The role of Cl- transport across the plasma membrane was studied in an early step of pollen grain germination in tobacco Nicotiana tabacum L. The Cl- channel blockers, 5-nitro-2-(3-phenylpropylamino)benzoic acid (NPPB) and niflumic acid, completely suppress the germination with IC(50) approximately 8 micro M. At this concentration NPPB reduces the rate of Cl- efflux out of pollen grain by 1.8-fold in the interval 5-12 min, and niflumic acid reduces the rate 1.2-fold. 4,4;-Diisothiocyanatostilbene-2,2;-disulfonic acid, a known inhibitor of Cl- channels and antiporters, completely suppresses germination as well (IC(50) = 240 micro M), but has no effect on the rate of Cl- efflux. Inhibitors of chloride co-transporters, such as furosemide, bumetanide, and bis(1,3-dibutylbarbituric acid)pentamethine oxonol, suppress the germination by less than 50%. This set of data suggests that NPPB-sensitive anion channels are involved in the activation of pollen grains in the early stage of germination.

Background: COVID-19 treatment remains a challenge for medicine because of the extremely short time for clinical studies of drug candidates, so the drug repurposing strategy, which implies the use of well-known and safe substances, is a promising approach.Objective: We present the results of an observational clinical study that focused on the influence of riboflavin (vitamin B2) supplementation on the immune markers of COVID-19 severity in patients with mental health disorders.Results: We have found that 10 mg of flavin mononucleotide (a soluble form of riboflavin) intramuscularly twice a day within 7 days correlated with the normalization of clinically relevant immune markers (neutrophils and lymphocytes counts, as well as their ratio) in COVID-19 patients. Additionally, we demonstrated that total leucocytes, neutrophils, and lymphocytes counts, as well as the neutrophils to leucocytes ratio (NLR), correlated with the severity of the disease. We also found that patients with organic disorders (F0 in ICD-10) demonstrated higher inflammation then patients with schizophrenia (F2 in ICD-10).Conclusion: We suggest that riboflavin supplementation could be promising for decreasing inflammation in COVID-19, and further evaluation is required.This observational clinical trial has been registered by the Sverzhevsky Research Institute of Clinical Otorhinolaryngology (Moscow, Russia), Protocol No. 4 dated 05/27/2020.

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We studied the possibility of K + and Cl -efflux from tobacco pollen grains during their activation in vitro or on the stigma of a pistil. For this purpose the X ray microanalysis and spectrofluorometry were applied. We found that the relative content of potassium and chlorine in the microvolume of pollen grain decreases during its hydration and activation on stigma. Efflux of these ions was found both in vivo and in vitro. In model in vitro experiments anion channel inhibitor NPPB ((5 nitro 2 (3 phenylpropylamino) ben zoic acid) in the concentration that was blocking pollen germination, reduced Cl -efflux; potassium channel inhibitor TEA (tetraethylammonium chloride) partially reduced K + efflux and lowered the percent of acti vated cells. Another blocker of potassium channels Ba 2+ caused severe decrease in cell volume and blocked the activation. In general, the obtained data demonstrates that the initiation of pollen germination both in vivo and in vitro involves the activation of K + and Cl -release. An important role in these processes is played by NPPB , TEA and Ba 2+ sensitive plasmalemma ion channels.