l-NAME prevents GM1 ganglioside-induced vasodilation in the rat brain

Uptake of severe acute respiratory syndrome coronavirus 2 spike protein mediated by angiotensin converting enzyme 2 and ganglioside in human cerebrovascular cells

Introduction

There is clinical evidence of neurological manifestations in coronavirus disease-19 (COVID-19). However, it is unclear whether differences in severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)/spike protein (SP) uptake by cells of the cerebrovasculature contribute to significant viral uptake to cause these symptoms.

Methods

Since the initial step in viral invasion is binding/uptake, we used fluorescently labeled wild type and mutant SARS-CoV-2/SP to study this process. Three cerebrovascular cell types were used (endothelial cells, pericytes, and vascular smooth muscle cells), in vitro.

Results

There was differential SARS-CoV-2/SP uptake by these cell types. Endothelial cells had the least uptake, which may limit SARS-CoV-2 uptake into brain from blood. Uptake was time and concentration dependent, and mediated by angiotensin converting enzyme 2 receptor (ACE2), and ganglioside (mono-sialotetrahexasylganglioside, GM1) that is predominantly expressed in the central nervous system and the cerebrovasculature. SARS-CoV-2/SPs with mutation sites, N501Y, E484K, and D614G, as seen in variants of interest, were also differentially taken up by these cell types. There was greater uptake compared to that of the wild type SARS-CoV-2/SP, but neutralization with anti-ACE2 or anti-GM1 antibodies was less effective.

Conclusion

The data suggested that in addition to ACE2, gangliosides are also an important entry point of SARS-CoV-2/SP into these cells. Since SARS-CoV-2/SP binding/uptake is the initial step in the viral penetration into cells, a longer exposure and higher titer are required for significant uptake into the normal brain. Gangliosides, including GM1, could be an additional potential SARS-CoV-2 and therapeutic target at the cerebrovasculature.

Fish oil attenuates methylmalonate-induced seizures

Methylmalonic acidemias are inherited metabolic disorders characterized by methylmalonate (MMA) accumulation and neurological dysfunction, including seizures. Dietary fatty acids are known as an important energy source and reduce seizure activity in selected acute animal models. This study investigated whether chronic treatment with fish oil or with oleic acid attenuates MMA-induced seizures and whether maintenance of Na(+),K(+)-ATPase activity was involved in such an effect. Adult male Wistar rats were given fish oil (85 mg/kg), oleic acid (85 mg/kg) or vehicle (0.42% aqueous Cremophor EL™, 4 mL/kg/body weight/day), p.o., for 75 days. On the 73th day a cannula was implanted in the right lateral ventricle with electrodes over the parietal cortex for EEG recording. On the 76th day the animals were injected with NaCl (2.5 μmol/2.5 μL, i.c.v.), or with MMA (2.5 μmol/2.5 μL, i.c.v.), and seizure activity was measured by electroencephagraphic (EEG) recording with concomitant behavior monitoring. The effect of prostaglandin E2 (PGE2) on Na(+),K(+)-ATPase activity of slices of cerebral cortex from NaCl-injected animals was determined. Fish oil increased the latency to MMA-induced tonic-clonic seizures, reduced the mean amplitude of ictal EEG recordings, and prevented PGE2-induced decrease of Na(+),K(+)-ATPase activity in cortical slices in vitro. Oleic acid decreased mean amplitude of ictal EEG recordings. The results support that fish oil decreases MMA-induced seizures. The decreased sensitivity of Na(+),K(+)-ATPase to the inhibitory effect of PGE2 in fish oil-treated animals may be related to the currently reported anticonvulsant activity.

Nitric oxide and potassium channels mediate GM1 ganglioside-induced vasorelaxation

Monosialotetrahexosylganglioside (GM1) is a glycosphingolipid present in most cell membranes that displays antioxidant and neuroprotective properties. It has been recently described that GM1 induces pial vessel vasodilation and increases NO( x ) content in cerebral cortex, which are fully prevented by the nitric oxide synthase inhibitor N(G)-nitro-L-arginine methyl ester (L-NAME). However, it is not known whether GM1 relaxes larger vessels, as well as the mechanisms by which GM1 causes vasorelaxation. In this study, we demonstrate that GM1 (10, 30, 100, 300 microM, 1 and 3 mM) induces vascular relaxation determined by isometric tension studies in rat mesenteric artery rings contracted with 1 microM phenylephrine. The vasorelaxation induced by GM1 was abolished by endothelium removal, by incubation with L-NAME (1 microM), and partially inhibited by the blockade of potassium channels by 1 mM tetraethylammonium, 10 microM glibenclamide, by the soluble guanylate cyclase inhibitor 1H-[1,2,4]oxadiazolo[4,3-alpha]quinoxalin-1-one (10 microM), and by 50 nM charybdotoxin, a blocker of large and intermediate conductance calcium-activated potassium channels. Moreover, GM1-induced relaxation was not affected by apamin (50 nM), a small conductance calcium-activated potassium channel blocker. The results indicate that direct and indirect nitric oxide pathways play a pivotal role in vasorelaxation induced by GM1, which is mediated mainly by potassium channels activation. We suggest that vasodilation may underlie some of the biological effects of exogenous GM1 ganglioside.

Protective and antioxidative effects of GM1 ganglioside in PC12 cells exposed to hydrogen peroxide are mediated by Trk tyrosine kinase

GM1 ganglioside was found to increase the survival of PC12 cells exposed to H(2)O(2), its action was blocked by Trk tyrosine kinase inhibitor K-252a. Thus, the inhibition of H(2)O(2) cytotoxic action by GM1 constituted 52.8 +/- 4.3%, but in the presence of 1.0 microM K-252a it was only 11.7 +/- 10.8%, i.e. the effect of GM1 became insignificant. Exposure to GM1 markedly reduced the increased accumulation of reactive oxygen species (ROS) and diminished the inactivation of Na(+),K(+)-ATPase induced in PC12 cells by H(2)O(2), but in the presence of K-252a GM1 did not change these metabolic parameters. The inhibitors of extracellular signal-regulated protein kinase, phosphatidyl inositol 3-kinase and protein kinase C decreased the effects of GM1. A combination of these protein kinase inhibitors reduced inhibition of H(2)O(2) cytotoxic action by GM1 to the larger extent than each of the inhibitors and practically abolished the ability of GM1 to decrease H(2)O(2)-induced ROS accumulation. The protective and antioxidative effects of GM1 in PC12 cells exposed to H(2)O(2) appear to be mediated by activation of Trk receptor tyrosine kinase and the protein kinases downstream from this enzyme.