The opioid peptide biphalin modulates human corneal epithelial wound healing in vitro
Abstract Background: Analgesic drugs, including nonselective opioids and non-steroidal anti-inflammatory drugs, should be used with great precautions to relieve pain after physical damage of the corneal epithelium because of their unfavorable effects on the wound-healing process. Biphalin is a synthetic opioid peptide that has been demonstrated to possesses a strong analgesic effect on rodents. The purpose of this study is to investigate the effects of biphalin on human corneal epithelium wound healing.Methods: An immortalized human corneal epithelial cell (HCEC) culture was used to test the effects of biphalin on wound healing. The toxicity of biphalin in various concentrations was measured with the MTT assay. The effect of 1 µM and 10 µM biphalin were tested on wound closure in an in vitro scratch assay of HCECs and for cell migration and proliferation separately. Naloxone, a non-selective competitive antagonist of opioid receptors, was also used to inhibit the effects of biphalin in all experiments.Results: Biphalin did not cause any toxic effect on HCECs in concentrations lower than 100 µM at various incubation time points. Biphalin increased the wound closure process significantly at 1 µM concentration in an in vitro scratch assay of HCECs (p < 0.05). It also increased the migration of HCECs significantly (p < 0.01). There was no significant difference between biphalin and control groups of HCECs in the Ki67 proliferation assay.Conclusion: Biphalin, a synthetic opioid peptide, has a potential role as a novel topical analgesic agent that promotes corneal epithelial wound healing. This role should be evaluated in further in vivo and clinical studies.