Spent hops extract (Humulus Lupulus L.) attenuates inflammation and angiogenesis of the retina via the nuclear factor-kappaB and protein kinase B/extracellular signal-regulated kinase pathways.

Spent hops extract (SHE) is a plant extract containing compounds with proven anti-inflammatory and anti-angiogenic activities. However, extract may exert synergic effects compared to its individual polyphenol components. Inflammatory diseases of the retina may lead to visual impairment, a reduction of the comfort of life, and even blindness due to the formation of new pathological blood vessels. More effective therapeutic options are being sought. The goal of the present study was to investigate the anti-inflammatory and anti-angiogenic potentials of SHE on human retinal pigment epithelial cells (ARPE-19) stimulated by lipopolysaccharide (LPS) or tumor necrosis factor alpha (TNF-α). The SHE (250 μg/mL) was found to downregulate the gene expression of interleukin 6 (IL-6) to 33% in LPS-triggered cells; it also reduced both matrix metalloproteinase 2 (MMP-2) and 9 (MMP-9) mRNA expression to 13% and 43% respectively, and their activity to 82% (MMP-2) and 57% (MMP-9), compared to TNF-α-stimulated cells. Also, SHE modulated the TNF-α-induced expression of vascular endothelial growth factor (VEGF) and endothelial growth factor receptor 2 (VEGFR2). It is possible that SHE inhibited retinal inflammation and angiogenesis by suppressing the nuclear factor kappa B (NF-κB), protein kinase B (Akt) and extracellular signal-regulated kinase (ERK) pathways. Our results demonstrate that SHE has anti-inflammatory and anti-angiogenic potential against retinal diseases. This is the first such study to report on the efficacy of SHE on retinal inflammatory diseases.