ZYKR1, a novel, potent, and peripherally selective kappa opioid receptor agonist reduces visceral pain and pruritus in animal models.

Opioid receptor agonists are effective analgesic agents. Central activation of the mu and/or kappa opioid receptors (KOR) is associated with CNS side effects, which limits their effectiveness. Recent studies indicated that peripherally restricted, selective KOR agonists were potent analgesics and devoid of CNS-related side effects. To confirm this hypothesis, we designed a novel, potent, and peripherally restricted KOR-selective agonist, ZYKR1. The analgesic efficacy, brain penetration and safety of ZYKR1 were assessed in pre-clinical models. ZYKR1 showed KOR agonistic activity in the cAMP assay, with an EC50 of 0.061 nM and more than 105-fold selectivity over the mu and delta opioid receptors (EC50 > 10 µM). ZYKR1 was not found to bind mu, delta opioid, and NOP receptors in radioligand binding assays. ZYKR1 produced concentration-dependent inhibition of electrically evoked contractions in isolated mouse vas deferens with an IC50 of 1.6 nM ZYKR1 showed peripheral restriction and potent analgesic efficacy in various in-vivo animal models (acetic acid induced visceral pain mouse model, ED50: 0.025 mg/kg, IV; ovariohysterectomy induced postoperative pain rat model, ED50: 0.023 mg/kg, IV; and C48/80 induced pruritus mouse model, ED50: 0.063 mg/kg, IV). In addition, ZYKR1 was devoid of motor coordination, physical dependence, dysphoria, and respiratory depression at 30, 400, 10 and 10-fold of efficacy dose, respectively. In conclusion, ZYKR1 has potent antinociceptive action in visceral pain and pruritus with limited CNS side effects in preclinical models owing to its peripheral restriction.

Renoprotective activity of aliskiren, a renin inhibitor in cyclosporine A induced hypertensive nephropathy in dTG mice.

BACKGROUND: Hypertensive nephropathy is moving up the charts to number 2 after diabetic nephropathy in terms of diagnostic frequency cited as causing end stage renal disease (ESRD). METHOD: Hypertensive nephropathy was produced in mildly hypertensive C57BL/6-(hREN)/(hAGT) double transgenic (dTG) mice with 20 mg/kg of cyclosporine A (CsA) administered subcutaneously (sc) daily for 28 days. CsA dose 20 mg/kg was selected for the study as this dose offered significant alteration in blood pressure, biochemical parameters and moderate nephropathy in kidney. Effect of aliskiren oral treatment twice daily consequently for 28 days at 10 mg/kg body weight was evaluated against CsA induced hypertensive nephropathy. Systolic blood pressure (SBP) was measured by non invasive tail cuff method. Kidney function test (blood urea nitrogen, serum creatinine, urea and uric acid) and kidney injury biomarker (tumor necrosis factor-alpha (TNF-α) and interlekin-6) level was assessed in serum, TNF-α, IL-6, transforming growth factor-beta1 (TGF-ß1) and kidney injury molecule-1 (KIM-1) was assayed in kidney homogenate. Urinary KIM-1 levels were assessed as an early biomarker of nephropathy. RESULT: Significant hypertensive nephropathy and increase in serum levels of biomarkers was observed in CsA treated animals when compared with Control group. Aliskiren treatment elicited significant renoprotection by preventing the increase in blood pressure and levels of serum biomarkers and also reduced the nephropathic alterations in the kidney histoarchitecture. CONCLUSION: A correlation between pharmacological, biochemical and histological findings has been established in mouse model. The present findings have indicated the renoprotective activity of aliskiren in CsA induced hypertensive nephropathy, which may be due to its antihypertensive, anti-inflammatory as well as anti-apoptopic action.

Ameliorative potential of aliskiren in experimental colitis in mice.

In the present study, we investigated the ameliorative potential of aliskiren in dextran sulfate sodium (DSS) induced colitis in mice. Aliskiren (3 and 10mg/kg, i.p.) was administered for 10 days from the day of DSS administration. The severity of colitis in mice was assessed using body weight loss, colon and spleen weight, hematological parameters, food intake, stool consistency, rectal bleeding and colon shortening. Colonic malondialdehyde (MDA), myeloperoxidase (MPO) and renin mRNA levels were also estimated. Furthermore, TNF-α and IL-6 in plasma and colon were analyzed. The results showed that aliskiren (10mg/kg, i.p.) significantly improved the severity of colitis by, decrease in weight loss, improvement in food intake and stool consistency, decrease in rectal bleeding, decrease in relative colon and spleen weight and improvement in colonic shortening. Aliskiren (10mg/kg, i.p.) improved blood hemoglobin, red blood cells (RBC) and hematocrit. Colonic malondialdehyde (MDA), MPO and histolopathological score were significantly diminished by aliskiren (10mg/kg, i.p.). Furthermore, aliskiren (10mg/kg, i.p.) significantly diminished the elevated levels of TNF-α, IL-6 and renin mRNA in inflammed colon. These results indicate involvement of renin in colitis and inhibition of renin by aliskiren ameliorates colitis.

Anti-nociceptive and anti-allodynic activity of aliskiren in various pain models.

In the present study, we have investigated the anti-nociceptive and anti-allodynic activity of the renin inhibitor, aliskiren, in various pain models. The anti-nociceptive activity of aliskiren was investigated in chemically-induced pain, orofacial pain and centrally mediated pain models. Anti-allodynic activity was evaluated in post-operative and neuropathic pain models. The levels of TNF-α and IL-6 were measured in homogenates of hind paw as markers of inflammation in formalin injected mice. Intraperitoneal administration of aliskiren (1-50mg/kg) showed anti-nociceptive activity in the writhing test, formalin hind paw test, capsaicin induced pain, and orofacial pain tests in ICR mice in a dose dependent manner. Aliskiren (50mg/kg, i.p.) reduced levels of TNF-α and IL-6 in hind paw homogenates of formalin-injected mice. Aliskiren (50mg/kg, i.p.) did not show any analgesic activity in hot-plate and tail-flick tests, indicating the absence of centrally mediated anti-nociceptive effects. On the other hand, intra-plantar administration of aliskiren (0.1, 0.5 and 1mg) showed analgesic activity in rat formalin tests, indicating a locally mediated effect. Aliskiren (30-100mg/kg, i.p.) showed anti-allodynic activity in post-operative pain and chronic constriction injury-induced neuropathic pain in Sprague Dawley rats. This data suggests that aliskiren may have the potential to be used as an anti-nociceptive and anti-allodynic agent.

Facile synthesis, ex-vivo and in vitro screening of 3-sulfonamide derivative of 5-(4-chlorophenyl)-1-(2,4-dichlorophenyl)-4-methyl-1H-pyrazole-3-carboxylic acid piperidin-1-ylamide (SR141716) a potent CB1 receptor antagonist.

Facile synthesis of biaryl pyrazole sulfonamide derivative of 5-(4-chlorophenyl)-1-(2,4-dichlorophenyl)-4-methyl-1H-pyrazole-3-carboxylic acid piperidin-1-ylamide (SR141716, 1) and an investigation of the effect of replacement of the -CO group in the compound 1 by the -SO(2) group in the aminopiperidine region is reported. Primary ex-vivo pharmacological testing and in vitro screening of sulfonamide derivative 2 showed the loss of CB1 receptor antagonism.