Phosphodiesterase 4 and 7 inhibitors produce protective effects against high glucose-induced neurotoxicity in PC12 cells via modulation of the oxidative stress, apoptosis and inflammation pathways.

Diabetic neuropathy (DN) is the most common diabetic complication. It is estimated diabetic population will increase to 592 million by the year 2035. This is while at least 50-60% of all diabetic patients will suffer from neuropathy in their lifetime. Oxidative stress, mitochondrial dysfunction, apoptosis, and inflammation are crucial pathways in development and progression of DN. Since there is also no selective and effective therapeutic agent to prevent or treat high glucose (HG)-induced neuronal cell injury, it is crucial to explore tools by which one can reduce factors related to these pathways. Phosphodiesterase 4 and 7 (PDE 4 and 7) regulate oxidative damage, neurodegenaration, and inflammatory responses through modulation of cyclic adenosine monophosphate (cAMP) level, and thus can be as important drug targets for regulating DN. The aim of this study was to evaluate the protective effects of inhibitors of PDE 4 and 7, named rolipram and BRL5048, on HG-induced neurotoxicity in PC12 cells as an in vitro cellular model for DN and determine the possible mechanisms for theirs effects. We report that the PC12 cells pre-treatment with rolipram (2 µM) and/or BRL5048 (0.2 µM) for 60 min and then exposing the cells to HG (4.5 g/L for 72 h) or normal glucose (NG) (1 g/L for 72 h) condition show: (1) significant attenuation in ROS, MDA and TNF-a levels, Bax/Bcl-2 ratio, expression of caspase 3 and UCP2 proteins; (2) significant increase in viability, GSH/GSSG ratio, MMP and ATP levels. All these data together led us to propose PDE 4 and 7 inhibitors, and specifically, rolipram and BRL5048, as potential drugs candidate to be further studied for the prevention and treatment of DN.

Exhaustion of T lymphocytes in the tumor microenvironment: Significance and effective mechanisms.

T lymphocytes play crucial roles in adaptive immune responses to tumors. However, due to different tolerance mechanisms and inhibitory effects of the tumor microenvironment (TME) on T cells, responses to tumors are insufficient. In fact, cellular and molecular suppressive mechanisms repress T cell responses in the TME, resulting in senescent, anergic and exhausted lymphocytes. Exhaustion is a poor responsive status of T cells, with up-regulated expression of inhibitory receptors, decreased production of effective cytokines, and reduced cytotoxic activity. Low immunogenicity of tumor antigens and inadequate presentation of tumor-specific antigens results in inappropriate activation of naive T lymphocytes against tumor antigens. Moreover, when effector cytotoxic T cells enter TME, they encounter a complicated network of cells and cytokines that suppress their effectiveness and turn them into exhausted T cells. Thus, the mechanism of T cell exhaustion in cancer is different from that in chronic infections. In this review we will discuss the main components such as inhibitory receptors, inflammatory cells, stromal cells, cytokine milieu as well as environmental and metabolic conditions in TME which play role in development of exhaustion. Furthermore, recent therapeutic methods available to overcome exhaustion will be discussed.

Alpha-lipoic acid and coenzyme Q10 combination ameliorates experimental diabetic neuropathy by modulating oxidative stress and apoptosis.

AIMS: Diabetic neuropathy (DN) is the most common complication of diabetes. Neuroprotective effects of alpha lipoic acid (ALA) and coenzyme Q10 (CoQ10) has been previously shown in DN, but underlying mechanisms involved not been exactly found. The present study explored the neuroprotective effects of ALA and Q10 combination in experimental DN by ameliorating oxidative stress and apoptosis. MAIN METHODS: We investigated the effects of CoQ10 (10 mg/kg, orally, five weeks) and/or ALA (100 mg/kg, orally, five weeks) in STZ (45 mg/kg, i.p.)- induced DN in rats. After treatments motor function, oxidative stress biomarkers, ATP levels, expression of caspase 3 and UCP2 proteins were assessed by open-field, biochemical and ELISA methods and Western blot analysis. Dorsal root ganglion (DRG) neurons were histologically examined using H&E staining method. KEY FINDINGS: ALA and/or CoQ10 treatment significantly (p < 0.05) attenuated DN - induced motor function deficiency by modulating distance moved and velocity. ALA and/or CoQ10 treatment dramatically suppressed DN - induced oxidative stress which was associated with decrease in LPO and ROS and increase in GSH and TAC in DRG neurons. ALA and/or CoQ10 was proved to prevent apoptosis and degeneration of DRG neurons, which appears to be mediated by regulating the expression of caspase 3 and UCP2 proteins, inducing ATP and improving DN-induced changes in DRG neurons. We found maximum effectiveness with ALA and CoQ10 combination on mentioned factors. SIGNIFICANCE: These results provide a possible basis of the underlying mechanism for application of ALA and CoQ10 combination in treatment of DN.