Neuroprotective substances: are they able to protect the pancreatic beta-cells too?

BACKGROUND

Growing evidences demonstrate a close relationship between type 2 diabetes (T2D) and neurodegenerative disorders such as Alzheimer's disease. The similarity of physiological and pathological processes, occurring in pancreatic β-cells and neurons over the course of these pathologies, allows to raise the question of the practicability of studying neuroprotective substances for their potential antidiabetic activity.

OBJECTIVE

This review analyzes studies of antidiabetic and cytoprotective action on pancreatic β-cells of the neuroprotective compounds that can attenuate the oxidative stress and enhance the expression of neurotrophins: low-molecular-weight NGF mimetic compound GK-2, selective anxiolytic afobazole, antidepressants lithium chloride and lithium carbonate on the rat streptozotocin model of T2D.

RESULTS

It was found that all above-listed neuroprotective substances have a pronounced antidiabetic activity. The decrease in the β-cells number, the average area of the pancreatic islets, as well as the violation of their morphological structure caused by the streptozotocin was significantly weakened by the therapy with the investigated neuroprotective substances. The extent of these morphological changes clearly correlates with the antihyperglycemic effect of these compounds.

CONCLUSION

The presented data indicate that the neuroprotective substances attenuating the damaging effect of oxidative stress and neurotrophins deficit cannot only protect neurons but also exert their cytoprotective effect towards pancreatic β-cells. These data may provide a theoretical basis for the further study of neuroprotective drugs as potential therapeutic options for T2D prevention and treatment.

Noopept Attenuates Diabetes-Mediated Neuropathic Pain and Oxidative Hippocampal Neurotoxicity via Inhibition of TRPV1 Channel in Rats

Neuropathic pain and oxidative neurotoxicity are two adverse main actions of diabetes mellitus (DM). The expression levels of calcium ion (Ca²⁺) permeable TRPV1 channels are high in the dorsal root ganglion (DRGs) and hippocampus (HIPPO). TRPV1 is activated by capsaicin and reactive free oxygen radicals (fROS) to mediate peripheral neuropathy and neurotoxicity. Noopept (NP) acted several protective antioxidant actions against oxidative neurotoxicity. As DM is known to increase the levels of fROS, the protective roles of antioxidant NP were evaluated on the DM-mediated neurotoxicity and neuropathic pain via the modulation of TRPV1 in rats. Thirty-six rats were equally divided into control, NP, DM (streptozotocin, STZ), and STZ + NP groups. A decrease on the STZ-mediated increase of neuropathic pain (via the analyses of Von Frey and hot plate) and blood glucose level was observed by the treatment of NP. A protective role of NP via downregulation of TRPV1 activity on the STZ-induced increase of apoptosis, mitochondrial fROS, lipid peroxidation, caspase -3 (CASP-3), caspase -9 (CASP-9), TRPV1 current density, glutathione (GSH), cytosolic free Zn²⁺, and Ca²⁺ concentrations in the DRGs and HIPPO was also observed. The STZ-mediated decrease of glutathione peroxidase, GSH, vitamin E, and β-carotene concentrations in the brain cortex, erythrocyte, liver, kidney, and plasma was also attenuated by the treatment of NP. The STZ-mediated increase of TRPV1, CASP-3, and CASP-9 expressions was decreased in the DRGs and HIPPO by the treatment of NP. In conclusion, the treatment of NP induced protective effects against STZ-induced adverse peripheral pain and HIPPO oxidative neurotoxicity. These effects might attribute to the potent antioxidant property of NP.

Application of Focal Photoinduced Thrombosis for Modeling Spinal Cord Ischemia

Typical ischemic damage to neurons were detected in the focus of experimental photothrombosis and in the transition zone. They were associated with symptoms of impaired motor functions and dysfunction of pelvic organs. The applied method of focal photothrombosis can be used for simulation of spinal cord ischemia for the development of methods for pharmacological correction and restoration of impaired sensorimotor functions.

Drug with Neuroprotective Properties Noopept Does Not Stimulate Cell Proliferation

Effects of Noopept (N-phenylacetyl-L-prolylglycine ethyl ester) on the relative level of proliferation marker Ki-67 and cell cycle parameters were studied in HEK293 and SH-SY5Y cell lines. The previously established multifactorial mechanism of action of the drug includes enhancement of neurotrophin NGF and BDNF expression and increase in HIF-1 activity. The possible mitogenic action of Noopept was estimated by its effect on cell proliferation. Noopept did not affect cell distribution over G1, S, G2 cell cycle phases and the relative level of proliferation marker Ki-67 in the cell lines under study. These data suggest that Noopept does not stimulate cell growth.

Effect of Noopept on Dynamics of Intracellular Calcium in Neurons of Cultured Rat Hippocampal Slices

A neuroprotective and nootropic drug Noopept increased the frequency of spontaneous calcium transients in neurons of CA1 radial layer in cultured rat hippocampal slices. In contrast, the drug exerted no significant effect on intracellular calcium concentration and its dynamics in neurons of hippocampal CA1 pyramidal layer.

Dipeptide Piracetam Analogue Noopept Improves Viability of Hippocampal HT-22 Neurons in the Glutamate Toxicity Model

Effect of noopept (N-phenylacetyl-prolylglycine ethyl ester) on viability of neurons exposed to neurotoxic action of glutamic acid (5 mM) was studied in vitro in immortalized mouse hippocampal HT-22 neurons. Noopept added to the medium before or after glutamic acid improved neuronal survival in a concentration range of 10-11-10-5 M. Comparison of the effective noopept concentrations determined in previous studies on cultured cortical and cerebellar neurons showed that hippocampal neurons are more sensitive to the protective effect of noopept.