Date Published: February 21, 2018
Publisher: Public Library of Science
Author(s): Haolin Sun, Longtao Qi, Shijun Wang, Xuwen Li, Chunde Li, Utpal Sen.
Apoptosis plays pivotal role in the pathogenesis of degenerative disc diseases, which is the primary contributor to low back pain. Although the role of hydrogen sulfide (H2S) in cell apoptosis is well appreciated, the effects and mechanism that H2S regulates the program death of intervertebral disc cell are not yet elucidated. In this study, we utilized the nucleus pulposus (NP) from patients with lumbar disc herniation to investigate the relationship between endogenous H2S and NP cells apoptosis in human. Furthermore, we analyzed primary rat NP cells to study the effects of exogenous H2S on hypoxia induced cell apoptosis. Human NP samples were obtained from patients with lumbar disc herniation and were divided into uncontained and contained herniation groups. Using immunohistochemistry staining and sulphur-sensitive electrode, we detected the expression of cystathionine-β-synthase (CBS) and cystathionine γ-lyase (CSE), as well as the production of endogenous H2S in human NP. Tunel staining showed increased apoptosis in NP from herniated disc; and there was significant correlation between H2S generation and apoptosis in human NP. CoCl2 was then used to induce hypoxia in cultured primary rat NP cells. Annexin V staining indicated that exogenous NaHS attenuated hypoxia induced apoptosis in rat NP cells. Furthermore, hypoxia significantly increased the levels of multiple apoptosis associated proteins (Fas, Cytochromes C, Caspase 9 and cleaved-Caspase-3) in cells, which were eliminated by NaHS.
Intervertebral disc degeneration is frequently associated with disc herniation, low back pain and sciatica, thus leads to global burden with severe health-care and socioeconomic consequences [1, 2]. Apoptosis is a prerequisite process for the development of nucleus pulposus (NP) cells and the maintenance of tissue homeostasis. However, excess apoptosis associated with hypoxia may lead to degenerative disc diseases [3, 4], which the underlying mechanisms remain largely unknown.
The intervertebral disc is the largest avascular structure in body. Within intervertebral disc, NP cells consume glucose to generate energy thus there is a small but significant consumption of oxygen . Aging and cumulative damages on intervertebral disc lead to degenerative changes in disc, which coincide with reduction in oxygen and other nutrition supply. In this manuscript, we document the endogenous generation of H2S in human intervertebral disc and demonstrate this endogenous H2S generation rate is associated with NP cells apoptosis. Using primary rat NP cells, we show that the hypoxia induced apoptosis can be attenuated by exogenous H2S donor.