Wen-Jun Luo1, Fan Yang2, Fei Yang1, Wei Sun2, Wei Zheng3, Xiao-Liang Wang2, Fang-Fang Wu1, Jiang-Lin Wang1, Jia-Shuang Wang4, Su-Min Guan5, Jun Chen6. 1. Institute for Biomedical Sciences of Pain, Tangdu Hospital, The Fourth Military Medical University, Xi'an 710038, People's Republic of China. 2. Institute for Biomedical Sciences of Pain, Tangdu Hospital, The Fourth Military Medical University, Xi'an 710038, People's Republic of China; Key Laboratory of Brain Stress and Behavior, People's Liberation Army, Xi'an 710038, People's Republic of China. 3. Department of Pain Medicine, Tianjin First Central Hospital, Tianjin 300192, People's Republic of China. 4. Department of Pain Medicine, Red-Cross Hospital, Jinan University, Guangzhou 510220, People's Republic of China. 5. School of Stomatology, The Fourth Military Medical University, Xi'an 710032, People's Republic of China. 6. Institute for Biomedical Sciences of Pain, Tangdu Hospital, The Fourth Military Medical University, Xi'an 710038, People's Republic of China; Key Laboratory of Brain Stress and Behavior, People's Liberation Army, Xi'an 710038, People's Republic of China; Beijing Institute for Brain Disorders, Beijing 100069, People's Republic of China.
Abstract
BACKGROUND: In a 5-year follow-up study in a hospital in southern China, it was shown that intervertebral foramen (IVF) injection of ozone at the involved segmental levels could significantly alleviate paroxysmal spontaneous pain and mechanical allodynia in patients with chronic, intractable postherpetic neuralgia (PHN) and improve the quality of life. However, so far no proof-of-concept studies in animals have been available. OBJECTIVE: This study was designed to investigate whether IVF ozone has an analgesic effect on animal models of neuropathic and inflammatory pain. STUDY DESIGN: Experimental trial in rats. SETTING: Institute for Biomedical Sciences of Pain. METHODS: By IVF injection, a volume of 50 µl containing 30 µg/mL ozone-oxygen mixture or 50 µl air was carried out on male Sprague-Dawley rats of naïve, inflammatory pain states produced by injections of either bee venom or complete Freud's adjuvant, and neuropathic pain state produced by spared nerve injury, respectively. The effects of IVF ozone on pain-related behaviors were evaluated for 2 weeks or one month. Then combined use of gabapentin (100 mg/1 kg body weight) with IVF ozone was evaluated in rats with neuropathic pain by intraperitoneal administration 5 days after the ozone treatment. Finally, the analgesic effects of another 4 drugs, AMD3100 (a CXCR4 antagonist), A-803467 (a selective Nav1.8 blocker), rapamycin (the mTOR inhibitor), and MGCD0103 (a selective histone deacetylase inhibitor) were evaluated for long term through IVF injection, respectively. RESULTS: (1) IVF injection of ozone at L4-5 was only effective in suppression of mechanical allodynia in rats with neuropathic pain but not with inflammatory pain; (2) the analgesic effects of IVF ozone lasted much longer (> 14 days) than other selective molecular target drugs (< 48 hours) inhibiting or antagonizing at Nav1.8 (A-803467), CXCR4 (AMD3100), mTOR (rapamycin), and histone deacetylase (MGCD0103); (3) combined use of systemic gabapentin and IVF ozone produced a synergistic analgesic effect in rats with neuropathic pain. LIMITATIONS: Evaluation of the possible analgesic effects of the intraplantar injection of ozone was not performed. CONCLUSIONS: In the present study, we provided a line of evidence for the first time that IVF injection of ozone selectively relieved neuropathic pain but not inflammatory pain, and enhanced the analgesic effect of gabapentin. KEY WORDS: Chronic pain, neuropathic pain, inflammatory pain, ozone therapy, interventional therapy, gabapentin, spared nerve injury, bee venom, complete Freud's adjuvant.
BACKGROUND: In a 5-year follow-up study in a hospital in southern China, it was shown that intervertebral foramen (IVF) injection of ozone at the involved segmental levels could significantly alleviate paroxysmal spontaneous pain and mechanical allodynia in patients with chronic, intractable postherpetic neuralgia (PHN) and improve the quality of life. However, so far no proof-of-concept studies in animals have been available. OBJECTIVE: This study was designed to investigate whether IVF ozone has an analgesic effect on animal models of neuropathic and inflammatory pain. STUDY DESIGN: Experimental trial in rats. SETTING: Institute for Biomedical Sciences of Pain. METHODS: By IVF injection, a volume of 50 µl containing 30 µg/mL ozone-oxygen mixture or 50 µl air was carried out on male Sprague-Dawley rats of naïve, inflammatory pain states produced by injections of either bee venom or complete Freud's adjuvant, and neuropathic pain state produced by spared nerve injury, respectively. The effects of IVF ozone on pain-related behaviors were evaluated for 2 weeks or one month. Then combined use of gabapentin (100 mg/1 kg body weight) with IVF ozone was evaluated in rats with neuropathic pain by intraperitoneal administration 5 days after the ozone treatment. Finally, the analgesic effects of another 4 drugs, AMD3100 (a CXCR4 antagonist), A-803467 (a selective Nav1.8 blocker), rapamycin (the mTOR inhibitor), and MGCD0103 (a selective histone deacetylase inhibitor) were evaluated for long term through IVF injection, respectively. RESULTS: (1) IVF injection of ozone at L4-5 was only effective in suppression of mechanical allodynia in rats with neuropathic pain but not with inflammatory pain; (2) the analgesic effects of IVF ozone lasted much longer (> 14 days) than other selective molecular target drugs (< 48 hours) inhibiting or antagonizing at Nav1.8 (A-803467), CXCR4 (AMD3100), mTOR (rapamycin), and histone deacetylase (MGCD0103); (3) combined use of systemic gabapentin and IVF ozone produced a synergistic analgesic effect in rats with neuropathic pain. LIMITATIONS: Evaluation of the possible analgesic effects of the intraplantar injection of ozone was not performed. CONCLUSIONS: In the present study, we provided a line of evidence for the first time that IVF injection of ozone selectively relieved neuropathic pain but not inflammatory pain, and enhanced the analgesic effect of gabapentin. KEY WORDS: Chronic pain, neuropathic pain, inflammatory pain, ozone therapy, interventional therapy, gabapentin, spared nerve injury, bee venom, complete Freud's adjuvant.