Pain
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Observational Study
Post-acute sensory neurological sequelae in patients with SARS-CoV-2 infection: the COVID-PN observational cohort study.
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection can cause neurological sequelae after the resolution of symptomatic COVID-19 illness, but the occurrence of peripheral neuropathy symptoms and cranial nerve dysfunction is unknown. This study aimed to characterize the occurrence and severity of pain and peripheral neuropathy symptoms in patients with SARS-CoV-2 infection. An observational cohort study included adults tested for a SARS-CoV-2 infection at an academic medical center (assigned as CV+ or control, based on test results). ⋯ The occurrence of pain in the extremities was higher in the CV+ group (24.2% vs 9.8%, OR = 2.95 [2.21-3.91]). SARS-CoV-2 infection was also associated with higher occurrence of peripheral neuropathy symptoms, after adjusting for the history of chronic pain and neuropathy (OR = 3.19 [2.37-4.29]). The results suggest that SARS-CoV-2 infection was independently associated with an increased risk of pain and peripheral neuropathy symptoms.
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Methylglyoxal (MGO) is a reactive dicarbonyl byproduct of glycolysis implicated in a growing number of neuropathic pain conditions, including chemotherapy-induced peripheral neuropathy, diabetic peripheral neuropathy, and radiculopathy with lumbar disk herniation. Recent studies show success in preclinical models treating these disorders with an interventional ketogenic diet. Here, we tested the hypothesis that a ketogenic diet modifies pathological MGO signaling as a mechanism underlying neuropathy improvement. ⋯ Mice receiving intraplantar MGO injection exhibit increased nociceptive behavior (lifting, licking, biting, and scratching), which was significantly reduced by coincubation with either acetoacetate or β-HB. Methylglyoxal increased phospho-extracellular signal-regulated kinase-positive cells in the spinal dorsal horn, and this evoked spinal activation was ameliorated by preincubation with acetoacetate or β-HB. These results suggest that a ketogenic diet and ketone bodies ameliorate MGO-evoked nociception, partially through detoxification of MGO, and provide rationale for therapeutic intervention with a ketogenic diet in MGO-driven pathologies.
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Astrocytic PTEN regulates neuropathic pain by facilitating HMGCR-dependent cholesterol biosynthesis.
Recent studies have noted the role of the phosphatase and tensin homolog deleted on chromosome 10 (PTEN) in developing neuropathic pain, but the underlying mechanisms are obscure. We found that PTEN was mainly expressed in astrocytes in the rat spinal cord and dramatically downregulated after chronic constriction injury (CCI). Intrathecal injection of a PTEN inhibitor induced pain-related behaviors in naive rats. ⋯ Finally, cholesterol replenishment attenuated CCI-induced pain and suppressed spinal glial activation. Taken together, these findings imply that spinal astrocytic PTEN plays a beneficial role in CCI-induced pain by regulating cholesterol biosynthesis, and an increased level of PTEN may accelerate cholesterol biosynthesis and reduce glial activation, thereby alleviating neuropathic pain. Recovery of PTEN or cholesterol might be an effective therapeutic strategy for neuropathic pain.