The crosstalk among TLR2, TLR4 and pathogenic pathways; a treasure trove for treatment of diabetic neuropathy

Pramipexole protects against diabetic neuropathy: Effect on oxidative stress, TLR4/IRAK-1/TRAF-6/NF-κB and downstream inflammatory mediators

BACKGROUND

Diabetic neuropathy (DN) is a serious microvascular complication and a major cause of morbidity and mortality in diabetes mellitus. It is characterized by neurodegeneration of terminal sensory nerve fibers with subsequent pain, loss of sensation, and paresthesia, thus compromising the quality of life of diabetic patients. It is considered the leading cause of non-traumatic amputations worldwide, reflecting the insufficiency of current therapies. Pramipexole (PPX) is a dopamine receptor agonist used for the treatment of Parkinson's disease. The current study aims to investigate the potential neuroprotective effect of PPX in an experimental model of DN.

METHODS

Sprague Dawley rats were randomly assigned into five groups: normal control, Normal + PPX (1 mg/kg) group, STZ control, STZ + PPX (0.25 and 1 mg/kg/day for eight weeks). The neuroprotective effect of PPX in rats was evaluated in terms of sciatic nerve histological alterations, oxidative stress, and protein expression of TLR4/MyD88/IRAK-1/TRAF-6/NF-κB axis and downstream inflammatory mediators.

RESULTS

PPX administration ameliorated histopathological signs of neuronal inflammation and apoptosis. Additionally, PPX attenuated STZ-induced sciatic nerve oxidative stress and downregulated neural tissue expression of TLR4, MyD88, IRAK-1, TRAF-6, NF-κB and downstream mediators (TNF-α, IL-1β and ICAM-1).

CONCLUSION

Collectively, the current study sheds light on PPX as a potential protective medication to alleviate neuropathy progression in diabetic patients. PPX neuroprotective effect can be attributed to modulating TLR4/ MyD88/IRAK-1/TRAF-6/ NF-κB axis signaling in nerve tissues with subsequent attenuation of oxidative stress and inflammation.

Astragalus Polysaccharide Ameliorates Renal Inflammatory Responses in a Diabetic Nephropathy by Suppressing the TLR4/NF-κB Pathway

Background

Diabetic nephropathy (DN), as a chronic inflammatory complication of diabetes, is characterized by hyperglycemia, albuminuria and edema, which ultimately becomes the leading cause of end-stage renal disease (ESRD). Astragalus polysaccharide (APS), extracted from the Astragalus membranaceus, was widely used in the treatment of diabetes mellitus. However, the functional roles of APS ameliorate inflammatory responses in DN, which remain poorly understood. Therefore, the purpose of this study was to explore the molecular mechanism of APS on DN in vivo and vitro models.

Methods

We explored the beneficial effects of APS in streptozotocin (STZ)-induced DN rat model and high glucose (HG)-treated glomerular podocyte model. The fasting blood glucose (FBG) and ratio of kidney weight to body weight were measured after 4 weeks of APS treatment. The renal injury parameters containing serum creatinine (Scr), blood urea nitrogen (BUN) and 24 h urinary protein were evaluated. The renal pathological examination was observed by hematoxylin-eosin (HE) staining. The levels of IL-1β, IL-6 and MCP-1 were evaluated by ELISA assay. The proliferation of podocytes was determined using CCK-8 assay and flow cytometry. qRT-PCR and Western blot analysis were performed to determine the amounts of TLR4/NF-κB-related gene expression.

Results

Our results indicated that APS effectively decreased the levels of FBG, BUN, Scr and renal pathological damage when compared with STZ-induced DN model group. Additionally, APS significantly ameliorated renal injury by reducing inflammatory cytokines IL-1β, IL-6, MCP-1 expression and inhibiting the TLR4/NF-κB pathway activity in DN rats. Consistent with the results in vitro, the HG-induced inflammatory response and proliferation of glomerular podocytes were also alleviated through APS administration.

Conclusion

We found that APS ameliorated DN renal injury, and the mechanisms perhaps related to relieving inflammatory responses and attenuating the TLR4/NF-κB signaling pathway.

Effect of Immunomodulating Extract and Some Isolates from Etlingera rubroloba A.D. Poulsen Fruits on Diabetic Patients with Tuberculosis

Diabetes mellitus (DM) is a disease easily complicated by tuberculosis (TB) due to impaired function of the innate immune response. The successes of the discovery of immunomodulatory compounds needs to be continued to introduce new insights into the innate immune response. In previous studies, plant compounds of Etlingera rubroloba A.D. Poulsen (E.rubroloba) were demonstrated to have potential as an immunomodulators. This study aims to isolate and identify the structure of the compounds of E.rubroloba fruit that could effectively improve the function of the innate immune response in individuals with DM infected with TB. The isolation and purification of the compounds of the E.rubroloba extract were carried out by radial chromatography (RC) and thin-layer chromatography (TLC). Identification of the isolated compound structures was determined by measuring the proton (¹H) and carbon (¹³C) nuclear magnetic resonance (NMR). In vitro testing was performed on the immunomodulating activity of the extracts and isolated compounds on DM model macrophages infected with TB antigens. This study succeeded at isolating and identifying the structures of two isolate compounds, namely Sinaphyl alcohol diacetat (BER-1), and Ergosterol peroxide (BER-6). The two isolates were more effective as immunomodulators than the positive controls were, which differed significantly (* p < 0.05) at the reducing interleukin-12 (IL-12) levels and Toll-like receptor-2 (TLR-2) protein expression and increasing the human leucocyte antigen-DR (HLA-DR) protein expression in DM infected with TB. The isolated compound was discovered in E. rubroloba fruits, which has been reported to have the potential to be developed as an immunomodulatory agent. Follow-up testing to determine the mechanism and effectiveness of these compounds as immunomodulators for DM patients is required so that they are not susceptible to TB infection.

Tropisetron improved testicular inflammation in the streptozotocin-induced diabetic rats: The role of toll-like receptor 4 (TLR4) and mir146a

As a serotonin antagonist, tropisetron positively affects blood glucose lowering, insulin synthesis, pancreas inflammation, and apoptosis in diabetes. Reproductive disorders are one of the diabetes-induced chronic complications. The present study aimed to evaluate the effect of tropisetron on diabetes-induced testicular inflammation, its signaling pathway, and mir146a. To this end, animals were assigned to the control, tropisetron, diabetes (DM), DM-tropisetron, and DM-glibenclamide groups. Streptozotocin (50 mg/kg) was intraperitoneally injected to provide diabetes. Tropisetron and glibenclamide were then administrated intraperitoneally for 2 weeks after diabetes induction. Testes histology, real-time polymerase chain reaction, western blot analysis, ELISA, and immunohistochemistry assays were also performed. The finding revealed that tropisetron significantly improved diabetes-induced testis damages, lowered TLR4, TRAF6, IRAK1, NF-κB, and caspase3 protein expressions, and decreased TNF-α and IL-1 levels. Moreover, the mir146a expression declined following the tropisetron treatment. This study demonstrated that the significant role of tropisetron in lowering testicular inflammation and apoptosis might have been due to the inhibition of the TLR4/IRAK1/TRAF6 signaling pathway and thereby the attenuation of NF-κB and caspase3 expression and inflammatory cytokines. Furthermore, the downregulation of mir146a, as an inflammatory microRNA interacting with TLR4, showed another pathway, through which tropisetron improved diabetes-induced testicular injuries.