Download Effects of Galectin-3 on Apoptosis in Human and Mouse

Effects of Galectin-3 on Apoptosis in Human and Mouse Melanocytes
Emily Galan, Amy Koshoffer, Raymond Boissy, Ph.D.
Department of Dermatology, University of Cincinnati
Introduction: Galectin-3 (Gal-3) is a carbohydrate binding protein associated with a role in
regulating apoptosis. Gal-3 localized in the cytosol protects the cell against apoptosis,
whereas Gal-3 in the nucleus yields the opposite effect. Visualization using
immunocytochemistry has shown Gal-3 to be concentrated in the cytoplasm of melanocytes.
Vitiligo is an acquired depigmentary disorder of the skin that affects approximately 1% of the
world’s population. Contact/Occupational Vitiligo results from apoptosis of cutaneous
melanocytes after exposure to phenol/catechol derivatives such as 4-tertyl-butyl-phenol (4TBP). Therapies targeted to rescuing melanocytes from apoptosis could potentially prevent or
reverse the effects of contact vitiligo.
Aims/Hypotheses: We hypothesized that Galectin-3 regulates apoptosis in the melanocyte
and loss or gain of Gal-3, induces or rescues, respectively, phenol/catechol induced
melanocyte apoptosis.
Methods: Neonatal foreskins obtained from Christ Hospital Nursery were used to establish
cell lines of light and dark melanocytes. Additional melanocytes were harvested from normal
and Gal-3 knockout mice. First, human melanocytes from light and dark lines along with
mouse melanocytes from control and knockout lines were treated with 4-TBP
(phenol/catechol derivative known to induce contact vitiligo) and Staurosporine (general
apoptosis inducer). Cell viability was assessed using an MTT assay. The experiement was
then repeated using human melanocytes from control and Gal-3 knockout lines.
Results: MTT assay analysis showed that the dark human melanocyte lines were more
vulnerable to apoptosis induced by 4-TBP than the light lines. Differences between the dark
and light human melanocyte lines treated with Staurosporine were not statistically significant.
For the mouse melanocytes, the KO mouse melanocytes were more resistant to apoptosis
induced by 4-TBP than the WT mice. Differences between the KO and WT mouse
melanocytes treated with Staurosporine were not statistically significant. Cell viability
between control human melanocytes and Gal-3 KO human melanocytes were not statistically
different for 4-TBP or Staurosporine.
Conclusions: Galectin-3 does not protect melanocytes from induced apoptosis.
Acknowledgements: This study was supported in part by NIH grant T35 DK