Liver X Receptor α Is Involved in Counteracting Mechanical Allodynia by Inhibiting Neuroinflammation in the Spinal Dorsal Horn.

BACKGROUND: Liver X receptors, including α and ß isoforms, are ligand-activated transcription factors. Whether liver X receptor α plays a role in neuropathic pain is unknown. METHODS: A spared nerve injury model was established in adult male rats and mice. Von Frey tests were performed to evaluate the neuropathic pain behavior; Western blot and immunohistochemistry were performed to understand the underlying mechanisms. RESULTS: Intrathecal injection of a specific liver X receptor agonist T0901317 or GW3965 could either prevent the development of mechanical allodynia or alleviate the established mechanical allodynia, both in rats and wild-type mice. GW3965 could inhibit the activation of glial cells and the expression of tumor necrosis factor-α (mean ± SD: 196 ± 48 vs. 119 ± 57; n = 6; P < 0.01) and interleukin 1ß (mean ± SD: 215 ± 69 vs. 158 ± 74; n = 6; P < 0.01) and increase the expression of interleukin 10 in the spinal dorsal horn. All of the above effects of GW3965 could be abolished by liver X receptor α mutation. Moreover, more glial cells were activated, and more interleukin 1ß was released in the spinal dorsal horn in liver X receptor α knockout mice than in wild-type mice after spared nerve injury. Aminoglutethimide, a neurosteroid synthesis inhibitor, blocked the inhibitory effect of T0901317 on mechanical allodynia, on the activation of glial cells, and on the expression of cytokines. CONCLUSIONS: Activation of liver X receptor α inhibits mechanical allodynia by inhibiting the activation of glial cells and rebalancing cytokines in the spinal dorsal horn via neurosteroids.

EXPRESS: Methylcobalamin ameliorates neuropathic pain induced by vincristine in rats: Effect on loss of peripheral nerve fibers and imbalance of cytokines in the spinal dorsal horn.

BACKGROUND: Vincristine, a widely used chemotherapeutic agent, often induces painful peripheral neuropathy and there are currently no effective drugs to prevent or treat this side effect. Previous studies have shown that methylcobalamin has potential analgesic effect in diabetic and chronic compression of dorsal root ganglion model; however, whether methylcobalamin has effect on vincristine-induced painful peripheral neuropathy is still unknown. RESULTS: We found that vincristine-induced mechanical allodynia and thermal hyperalgesia, accompanied by a significant loss of intraepidermal nerve fibers in the plantar hind paw skin and an increase in the incidence of atypical mitochondria in the sciatic nerve. Moreover, in the spinal dorsal horn, the activity of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase and the protein expression of p-p65 as well as tumor necrosis factor a was increased, whereas the protein expression of IL-10 was decreased following vincristine treatment. Furthermore, intraperitoneal injection of methylcobalamin could dose dependently attenuate vincristine-induced mechanical allodynia and thermal hyperalgesia, which was associated with intraepidermal nerve fibers rescue, and atypical mitochondria prevalence decrease in the sciatic nerve. Moreover, methylcobalamin inhibited the activation of NADPH oxidase and the downstream NF-kB pathway. Production of tumor necrosis factor a was also decreased and production of IL-10 was increased in the spinal dorsal horn following methylcobalamin treatment. Intrathecal injection of Phorbol-12-Myristate-13-Acetate, a NADPH oxidase activator, could completely block the analgesic effect of methylcobalamin. CONCLUSIONS: Methylcobalamin attenuated vincrinstine-induced neuropathic pain, which was accompanied by inhibition of intraepidermal nerve fibers loss and mitochondria impairment. Inhibiting the activation of NADPH oxidase and the downstream NF-kB pathway, resulting in the rebalancing of proinflammatory and anti-inflammatory cytokines in the spinal dorsal horn might also be involved. These findings might provide potential target for preventing vincristine-induced neuropathic pain.

Comparative Effectiveness of Midazolam, Propofol, and Dexmedetomidine in Patients With or at Risk for Acute Respiratory Distress Syndrome: A Propensity Score-Matched Cohort Study.

Background: Sedatives are commonly used in patients with or at risk for acute respiratory distress syndrome (ARDS) during mechanical ventilation. To systematically compare the outcomes of sedation with midazolam, propofol, and dexmedetomidine in patients with or at risk for ARDS. Methods: We developed a dataset of real-world data to enable the comparison of the effectiveness and safety of sedatives and the associated outcomes from the MIMIC-III database and the eICU Collaborative Research database. We performed a systematic study with six cohorts to estimate the relative risks of outcomes among patients administered different sedatives. Propensity score matching was performed to generate a balanced 1:1 matched cohort and to identify potential prognostic factors. The outcomes included hospital mortality, duration of mechanical ventilation, length of intensive care unit stay, length of hospitalization, and likelihood of being discharged home. Results: We performed 60 calibrated analyses among all groups and outcomes with 17,410 eligible patients. Sedation with dexmedetomidine was associated with a lower in-hospital mortality rate than sedation with midazolam and propofol or sedation without dexmedetomidine (p < 0.001). When compared with no sedation, the use of midazolam, propofol or dexmedetomidine was associated with a longer ICU stay and longer hospitalization duration (p < 0.01). Patients treated with midazolam were relatively less likely to be discharged home (p < 0.05). Conclusion: Patients treated with dexmedetomidine had a reduced risk of mortality. These data suggest that dexmedetomidine may be the preferred sedative in patients with or at risk for ARDS.

Foxo1 selectively regulates static mechanical pain by interacting with Nav1.7.

ABSTRACT: Mechanical allodynia is a debilitating condition for millions of patients with chronic pain. Mechanical allodynia can manifest in distinct forms, including brush-evoked dynamic and filament-evoked static allodynia. In the nervous system, the forkhead protein Foxo1 plays a critical role in neuronal structures and functions. However, the role of Foxo1 in the somatosensory signal remains unclear. Here, we found that Foxo1 selectively regulated static mechanical pain. Foxo1 knockdown decreased sensitivity to static mechanical stimuli in normal rats and attenuated static mechanical allodynia in rat models for neuropathic, inflammatory, and chemotherapy pain. Conversely, Foxo1 overexpression selectively enhanced sensitivity to static mechanical stimuli and provoked static mechanical allodynia. Furthermore, Foxo1 interacted with voltage-gated sodium Nav1.7 channels and increased the Nav1.7 current density by accelerating activation rather than by changing the expression of Nav1.7 in dorsal root ganglia neurons. In addition, the serum level of Foxo1 was found to be increased in chronic pain patients and to be positively correlated with the severity of chronic pain. Altogether, our findings suggest that serum Foxo1 level could be used as a biological marker for prediction and diagnosis of chronic pain. Moreover, selective blockade of Foxo1/Nav1.7 interaction may offer a new therapeutic approach in patients with mechanical pain.

Bulleyaconitine A preferably reduces tetrodotoxin-sensitive sodium current in uninjured dorsal root ganglion neurons of neuropathic rats probably via inhibition of protein kinase C.

Oral Bulleyaconitine A (BLA) is effective for treating neuropathic pain in human patients, but the underlying mechanism is poorly understood. Here, we tested whether BLA blocked voltage-gated sodium channels (VGSCs) in dorsal root ganglion (DRG) neurons. Compelling evidence shows that voltage-gated sodium channels are upregulated in uninjured DRG neurons but downregulated in injured ones following peripheral nerve injury. We found that BLA preferably inhibited Na currents in uninjured DRG neurons in neuropathic rats. Compared to sham rats, IC50 values for resting and inactivated Na currents were 113 and 74 times lower in injured and uninjured neurons of L4-6 DRGs in spared nerve injury (SNI) rats (4.55 and 0.56 nM) and were 688 and 518 times lower in the uninjured L4 and L6 DRG neurons of L5 spinal nerve ligation (L5-SNL) rats. The use-dependent blockage of BLA on Na currents was more potent in neuropathic rats compared to sham rats. Bulleyaconitine A facilitated the inactivation of Na channels in each group. IC50 values for resting and inactivated tetrodotoxin-sensitive (TTX-S) channels were 1855 and 1843 times lower than those for TTX-resistant channels in the uninjured neurons of L5 spinal nerve ligation rats. The upregulation of protein kinase C was associated with the preferable effect of BLA on TTX-S Na channels in the uninjured DRG neurons. Local application of BLA onto L4-6 DRGs at 0.1 to 10 nM dose-dependently alleviated the mechanical allodynia and thermal hyperalgesia in L5 spinal nerve ligation model. Thus, preferable blockage of TTX-S Na channels in uninjured DRG neurons may contribute to BLA's antineuropathic pain effect.