Algerian propolis: between protection of normal cells and potentialisation of the anticancer effects of doxorubicin against breast cancer cells via P-glycoprotein inhibition and cell cycle arrest in the S phase

Breast cancer is a common cancer and is the leading cause of cancer-related deaths among women worldwide. Studies have shown that breast cancer is a heterogeneous tumor with varying response to treatments. The clinical use of doxorubicin (Dox) in the treatment of cancer is limited by its cardiotoxicity which results in often fatal heart failure and the development of multidrug resistance. Therefore, new therapeutic strategies and targets are underscored. Propolis has been reported to show a broad spectrum of biological activities including anticancer activity. In this study, we investigated the role of propolis on the antitumor effects of Dox on breast cancer cells (MDA-MB-231) and its ability to provide protection against Dox-mediated damage on normal cells (MRC-5). Modifications in cell viability, apoptosis induction, cell cycle progression and permeability glycoprotein (P-gp) activity of breast cancer cells in vitro were evaluated. Propolis combined with Dox inhibited cell growth in a dose dependent manner by inducing cell cycle arrest in the S phase and caspase-dependent apoptosis. In the presence of propolis, the IC₅₀ of Dox against MDA-MB-231 cells decreased by 10-fold. The increased sensitivity of cancer cells to the combined treatment was explained by the capacity of propolis to cause a significant increase in Dox content in MDA-MB-231. Very interestingly, Algerian propolis showed its ability to inhibit efficiently P-gp function in comparison with verapamil, reference P-gp modulator, which proves the efficacy of propolis to reverse the problem of multidrug resistance. Our results showed also that propolis could protect normal cells from deleterious effects of Dox by amelioration of cell viability. In conclusion, the obtained results indicate that Algerian propolis potentiated the antitumor effects of Dox on breast cancer cells and could reduce the problem of multidrug resistance. Therefore, Algerian propolis may be an effective agent in a combined treatment with Dox for increased therapeutic efficacy against breast cancer. Clinically, our results are relevant because with this combined therapy it may be possible to counter the problem of cancer cell resistance while reducing the problem of toxicity on normal cells.

THE EFFECT OF SALBUTAMOL ON PGC-1 α AND GLUT4 mRNA EXPRESSION IN THE LIVER AND MUSCLE OF ELDERLY DIABETIC MICE

Background

Peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α) plays an important role in the regulation of cellular energy metabolism, and it is involved in obesity and type 2 diabetes mellitus (T2DM). Its expression is elevated in the liver of T2DM mouse models. Literature reports show that chronic β2 stimulation improved insulin sensitivity in T2DM.

Objectives

We aimed to test the hypotheses that chronic β2 stimulation-induced improvement in insulin sensitivity involves changes in the expression of PGC-1α and glucose transporter 4 (GLUT4).

Animals and Methods

We fed a locally inbred, 8 months old mice, a high fat diet (HFD) to induce diabetes. These mice gained weight and became insulin resistant. The β2 agonist salbutamol had a beneficial effect on both glucose tolerance and insulin sensitivity after 4 weeks.

Results

Salbutamol beneficial effect persisted after 4 weeks of its discontinuation. HFD caused an up regulation of the hepatic PGC-1 α expression by 5.23 folds (P< 0.041) and salbutamol reversed this effect and caused a down regulation by 30.3 folds (P< 0.0001). PGC-1 α and GLUT4 expression in the muscle was not affected by salbutamol (P> 0.05).

Conclusion

Down regulation of the liver's PGC-1 α contributes to the beneficial effect of the chronic β2 stimulation on glucose tolerance and insulin sensitivity in T2DM mice.

Life-threatening hyperkalemia after intravenous labetolol injection for hypertensive emergency in a hemodialysis patient

Intravenous labetolol, a nonselective alpha- and beta-blocking drug, is commonly used to treat severe hypertension. Nonselective beta-blockers can cause hyperkalemia, especially in patients with renal failure. One series reported 3 renal transplant patients who had hyperkalemia after labetolol infusion, but none of these patients developed any serious complication. We report a case of life-threatening hyperkalemia (serum [K+] 9.9 mEq/l) with ventricular tachycardia and hypotension in a patient on maintenance hemodialysis who received labetolol for a hypertensive emergency. Physicians should be aware of this potentially lethal complication, which is easily preventable.