The Underlying Mechanisms Of Selective Phosphodiesterase-2A Inhibitor And Oxygen/ozone With Low Concentration In Chronic Radiculitis Rats

Background:Lumbar intervertebral disc herniation is a common disorder,accompanied by radiculopathy.Radiculopathy is characterized by the inflammation of spinal nerve roots,causing leg pain.It is well known that chronic radiculopathic pain seriously compromises the quality of patients' life.Previously published data evidence that mechanical compression and radicular inflammation play a key role in the origin of radicular pain induced by lumbar inervertebral disc herniation.Some scholars succeeded to establish a rat model of non-compressive lumbar disc herniation(NCLDH)with transplanted nucleus pulposus(NP).But the mechanisms in radicular inflammation are not utterly clear.Phosphodiesterases(PDEs)are enzymes that can hydrolyze cAMP or cGMP.PDEs are divided into 11 subfamilies(PDE1 to PDE11).PDE2A is a dual-function PDEs that can hydrolyze both cAMP and cGMP.Recent experimental reports have demonstrated that inhibitors of some PDEs subfamilies can inhibit pro-inflammatory cytokines release through cAMP/cGMP signaling pathways in cardiac failure,pulmonary hypertension,erectile dysfunction,depression and sepsis.Some studies found that PDE2A inhibitors have anti-inflammtory in pulmonary hypertension and osteoarthritis pain.But no study reported that whether PDE2A inhibitors can relieve the radicular imflammation induced by lumbar intervertebral disc herniation.Recently,oxygen/ozone therapy is widely applied in the treatment of lumbar disc herniation,radiculitis,myofascial pain syndrome and arthralgia in clinic of pain management.And it had been reported satisfied effects in the treatment of intervertebral disc herniation with/without radiculopathy in both clinic and trials.However,there is little study aimed to investigate the underlying mechanisms about intrathecal injection of oxygen/ozone with low concentration in radiculopathy induced by intervertebral disc herniation.Purpose:The present study aimed to investigate whether intrathecal administration of PDE2A inhibitor,Bay 60-7550 and oxygen/ozone with low concentration could alleviate mechanical allodynia in non-compressive lumbar disc herniation(NCLDH)rats and the underlying mechanisms.Methods:Part ?:Rats were divided into four groups(n=8):sham group(sham operation+vehicle),vehicle group(NCLDH+vehicle),Bay 0.1 group(NCLDH+Bay 60-7550 0.1 mg/kg)and Bay 1.0 group(NCLDH+Bay 60-7550 1.0 mg/kg).NCLDH rats by autologous nucleus pulposus(NP)implantation were established.Mechanical PWTs were analyzed from the day before surgery to day 7 after surgery.The ipsilateral lumbar(L4-6)segments of the spinal dorsal horns were removed at day 7 post-operation Tumor necrosis factor ?(TNF-?)interleukin-1?(IL-1?)interleukin-6(IL-6),cyclic adenosine monophosphate(cAMP),and cyclic guanosine monophosphate(cGMP)expressions were measured by ELISA.PDE2A mRNA and protein expressions in spinal cord were measured by Real-Time PCR and Western blot.Part ?:Rats were divided into 5 groups(n=8):sham group(sham operation+filtered air),control group(NCLDH+filtered air),O3 10?g/ml group(NCLDH+10?g/ml oxygen/ozone),O3 20?g/ml group(NCLDH+20?g/ml oxygen/ozone),O3 30?g/ml group(NCLDH+30?g/ml oxygen ozone).NCLDH rats were established.Mechanical PWTs were analyzed from day-1 before surgery to day 7 after surgery.The ipsilateral lumbar(L4-6)spinal dorsal horns were separated at day 7 post-surgery.The expressions of TNF-?,IL-1?,IL-6,cAMP and cGMP were measured by ELISA.The mRNA and protein expressions of spinal PDE2A and NF-KB/p65 were assayed by Real-Time PCR and Western blot.Results:Part ?:NCLDH rats were established successfully.Mechanical PWTs were decreased significantly,with spinal TNF-?,IL-1?,IL-6,cAMP and cAMP significant increasing in vehicle group and Bay groups.At day 7,spinal PDE2A mRNA and protein were increased significantly.Intrathecal injection of the PDE2A inhibitor,Bay 60-7550,significantly up-regulated mechanical PWTs,down-regulated spinal TNF-?,IL-1? and IL-6 over-expressions.Moreover,Bay 60-7550 significantly increased the expression of spinal cAMP,as well as cGMP.The effects were in a more remarkable manner.Furthermore,1.0mg/kg Bay 60-7550 decreased the over-expression of spinal PDE2A in NCLDH rats.Part ?:Chronic radiculitis rats by NCLDH were established.Intrathecal administration of 10,20,30pg/ml oxygen/ozone increased mechanical PWTs,decreased spinal TNF-?,IL-1? and IL-6,and increased spinal cAMP and cGMP.And the effects were most remarkable in 20?g/ml oxygen/ozone.At the same time,20?g/ml oxygen/ozone down-regulated the mRNA and protein over-expressions of spinal PDE2A and NF-KB/p65 in NCLDH rats.Conclusions:NCLDH rats were successfully established.Bay 60-7550 alleviated mechanical allodynia and over-expressions of spinal TNF-?,IL-1? and IL-6 in NCLDH rats,which might be associated with cAMP/cGMP.Intrathecal oxygen/ozone with 10,20,30?g/ml attenuated mechanical allodynia probably via PDE2A-cAMP/cGMP-NF-KB/p65 signaling pathway in NCLDH rats.Thus,spinal PDE2A might be associated with inflammatory pain.PDE2A inhibitor and oxygen/ozone with low concentration may represent analgesic strategy for radiculitis and lumbar disc herniation.And oxygen/ozone with 20?g/ml might be the optimal concentration.