Hypoxia promotes chemoresistance in acute lymphoblastic leukemia cell lines by modulating death signaling pathways.

BACKGROUND: Several studies show that bone marrow (BM) microenvironment and hypoxia condition can promote the survival of leukemic cells and induce resistance to anti-leukemic drugs. However, the molecular mechanism for chemoresistance by hypoxia is not fully understood. METHODS: In the present study, we investigated the effect of hypoxia on resistance to two therapies, methotrexate (MTX) and prednisolone (PRD), in two cell models for acute lymphoblastic leukemia (ALL). To look for an implication of hypoxia in chemoresistance, cell viability, total cell density and cell proliferation were analyzed. Survival and death signaling pathways were also screened by "reverse phase protein array" (RPPA) and western blotting experiments conducted on selected proteins to confirm the results. RESULTS: We found that hypoxia promotes chemoresistance in both ALL cell lines. The induction of drug-resistance by hypoxia was not associated with an increase in total cell density nor an increase in cell proliferation. Using RPPA, we show that chemoresistance induced by hypoxia was mediated through an alteration of cell death signaling pathways. This protective effect of hypoxia seems to occur via a decrease in pro-apoptotic proteins and an increase in anti-apoptotic proteins. The results were confirmed by immunoblotting. Indeed, hypoxia is able to modulate the expression of anti-apoptotic proteins independently of chemotherapy while a pro-apoptotic signal induced by a chemotherapy is not modulated by hypoxia. CONCLUSIONS: Hypoxia is a factor in leukemia cell resistance and for two conventional chemotherapies modulates cell death signaling pathways without affecting total cell density or cell proliferation.

[How can we optimize medical orderings in intensive care unit (ICU)?]. / Optimisation des prescriptions en réanimation.

OBJECTIVES: To evaluate whether intensivists would accept to optimize their orderings of biological samplings, x-rays and target drugs and to assess the consequence on patient's outcome. STUDY DESIGN: Monocentric evaluation of medical economic procedure. METHODS: Meetings of consultants, registrars and residents started on Dec 21, 2006 with two to three sessions a year in order to evaluate the process of medical ordering. The physicians and pharmacists gave the results of orderings at each meeting. Orderings of systematic samplings, bedside x-rays and unjustified expansive drugs were discouraged, but target samplings and lung ultrasonography were encouraged. New residents were systematically taught about this programme. Meanwhile, monthly morbidity-mortality meetings were pursued in order to assess the consequences of this politics. RESULTS: While ICU total production increased by 3.4% and potentially evitable deaths decreased by 34%, annual expenses decreased by approximatively € 777,000 from 2006 to 2008. This was due to decreased orderings in biology by 30%, bedside x-rays by 10%, computed tomographic scans by 16% and target drugs by 35%. However, an increased ordering in four target drugs was observed in 2008 as compared with 2007. CONCLUSION: Multidisciplinary optimization of medical ordering can be efficient in ICU. However, a profit-sharing with ordering physicians would be necessary to prolong these effects.

Hormonal and metabolic effects of somatostatin in diabetic patients submitted to an i.v. arginine infusion.

Hormonal and metabolic effects of a synthetic linear somatostatin were tested in insulin-dependent subjects submitted to an intravenous arginine infusion. Arginine alone induced a rise in plasma growth hormone (HGH) and glucagon (IRG) concentrations but did not affect the spontaneous diurnal decrease of plasma cortisol; blood glucose concentration rose while that of alanine decreased suggesting enhanced gluconeogenesis; concentrations of plasma free fatty acids (FFA) and 3-hydroxybutyrate decreased. Somatostatin, at three different dosages, markedly influenced these patterns: HGH response to arginine was suppressed by the lowest somatostatin dose; IRG response was progressively inhibited by increasing doses of somatostatin but never reached zero; cortisol level was not decreased but slightly increased by somatostatin. Substrate responses to arginine were also modified by somatostatin: alanine disappearance was impaired, this effect being dose-related; plasma FFA and 3-hydroxybutyrate concentrations showed a significant increase rather than decrease, consistent with somatostatin suppression of residual insulin secretion. Tolerance to somatostatin was good and no alteration of hemostasis was observed.

[Lactic acidosis induced by excessive ingestion of metformin]. / Acidose lactique induite par l'ingestion excessive de metformine

The authors report on a case of lethal lactate acidosis during acute metformine and barbiturate poisoning. The study of energetic substrates and glucoregulation hormones demonstrated a blockade of hepatic gluconeogenesis.

Characterization of phenformin and metabolites in plasma.

A colorimetric assay of biguanides was adapted for small volumes of plasma and its specificity was improved. This method is based on the reaction of guanidine groups with alpha-naphtol-diacetyl. Interference of endogenous guanidine derivatives and of the water-soluble metabolites of phenformin can be excluded by the extraction procedure. Counting of plasma fractions from 14C-phenformin-injected rats and thin-layer chromatography, before and after treatment with beta-glucuronidase, were also performed: the results suggest that after adequate extraction of plasma, the colorimetric assay measures specifically the biologically active phenformin. Results of this assay in plasma from biguanide-induced lactic acidotic patients and rats are given and compared with controls : results are consistent with the hypothesis of an accumulation of biologically active biguanide in such cases.

Phenformin-induced lactic acidosis in diabetic patients.

Eighteen diabetic patients with lactic acidosis (L.A.) were analyzed for possible causal factors, metabolic changes, and efficacy of treatment. An antecedent phenformin therapy was performed in fifteen cases and was associated with renal insufficiency in ten cases and liver disease in eight cases. Tissular anoxia of primary hemodynamic or respiratory origin was absent in all cases. The severe metabolic acidosis (pH m.93 +/- 0,03; HCO3-= 6 +/- 1 MM; PaCO2 = 18 +/- 2 MM. Hg) and hyperlactatemia (14.2 +/- 0.3 mM) were associated with high lactate/pyruvate ration (70 +/- 22). High alanine levels (up to 4.6 mM) were measured in some of these patients. High beta-hydroxybutrate levels were sometimes measured (up to 7.6 mM), and substantial amounts of acetoacetate were also detected in twelve cases. Glucagon level was always increased (1,050 +/- 240 pg./ml.), and insulin/glucagon ratio was low. Cortisol (49 +/- 10 mug./100 ml.) and HGH (10.8 +/- 0.6 ng./ml.) were also elevated. Increased plasma levels of phenformin were measured in five L.A. diabetic subjects (50 +/- 5 mug./ml.) by comparison with other phenformin-treated diabetic subjects. The specificity of the assay was investigated, and phenformin metabolites were characterized by thin-layer chromatography. Por the treatment of L.A., adjunction of dialysis and furosemide improved the efficacy of early and massive sodium bicarbonate infusion. It is suggested that accumulation of phenformin via renal insufficiency plays a determinant role in causing L.A. through an impairment of lactate metabolism in the liver. An accelerated epuration of the drug may be helpful in therapy of L.A. Phenformin treatment should be avoided in case of renal and/or liver insufficiency.

[Aseptic osteonecrosis in renal transplantation ; apropos of 29 cases]. / L'ostéonécrose aseptique de la transplantation rénale. A propos de 29 cas

Over a period of observation of 14 years, one or more aspetic osteonecroses (AON) were discovered in 29 patients who had undergone renal transplantation. Altogether 64 AON were discovered. In patients who had survived at least 1 year, the frequency of this lesion was 18 percent. These transplantation necroses were often bilateral (16 cases out of 21 AON of the femoral head) or multiple (6 patients presenting AON in more than 3 sites) ; necroses were sometimes found in unusual sites (shoulder, ankle, upper end of the tibia, scaphoid, condyle of the humerus). The AONs of the lower limbs were remarkable because of their extent and because of the rapid evolution of the radiological signs. This is in contrast to the moderate nature of the pain. Latent types of necrosis are also found (3 cases of AON of the femoral head). During a search for factors favouring the development of AON, the authors noted that the average duration of haemodialysis was longer in the patients with AON than in a control group of transplant patients. The average daily dose of corticoids for the first six months after transplantation was not significantly different in the two groups studied. However, the 15 patients with transplants who were not given corticoids did not develop AON.

[Radiographic aspects of aseptic osteonecrosis following renal transplantation. Apropos of 65 localizations in 30 patients]. / Aspects radiographiques des ostéonécroses aseptiques de la transplantation rénale. A propos de 65 localisations chez 30 malades

The authors report 30 cases of aseptic osteonecrosis in 65 different bones, including 37 hips, 13 knees, 5 taluses, 1 cuboid, 8 shoulders, 1 humeral condyle, following renal transplantation. One patient had osteonecrosis in six different bones. In 24 cases, the necrosis occurred before the end of the 18th month following the graftmin 21 cases, radiodiagnosis of the first localisation was made before the end of the first month following the first clinical sign. The usual presenting symptom of osteonecrosis is a clear, sub-chondral crescent. In 2/3rds of cases of osteonecrosis of the femoral neck, there is a rapidly destructive form often well tolerated clinically. In 1/3rd of cases, the course was slow with mainly osteocondensation. The course is particularly destructive when, following failure of the graft, the transplanted patient is submitted to periodic hemodialysis. In 8 cases, the femoral condyles were involved, and in 4, the tibial condylesm the appearance may be that of osteochondritis dissecans, but more often the course resembles the destructive form of aseptic necrosis of the femoral head. Shoulder involvement leads to a radiological picture identical with that of the hips. One transplanted patient out of 5, has a chance to develop osteonecrosis within two years following the graft.