Subclinical neuropathy in diabetic patients: a risk factor for bilateral lower limb neurological deficit following spinal anesthesia?

High glucose and bupivacaine‑induced cytotoxicity is mediated by enhanced apoptosis and impaired autophagy via the PERK‑ATF4‑CHOP and IRE1‑TRAF2 signaling pathways

Bupivacaine has previously been reported to induce neurotoxicity, which is further enhanced by high glucose levels. In the present study, the underlying molecular mechanisms via which bupivacaine induces cytotoxicity under high glucose conditions were investigated in cultured human SH-SY5Y cells. In order to identify the optimal concentrations of glucose and bupivacaine that induced cytotoxicity, SH-SY5Y cells were treated with 30–100 mM glucose and 0.5–1.0 mM bupivacaine. Based on the dose response experiments, 50 mM glucose and 0.5 mM bupivacaine was used in the present study. The effects that 3-MA (autophagy inhibitor) and rapamycin (RAPA; autophagy inducer) exerted on cell apoptosis, autophagy and the expression of protein kinase R-like endoplasmic reticulum kinase (PERK)-activating transcription factor 4 (ATF4)-C/EBP-homologous protein (CHOP) and inositol-requiring enzyme 1 (IRE1)-tumor necrosis factor receptor associated factor 2 (TRAF2) signaling proteins were measured in high glucose and bupivacaine-treated cells. Cell viability was measured using a Cell Counting Kit-8 assay, cell apoptosis was assessed using flow cytometry, and protein expression was determined using western blot analyses. Compared with the control group, high glucose and bupivacaine significantly increased ATF4, CHOP and caspase-12 expression, increased apoptosis, and decreased p-IRE1, TRAF2, LC3-II/LC3-I and Beclin1 expression. Promoting autophagy with RAPA partly reversed the high glucose and bupivacaine-induced changes in p-PERK, CHOP, TRAF2, Beclin1, caspase-12 and apoptosis, while inhibiting autophagy with 3-MA further enhanced the changes in ATF4, CHOP, p-IRE1, TRAF2 and apoptosis. High glucose and bupivacaine induced cytotoxicity in SH-SY5Y cells, at least in part, through enhancing cell apoptosis and inhibiting autophagy via the PERK-ATF4-CHOP and IRE1-TRAF2 signaling pathways.

Effects of hyperbaric factors on lidocaine-induced apoptosis in spinal neurons and the role of p38 mitogen-activated protein kinase in rats with diabetic neuropathic pain

The application of lidocaine can lead to nerve damage. Evidence suggests that patients with diabetic neuropathy are at a higher risk for neurotoxicity. In the present study, the successful induction of diabetic neuropathic pain (DNP) in rats via a high-sugar, high-fat diet and intraperitoneal injection of 1% streptozotocin was verified and pronounced tactile allodynia was observed. It was found that intrathecal injections of hyperbaric lidocaine produced motor blocks of longer durations in the DNP model rats than in nondiabetic rats, or in DNP model rats injected with isobaric lidocaine. Histology of the lumbar 4-5 spinal cord revealed a significant difference in neuropathology between the DNP and nondiabetic rats. Moreover, edematous neurons and TUNEL-positive cells were observed in the hyperbaric lidocaine group. It was also found that the inhibition of p38 mitogen-activated protein kinase (p38MAPK) played a neuroprotective role in response to hyperbaric lidocaine-induced apoptosis in DNP rats, which indicates that p38MAPK plays a key role in the regulation of hyperbaric lidocaine-induced apoptosis in DNP rats. These findings suggest that hyperbaric lidocaine can promote spinal cord neuronal apoptosis in rats with DNP. Furthermore, p38MAPK might play a key role in the regulation of hyperbaric lidocaine-induced apoptosis in rats with DNP.