Thermal hyperalgesia and light touch allodynia after intradermal Mycobacterium butyricum administration in rat

A new promising simultaneous approach for attenuating type II diabetes mellitus induced neuropathic pain in rats: iNOS inhibition and neuroregeneration

In view of the pathologic basis for the treatment of diabetic neuropathy, it is important to enhance nerve regeneration as well as prevent nerve degeneration. So, in the present study, we have investigated the effect of S-Methylisothiourea Sulfate (selective iNOS inhibitor) and Citicoline, alone and in combination, on Type II diabetes mellitus induced neuropathic pain in wistar rats. Type II diabetes was induced by providing high fat diet and low dose of Streptozotocin for 35 days in rats. Type II diabetes mellitus was assessed in terms of increased glucose, triglycerides, cholesterol, LDL levels, glucose tolerance and decrease in HDL levels. Neuropathy as the complication of type II diabetes was assessed in terms of decreased nerve conduction velocity, mechanical and thermal hyperalgesia and cold allodynia. Oxidative stress was assessed in sciatic nerve and showed increase in LPO and nitrite levels whereas decrease was shown in GSH and catalase activity. Axonal degeneration marked by nerve fibre dearrangement and demyelination was observed in histopathological studies. SMT (iNOS inhibitor), Citicoline and low dose combination of both drugs significantly attenuates the diabetic neuropathic pain assessed in terms of parameters employed. Thus, it may be concluded that simultaneous administration of SMT and Citicoline may provide potential therapeutics for diabetic neuropathic pain.

Role of TNF in sickness behavior and allodynia during the acute phase of Chagas' disease

Chagas disease, caused by the intracellular protozoan Trypanosoma cruzi, is associated with inflammation, discomfort and pain during the acute phase. The influence of TNF-α (tumor necrosis factor) in this disease outcome is controversial. In this way, the aim of this work was to determine the role of the TNF-α blocker etanercept in the pain, discomfort, and survival during the Chagas' acute phase of mice experimentally infected with a wild virulent strain of T. cruzi. The infection with this wild strain was responsible for a severe visceral inflammation and said parasite showed a tropism in peritoneal fluid cells. Etanercept was able to restore spontaneous vertical and horizontal activities during the second week after infection and to abolish mechanical allodynia during the first week after infection. Finally, etanercept delayed the mortality without any effect on the parasitemia rates. This is the first report that correlates sickness behavior and allodynia with TNF-α and suggests that this cytokine may play an important role in the physiopathology of the acute phase.

Effect of dipyrone and thalidomide alone and in combination on STZ-induced diabetic neuropathic pain

Diabetic neuropathy is recognized as one of the most common complications of chronic diabetes, but its pathophysiological mechanism is complex and yet to be completely explored. Monotherapy with conventional analgesics fails to provide adequate pain relief in peripheral diabetic neuropathy. There are a number of evidence suggesting that tumor necrosis factor (TNF-α) plays an important role in the pathogenesis of peripheral diabetic neuropathy. TNF-α up-regulation activates nuclear factor κB, which further up-regulates cyclooxygenase (COX)-2 leading to altered prostaglandin profile. Inhibition of TNF-α and COX-2 provides beneficial effect on diabetic neuropathy by decreasing the oxidative stress level and by preventing neuronal hypersensitivity due to an increased prostaglandin level. The present study was designed to assess the effect of dipyrone and thalidomide on streptozotocin (STZ)-induced neuropathic pain behavior in rats. STZ 50 mg/kg, i.p. was administered to induce experimental diabetes in the rats. Three weeks following STZ, dipyrone (300 and 600 mg/kg, i.p.) and thalidomide (25 and 50 mg/kg, i.p.) alone and subeffective dose combination of dipyrone and thalidomide (300 and 25 mg/kg(-1), i.p.) administered daily for 2 weeks significantly attenuated thermal hyperalgesia, mechanical allodynia, and formalin-induced phase-2 flinching response. Moreover, the subeffective dose combination of dipyrone and thalidomide and preemptive treatment with thalidomide (50 mg/kg) reduces oxidative stress in diabetic rats. In conclusion, the combination of subeffective dose of dipyrone and thalidomide prevented the development and maintenance of experimental diabetic neuropathy. The combination of thalidomide (TNF-α inhibitor) and dipyrone (COX inhibitor) may be used as a potential therapeutic agent for the treatment of diabetic neuropathy.

Anti-inflammatory and antihyperalgesic effects of the combination of ibuprofen and hemin in adjuvant-induced arthritis in the Wistar rat

AIM

Although, pharmacological activation of heme oxygenase (HO)-1 has shown to produce ameliorative effects in various experimental models of inflammation, but such beneficial effects have not been observed in adjuvant-induced arthritis. Further, the upregulated activity of HO-1 has been implicated in the pathogenesis of adjuvant arthritis. The present study was designed to investigate the anti-inflammatory and antihyperalgesic effects of the prophylactic use of hemin alone and/or in combination with ibuprofen using adjuvant-induced arthritis in Wistar rat.

METHODS

Arthritis was induced by an intradermal injection of complete Freund's adjuvant (CFA) into left hind paw. Paw volume, thermal hyperalgesia, mechanical allodynia, joint stiffness and mobility behaviors (score) were measured.

RESULTS

Administration of ibuprofen (8.75, 17.5, 35 mg/kg/day, p.o.) and hemin (1, 5, 10 mg/kg/day, i.p.) were significantly effective in suppressing CFA-induced paw oedema, thermal and mechanical hyperalgesia, joint stiffness and mobility. The combination of low doses of ibuprofen (8.75 mg/kg, p.o.) and hemin (1 mg/kg, i.p.) significantly reduced paw volume, thermal and mechanical hyperalgesia, as compared to the individual dose of the ibuprofen and hemin alone.

CONCLUSIONS

Hence, it may be concluded that the prophylactic administration of either hemin produced significantly enhanced anti-inflammatory and analgesic effects. Further, concurrent low dose administration of hemin and ibuprofen produced significantly enhanced anti-inflammatory and analgesic effects, as compared to the either treatment alone, in CFA-induced arthritis in Wistar rats.