Manual Therapy Reduces Pain Behavior and Oxidative Stress in a Murine Model of Complex Regional Pain Syndrome Type I

Complex regional pain syndrome type I (CRPS-I) is a chronic painful condition. We investigated whether manual therapy (MT), in a chronic post-ischemia pain (CPIP) model, is capable of reducing pain behavior and oxidative stress. Male Swiss mice were subjected to ischemia-reperfusion (IR) to mimic CRPS-I. Animals received ankle joint mobilization 48h after the IR procedure, and response to mechanical stimuli was evaluated. For biochemical analyses, mitochondrial function as well as oxidative stress thiobarbituric acid reactive substances (TBARS), protein carbonyls, antioxidant enzymes superoxide dismutase (SOD) and catalase (CAT) levels were determined. IR induced mechanical hyperalgesia which was subsequently reduced by acute MT treatment. The concentrations of oxidative stress parameters were increased following IR with MT treatment preventing these increases in malondialdehyde (MDA) and carbonyls protein. IR diminished the levels of SOD and CAT activity and MT treatment prevented this decrease in CAT but not in SOD activity. IR also diminished mitochondrial complex activity, and MT treatment was ineffective in preventing this decrease. In conclusion, repeated sessions of MT resulted in antihyperalgesic effects mediated, at least partially, through the prevention of an increase of MDA and protein carbonyls levels and an improvement in the antioxidant defense system.

Glycogen synthase kinase 3-specific inhibitor AR-A014418 decreases neuropathic pain in mice: evidence for the mechanisms of action

The present study examined the antihyperalgesic effect of a specific inhibitor of Glycogen Synthase Kinase 3 (GSK3), AR-A014418, on the partial ligation of the sciatic nerve (PSNL), a neuropathic pain model in mice and investigated some mechanisms of action. AR-A014418 (0.01-1 mg/kg) administered by intraperitoneal route (i.p.) inhibited mechanical hyperalgesia. This action started 30 min after i.p. administration and remained significant up to 2 h. When administered daily for 5 days, AR-A014418 (0.3 mg/kg, i.p.) significantly reduced the mechanical hyperalgesia caused by PSNL. Intraperitoneal (i.p.) treatment with AR-A014418 (0.3 mg/kg) also significantly inhibited cold hyperalgesia induced by PSNL. Pre-administration of PCPA (100 mg/kg, i.p., inhibitor of serotonin synthesis) and AMPT (100 mg/kg, i.p., inhibitor of tyrosine hydroxylase), but not l-arginine (600 mg/kg, i.p., a nitric oxide precursor), significantly reduced the mechanical hyperalgesia elicited by AR-A014418. Furthermore, the administration of AR-A014418 significantly prevented the increase of TNF-α (inhibition of 76±8%) and IL-1β (inhibition of 62±10%), but did not alter lumbar spinal cord IL1-ra and IL-10 levels. Finally, intraperitoneal administration of AR-A014418 did not affect locomotor activity in the open-field test. Taken together, these results provide experimental evidence indicating that AR-A014418 produces marked antihyperalgesic effects in neuropathic pain in mice, possibly due to mechanisms that reduce proinflammatory cytokines, as well as increases in serotonergic and catecholaminergic pathways. The present study suggests that GSK3 may be a novel pharmacological target for the treatment of neuropathic pain and AR-A014418 might be a potential molecule of interest for chronic pain relief.

Oleaginous extract from the fruits Pterodon pubescens Benth induces antinociception in animal models of acute and chronic pain

ETHNOPHARMACOLOGICAL RELEVANCE

Pterodon pubescens Benth is a medicinal plant commonly used for therapeutic purposes in folk medicine for rheumatic diseases' treatment. In the present work we analyzed the chemical composition of the oleaginous extract of P. pubescens Benth (OEPp) and extended the antinociceptive effect of OEPp evaluating its role on animal models of acute and chronic pain.

MATERIALS AND METHODS

The antinociceptive and antiedematogenic effects of OEPp (3-100mg/kg, i.g.) were evaluated in the formalin test; mechanical allodynia in the postoperative pain and complex regional pain syndrome type-I (CRPS-I) animal models; and thermal hyperalgesia was induced by plantar incision. Finally, we performed a phytochemical analysis of OEPp.

RESULTS

The chemical composition of OEPp was analyzed by mass spectrometry (GC/MS) and eight sesquiterpene compounds were identified, i.e. three major sesquiterpene (E-cariofilene, γ-muurolene, biciclogermacrene), and nine vouacapane diterpenes, four of which showed in major concentration (6α-acetoxyvouacapane, 6α,7β-dimetoxivouacapan-17-ene, 6α-acetoxy,7β-hidroxyvouacapane, 6α,7β-diacetoxycouacapane). Furthermore, the results of the present study demonstrate, for the first time, that the OEPp reduced mechanical allodynia in the postoperative pain and CRPS-I animal models. OEPp also increased the paw withdrawal latency in hot- and cold-plate tests in the postoperative pain model. In addition, the present work confirms and extends previous data from literature showing that systemic administration of OEPp caused significant inhibition against both phases of pain response to formalin intraplantar injection and edema formation.

CONCLUSIONS

Together, present and previous findings show that OEPp given intra-gastrically caused significant inhibition against both phases of formalin intraplantar injection and effectively inhibited mechanical and thermal hyperalgesia in the postoperative pain and CRPS-I animal models.