Preclinical Evaluation of a Novel Once-a-Day Brimonidine Ophthalmic Nanosuspension.

Purpose: This article aims to describe a preclinical proof of concept for a novel once-a-day (OD) brimonidine ophthalmic nanosuspension. Methods: The preclinical proof of concept was established using New Zealand white rabbits as animal models. Dose-finding, multiple-dose efficacy, ocular pharmacokinetic, and hemodynamic studies were performed in normotensive rabbits. Steroid-induced ocular hypertension model in rabbits was used to study efficacy in glaucomatous pathophysiology. The test (0.35% OD suspension) and reference (0.15% three times a day [TID] solution) were compared. Results: The intraocular pressure (IOP) reduction was sustained for 0.35% and 0.5% strengths but not for other lower strengths tested or reference strengths. A 0.35% OD suspension reduced IOP >2 mmHg after 24 h of dosing, which was not seen with the reference. After multiple dosing, 0.35% OD suspension reduced IOP by 4-6 mmHg after 24 h, which was comparable to the 0.15% TID reference solution. An ocular pharmacokinetic study showed that the brimonidine was rapidly absorbed and distributed throughout the eye after topical administration. Concentration was higher in tissues with high α2 receptors, such as cornea-conjunctiva, iris/ciliary body, and choroid/retina. The steady-state concentrations in these organs were also significant after 24 h of the last dose. There was an indication of increased plasma levels, so a hemodynamic study was performed to assess any adverse effects. All hemodynamic parameters were normal and no new unusual safety findings were observed. Conclusions: The study demonstrated that the novel brimonidine 0.35% ophthalmic nanosuspension is both safe and effective when administered OD and is comparable to the marketed reference formulation administered TID.

Enhanced antitumor activity of doxorubicin by naringenin and metformin in breast carcinoma: an experimental study.

Breast cancer is the most common malignancy in women worldwide. Strategies for cancer chemotherapy commonly require the use of combination therapy for better outcomes of results. The present work is aimed to evaluate the potential of naringenin and metformin concomitant addition with doxorubicin chemotherapy against experimental breast carcinoma. The antitumor potential of drugs under the study was evaluated against methylnitrosourea (MNU)-induced breast cancer in rats and 4T1 cells-induced orthotopic breast cancer mouse model. Parameters like tumor growth, body weight, survival rate, blood glucose, hematology, and histology were determined. There was a marked reduction in tumor weight and an observed decrease in tumor multiplicity by naringenin and metformin concomitant addition with doxorubicin against MNU-induced breast carcinoma. Likewise, naringenin and metformin with doxorubicin showed a significant reduction of tumor volume and tumor weight (p < 0.01) in 4T1-induced orthotopic mouse model as compared to the same dose of doxorubicin alone, suggesting combination treatment enhanced antitumor activity in vivo. Furthermore, histology of tumor biopsies presented the improved antitumor activity of doxorubicin via increasing tumor necrosis. Hematological parameters, body weight, and survival data presented remarkable safety of combination treatment without compromising efficacy using 50% lower dose of doxorubicin as compared to the large dose of doxorubicin alone. These results demonstrate that naringenin and metformin enhanced the antitumor effect of doxorubicin in animal models of breast carcinoma, and therefore can be useful as an adjunct treatment with doxorubicin to increase its effectiveness at the lower dose level for the treatment of cancer.

Combining naringenin and metformin with doxorubicin enhances anticancer activity against triple-negative breast cancer in vitro and in vivo.

Triple-negative breast cancer (TNBC) grows fast and represents poor prognosis and management. This work is aimed to determine the effect of concomitant use of naringenin and metformin with doxorubicin chemotherapy using in vitro and in vivo breast carcinoma models. Cell viability and xenograft study were performed using TNBC cell lines. The use of naringenin and metformin together with doxorubicin, have shown a significant increase in cytotoxicity when compared with the same concentration of doxorubicin alone in MDA-MB-231 cells and 4T1 cells in vitro. In the xenograft mouse model, a significant reduction of tumor volume and tumor weight was observed in contrast to a similar dose of doxorubicin alone; suggesting combining treatment enhanced antitumor activity in vivo. Besides, H&E and Ki-67 staining of tumor biopsies showed enhancement of the antitumor activity via increasing necrosis and inhibiting cell proliferation respectively. Additionally, there was no marked change observed in the organ weights, blood glucose, cardiac histology and cardiac Troponin I levels under the study treatment groups. The beneficial effects of using both the naringenin and metformin along with the lower dose of doxorubicin were evident from the reduced dose-related body weight loss and increase in cytokines (TNF-α and IL-1ß) compared to a large dose of doxorubicin alone. Thus, naringenin and metformin combination with doxorubicin found useful as an adjunct therapy to improve the effectiveness of doxorubicin at the lower dose against the breast carcinoma.

Possible role of opioids and KATP channels in neuroprotective effect of postconditioning in mice.

The present study was designed to investigate the possible role of opioids and K(ATP) channels in ischemic postconditioning-induced reversal of global cerebral ischemia and reperfusion (I/R) induced neuronal injury. Mice were subjected to global ischemia by bilateral carotid artery occlusion for 10 min followed by reperfusion for 24 h, to produce neuronal injury. Ischemic postconditioning was induced by three episodes of carotid artery occlusion and reperfusion of 10 s each, immediately after global ischemia. Morphine postconditioning was induced by administration of morphine (5 mg/kg i.v.), 5 min prior to reperfusion. Naloxone (5 mg/kg i.v.), opioid receptor antagonist, and glibenclamide (5 mg/kg i.v.), K(ATP) channel blocker were administered 10 min before global ischemia. Extent of cerebral injury was assessed by measuring cerebral infarct size using triphenyl tetrazolium chloride (TTC) staining. Short-term memory was evaluated using the elevated plus maze test, while degree of motor incoordination was evaluated using inclined beam-walking, rota-rod and lateral push tests. Bilateral carotid artery occlusion followed by reperfusion resulted in significant increase in infarct size, impairment in short-term memory and motor co-ordination. Ischemic/morphine postconditioning significantly attenuated I/R induced neuronal injury and behavioural alterations. Pretreatments with naloxone and glibenclamide attenuated the neuroprotective effects of ischemic/morphine postconditioning. It may be concluded that ischemic/morphine postconditioning protects I/R induced cerebral injury via activating opioid receptor and K(ATP) channel opening.