Abstract
The Smyth line (SL) chicken model for vitiligo exhibits spontaneous, autoimmune loss of melanocytes in growing feathers. Onset of SL vitiligo (SLV) can be observed between 6 and 20 wks of age and affects 85-95% of SL chickens. Multiple factors contribute to the melanocytes’ cell death, including genetic susceptibility to vitiligo as well as environmental factors that trigger autoimmune loss of SL melanocytes (e.g., live turkey herpesvirus (HVT) administration at hatch). In humans, phenolic derivatives, such as 4-tertiary butyl phenol (4-TBP), have been shown to trigger vitiligo in susceptible individuals. 4-TBP is structurally similar to tyrosine, the initial substrate of tyrosinase in melanin synthesis. In addition to interfering with melanin production, 4-TBP exposure results in oxidative stress. To examine the effect of 4-TBP in SL and control chickens, pigmented growing feathers were collected from 1, 4 and 7 week-old SL, Brown Line (BL, parental control, <1% vitiligo) and Light Brown Leghorn (LBL, vitiligo resistant) chickens that did or did not receive HVT. The newest three mm growth (the melanocyte-containing, active pigmentation site) of the feathers was cultured with 4-TPB (200 μM) and the production of oxidative radicals was monitored in vitro. Independent of HVT treatment, 4-TBP induced more oxidative stress (P < 0.05) in feathers from SL than BL and LBL chickens, suggesting heightened sensitivity of melanocytes to 4-TBP in vitiligo-prone SL chickens.
