Marc Aprahamian

New Approach for Oral Administration of Insulin With Polyalkylcyanoacrylate Nanocapsules as Drug Carrier

Polyalkylcyanoacrylate nanocapsules (mean size 220 nm), composed of spheric polymeric structures, have been used as a drug carrier for insulin. The rate of encapsulation of insulin is 54.9%, and we studied the therapeutic efficiency of the nanocapsules in diabetic and normal rats. When administered subcutaneously, insulin-loaded nanocapsules prolonged the hypoglycemic effect of insulin; the duration of this effect increased with the doses. When administered orally by force-feeding to diabetic rats, insulin nanocapsules (12.5, 25, and 50 U/kg) decreased fasted glycemia 50–60% by day 2. This effect was maintained for 6 or 20 days with 12.5 or 50 U/kg, respectively. Only the dose of 100 U/kg decreased fed glycemia by 25% in diabetic rats. In normal rats, hyperglycemia induced by an oral glucose load was reduced by 50% with the same dose of oral insulin nanocapsules. We concluded that polyalkylcyanoacrylate nanocapsules preserve the therapeutic effect of insulin when administered orally and prolong this effect when administered subcutaneously and orally.

Nanocapsules as carriers for oral peptide delivery

Abstract Nanocapsules composed of biodegradable spherical polymeric vesicles, less than 300 nm in diameter, were applied for the oral administration of peptides, especially insulin. Nanocapsules were formed by interfacial polymerisation of isobutyl 2-cyanoacrylate around a lipidic phase, the peptide being added to this latter. When administered intragastrically in diabetic rats, insulinloaded nanocapsules reduced markedly glycemia measured after an overnight fast. This effect occurred from the second day up to 20 days depending on the dose of insulin administered. In normal rats or dogs, insulin-loaded nanocapsules reduced the glucose-induced peak of hyperglycemia. Thus, nanocapsules are able to preserve the biological effect of insulin after oral administration. They protect insulin against degradation by proteolytic enzymes; they transport insulin rapidly through the intestinal epithelium; and they change the tissular distribution of iodine-125 after oral administration of labeled insulin-loaded nanocapsules.

The effect of site of administration in the gastrointestinal tract on the absorption of insulin from nanocapsules in diabetic rats.

Abstract— Isobutylcyanoacrylate nanocapsules have been used as drug carriers for the enteral absorption of insulin. Their absorption has been studied by measuring fasted glycaemia in streptozotocin‐induced diabetic rats after a single administration of encapsulated insulin (100 units kg−1) at various sites along the gastrointestinal tract. Glycaemia decreased from the second day, the intensity and duration depending on the site of administration (65% ileum, 59% stomach, 52% duodenum and jejunum, 34% colon). This hypoglycaemic effect lasted up to the 18th day after administration for ileum and jejunum, the 15th day for stomach and duodenum, and the 13th day for colon. In‐vitro, nanocapsules protect insulin against proteolysis from pepsin, chymotrypsin and trypsin. These results suggest (i) that insulin is protected by nanocapsules in the gastrointestinal tract, (ii) that it is absorbed in an active form, and (iii) that ileum is he most potent site of absorption.

Improvement of Gemcitabine-Based Therapy of Pancreatic Carcinoma by Means of Oncolytic Parvovirus H-1PV

Pancreatic carcinoma is a gastrointestinal malignancy with poor prognosis. Treatment with gemcitabine, the most potent chemotherapeutic against this cancer up to date, is not curative, and resistance may appear. Complementary treatment with an oncolytic virus, such as the rat parvovirus H-1PV, which is infectious but nonpathogenic in humans, emerges as an innovative option. Purpose: To prove that combining gemcitabine and H-1PV in a model of pancreatic carcinoma may reduce the dosage of the toxic drug and/or improve the overall anticancer effect. Experimental Design: Pancreatic tumors were implanted orthotopically in Lewis rats or subcutaneously in nude mice and treated with gemcitabine, H-1PV, or both according to different regimens. Tumor size was monitored by micro-computed tomography, whereas bone marrow, liver, and kidney functions were monitored by measuring clinically relevant markers. Human pancreatic cell lines and gemcitabine-resistant derivatives were tested in vitro for sensitivity to H-1PV infection with or without gemcitabine. Results:In vitro studies proved that combining gemcitabine with H-1PV resulted in synergistic cytotoxic effects and achieved an up to 15-fold reduction in the 50% effective concentration of the drug, with drug-resistant cells remaining sensitive to virus killing. Toxicologic screening showed that H-1PV had an excellent safety profile when applied alone or in combination with gemcitabine. The benefits of applying H-1PV as a second-line treatment after gemcitabine included reduction of tumor growth, prolonged survival of the animals, and absence of metastases on CT-scans. Conclusion: In addition to their potential use as monotherapy for pancreatic cancer, parvoviruses can be best combined with gemcitabine in a two-step protocol.

K-ras oncogene silencing strategy reduces tumor growth and enhances gemcitabine chemotherapy efficacy for pancreatic cancer treatment

Pancreatic adenocarcinoma remains a fatal disease characterized by rapid tumor progression, high metastatic potential and profound chemoresistance. Gemcitabine is the current standard chemotherapy for advanced pancreatic cancer, but it is still far from optimal and novel therapeutic strategies are needed urgently. Mutations in the k‐ras gene have been found in more than 90% of pancreatic cancers and are believed to play a key role in this malignancy. Thus, the goal of this study was to investigate the impact of k‐ras oncogene silencing on pancreatic tumor growth. Additionally, we examined whether combining k‐ras small interfering RNA (siRNA) with gemcitabine has therapeutic potential for pancreatic cancer. The treatment of tumor cell cultures with the corresponding k‐ras siRNA resulted in a significant inhibition of k‐ras endogenous expression and cell proliferation. In vivo, tumor xenografts were significantly reduced with k‐ras siRNAGAT delivered by electroporation. Moreover, combined treatment with pSsik‐rasGAT plus gemcitabine resulted in strong growth inhibition of orthotopic pancreatic tumors. Survival rate was significantly prolonged and the mean tumor volume was dramatically reduced in mice receiving the combined treatment compared with single agents. Collectively, these findings show that targeting mutant k‐ras through specific siRNA might be effective for k‐ras oncogene silencing and tumor growth inhibition. The improvement of gemcitabine‐based chemotherapy suggests that this strategy might be used therapeutically against human pancreatic cancer to potentiate the effects of conventional therapy. (Cancer Sci 2007; 98: 1128–1136)

Carrier cell-mediated delivery of oncolytic parvoviruses for targeting metastases.

Over the last few years, naturally occurring or genetically manipulated oncolytic viruses gained increasing attention as novel therapeutics for cancer treatment. The present work provides proof of principle that an organotropic cell‐based carrier system is suitable to deliver oncolytic parvoviruses to a tissue known to be a target for the formation of metastases. Carrier cells were inactivated by γ‐irradiation after infection, which was found not to affect the production and release of parvoviruses that were capable of lysing cocultured target neoplastic cells. Although systemically administered parvovirus H‐1 showed a pronounced therapeutic effect against the development of established Morris hepatoma (MH3924A) lung metastases, the carrier cell strategy offered a number of advantages. Infected carriers were able to sustain H‐1 virus expression for 6 days in the lungs of rats affected by metastatic disease and to reduce the spreading of the virus to peripheral organs. Compared to direct virus injection, the carrier cell protocol led to an improved therapeutic effect (metastases suppression) and a lesser generation of virus‐neutralizing antibodies. These data support the use of carrier cells to deliver oncolytic viruses and/or viral vectors locally in tumors and, more particularly, metastases.

Polyalkylcyanoacrylate nanocapsules increase the intestinal absorption of a lipophilic drug

Abstract The advantage of a polymeric drug carrier, poly-isobutylcyanoacrylate nanocapsules, in the intestinal absorption of a lipophilic drug (Lipiodol) has been investigated in the dog. Lipiodol, an iodized oil, was characterized by X-ray emission of iodine in a scanning electron microscope fitted with an X-ray microprobe analyser. Nanocapsules, administered in the jejunal lumen, increased the absorption of Lipiodol: the plasma level of iodine was maximal 45 min after the administration of Lipiodol emulsion (3 times basal value) and nanocapsules (3.5 times). Then iodemia decreased again but remained 2.5-fold higher than control values 105 min after the administration of nanocapsules. At the cellular level, nanocapsules accelerate, intensify and prolong the passage of iodine through the intestinal mucosa. These results could be explained by a direct transport of the drug by nanocapsules through the mucosa, or by increasing the intraluminal concentration of the drug close to absorptive cells.

Effect of Pantothenic Acid and Ascorbic Acid Supplementation on Human Skin Wound Healing Process

This study aimed at testing human skin wound healing improvement by a 21-day supplementation of 1.0 g ascorbic acid (AA) and 0.2 g pantothenic acid (PA). 49 patients undergoing surgery for tattoos, by the successive resections procedure, entered a double-blind, prospective and randomized study. Tests performed on both skin and scars determined: hydroxyproline concentrations, number of fibroblasts, trace element contents and mechanical properties. In the 18 supplemented patients, it was shown that in skin (day 8) Fe increased (p < 0.05) and Mn decreased (p < 0.05); in scars (day 21), Cu (p = 0.07) and Mn (p < 0.01) decreased, and Mg (p < 0.05) increased; the mechanical properties of scars in group A were significantly correlated to their contents in Fe, Cu and Zn, whereas no correlation was shown in group B. In blood, AA increased after surgery with supplementation, whereas it decreased in controls. Although no major improvement of the would healing process could be documented in this study, our results suggest that the benefit of AA and PA supplementation could be due to the variations of the trace elements, as they are correlated to mechanical properties of the scars.

Dual Effect of Laparoscopy on Cell-Mediated Immunity

Laparoscopic influence on cell-mediated immunity and tumour evolution is controversial. The objective of the present study was to assess tumour growth and immune patterns after laparoscopy on an experimental study. Lewis rats, bearing an intrapancreatic ductal carcinoma randomly underwent one of the following 2-hour procedures: anaesthesia, laparotomy or CO2 pneumoperitoneum. Cell-mediated immunity was investigated through determination of serum IL1β concentrations by ELISA and TNFα, IL6 and iNOS gene transcriptions in blood white cells and peritoneal cells by RT-PCR 1 day after operation. Tumour growth and spread patterns were assessed on anatomopathological examination 2 weeks after surgery. Tumour growth and spread were unaffected no matter what procedure was applied, but port-site seeding occurred in half of the cases undergoing laparoscopy. No significant change in acute-phase protein response, represented by IL1β serum concentration, was found after laparoscopy. TNFα, IL6 and inducible NO synthase gene transcriptions were enhanced in blood white cells and depressed in peritoneal immune cells after laparoscopy. In our experimental conditions, cell-mediated immune response to CO2 pneumoperitoneum seems to be a good systemic immune activation and a less acute peritoneal immune response as opposed to control laparoscopy. This early impairment of peritoneal macrophage immune activity, observed after a long-lasting CO2 pneumoperitoneum, might be responsible for the high rate of port site recurrence.

Trophic effect of bombesin on the rat pancreas: Is it mediated by the release of gastrin or cholecystokinin?

This work investigates the effect, on the rat pancreas, of a chronic administration of bombesin in function of the dose and duration of treatment and examines whether this effect may be mediated by the release of endogenous gastrin or cholecystokinin. Bombesin, administered three times daily for 5 or 15 days, induced a marked increase in pancreatic weight, its protein, RNA and enzyme contents with the dose of 10 micrograms/kg body weight; the ratios of pancreatic weight, protein and RNA contents to DNA contents increased significantly after a 5 day treatment, suggesting cellular hypertrophy. Pancreatic DNA content was markedly enhanced after a 15 day treatment, suggesting cellular hyperplasia. Antrectomy decreased plasma gastrin levels, but did not alter the pancreatico-trophic action of a 10 micrograms/kg bombesin treatment for 5 days. Proglumide, an inhibitor of cholecystokinin and gastrin in the pancreas, did not affect the growth of the pancreas induced by a 10 micrograms/kg bombesin treatment for 5 days. It is concluded that chronic bombesin induces, in the rat pancreas, cellular hypertrophy or hyperplasia depending on the duration of treatment. Pancreatic hypertrophy is not mediated by the release of endogenous gastrin or cholecystokinin.