Abstract
Recently, numerous studies have suggested that osteoporosis was likely to connect with environmental pollutants including vehicle exhaust fumes from diesel engines and cigarette smoke. The main components of these pollutants are well known as polycyclic aromatic hydrocarbons (PAHs). Bezno(a)pyrene (BaP) is a member of PAHs. Here, we investigate the effects of low-dose BaP on the myogenic differentiation and myotube formation in skeletal myoblasts. The results demonstrated that low dose BaP (0.25 and 0.5 μM) significantly inhibited the myotube formation after 4 days of differentiation in C2C12 myoblasts, as well as in primary human myoblasts. Next we hypothesized that BaP would interfere the proliferation of myoblast growth resulting in the poor myotube formation. In the growth culture, C2C12 myoblasts were pretreated BaP during short- to long-period and then measure the level of cell number by trypan blue staining. As expected, the cells pretreated for 2-day with BaP were dramatically decreased until 10-day, indicating BaP could disrupt C2C12 myoblast growth. Furthermore, the suppressed mechanism in myogenic differentiation was via diminishing the differentiation-associated protein expressions of myosin heavy chain (MHC), phospho-akt, MyoD and myogenin. Estrogen receptors (ER) antagonist ICI182780 effectively enhanced the inhibitory effect of BaP on the expressions of MHC and myoD, while the agonist 17β-estradiol could reverse the inhibitory effect of BaP. Taken together, these results suggest that low-dose BaP intervenes in skeletal muscle differentiation and myotube formation via an antagonism on ER.
