Luteolin is a common flavonoid abundantly present in several plant products, including broccoli, pepper, thyme, and celery. Studies have shown that luteolin possesses beneficial neuroprotective effects both in vitro and in vivo. It also has antioxidant and immunomodulatory properties.
Animal and Clinical Studies
Hendriks and colleagues administered luteolin (50 mg/kg/day) to rats with EAE. They reported that both oral and intraperitoneal administration of luteolin suppressed behavioral deficits, prevented relapse, and reduced inflammation and axonal damage.77 Furthermore, it was recently reported that exposure to a special mixture of palmitoylethanolamide/luteolin promoted the maturation of oligodendrocyte precursor cells that make myelin sheet around neurons.78 Conversely, Verbeek et al. reported that oral administration of luteolin (10 mg/day) delayed the recovery of behavioral deficits rather than reducing disease severity.
Some clinical trials show the effectiveness of luteolin on autism, diabetes mellitus type 2, and some kinds of cancers. However, there are no clinical trials on patients with MS.
Recently, the effects of the flavone luteolin on human cultured keratinocytes were investigated (Weng et al., 2014). Authors showed that TNF, at the concentration of 50 ng/mL, produced significant production of IL-6, IL-8 and VEGF from primary keratinocytes and human HaCaT cells. Luteolin pretreatment (at concentrations of 10–100 µM) inhibited in a concentration-dependent manner both mRNA expression and release of all mediators.
Luteolin reduced also the TNF-induced mRNA expression of RELA gene that encoding the NF-κB subunit NF-κB p65. The gene expression of RELA is increased in human psoriatic skin. Moreover, the flavone decreased TNF-induced phosphorylation, DNA binding and nuclear translocation of NF-κB. A previous work demonstrated the ability of luteolin to decrease TNF-triggered phosphorylation, nuclear translocation and DNA-binding activity of NF-κB (Zbytek et al., 2003). Of interest is the inhibition of IL-6 gene expression and secretion by luteolin, since IL-6 is a requisite to drive maturation of Th17 cells, also involved in the pathogenesis of psoriasis and the significant decrease of HaCaT, but not normal keratinocyte proliferation. The flavone is lipid-soluble. This characteristic may be useful for the development of topical formulations that easily penetrate the skin.