by cold allodynia and thermal hyperalgesia tests. Histopathological changes of the pancreas and sciatic nerve were evaluated by the Gaussian adaptive threshold method. Feed and drinking intake, blood glucose levels, body weight, and sciatic nerve proinflammatory cytokines were also measured.

Results

There were increases in blood glucose levels, feed and drink intake, levels of MDA, TNF-α, IL-6, NFκB, and iNOS; decrease in catalase level; and damage to the sciatic nerve in the vehicle-treated DPN rat model compared with normal rats (p < 0.05). Meanwhile, significant decrease in weight, number of pancreatic β cells, latency times for thermal hyperalgesia as well as cold allodynia were observed in this group of rats. RFO administration at 0.6 and 1.2 mL/kg significantly improved all of the measured indices, except for iNOS, where only decreasing trend was observed. Pregabalin did not affect blood glucose levels, body weight or pancreatic β cells but improved thermal hyperalgesia as well as cold allodynia, the sciatic nerve cell counts, TNF-α IL-6, NFκB, and iNOS levels.

Conclusion

RFO improves DPN by neuroprotective effect through the involvement of the oxidative and neuroinflammatory pathways.

Epalrestat Alleviates Reactive Oxygen Species and Endoplasmic Reticulum Stress by Maintaining Glycosylation in IMS32 Schwann Cells Under Exposure to Galactosemic Conditions

Aldose reductase (AR), a rate-limiting enzyme in the polyol pathway, mediates the conversion of several substrates, including glucose and galactose. In rodents, galactosemia induced by galactose feeding has been shown to develop peripheral nerve lesions resembling diabetic peripheral neuropathy. However, the mechanisms by which AR-mediated responses elicited Schwan cell lesions under galactosemic conditions remain unresolved. To investigate this, we examined the mechanism of high-galactose-induced damage mediated by AR using AR inhibitors such as ranirestat and epalrestat. The exposure of IMS32 Schwann cells under high-galactose conditions led to galactitol accumulation, the increased production of reactive oxygen species (ROS), endoplasmic reticulum (ER) stress, impaired mitochondrial morphology and membrane potential, decreased glycolysis, and aberrant glycosylation. Under these experimental conditions, ranirestat inhibited intracellular galactitol in a dose-dependent manner, whereas epalrestat failed to inhibit it. Interestingly, even at low concentrations where epalrestat did not inhibit AR activity, it prevented increased ROS production, ER stress, decreased glycolysis, and aberrant RCA120-binding glycosylation; however, no effect of ranirestat on the glycosylation was observed. Epalrestat and ranirestat did not recover mitochondrial morphology. These findings suggest that ER stress is induced by aberrant glycosylation under galactosemic conditions and that epalrestat may be effective in maintaining proper glycosylation in Schwann cells in these conditions.

Immortalized Schwann cell lines as useful tools for pathogenesis-based therapeutic approaches to diabetic peripheral neuropathy

Growing evidence suggests that hyperglycemia-related abnormalities in Schwann cells play a pivotal role in the development and progression of diabetic peripheral neuropathy (DPN). Several immortalized Schwann cell lines have been established in our laboratory and utilized for the study of DPN; IMS32 from normal ICR mice, 1970C3 from normal C57BL/6 mice, IWARS1 and IKARS1 from wild-type and aldose reductase-deficient C57BL/6 mice, and IFRS1 from normal Fischer 344 rats. These cell lines retain biological features of Schwann cells and display high proliferative activities that enable us to perform molecular and biochemical analyses. In addition, these cells have exhibited metabolic alterations under exposure to diabetes-associated conditions, such as hyperglycemia, dyslipidemia, glycative and oxidative stress load. Herein, recent studies with these cell lines regarding the pathogenic factors of DPN (augmentation of the polyol and other collateral glycolysis pathways, glycative and oxidative stress-induced cell injury, autophagic and proteostatic disturbances, etc.) and therapeutic strategies targeting these factors are introduced.

Potent Efficacy of 3-Amino-4-hydroxy Benzoic Acid, a Small Molecule Having Anti-fibrotic Activity, in a Mouse Model of Non-alcoholic Steatohepatitis

Non-alcoholic steatohepatitis (NASH), which is on the rise due to the increasing obese population and changing lifestyles, causes fibrosis over time and carries the risk of progression to cirrhosis and hepatocellular carcinoma. However, there are no approved effective treatments for NASH. Recent studies suggest that increased lipid metabolism and reduced nitric oxide content are responsible for NASH; 3-amino-4-hydroxy benzoic acid (AHBA) was identified as an inhibitor for the phosphatase activity of soluble epoxy hydrolase, which in turn inhibits lipid metabolism and endothelial nitric oxide synthase activity. The aim of this study was to assess the efficacy of AHBA in a mouse model of NASH. NASH was induced in mice by streptozotocin administration and a high-fat diet loading. The efficacy of AHBA was determined by measuring liver function using serum and liver samples and conducting a morphological assessment. AHBA considerably attenuated the increase in the liver weight and alkaline phosphatase content, which occurred due to the progression of NASH. Hepatocellular steatosis, inflammatory cell infiltration, and hepatocellular ballooning of hepatocytes remained unaltered. In contrast, AHBA treatment significantly ameliorated the fibrotic alterations within liver tissue that were induced by the onset of NASH. These results demonstrate the potential of AHBA as a therapeutic pharmaceutical compound that can treat NASH.

SMTP-44D Inhibits Atherosclerotic Plaque Formation in Apolipoprotein-E Null Mice Partly by Suppressing the AGEs-RAGE Axis

SMTP-44D has been reported to have anti-oxidative and anti-inflammatory reactions, including reduced expression of receptor for advanced glycation end products (RAGE) in experimental diabetic neuropathy. Although activation of RAGE with its ligands, and advanced glycation end products (AGEs), play a crucial role in atherosclerotic cardiovascular disease, a leading cause of death in diabetic patients, it remains unclear whether SMTP-44D could inhibit experimental atherosclerosis by suppressing the AGEs–RAGE axis. In this study, we investigated the effects of SMTP-44D on atherosclerotic plaque formation and expression of AGEs in apolipoprotein-E null (Apoe−/−) mice. We further studied here whether and how SMTP-44D inhibited foam cell formation of macrophages isolated from Apoe−/− mice ex vivo. Although administration of SMTP-44D to Apoe−/− mice did not affect clinical or biochemical parameters, it significantly decreased the surface area of atherosclerotic lesions and reduced the atheromatous plaque size, macrophage infiltration, and AGEs accumulation in the aortic roots. SMTP-44D bound to immobilized RAGE and subsequently attenuated the interaction of AGEs with RAGE in vitro. Furthermore, foam cell formation evaluated by Dil-oxidized low-density lipoprotein (ox-LDL) uptake, and gene expression of RAGE, cyclin-dependent kinase 5 (Cdk5) and CD36 in macrophages isolated from SMTP-44D-treated Apoe−/− mice were significantly decreased compared with those from saline-treated mice. Gene expression levels of RAGE and Cdk5 were highly correlated with each other, the latter of which was also positively associated with that of CD36. The present study suggests that SMTP-44D may inhibit atherosclerotic plaque formation in Apoe−/− mice partly by blocking the AGEs-RAGE-induced ox-LDL uptake into macrophages via the suppression of Cdk5-CD36 pathway.

The effect of hand therapy on alleviating chemotherapy-induced peripheral neuropathy in a model mouse

The use of neurotoxic chemotherapeutic agents induces numbness in the limbs through chemotherapy-induced peripheral neuropathy (CIPN). Recently, we found that hand therapy involving finger massage improved mild to moderate numbness in CIPN patients. In this study, we behaviorally, physiologically, pathologically, and histologically investigated the mechanisms underlying hand therapy-induced numbness improvement in a CIPN model mouse. Hand therapy was performed for 21 days after the disease induction. Its effects were evaluated using mechanical and thermal thresholds and blood flow in the bilateral hind paw. Moreover, 14 days after the hand therapy was administered, we assessed the blood flow and conduction velocity in the sciatic nerve, the level of serum galectin-3, and the histological myelin and epidermis-related changes in the hindfoot tissue. Hand therapy significantly improved allodynia, hyperalgesia, blood flow, conduction velocity, serum galectin-3, and epidermal thickness in the CIPN model mouse. Furthermore, we observed the images of repairs of the myelin degeneration. Thus, we found that hand therapy could improve numbness in the CIPN model mouse and that it could help to repair peripheral nerves by promoting blood circulation in the limbs.

Role of c-miR-21, c-miR-126, Redox Status, and Inflammatory Conditions as Potential Predictors of Vascular Damage in T2DM Patients

The development of type 2 diabetes mellitus (T2DM) vascular complications (VCs) is associated with oxidative stress and chronic inflammation and can result in endothelial dysfunctions. Circulating microRNAs play an important role in epigenetic regulation of the etiology of T2DM. We studied 30 healthy volunteers, 26 T2DM patients with no complications, and 26 T2DM patients with VCs, to look for new biomarkers indicating a risk of developing VCs in T2DM patients. Peripheral blood samples were used to determine redox state, by measuring the endogenous antioxidant defense system (superoxide dismutase, SOD; catalase, CAT; glutathione reductase, GRd; glutathione peroxidase, GPx; and glucose-6-phosphate dehydrogenase, G6DP) and markers of oxidative damage (advanced oxidation protein products, AOPP; lipid peroxidation, LPO). Additionally, inflammatory marker levels (IL-1, IL-6, IL-18, and TNF-α), c-miR-21, and c-miR-126 expression were analyzed. T2DM patients showed the highest oxidative damage with increased GSSG/GSH ratios, LPO, and AOPP levels. In both diabetic groups, we found that diminished SOD activity was accompanied by increased CAT and decreased GRd and G6PD activities. Diabetic patients presented with increased relative expression of c-miR-21 and decreased relative expression of c-miR-126. Overall, c-miR-21, SOD, CAT, and IL-6 had high predictive values for diabetes diagnoses. Finally, our data demonstrated that IL-6 exhibited predictive value for VC development in the studied population. Moreover, c-miR-21 and c-miR-126, along with GPx and AOPP levels, should be considered possible markers for VC development in future studies.

Paeoniflorin Ameliorates BiPN by Reducing IL6 Levels and Regulating PARKIN-Mediated Mitochondrial Autophagy

Background

Bortezomib-induced peripheral neuropathy (BiPN) is a common complication of multiple myeloma (MM) treatment that seriously affects the quality of life of patients. The purpose of the present study was to explore the therapeutic effect of paeoniflorin on BiPN and its possible mechanism.

Methods

ELISA was used to measure the level of interleukin-6 (IL6) in the plasma of MM patients, and bioinformatics analysis was used to predict the mechanism underlying the effect of paeoniflorin on peripheral neuropathy. Cell and animal models of BiPN were constructed to evaluate mitochondrial function by measuring cell viability and mitochondrial quality and labeling mitochondria with MitoTracker Green. Nerve injury in mice with BiPN was assessed by behavioral tests, evaluation of motor nerve conduction velocity, hematoxylin-eosin (HE) staining, electron microscopy and analysis of the levels of reactive oxygen species (ROS). Western blotting and immunohistochemistry (IHC) were used to assess the expression of autophagy-related proteins.

Results

In MM patients, IL6 levels were positively correlated with the degree of PN. The results of bioinformatics analysis suggested that paeoniflorin ameliorated PN by altering inflammation levels and mitochondrial autophagy. Paeoniflorin increased PC12 cell viability and mitochondrial autophagy levels, alleviated mitochondrial damage, and reduced IL6 levels. In addition, paeoniflorin effectively improved the behavior of mice with BiPN, relieved sciatic nerve injury in mice, increased the expression of LC3II/I, beclin-1, and Parkin in sciatic nerve cells, and increased the expression of LC3B and Parkin in the nerve tissue.

Conclusion

The present study confirmed that paeoniflorin significantly ameliorated peripheral neuropathy (PN) caused by bortezomib, possibly by reducing IL6 levels to regulate PARKIN-mediated mitochondrial autophagy and mitochondrial damage.

Progress in Isoindolone Alkaloid Derivatives from Marine Microorganism: Pharmacology, Preparation, and Mechanism

Compound 1 (SMTP-7, also FGFC1), an isoindolone alkaloid from marine fungi Starchbotrys longispora FG216 and fungi Stachybotrys microspora IFO 30018, possessed diverse bioactivities such as thrombolysis, anti-inflammatory and anti-oxidative properties, and so on. It may be widely used for the treatment of various diseases, including cerebral infarction, stroke, ischemia/reperfusion damage, acute kidney injury, etc. Especially in cerebral infarction, compound 1 could reduce hemorrhagic transformation along with thrombolytic therapy, as the traditional therapies are accompanied with bleeding risks. In the latest studies, compound 1 selectively inhibited the growth of NSCLC cells with EGFR mutation, thus demonstrating its excellent anti-cancer activity. Herein, we summarized pharmacological activities, preparation of staplabin congeners—especially compound 1—and the mechanism of compound 1, with potential therapeutic applications.

SMTP-44D Exerts Antioxidant and Anti-Inflammatory Effects through Its Soluble Epoxide Hydrolase Inhibitory Action in Immortalized Mouse Schwann Cells upon High Glucose Treatment

Diabetic neuropathy (DN) is a major complication of diabetes mellitus. We have previously reported the efficacy of Stachybotrys microspora triprenyl phenol-44D (SMTP-44D) for DN through its potential antioxidant and anti-inflammatory activities. However, the mechanisms underlying the antioxidant and anti-inflammatory activities of SMTP-44D remain unclear. The present study aimed to explore the mechanism of these effects of SMTP-44D in regard to its inhibition of soluble epoxide hydrolase (sEH) in immortalized mouse Schwann cells (IMS32) following high glucose treatment. IMS32 cells were incubated in a high glucose medium for 48 h and then treated with SMTP-44D for 48 h. After incubation, the ratio of epoxyeicosatrienoic acids (EETs) to dihydroxyeicosatrienoic acids (DHETs), oxidative stress markers, such as NADPH oxidase-1 and malondialdehyde, inflammatory factors, such as the ratio of nuclear to cytosolic levels of NF-κB and the levels of IL-6, MCP-1, MMP-9, the receptor for the advanced glycation end product (RAGE), and apoptosis, were evaluated. SMTP-44D treatment considerably increased the ratio of EETs to DHETs and mitigated oxidative stress, inflammation, RAGE induction, and apoptosis after high glucose treatment. In conclusion, SMTP-44D can suppress the induction of apoptosis by exerting antioxidant and anti-inflammatory effects, possibly through sEH inhibition. SMTP-44D can be a potential therapeutic agent against DN.

Evaluation of in vitro transdermal permeation, mass spectrometric imaging, and in vivo analgesic effects of pregabalin using a pluronic lecithin organogel formulation in mice

In clinical practice, pregabalin is orally administered for neuropathic pain, but causes severe central nervous system side effects, such as dizziness, which results in dose limitation or discontinuation. To reduce the central side effects of pregabalin, we developed four pregabalin preparations for transdermal application: 0.4% aqueous solution, pluronic lecithin organogel (PLO gel), hydrophilic cream, and lipophilic cream. Transdermal permeabilities of pregabalin among the four formulations were compared in vitro using hairless mouse skin. The longitudinal distribution of pregabalin within the skin was analyzed using mass spectrometric (MS) imaging. Furthermore, the in vivo analgesic effects of the formulations were evaluated using the von Frey filament test in a mouse model of diabetic neuropathy (DN). The PLO gel showed the highest permeability of pregabalin, followed by the aqueous solution, and no permeation was observed in the two cream formulations. The MS imaging analysis showed that pregabalin was distributed up to the dermis in the PLO gel 1 h after application, while the aqueous solution was distributed near the epidermis. A significant analgesic effect (p < .05) was observed 1.5 h after PLO gel application in the DN model mice, but the aqueous solution had no effect. This study indicated for the first time that pregabalin penetrated beyond the skin epidermis up to the dermis, from the PLO gel formulation, and that the application of this formulation exhibited an in vivo analgesic effect in the mouse model of DN.

Myokines: Novel therapeutic targets for diabetic nephropathy

With the increasing incidence of diabetic nephropathy (DN), there is an urgent need to find effective DN preventive and therapeutic modalities. It is widely believed that effective exercise is good for health. However, the beneficial role of exercise in kidney disease, especially in DN, and the underlying molecular mechanisms have rarely been reported. Muscle is not only an important motor organ but also an important endocrine organ, secreting a group of proteins called "myokines" into the blood circulation. Circulating myokines then move to various target organs to play different biological roles. In this review, we summarize the currently known myokines and the progress in research relating them to DN and discuss its potential as a therapeutic target for DN.

Animal models of diabetic microvascular complications: Relevance to clinical features

Diabetes has become more common in recent years worldwide, and this growth is projected to continue in the future. The primary concern with diabetes is developing various complications, which significantly contribute to the disease's mortality and morbidity. Over time, the condition progresses from the pre-diabetic to the diabetic stage and then to the development of complications. Years and enormous resources are required to evaluate pharmacological interventions to prevent or delay the progression of disease or complications in humans. Appropriate screening models are required to gain a better understanding of both pathogenesis and potential therapeutic agents. Different species of animals are used to evaluate the pharmacological potentials and study the pathogenesis of the disease. Animal models are essential for research because they represent most of the structural, functional, and biochemical characteristics of human diseases. An ideal screening model should mimic the pathogenesis of the disease with identifiable characteristics. A thorough understanding of animal models is required for the experimental design to select an appropriate model. Each animal model has certain advantages and limitations. The present manuscript describes the animal models and their diagnostic characteristics to evaluate microvascular diabetic complications.