Role of Spinal Cord Akt-mTOR Signaling Pathways in Postoperative Hyperalgesia Induced by Plantar Incision in Mice.

Poor postoperative pain (POP) control increases perioperative morbidity, prolongs hospitalization days, and causes chronic pain. However, the specific mechanism(s) underlying POP is unclear and the identification of optimal perioperative treatment remains elusive. Akt and mammalian target of rapamycin (mTOR) are expressed in the spinal cord, dorsal root ganglion, and sensory axons. In this study, we explored the role of Akt and mTOR in pain-related behaviors induced by plantar incision in mice. Plantar incision activated spinal Akt and mTOR in a dose-dependent manner. Pre-treatment with Akt inhibitors intrathecally prevented the activation of mTOR dose-dependently. In addition, blocking the Akt-mTOR signaling cascade attenuated pain-related behaviors and spinal Fos protein expression induced by plantar incision. Our observations demonstrate that Akt-mTOR might be a potential therapeutic target for the treatment of POP.

Post-surgical inhibition of phosphatidylinositol 3-kinase attenuates the plantar incision-induced postoperative pain behavior via spinal Akt activation in male mice.

BACKGROUND: Postoperative pain (POP) is a severe acute pain encountered in patients suffering from an operation, and is less than adequately controlled by the currently available analgesics. Phosphatidylinositol 3-kinase (PI3K) has been reported to have an important role in neuropathic and inflammatory pain. Our previous research revealed that pre-surgical inhibition of spinal PI3K alleviated the pain behavior induced by plantar incision in mice. The aim of this study was to clarify whether post-surgical inhibition of PI3K would attenuate the POP and the underlying mechanisms. METHODS: A POP model was established by plantar incision in Kunming mice. A behavioral test was performed to determine mechanical allodynia, thermal hyperalgesia, and cumulative pain scores. The spinal Fos was detected by immunohistochemistry. The spinal expression of protein kinase B (Akt) or phosphorylated Akt (pAkt) was explored using western blot. The cellular location of pAkt was determined by immunofluorescence. RESULTS: Post-surgical inhibition of PI3K attenuated mechanical allodynia, thermal hyperalgesia, and cumulative pain scores induced by plantar incision significantly in male mice, and mildly in female mice. Post-surgical inhibition of PI3K attenuated the expression of spinal Fos in male mice. Plantar incision induced a time-dependent expression of spinal pAkt in male mice, which was primarily expressed in the spinal dorsal horn, and localized with the neuron and microglia's marker. Post-surgical inhibition of PI3K attenuated the activation of Akt induced by plantar incision in male mice as well. CONCLUSIONS: We concluded that post-surgical inhibition of PI3K could attenuate the pain-related behaviors induced by plantar incision, by suppressing the activation of spinal Akt in male mice. This finding might be used in clinical studies to reach a better understanding of POP mechanisms and optimal treatment.

The Role of Alpha-Lipoic Acid in the Pathomechanism of Acute Ischemic Stroke.

BACKGROUND/AIMS: Ischemic stroke results in increased cerebral infarction, neurological deficits and neuroinflammation. The underlying mechanisms involving the anti-inflammatory and neuroprotective properties of α-Lipoic acid (α-LA) remain poorly understood. Herein, we investigated the potential role of α-LA in a middle cerebral artery occlusion (MCAO) rat model and an in vitro lipopolysaccharide (LPS)-induced microglia inflammation model. METHODS: In the in vivo study, infarct volume was examined by TTC staining and Garcia score was used to evaluate neurologic recovery. The cytokines were evaluated by enzyme-linked immunosorbent assay, and protein expression of microglia phenotype and NF-κB were measured using western blot. In the in vitro study, the expressions of microglia M1/M2 phenotype were evaluated using qRT-PCR, and immunofluorescence staining was used to assess the nuclear translocation of NF-κB. RESULTS: Both 20 mg/kg and 40 mg/kg of α-LA alleviated infarct size, brain edema, and neurological deficits. Furthermore, α-LA induced the polarization of microglia to the M2 phenotype, modulated the expression of IL-1ß, IL-6, TNF-α and IL-10, and attenuated the activation of NF-κB after MCAO. α-LA inhibited the expression of M1 markers, increased activation of the M2 markers, and suppressed the nuclear translocation of NF-κB in LPS-stimulated BV2 microglia. CONCLUSIONS: α-LA improved neurological outcome in experimental stroke via modulating microglia M1/M2 polarization. The potential mechanism of α-LA might be mediated by inhibition of NF-κB activation via regulating phosphorylation and nuclear translocation of p65.

α-Lipoic Acid Promotes Neurological Recovery After Ischemic Stroke by Activating the Nrf2/HO-1 Pathway to Attenuate Oxidative Damage.

BACKGROUND/AIMS: Alpha-lipoic acid (α-LA) has been demonstrated to be protective against cerebral ischemia injury. Herein, we investigate the neuroprotective effect and underlying mechanisms of α-LA. METHODS: In vivo study, α-LA was administered intravenously upon reperfusion of transient middle cerebral artery occlusion. Garcia score was used to evaluate neurologic recovery. Infarct volume was examined by TTC staining, and oxidative damage was evaluated by ELISA assay. In an in vitro study, neurons were pretreated with α-LA at different doses and then subjected to OGD. Lentiviral vectors were applied to knockdown nuclear factor-erythroid 2-related factor-2 (Nrf2) or heme oxygenase-1 (HO-1). Cell viability was measured using CCK8. Protein expression was evaluated using western blot, and immunofluorescence staining was assessed. RESULTS: α-LA significantly reduced the infarct volume, brain edema, and oxidative damage and promoted neurologic recovery in rats. Pretreatment of α-LA caused an obvious increase in cell viability and a decrease in intracellular reactive oxygen species. Western blot analyses and immunofluorescence staining demonstrated a distinct increase in Nrf2 and HO-1 protein expression. Conversely, knockdown of Nrf2 or HO-1 resulted in the down-regulation of HO-1 protein and inhibited the neuroprotective effect of α-LA. CONCLUSION: α-LA treatment is neuroprotective and promotes functional recovery after ischemic stroke by attenuating oxidative damage, which is partially mediated by the Nrf2/HO-1 pathway.