cytochrome-c-t and Intervertebral-Disc-Displacement

IL-1β has been reported highly expressed in degenerative intervertebral disc, and our previous study indicated IL-1β facilitates apoptosis of human degenerative nucleus pulposus (NP) cell. However, the underlying molecular mechanism remains unclear. We here demonstrate that IL-1β played a significantly pro-apoptotic effect under serum deprivation. IL-1β decreased Bcl-2/Bax ratio and enhanced cytochrome C released from mitochondria to cytosol, which proved mitochondria-meidated apoptosis was induced. Subsequently, mitochondria damage was detected under IL-1β stimualtion. In addition, IL-1β-mediated injuried mitochondria contributes to activate autophagy. However, pretreatment with the autophagy inhibitor 3-methyladenine showed the potential in further elevating the apoptosis rate induced by IL-1β in NP cells. Our results indicated that the mitochondrial pathway was involved in IL-1β-induced apoptosis of NP cells. Meanwhile, the damaged mitochondria-induced autophagy played a protective role against apoptosis, suggesting a postive feedback mechanism under inflammatory stress.

Topics: Apoptosis; Autophagy; Cytochromes c; Humans; Interleukin-1beta; Intervertebral Disc Degeneration; Intervertebral Disc Displacement; Mitochondria; Nucleus Pulposus

Two main pathways of Fas-mediated apoptosis have been identified: the Type-I (death-inducing signaling complex) pathway and the Type-II (mitochondrial) pathway. While apoptotic cell death has been implicated in lumbar degenerative disc disease, we are not aware of any studies in which surgically removed discs from live humans have been examined to determine which of the two pathways is involved in the apoptosis of disc cells. As an initial step in the development of therapies to inhibit inappropriate or premature apoptosis of disc cells, our objective was to determine which pathway is involved.. We examined thirty-two samples of herniated lumbar disc tissue with use of immunohistochemical staining and Western blot analysis to determine the presence of several proteins, including caspase-8 (associated with the Type-I pathway); BID (BH3 interacting domain death agonist), cytochrome-c, and caspase-9 (associated with the Type-II pathway); and caspase-3 (an executioner of apoptosis). The TUNEL (terminal deoxynucleotidyl transferase [TDT]-mediated dUTP nick end labeling) assay was performed to confirm the occurrence of apoptosis of the disc cells.. The proteins associated with the Type-II pathway (BID, cytochrome-c, and caspase-9) stained positively in all samples. Although the protein associated with the Type-I pathway (caspase-8) was not detected on immunohistochemical analysis, a small amount of caspase-8 was detected on Western blot analysis. However, the expression of Type-II proteins was still higher than the expression of caspase-8 on Western blot analysis. The expression of caspase-3 was identified in all samples with immunohistochemical and Western blot analysis. TUNEL-positive disc cells were identified in all samples.. The results of the present study suggest that human disc cells are Type-II cells, which undergo apoptotic cell death through mitochondrial involvement.

Topics: Adult; Apoptosis; BH3 Interacting Domain Death Agonist Protein; Blotting, Western; Carrier Proteins; Caspase 3; Caspase 8; Caspase 9; Caspases; Cytochromes c; fas Receptor; Female; Humans; Immunohistochemistry; In Situ Nick-End Labeling; Intervertebral Disc; Intervertebral Disc Displacement; Lumbar Vertebrae; Male; Middle Aged; Mitochondria