Ouhida Benrezzak

PEG-coated Poly(lactic acid) Nanoparticles for the Delivery of Hexadecafluoro Zinc Phthalocyanine to EMT-6 Mouse Mammary Tumours

Hexadecafluoro zinc phthalocyanine (ZnPcF16), a second generation sensitizer for the photodynamic therapy of cancer, was incorporated in three vehicles: poly(d,l‐lactic acid) (PLA) nanoparticles, polyethylene glycol (PEG)‐coated nanoparticles and a Cremophor EL (CRM) oil‐water emulsion. Nanoparticles were prepared by the salting‐out procedure. Biodistribution of the dye was assessed by fluorescence in EMT‐6 mammary tumour bearing mice after intravenous injection of 1 μmol kg−1 ZnPcF16.

Purine signaling and potential new therapeutic approach: possible outcomes of NTPDase inhibition.

Interest for extracellular nucleotides has increased since the pioneer work of Burnstock in the early seventies. Research on cellular functions modulated by purines and pyrimidines has led to the identification and characterization of the different components of purine signaling, namely purinoceptors and ecto-nucleotidases. Receptors for tri- and diphosphonucleosides, known as P2 nucleotide receptors, are designated either P2Y receptors, for those coupled to G-proteins, or P2X for those which are ligand gated-ion channels. Ecto-nucleoside triphosphate diphosphohydrolase (NTPDase; EC 3.6.1.5), previously identified as ecto-ATPase, ecto-ATPDase or CD39, is now considered as the main ecto-nucleotidase responsible for the sequential hydrolysis of beta and gamma phosphates of tri- and diphosphonucleosides. More recently, research has been focused on the development of specific agonists and antagonists to P2 purinoceptors. The need to develop specific inhibitors for NTPDase to understand the role of this enzyme has clearly emerged. This paper covers the development of specific molecules targeting purinergic signaling, more specifically the inhibition of NTPDase and their impact on the different physiological systems.

Folyamines and pancreatic growth induced by caerulein

Activation of polyamine metabolism may be important to initiation of pancreatic cell growth. We are reporting that such activation did occur during pancreatic growth initiation by caerulein, a cholecystokinin analog. Maximal increases in total putrescine (319%), spermidine (63%) and spermine (50%) were observed 12, 96 and 96 hr respectively after the beginning of the caerulein treatment. This time period coincides with pancreatic hypertrophy and hyperplasia as characterized by increased cell mass and DNA content. Rates of pancreatic weight and DNA content increases were significantly correlated with total spermidine and spermine contents. These data suggest that polyamine biosynthesis is closely associated with pancreatic growth.

Effects of α-difluoromethylornithine on pancreatic growth induced by caerulein

Abstract The role of ornithine decarboxylase and of polyamines was investigated on caerulein-induced pancreatic growth by the use of α-difluoromethylornithine (DFMO), an enzyme-activated irreversible inhibitor of ornithine decarboxylase. By itself, DFMO did not affect the pancreatic gland at all but when combined with caerulein, it reduced the increases in DNA synthesis and DNA content initiated by the cholecystokinin analog. The general hypertrophic action of caerulein was not affected by DFMO but specific increases in amylase and chymotrypsin concentrations were observed after 2 days of caerulein. The effect on amylase concentration was further increased after 4 days but that on chymotrypsin was reversed, showing a significant decrease. These data suggest that the polyamines might be involved in pancreatic growth that is stimulated by caerulein and that their action could be mainly oriented towards cellularity. The specific decreases obtained in DNA synthesis and content brought about by DFMO support this observation.

Reversal of α-difluoromethylornithine inhibition of caerulein-induced pancreatic growth by putrescine

The role of ornithine decarboxylase and of polyamines was investigated on caerulein-induced pancreatic growth through the use of alpha-difluoromethylornithine (DFMO) and putrescine. Caerulein, the cholecystokinin analog, given at a dose of 1 microgram . kg-1 three times a day was associated with pancreatic hyperplasia and hypertrophy after 2 and 4 days of treatment. The present study shows that putrescine, given once daily i.p. at a dose of 300 mumol . kg-1, can reverse the previously observed DFMO inhibition on pancreatic DNA content increments stimulated by caerulein. It was also observed that putrescine inhibits severely the 2-day caerulein-induced pancreatic hypertrophy, yet interferes only moderately with 4 days of caerulein treatment. These data lend further support to the involvement of ornithine decarboxylase and polyamines in induced pancreatic growth.

The ability of staurosporine to modulate pancreatic acinar cell desensitization by TPA, carbamylcholine and caerulein

The implication of protein kinase C in the phenomenon of pancreatic acinar cell desensitization to carbamylcholine, caerulein and the phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA) was investigated using a potent PKC inhibitor, staurosporine. At a concentration of 1 microM, staurosporine caused a maximum 64% inhibition of amylase release from rat pancreatic acini stimulated by 100 nM TPA. At 100 nM, staurosporine reduced by 50 to 55% amylase secretion elicited by maximal concentrations of carbamylcholine or caerulein without affecting their potency. Staurosporine was also able to prevent completely desensitization by TPA of the subsequent secretory response to carbamylcholine and caerulein. Furthermore, staurosporine also totally prevented desensitization by caerulein of the subsequent secretory response to caerulein. In contrast, staurosporine only partially prevented desensitization by carbamylcholine of the subsequent secretory response to carbamylcholine. These results indicate that staurosporine is a potent inhibitor of protein kinase C as it inhibited the secretory response to carbamylcholine, caerulein and TPA. They also suggest that desensitization of the secretory response induced by TPA and caerulein used a common pathway involving protein kinase C activation. Finally, desensitization by carbamylcholine is more complex as it is only partially prevented at staurosporine; therefore, protein kinase C activation seems to be one of the factors involved.

Effects of cerulein and epidermal growth factor on pancreatic growth in the reserpinized rat model

This study was undertaken to determine the effect of reserpine on rat pancreatic growth, to evaluate if reserpine-caused alterations can be prevented by epidermal growth factor (EGF) and/or cerulein treatment, to evaluate the time course of rat pancreas recovery after reserpine, and to determine if EGF and/or cerulein treatment can accelerate such a recovery. In the first experiment, three groups of male Sprague-Dawley rats (250-265 g) were used. Ad libitum-fed control animals received the reserpine vehicle, and one experimental group received reserpine (1 mg kg-1 day-1 for 7 days) while the other, pair-fed group received the reserpine vehicle with a reduced amount of food to result in malnourishment. Rats from each of these three groups were also assigned to one of four treatments consisting of saline, EGF (10 micrograms kg-1), cerulein (1 microgram kg-1), or a combination (same doses) twice a day for 7 days. In the morning of the 8th day, after an overnight fat, rats were killed. In the second experiment, rats were selected and treated with reserpine or the vehicle as described in experiment 1; after the 7-day treatment, a first cohort of animals was allowed a 30-day recovery period. Three other groups (an ad libitum-fed control, a pair-fed, and a reserpine group) were allowed a 6-day recovery period during which they were treated subcutaneously, twice a day, with either saline, EGF (10 micrograms kg-1), cerulein (1 microgram kg-1), or a combination (same doses). On the morning of the 31st or 7th day, after an overnight fat, rats were killed. After death, all pancreata were examined for weight and protein, amylase, chymotrypsinogen, RNA, and DNA content. In the ad libitum-fed control group, EGF caused pancreatic hypertrophy, whereas cerulein was associated with hypertrophy and hyperplasia. In the pair-fed malnourished group, the EGF effect was limited to slight increases in pancreatic weight and cell mass whereas cerulein caused hypertrophy; EGF plus cerulein caused pancreatic hyperplasia. In the reserpine group, EGF had no effect, whereas cerulein caused pancreatic hypertrophy and an increase in DNA content above the reserpine control. After 30 days of recovery, pancreata of pair-fed animals and those of reserpine-treated animals were comparable with those of the ad libitum-fed control rats with the exception of amylase levels, which remained reduced in the reserpine group.(ABSTRACT TRUNCATED AT 400 WORDS)

Alterations of pancreatic amylase secretion in the reserpinized rat model of cystic fibrosis

SummaryReserpine treatment resulted in altered enzyme secretion from rat pancreatic acini in response to carbamylcholine and secretin(1,2). This study was undertaken: (1) To evaluate if the alterations caused by reserpine can be prevented by EGF and/or cerulein treatments; (2) To determine the time-course of secretion recovery after reserpine treatment; and (3) To establish if EGF and/or cerulein treatments can accelerate such a recovery after the reserpine treatment. Male Sprague-Dawley rats (250-265 g) were used in these experiments. In experiment I, rats divided into three groups received either reserpine (R) or the reserpine vehicle for the controls (C) and the pair-fed controls (PF) for 7 d. During treatment, PF and R rats were given SC, twice a day, saline, EGF (10 μg/kg), cerulein (1 μg/kg), or both at the same dose. C rats received saline in gelatin. In experiment II, rats were treated for 7 d with reserpine or the vehicle as described in experiment I, were allowed a 30-d recovery period and then were killed. In experiment III, C, PF, and R rats were treated for 7 d as described in experiment I; on the 8th d and for the next 6 d, reserpine rats received saline (reserpine-saline), cerulein, EGF, or both cerulein + EGF at the same dose as indicated in experiment I. C and PF rats received saline in gelatin. After sacrifice, acini were prepared, and amylase dose-response curves to carbamylcholine (Cch) and secretin were established. EGF, cerulein, or their combination given to R rats did not improve the desensitized secretory response to Cch. The secretory responses to secretin remained altered in PF and R rats even after the hormonal treatment. After 30 d of recovery, normal secretory responses to Cch and to secretin were found in the PF- and R-treated rats; this recovery was also observed as early as 6 d in PF and R rats, and it was impaired by the cerulein treatment. In conclusion, under the present regimen, EGF did not have any major impact on the recovery process or prevention of the alterations caused by malnutrition and reserpine. Cerulein was the most potent factor capable of promoting recovery or preventing alterations of total pancreatic amylase concentration in the reserpinized rat model; however, it failed to prevent desensitization of amylase release to Cch or decreases of acinar cells’ response to secretin. Finally, the CCK analog prevented recovery of the secretory responses to Cch and secretin observed in the absence of any treatment.