Riboflavin may ameliorate neurological motor disability but not spatial learning and memory impairments in murine model of multiple sclerosis

Avian riboflavin deficiency causes reliably reproducible peripheral nerve demyelination and, with vitamin supplementation, rapid remyelination

Riboflavin deficiency produces severe peripheral neve demyelination in young, rapidly growing chickens. While this naturally-occurring vitamin B2 deficiency can cause a debilitating peripheral neuropathy, and mortality, in poultry flocks, it can also be a useful experimental animal model to study the pathogenesis of reliably reproducible peripheral nerve demyelination. Moreover, restitution of normal riboflavin levels in deficient birds results in brisk remyelination. It is the only acquired, primary, demyelinating tomaculous neuropathy described to date in animals. The only other substance that causes peripheral nerve demyelination similar to avian riboflavin deficiency is tellurium and the pathologic features of the peripheral neuropathy produced by this developmental neurotoxin in weanling rats are also described.

Riboflavin Inhibits Histamine-Dependent Itch by Modulating Transient Receptor Potential Vanilloid 1 (TRPV1)

Riboflavin, also known as vitamin B₂, isfound in foods and is used as a dietary supplement. Its deficiency (also called ariboflavinosis) results in some skin lesions and inflammations, such as stomatitis, cheilosis, oily scaly skin rashes, and itchy, watery eyes. Various therapeutic effects of riboflavin, such as anticancer, antioxidant, anti-inflammatory, and anti-nociceptive effects, are well known. Although some studies have identified the clinical effect of riboflavin on skin problems, including itch and inflammation, its underlying mechanism of action remains unknown. In this study, we investigated the molecular mechanism of the effects of riboflavin on histamine-dependent itch based on behavioral tests and electrophysiological experiments. Riboflavin significantly reduced histamine-induced scratching behaviors in mice and histamine-induced discharges in single-nerve fiber recordings, while it did not alter motor function in the rotarod test. In cultured dorsal root ganglion (DRG) neurons, riboflavin showed a dose-dependent inhibitory effect on the histamine- and capsaicin-induced inward current. Further tests wereconducted to determine whether two endogenous metabolites of riboflavin, flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD), have similar effects to those of riboflavin. Here, FMN, but not FAD, significantly inhibited capsaicin-induced currents and itching responses caused by histamine. In addition, in transient receptor potential vanilloid 1 (TRPV1)-transfected HEK293 cells, both riboflavin and FMN blocked capsaicin-induced currents, whereas FAD did not. These results revealed that riboflavin inhibits histamine-dependent itch by modulating TRPV1 activity. This study will be helpful in understanding how riboflavin exerts antipruritic effects and suggests that it might be a useful drug for the treatment of histamine-dependent itch.