Inhibition of lysyl oxidase-like 1 (LOXL1) expression arrests liver fibrosis progression in cirrhosis by reducing elastin crosslinking

Mature crosslinked-poly-elastin deposition has been found to be associated with liver fibrosis. However, the regulation of crosslinked/insoluble elastin in liver fibrosis remains largely unknown. Here, we investigated the contribution of lysyl oxidases (LOXs) family, mediated elastin crosslinking, to liver fibrogenesis. We established carbon tetrachloride (CCl4)-induced liver fibrotic and cirrhotic models and found that crosslinked/insoluble elastin levels spiked only in cirrhosis stage during disease progression, in comparison to collagen I levels which increased continuously though all stages. Among the LOXs family members, only LOX-like 1 (LOXL1) levels were coincident with the appearance of crosslinked/insoluble elastin. These coincidences included that LOXL1 expression increased (34 fold) in cirrhosis, localized with a-smooth muscle actin (SMA) and was absent in normal and fibrotic livers. In LX-2 cells, LOXL1 silencing arrested expression of alpha-SMA, elastin and collagen I. Our previously characterized adeno-associated vector (AAV) 2/8 shRNA was shown to effectively down regulate LOXL1 expression in CCl4 induced fibrosis mice models. These resulted in delicate and thinner septa and less crosslinked elastin, with a 58% loss of elastin area and 51% decrease of collagen area. Our findings strongly suggested that elastin crosslinking and LOXL1 were co-associated with liver cirrhosis, while selective inhibition of LOXL1 arrested disease progression by reducing crosslinking of elastin.