Analgesic Effectiveness and Dorsal Root Ganglia Protein Modulation of a Peripheral Adenosine Monophosphate Kinase Alpha Activator (O304) Following Lumbar Disk Puncture in the Mouse

Abstract

BACKGROUND: Disk herniation is a primary cause of radicular back pain. The purpose of this study was to evaluate the antiallodynic effective dose in 50% of the sample (ED 50 ) and dorsal root ganglion (DRG) protein modulation of a peripheral direct adenosine monophosphate kinase alpha (AMPKα) activator (O304) in a murine model of lumbar disk puncture. METHODS: Male (n = 28) and female (n = 28) mice (C57BL6/J) were assessed for hind paw withdrawal threshold (PWT) and burrowing. Abdominal surgery was performed on all mice, and 48 received a lumbar disk puncture (27-G needle), with 8 serving as nondisk puncture controls. Assessments were repeated at day 7, and mice were then randomized into 5 groups of equal numbers of males and females: O304 at 100 mg/kg (n = 10), 150 mg/kg (n = 10), 200 mg/ kg (n = 10), and 250 mg/kg (n = 10) or drug vehicle (n = 8). Starting on day 7, mice received daily gavages of O304 or vehicle for 7 days. On days 14 and 21 PWT and on day 14 burrowing were assessed. The area under the PWT by time curve (AUC) from day 7 to 21 was determined by trapezoidal integration. DRG protein modulation was evaluated in male (n = 10) and female (n = 10) mice (C57BL6/J). Following disk puncture, mice were randomized to receive O304 200 mg/kg or vehicle for 7 days starting on day 7. On day 14, mice were euthanized; the DRG harvested and immunoblot performed for mammalian target of rapamycin (mTOR), transient receptor potential ankyrin 1 (TRPA1), phosphorylated adenosine monophosphate kinase (p-AMPK), phosphorylated extracellular signal-regulated kinase (p-ERK), phosphorylated eukaryotic translation initiation factor 2 subunit 1 (p-EIF2S1), phosphorylated eukaryotic translation initiation factor 4e (p-EIF4E), and glyceraldehyde 3-phosphate dehydrogenase (GADPH). RESULTS: Disk puncture decreased PWT greater in female mice compared with male mice and decreased burrowing at 7 days. PWTs were increased with increasing doses of O304 from 150 to 250 mg/g on day 14 and sustained through day 21. The ED 50 (95% confidence interval [CI]) for reducing mechanical allodynia was 140 (118-164) mg/kg. Burrowing was not increased at day 14 compared to day 7 by O304 administration. Compared to vehicle-treated animals, O304 increased (95% CI) the p-AMPK/GADPH ratio, difference 0.27 (0.08-0.45; P = .004) and decreased (95% CI) the ratios of p-TRPA1, p-ERK1/2, pEIF4E, and p-EIF2S1 to GADPH by −0.49 (−0.61 to −0.37; P < .001), −0.53 (−0.76 to −0.29; P < .001), −0.27 (−0.42 to 0.11; P = .001), and −0.21 (−0.32 to −0.08; P = .003) in the DRG, respectively. CONCLUSIONS: The direct peripheral AMPK activator O304 reduced allodynia in a dose-dependent manner, and immunoblot studies of the DRG showed that O304 increased p-AMPK and decreased TRPA1, p-ERK1/2, as well as translation factors involved in neuroplasticity. Our findings confirm the role of peripheral AMPKα activation in modulating nociceptive pain. (Anesth Analg 2022;135:1293-303) KEY POINTS• Question: Does the direct peripheral adenosine monophosphate kinase alpha (AMPKα) activa...

Deficient AMPK activity contributes to hyperexcitability in peripheral nociceptive sensory neurons and thermal hyperalgesia in lupus mice

“…We found that suppression of AMPK activity results in elevation of resting membrane potentials, reduction of AP activation thresholds, and rheobases in nociceptive DRG neurons, which ultimately leads to enhanced nociceptive neuronal excitability and contributes to the genesis of chronic pain induced by lupus disease. Given that suppression of AMPK activity in nociceptive DRG neurons is implicated in the development of pathological pain induced by incision [ 60 ] and lumbar disk puncture [ 61 ] in both male and female rodents, it is conceivable that AMPK in nociceptive DRG neurons could also plays an important role in the development of chronic pain caused by lupus disease in females. Further studies are warranted to validate this notion.…”