L-NMMA delays apoptosis in the nucleus pulposus cells of intervertebral discs

Chun-Lei Liu, Xiang-Jiang Wang, Yi-He Hu, Bei-Ji Lu, Gui-Qing Wang
Apoptosis plays an important role in degeneration of Nucleus Pulposus (NP) cells. L-Monomethyl-Arginine (L-NMMA) is an analogue of L-arginine and can be inactivated irreversibly by induced NOS (iNOS). L-NMMA can also compete with L-arginine for binding sites on iNOS molecules. In addition, L-NMMA has been reported to influence the apoptosis of hyaline cartilage cells in vitro. Thus, we hypothesized that L-NMMA would influence the apoptosis of NP cells in vitro. Rabbit primary NP cells were
more » ... NP cells were cultured and subjected to flow cytometry to determine the levels of apoptosis in each group at each time point. Western blotting was performed to detect the Bcl-2/Bax ratio, as well as protein levels of caspase-3 and caspase-9. A significant increase in apoptosis was observed between the NP cells cultured with 1% FBS medium with versus without L-NMMA (P<0.01). Likewise, the Bcl-2/Bax ratio was also increased in NP cells cultured in 1% FBS with L-NMMA, versus those cultured without L-NMMA (P<0.05). Meanwhile, the activity levels of both caspase-3 and caspase-9 were reduced in the presence of L-NMMA, compared with levels observed in the absence of L-NMMA (P<0.01). This study showed that L-NMMA treatment delayed the senescence and apoptosis of NP cells in vitro, raising the possibility that L-NMMA may be a novel treatment to delay intervertebral disc degeneration.