Parkinson's disease (PD) is a neurodegenerative disease characterized by the loss of dopaminergic (DA) neurons in the substantia nigra pars compacta. Non-motor symptoms appear 20 years before the onset of classic motor symptoms of PD. The TRP family of ion channels may be associated with the development of neurodegenerative diseases (including PD). TRPV4 channels are involved in the disruption of the barrier function of the gastrointestinal (GI) tract, suppression of the contractile activity of the colon, and delay in defecation. TRPM8 dysfunction is associated with the development of inflammatory processes in the body, suppression of the contractile activity of the intestines.
Therefore, the aim of the dissertation research was to establish a relevant model of PD for studying the mechanisms of impaired motor-evacuatory and barrier function of the intestine and the role of TRРV4 and TRPM8 ion channels in them.
The following research methods were used to perform the work: stereotaxic operations for PD modeling, behavioral tests, western blot, immunohistochemistry, physiological methods, the method of bacteriological cultures, biochemical methods, methods of variational statistics.
We have shown for the first time that LPS- and 6-ОНDА-PD in rats and the rotenone model of PD in mice show functional disorders of the secretory-motor function of the GI tract, but the direction of disorders is specific to the 6-ОНDА model in rats and the rotenone model of PD in mice corresponds to the clinical course of PD.
7 months after modeling 6-ОНDА-PD, indicators of behavioral and locomotor reactions became less pronounced in comparison with the 1st. After 7 months, the body weight, the amount of food consumed, the amount of lactose-positive E.coli and the disappearance of lactose-negative E.coli, and the speed of intestinal transit decreased compared to the control. Qualitative changes in mucus glycoproteins were also observed 7 months after modeling 6-ОНDА-PD.
We showed a 2-fold decrease in the level of TH, the disappearance of TRPM8 and a 2-fold increase in TRPV4 ion channels in the colon of rats. TH-, ТRРV4- and ТRРМ8-positive staining was localized apically on the epitheliocytes of the colon of rats.
Activation of ТRPV4 with the agonist GSK1016790A (0.3 μM) led to a decrease in the maximal peak contraction and contraction area of the isolated colon section, as well as inhibition of KCl-stimulated contractile activity of colonic smooth muscle preparations of rats with 6-ОНDА-PD.
Activation of TRPM8 channels by menthol (100 μM) against the background of carbachol action did not lead to changes in the maximal peak of the contraction, as well as the area under the curve. A similar effect was observed in rats with 6-OHDA-PD. There was a tendency to decrease the amplitude of the contractions of the smooth muscle strips of the colon of rats with the 6-ОНDА model upon activation of TRPM8 channels by menthol.
Rats with 6-OHDA-PD showed a lower level of ion secretion in response to the stimulatory effect of carbachol, as well as a tendency to increase transepithelial permeability. In rats with 6-OHDA-PD, the TRPV4 channel agonist did not affect the basal electrogenic transport of ions, but inhibited the stimulating effect of carbachol.
The administration of menthol did not cause changes in the parameters of the basal short-circuit current in both studied groups. We did not observe such an effect in rats with 6-OHDA-PD.
Administration of C60 fullerene (C60FAS): prevented 6-OHDA-induced destruction of DA neurons in the midbrain, which was reflected in a greater intensity of TН staining in the midbrain of rats compared to the 6-OHDA+SPS group; reduced the level of anxiety in rats with PD; improved food behavior; the rate of transit and the level of carbacholin-stimulated motor activity of the colon of rats with PD were restored. Аdministration of C60FAS had side effects: accumulation of C60FAS particles in the pancreas; increase in phagocytic activity of peritoneal macrophages; a slight shift in the antioxidant-prooxidant system of the brain with a more profound negative effect on the glutathione system. This may indicate a toxic side effect of C60FAS and should be considered in further studies on the use of C60FAS in the treatment of PD.
Thus, the paper showed that 6-ОНDА-, LPS- and rotenone models of PD are accompanied by disorders from the GI tract. The 6-ОНDА model of PD in rats is relevant to the clinical course of PD, and disorders from the GI tract are reproduced even in distant terms after modeling; TRPV4 and TRPM8 ion channels are involved in the pathogenesis of intestinal secretomotor function in the 6-ОНDА model of PD in rats, and the regulatory pathways mediated by them are impaired; the aqueous solution of C60FAS is promising for the complex recovery of central symptoms of PD and the motor function of the GI tract in PD, but it shows a toxic side effect in the rat model of 6-ОНDА- PD in vivo.
