Abstract
The cutaneous wound healing process is tightly regulated by a range of cellular responses, including migration. Sphingosine-1-phosphate (S1P) is a signaling lipid produced in keratinocytes (KC) and it is known to stimulate skin wound repair through increased KC migration. Of the multifunctional triterpene ginsenosides, Rb1 enhances cutaneous wound healing process by increasing KC migration, but cellular mechanisms responsible for the Rb1-mediated increase in KC migration are largely unknown. Therefore, we hypothesized that, and assessed whether, Rb1 could stimulate KC migration through S1P-dependent mechanisms. Rb1 significantly increases S1P production by regulating the activity of metabolic conversion enzymes associated with S1P generation and degradation, sphingosine kinase 1 (SPHK1) and S1P lyase, respectively, in parallel with enhanced KC migration. However, blockade of ceramide to S1P metabolic conversion using a specific inhibitor of SPHK1 attenuated the expected Rb1-mediated increase in KC migration. Furthermore, a pan-S1P receptor inhibitor pertussis toxin significantly attenuated Rb1-induced stimulation of KC migration. Moreover, the Rb1-induced increases in KC migration required S1P receptor(s)-mediated activation of ERK1/2 and NF-κB, leading to production of key cutaneous migrating proteins, matrix metalloproteinase (MMP)-2 and MMP-9. Taken together, the results show that Rb1 stimulates KC migration through an S1P→S1P receptor(s)→ERK1/2→NF-κB→MMP-2/-9 pathway. This research revealed a previously unidentified cellular mechanism for Rb1 in enhancing KC migration and pointing to a new therapeutic approach to stimulate the cutaneous wound healing process.