ABSTRACT
The Janus kinase (JAK)/signal transducer and activator of transcription (STAT) signalling pathway is one of the most important in transducing signals from the cell surface to the nucleus in response to cytokines. In the present study, we investigated chronological alteration and cellular location of JAK1, STAT3, phosphorylated (p)-Tyr1022/1023-JAK1, p-Tyr705-STAT3, and interleukin-6 (IL-6) following spinal cord injury (SCI) in mice. Western blot analysis showed JAK1 to be significantly phosphorylated at Tyr1022/1023 from 6 h after SCI, peaking at 12 h and gradually decreasing thereafter, accompanied by phosphorylation of STAT3 at Tyr705 with a similar time course. ELISA analysis showed the concentration of IL-6 in injured spinal cord to also significantly increase from 3 h after SCI, peaking at 12 h, then gradually decreasing. Immunohistochemistry revealed p-Tyr1022/1023-JAK1, p-Tyr705-STAT3, and IL-6 to be mainly expressed in neurons of the anterior horns at 12 h after SCI. Pretreatment with a JAK inhibitor, AG-490, suppressed phosphorylation of JAK1 and STAT3 at 12 h after SCI, reducing recovery of motor functions. These findings suggest that SCI at the acute stage produces IL-6 mainly in neurons of the injured spinal cord, which activates the JAK/STAT pathway, and that this pathway may be involved with neuronal response to SCI.
Subject(s)
Neurons/physiology , Protein-Tyrosine Kinases/metabolism , STAT3 Transcription Factor/metabolism , Signal Transduction/physiology , Spinal Cord Injuries/physiopathology , Animals , Dimethyl Sulfoxide/pharmacology , Disease Models, Animal , Enzyme Inhibitors/pharmacology , Female , Janus Kinase 1 , Mice , Mice, Inbred C57BL , Tyrphostins/pharmacologyABSTRACT
The Janus kinase-signal transducer and activator of transcription (JAK-STAT) is one of the most important signaling pathways transducing signals from the cell surface in response to cytokines. Subarachnoid hemorrhage (SAH) produces cytokines in the CSF. We investigated whether this signaling pathway is activated in the rat basilar artery after SAH by cytokines. In a rat single-hemorrhage model of SAH, basilar arteries and CSF were obtained until 7 days after SAH. The concentration of interleukin-6 (IL-6) in CSF was measured by ELISA. Western blot analysis with JAK1, phosphospecific-JAK1, STAT3, phosphospecific STAT3 at Tyr705 and Ser727, cyclooxygenase-2 (COX-2), and actin antibodies was performed in basilar artery. The expressions of STAT3, phosphospecific STAT3 at Tyr705 and Ser727, and COX-2 in basilar artery were examined by immunohistochemical studies. The concentration of IL-6 immediately increased after SAH and Western blot analysis revealed that JAK1 was phosphorylated within 2 h, accompanied by phosphorylation of STAT3 at Tyr705, extending to Ser727 at days 1-2. Immunohistochemistry revealed phosphorylation of STAT3 to occur in endothelial and smooth muscle cells of the basilar artery. In addition, intracisternal injection of IL-6 by itself significantly increased phosphorylation of STAT3 at Tyr705 and Ser727. Expression of COX-2 was also upregulated in endothelial cells of the basilar artery. These results indicate that SAH produces the proinflammatory cytokine IL-6 in the CSF, which activates the JAK-STAT signaling pathway in the basilar artery and induces transcription of immediate early genes.
Subject(s)
Basilar Artery/physiopathology , Interleukin-6/cerebrospinal fluid , Protein-Tyrosine Kinases/metabolism , STAT3 Transcription Factor/metabolism , Signal Transduction/physiology , Subarachnoid Hemorrhage/physiopathology , Animals , Cyclooxygenase 2/metabolism , Cytokines/metabolism , Disease Models, Animal , Endothelium, Vascular/metabolism , Immunohistochemistry , Interleukin-6/pharmacology , Janus Kinase 1 , Muscle, Smooth, Vascular/metabolism , Phosphorylation , Phosphoserine/metabolism , Phosphotyrosine/metabolism , Rats , Subarachnoid Hemorrhage/enzymology , Subarachnoid Hemorrhage/geneticsABSTRACT
Although atlantoaxial transarticular screw fixation is technically demanding and there is a significant risk of vertebral artery (VA) injury, transarticular screw insertion in the middle and lower cervical spine is simple and can be performed safely with the aid of lateral fluoroscopic guidance. The authors describe the surgical techniques and outcome of transarticular screw fixation in the middle and lower cervical spine. Transarticular screw insertion into C2-3 or caudal cervical joints was performed from the articular pillar, directing the screw anterocaudally to penetrate the facet joint and the anterior cortex of the articular pillar, parallel to the sagittal plane. Because the VA and the nerve roots are anterior to the articular pillar at these levels, the screw can be placed safely with the assistance of lateral fluoroscopic guidance. Twenty-five patients ranging in age from 15 to 84 years underwent transarticular screw fixation, with a total of 81 screws. The transarticular screw was used as an anchor screw in combination with posterior cervical instrumentation in 19 patients and for facet screw fixation itself in six patients. Screw placement was successful and uncomplicated in all cases. The follow-up period ranged from 3 months to 5 years. No instance of screw backout or loosening was identified radiographically; fusion was achieved in all patients. Biomechanical strength is maintained by penetrating four cortical layers. When performed appropriately, this method is safe and reliable and deserves more widespread use.
