Articles: hyperalgesia-pathology.
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The symptoms of lumbar disc herniation, such as low back pain and sciatica, have been associated with local release of cytokines following the inflammatory process induced by the contact of the nucleus pulposus (NP) with the spinal nerve. ⋯ Together our results indicate that specific cytokines released during the inflammatory process induced by the herniated intervertebral disc play fundamental role in the development of the two modalities of hyperalgesia (mechanical and thermal) and that the maintenance of this inflammation may be the most important point for the chronification of the pain.
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Most post-herpetic neuralgia (PHN) patients suffer from tactile allodynia (pain evoked by lightly touching the skin) and it is frequently the dominant clinical manifestation. The pathophysiology of tactile allodynia in PHN patients is poorly understood and this is one of the major limits to the development of appropriate therapies. Epidermal nerve fibres (ENFs) are free nerve endings of small-diameter A-delta and C primary afferents, which can easily be assessed by neurodiagnostic skin biopsy (NSB). ⋯ Results showed that epidermal innervation was lower in the allodynic skin than in the contralateral skin, although there was great variability among patients. There was no correlation between severity of allodynia and epidermal innervation of the PHN skin. In conclusion, the present study further indicates peripheral nervous system involvement in PHN but does not support a direct correlation between epidermal innervation changes and tactile allodynia.
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Diabetes comorbidities include disabling peripheral neuropathy (DPN) and an increased risk of developing cancer. Antimitotic drugs, such as paclitaxel, are well known to facilitate the occurrence of peripheral neuropathy. Practitioners frequently observe the development or co-occurrence of enhanced DPN, especially cold sensitivity, in diabetic patients during chemotherapy. ⋯ Moreover, mRNA levels of glutathione peroxidase 4 and glutathione-S-reductase were significantly lower in diabetic groups treated with paclitaxel. Finally, TRPA1 gene expression was enhanced by 45% in diabetic rats. Paclitaxel potentiation of cold hyperalgesia in diabetes may result from the combination of increased mitochondrial ROS production and poor radical detoxification induced by paclitaxel treatment and diabetes-related overexpression of TRPA1.
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Matrix metalloproteinases (MMPs) have been implicated in the modulation of synaptic plasticity, glial activation, and long-term potentiation in the CNS. Here we demonstrate for the first time a mechanism for the regulation of nociceptive processing by spinal MMP-3 during peripheral inflammation. We first determined by western blotting that the catalytic (active) form of MMP-3 (cMMP-3) is increased in lumbar spinal cord following peripheral inflammation in rats. ⋯ The hypersensitivity behavior is prevented by intrathecal etanercept (TNF blockade). Treatment with cMMP-3 resulted in an increase in TNF release from spinal primary microglial, but not astrocyte cultures. These findings thus present direct evidence implicating MMP-3 in the coordination of spinal nociceptive processing via a spinal TNF-dependent mechanism.
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Endometriosis is an enigmatic painful disorder whose pain symptoms remain difficult to alleviate in large part because the disorder is defined by extrauteral endometrial growths whose contribution to pain is poorly understood. A rat model (ENDO) involves autotransplanting on abdominal arteries uterine segments that grow into vascularized cysts that become innervated with sensory and sympathetic fibers. ENDO rats exhibit vaginal hyperalgesia. ⋯ Thus, abnormally-active innervation of ectopic growths occurs before hyperalgesia develops, supporting the hypothesis. These findings suggest that painful endometriosis can be classified as a mixed inflammatory/neuropathic pain condition, which opens new avenues for pain relief. The findings also have implications beyond endometriosis by suggesting that functionality of any transplanted tissue can be influenced by the innervation it acquires.