This paper reports an investigation of the ability of propolis extract (a resinous substance collected by honeybees from various plant sources) to restore the collapse of mitochondrial membrane potential induced by ferulenol, a sesquiterpene prenylated coumarin derivative isolated from the plant Ferula vesceritensis . We show that ferulenol was able to induce the permeability transition pore (PTP) opening. This effect is caused by the interaction of the compound with the mitochondrial respiratory chain, more particularly by the fall of membrane potential and the inhibition of complex II. We have previously demonstrated that this inhibition results from a limitation of electron transfers involved in the respiratory chain and initiated by the reduction of ubiquinone. We hypothesized that the protective effect of propolis could be due to a direct action on mitochondrial functions. So we have investigated in vitro the mitochondrial effects of Algerian propolis using rat liver mitochondria, by analysing their effects on membrane potential, mitochondrial respiration and mitochondrial swelling. We show that propolis extract was able to restore the fall of mitochondrial membrane potential. Taken together these data reveal that propolis extract may be an interesting inhibitor of PTP and provide an additional mechanism by which the natural product propolis extract may restore the mitochondrial membrane potential and to prevent apoptotic process.

We evaluated the effects of propolis extract on renal oxidative stress induced by doxorubicin throughout an analytical and pharmacological study of the eastern Algerian propolis using thin layer chromatography, ultra-violet-high-performance liquid chromatography) and gas chromatography-mass spectrometry. The pharmacological study was carried out in vivo on Wistar rat pre-treated with propolis extract 100 mg/kg/day for seven days. Doxorubicin at 10 mg/kg of body weight was administered intravenously on Day 7. Serum creatinine concentration, scavenging effect of flavonoids, lipid peroxidation and glutathione concentration were measured. Chemical analysis allowed identification and quantification of the phenolic compounds including pinostrombin chalcone (38.91%), galangin (18.95%), naringenin (14.27%), tectochrysin (25.09%), methoxychrysin (1.14%) and a prenylated coumarin compound suberosin (1.65%). The total flavonoid concentration in the propolis extract was 370 mg (quercetin equivalents QE) /g dry weight (QE/g DWPE). Propolis extract restored the renal functions and reduced the toxic effect of doxorubicin. These data show a protective effect of Algerian propolis extract against doxorubicin-induced oxidative stress.

Taken together, Algerian propolis reverses multidrug resistance in resistant human lung adenocarcima cells through direct inhibiting the transport function of pgp-pump resulting in enhancing intracellular DOX-accumulation, G0/G1 cell cycle arrest and apoptosis induction. Thus, propolis could be developed as chemotherapeutic agent for reversing multidrug resistance.

In conclusion, propolis sensitize pancreatic cancer cells to DOX via enhancing the intracellular retention of DOX due to blocking the efflux activity of P-gp pump, inducing cell cycle arrest and increasing apoptosis, finding that improuve the synergism of antitumor effect of Algerian propolis and DOX in pancreatic cancer cell line. Therefore, Algerian propolis may be an effective agent in a combined treatment with doxorubicin for increased therapeutic efficacy against pancreatic cancer.

No abstract