The results of the research indicate that some of the investigated compounds reduced effectively either both phases of the test or were able to attenuate pain during only the acute or late phase of the formalin test. These properties, which are particularly strong in case of the compounds 1-3, 5, 6, 9 and 14, might be relevant for the development of novel analgesic-active compounds and their possible use in neuropathic pain syndromes.

Diabetes mellitus is a metabolic disease characterized by hyperglycemia due to defects in insulin secretion or its action. Complications from long-term diabetes consist of numerous biochemical, molecular, and functional tissue alterations, including inflammation, oxidative stress, and neuropathic pain. There is also a link between diabetes mellitus and vascular dementia or Alzheimer’s disease. Hence, it is important to treat diabetic complications using drugs which do not aggravate symptoms induced by the disease itself. Pregabalin is widely used for the treatment of diabetic neuropathic pain, but little is known about its impact on cognition or inflammation-related proteins in diabetic patients. Thus, this study aimed to evaluate the effect of intraperitoneal (ip) pregabalin on contextual memory and the expression of inflammatory state-related proteins in the brains of diabetic, streptozotocin (STZ)-treated mice. STZ (200 mg/kg, ip) was used to induce diabetes mellitus. To assess the impact of pregabalin (10 mg/kg) on contextual memory, a passive avoidance task was applied. Locomotor and exploratory activities in pregabalin-treated diabetic mice were assessed by using activity cages. Using Western blot analysis, the expression of cyclooxygenase-2 (COX-2), cytosolic prostaglandin E synthase (cPGES), nuclear factor (erythroid-derived 2)-like 2 (Nrf2), nuclear factor-ĸB (NF-ĸB) p50 and p65, aryl hydrocarbon receptor (AhR), as well as glucose transporter type-4 (GLUT4) was assessed in mouse brains after pregabalin treatment. Pregabalin did not aggravate STZ-induced learning deficits in vivo or influence animals’ locomotor activity. We observed significantly lower expression of COX-2, cPGES, and NF-κB p50 subunit, and higher expression of AhR and Nrf2 in the brains of pregabalin-treated mice in comparison to STZ-treated controls, which suggested immunomodulatory and anti-inflammatory effects of pregabalin. Antioxidant properties of pregabalin in the brains of diabetic animals were also demonstrated. Pregabalin does not potentiate STZ-induced cognitive decline, and it has antioxidant, immunomodulatory, and anti-inflammatory properties in mice. These results confirm the validity of its use in diabetic patients.Graphical abstractEffect of pregabalin on fear-motivated memory and markers of brain tissue inflammation in diabetic mice

Xanthone derivatives of acetic, propionic and 2-methylpropionic acids were synthesized and assayed for their anti-inflammatory, analgesic and ulcerogenic activities. Compound 8 causes a dose-dependent diminution of paw edema (up to 61%) in the carrageenan model and at the highest tested dose reduces mechanical hyperalgesia in the Randall-Selitto test more effectively than the reference compound (~75% and ~32%, respectively). It shows high in vitro metabolic stability (Clint=12.5 μL/mg/min, t1/2=138.6 min) in the rat liver microsomes. None of the studied xanthone derivatives are ulcerogenic. The results of the present study suggest that compound 8 can be of interest in the future for the search for antinociceptive and antiedematous agents devoid of ulcerogenic effect.

The present study demonstrated for the first time that chronic treatment with zinc salt exhibits anti-inflammatory activity. Besides, anti-ulcerogenic activity and the enhancing properties of zinc to ketoprofen induced anti-inflammatory and analgesic activity were also shown.

ZHA enhanced the anti-inflammatory effect of ketoprofen.