Aminoglycoside nephrotoxicity.

The main constraints to the administration of aminoglycosides (AG) are risks of nephrotoxicity and ototoxicity, which can lead to renal and vestibular failure. AG accumulation in the kidney may be related to the dosing schedule. As a result, administration of larger doses on a less frequent basis may reduce the drug accumulation in the renal cortex. Many methods have been proposed to reduce AG nephrotoxicity. (1) Molecular modeling and analog synthesis could lead to intrinsically less toxic AG but this approach is time consuming and expensive. Protective approaches such as the co-administration of polyaspartic acid or defferoxamine appear to be very promising in clinical practice. (2) Population pharmacokinetic computer programs, used to control AG serum concentrations, are correct predictors of efficacy but the estimated concentrations in the second compartment are not reliable predictors of nephrotoxicity because they do not take into account non-linear processes such as the AG uptake in the renal cortex or the tubuloglomerular feedback. (3) Finally, modelling the AG nephrotoxicity with probabilistic approaches and/or with deterministic approaches seems to be very promising. These two approaches appear to be not competitive but very complementary in clinical practice. The probabilistic model can be used to predict nephrotoxicity at the beginning the treatment. The deterministic model can be used to simulate and control nephrotoxicity when it is already unfolding and the treatment must be given for a long period of time.

[PK/PD modeling of aminoglycoside nephrotoxicity]. / Un modèle PK/PD de la néphrotoxicité des aminoglycosides.

Aminoglycosides are bactericidial antibiotics with a serum concentration-dependent activity. They are mainly eliminated by the kidneys and the main difficulty arising in clinical use is their uptake by the renal cortex which leads to nephrotoxicity. An ototoxicity is also reported. We propose a PK/PD modelling of aminoglycoside nephrotoxicity which unifies more fourty years of physiological knowledge. This deterministic model successively describes the pharmacokinetics of aminoglycosides, their storage into renal cortex, their effect on renal cells, their consequences on the renal function through tubuloglomerular feedback and the changes in the serum concentrations of creatinine that is considered as a toxicity marker. The simulation of the model displays the leading effect of the shape and daily-time of administration schedule on the search for minimizing toxicity.

[Efficacy and toxicity of aminoglycoside therapy in the elderly: combined effect of both once-daily regimen and therapeutic drug monitoring]. / Efficacité thérapeutique et toxicité des aminosides chez la personne âgée: influence combinée des nouvelles stratégies thérapeutiques et de l'adaptation de posologie.

UNLABELLED: This study was aimed to compare with previous results (Grillot et al., 1994), the efficacy of amikacin adaptive optimal control in a geriatric hospital. PATIENTS: During six months, 32 patients (aged of 82 +/- 8 years) were included versus 51 during two years (aged of 80 +/- 5). The mean age was not different between the two populations (NS, Student test). They received amikacin initial dosage of 17.7 +/- 5.1 mg/kg/d (vs 13.3 +/- 3.5 for the reference study) and maintenance dosage of 15.1 +/- 4.8 mg/kg/d (vs 11.8 +/- 5.1 for the reference study). METHOD: Two efficacy outcomes (E1 and E2) and 1 toxicity outcome (T) were taken into account: E1 estimated the effect of adaptive control on maximal drug level, E2: overall recovery. Toxicity outcome was used: T the nephrotoxicity (increasing creatininémia over 44 mumol/l). RESULTS: All the results are given versus the reference study. 57.6% versus 29.4% of adaptive strategy were once-a-day. E1: Chi square test show that initial dosage and maintenance dosage are greater our study than the previous one (p < 0.05: 78.8% versus 5.9% for initial dosage, 84.4% versus 13.8% for maintenance dosage). E2: 73.6% overall of recovery versus 77% (NS, Chi square test). T: 94% versus 85% (p < 0.05, Chi square test) of creatininemia variation are lower than 44 mumol/l. Duration of treatment is 9.8 +/- 4.8 versus 15 +/- 9 days (p < 0.5, Student test). CONCLUSIONS: Once-a-day strategy in amikacin therapeutic regimen is no more efficient but decreases toxicity and duration treatment.

IL-6 and IL-8 production by human bone marrow stromal cells.

By using a specific enzyme-linked immunosorbent assay, the authors demonstrated that human bone marrow stromal cells produce IL-6 and IL-8. Their synthesis is enhanced in a dose-dependent manner after stimulation with lipopolysaccharide (LPS) and phorbol myristate acetate (PMA). Interleukin 6 (IL-6) and IL-8 production in response to PMA were markedly diminished by the PKC inhibitor staurosporine. IL-6 (10 ng/ml) stimulated IL-8 production with 0% and 10% fetal calf serum (FCS) in the culture medium. In similar conditions, IL-8 (10 ng/ml) enhanced IL-6 production. IL-1 alpha, IL-1 beta, and IL-3, tumour necrosis factor alpha (TNF-alpha), Stem cell factor (SCF) and granulocyte-macrophage colony-stimulating factor (GM-CSF) (at 10 ng/ml) stimulated IL-6 and IL-8 production in 0% and 10% FCS. G-CSF stimulated and IL-4 inhibited IL-8 production in 10% FCS. IL-2, IL-4 and bFGF stimulated IL-6 production in 0% FCS. These results suggest that bone marrow stromal cells might represent a major source for the cytokine-regulated local production of IL-6 and IL-8 inside human bone marrow.

Spontaneous and inducible production of leukaemia inhibitory factor by human bone marrow stromal cells.

Leukaemia inhibitory factor (LIF) acts on the growth and differentiation of haematopoietic cells. By using a specific enzyme-linked immunosorbent assay for human LIF, we demonstrate that human bone marrow stromal cells produce LIF. LIF synthesis is enhanced in a dose-dependent manner after stimulation with lipopolysaccharide (LPS) and phorbol 12-myristate 13-acetate (PMAS). LIF production in response to PMA is PKC-dependent since the two PKC inhibitors sphingosine and staurosporine markedly diminished it. Interleukin 1alpha (IL-1alpha), IL-1beta, IL-3, IL-6, IL-8, tumour necrosis factor (TNF-alpha) and SCF (both at 10 ng/ml) stimulate LIF production. By contrast macrophage colony-stimulating factor (M-CSF), granulocyte (G)-CSF, GM-CSF, basic fibroblast growth factor (bFGF), platelet-activating factor (PAF), protaglandin E2 (PGE2), leukotriene B4 (LTB4), and leukotriene C4 (LTC4) did not. These results suggest that bone marrow stromal cells might represent a major source for the cytokine-regulated local production of LIF inside human bone marrow.

Platelet-activating factor and antagonists modulate DNA synthesis in human bone marrow stromal cell cultures.

Platelet-activating factor (PAF) is present in the human bone marrow. We have investigated the effect of PAF and antagonists (BN 52,021 and CV 3988) on the growth of human marrow stromal cells. PAF (1 microM) stimulates and PAF antagonists (0.1-1 microM) inhibit [3H]thymidine incorporation in cells grown in 5% serum. The catabolism of PAF by stromal cells was inhibited by CV 3988 suggesting the presence of specific PAF receptor on cells. PAF and antagonists (0.1 nM-10 microM) had no effect on cells cultured in high serum concentration (20%) or in low serum concentration (1%) with 0.5 ng/ml of basic fibroblast growth factor (bFGF). This study indicates for the first time that PAF modulates the serum-induced but not the bFGF-induced growth of marrow stromal cells. The interactions between PAF and stromal cells during inflammatory marrow events such as myelofibrosis deserve to be assessed.

Presence and metabolism of lyso platelet-activating factor in human bone marrow.

Lyso platelet-activating factor (PAF) is the precursor of PAF, an inflammatory phospholipid molecule present in human bone marrow. The present study shows that in healthy volunteers lyso PAF concentrations are significantly lower (P = 0.0001, Mann-Whitney U-test) in bone marrow plasma (594 +/- 67 ng/ml, n = 47) than in blood plasma (1448 +/- 99 ng/ml, n = 31). Marrow plasma lyso PAF concentrations are similar in patients with lymphoid and nonlymphoid malignancies as compared with controls. Freshly isolated mononuclear marrow cells and cultures of marrow stromal cells contain lyso PAF. Experiments with [3H]lyso PAF indicate that human mononuclear bone marrow cells and marrow stromal cells actively acylate lyso PAF into a 1-alkyl analogue of phosphatidylcholine. Results of this investigation indicate: (1) that lyso PAF is present in human marrow cells and plasma; and (2) that marrow cells and stromal cells metabolize it, thus suggesting their role in the regulation of lyso PAF amounts in human bone marrow.

Spontaneous and inducible production of macrophage colony-stimulating factor by human bone marrow stromal cells.

Macrophage Colony-Stimulating Factor (M-CSF), which is permanently present in blood and human bone marrow, regulates the proliferation, differentiation and functions of cells of the mononuclear-phagocytic lineage. By using Reverse-Transcriptase Polymerase Chain Reaction (RT-PCR) we demonstrate that human marrow stromal cells express two types of M-CSF transcripts that are translated into the secreted form and the membrane anchored form. By using a specific and sensitive ELISA, we found that the spontaneous production of M-CSF by human marrow stromal cells is enhanced after stimulation with lipopolysaccharide (LPS), phorbol myristic acetate (PMA) and most interestingly by the lipidic mediator of inflammation platelet-activating factor (PAF). Thus, marrow stromal cells might represent a regulated cell source of bone marrow-derived M-CSF. These results not only emphasize the importance of the bone marrow environment in the control of human hematopoiesis but also evidence, for the first time, the potential role of PAF in the marrow cytokine network during inflammatory processes.

Production and metabolism of platelet-activating factor by human bone marrow cells.

Platelet-activating factor (PAF) is a phospholipid mediator of inflammation present in the human bone marrow. Freshly isolated human mononuclear bone marrow cells and marrow stromal cell cultures produced PAF under calcium ionophore (2 microM) and LPS (10 micrograms/ml) stimulation. By contrast, M-CSF (1000 U/ml), GM-CSF (100 ng/ml), IL1, IL3, IL6 and stem cell factor (10 ng/ml) did not stimulate PAF production. Marrow stromal cells produced 50-fold more PAF than freshly isolated mononuclear marrow cells, suggesting that stromal cells might be the major source of the human marrow-derived PAF. Mononuclear marrow cells and stromal cell cultures metabolized PAF with 1-alkyl-2-acyl-glycerophosphocholine as the major metabolic product. PMSF and p-BPB decreased the catabolism of PAF by freshly isolated marrow cells, but not by stromal cell cultures. While stromal cells rather than haematopoietic progenitors might be a major source of the human bone-marrow-derived PAF, both cell types metabolize it, suggesting their putative role in the regulation of PAF concentration in the human bone marrow.

Tumour necrosis factor-alpha (TNFalpha) stimulates the growth of human bone marrow stromal cells.

This study reports that TNF-alpha is a potent mitogen for human bone marrow sternal cells in vitro (assessed by [(3)H]-thymidine incorporation into DNA and cell counts). In contrast, cytokines such as IL-1alpha, IL-1beta, IL-2, IL-3, IL-4, IL-6, LIF, SCF, M-CSF, G-CSF and GM-CSF had no effect. The effect of TNF-alpha on the growth of human bone marrow stromal cells could be of importance during inflammatory processes which take place in the marrow, for example marrow fibrosis.

Comparative virulence between different strains of Listeria in zebrafish (Brachydanio rerio) and mice.

Listeriosis is a disease found in most animal species but is relatively uncommon in fish. We studied the relationship between Listeria and zebrafish by injecting Brachydanio rerio intraperitoneally with different Listeria strains having pathological or food-stuff origins. We then compared these results with those obtained in Swiss mice. Experimental Listeriosis in Zebrafish differs greatly from that observed in mice. The 50% lethal dose (LD50) previously determined was much higher than that observed in mice. In fish, a good correlation exists between infection found in renal tissue, an important lymphoïd organ and that present in whole fish (p < 0.001). Infection kinetics showed that, in contrast with mice, L. monocytogenes was unable to multiply in fish. Differential blood counts showed the development of an immune response in fish. The difference in the expression of Listeria virulence between Zebrafish and mice was also seen in their reactions to different wild strains inoculate i.p. Strains belonging the innocua, ivanovii, seeligeri and welshimeri were weakly or not virulent in mice but virulent in fish. Nevertheless, as in mice, differences in virulence existed between strains of L. monocytogenes belonging to serovars 4b, 1/2a, 1/2b and 1/2c.

PAF and hematopoiesis. VIII. Biosynthesis and metabolism of PAF by human bone marrow stromal cells.

Human bone marrow stromal cells were studied for their ability to synthesize and to metabolize platelet-activating factor (PAF), a lipidic compound with potent immunoregulatory properties. When stimulated with 2 microM calcium ionophore for 60 minutes, cultures of stromal cells increased their PAF production (3.52 +/- 0.91 ng/1 x 10(6) cells) compared with controls (0.82 +/- 0.13 ng/1 x 10(6) cells). Addition of exogenous lyso PAF (100 nM) and acetyl-CoA (100 microM) during calcium ionophore stimulation did not change the PAF production. The synthesis of PAF was not influenced by the concentration of albumin in the incubation buffer. The PAF from stromal cells exhibited a hexadecyl chain at the sn-1 position of the molecule, as determined by reverse-phase HPLC. While stromal cells contained low amounts of PAF acetylhydrolase activity and did not secrete it in the culture medium, they metabolized exogenous PAF with 1-alkyl-2-acyl-glycero-phosphocholine and neutral lipids as the major metabolic products. The present results are the first to demonstrate the synthesis and metabolism of PAF by human bone marrow stromal cells. These data suggest that they might be a source of the PAF found in the human bone marrow and/or might be important in the regulation of its levels. The role of PAF on the proliferation and functions of human hematopoietic cells deserves investigation.

Copper and zinc exposure of zebrafish, Brachydanio rerio (Hamilton-Buchaman): effects in experimental Listeria infection.

To investigate the effects of heavy metals on susceptibility of fish to Listeriosis, normal zebrafish, Brachydanio rerio (Hamilton-Buchanan), were exposed to varying concentrations of zinc (0.05, 0.15, and 0.25 mg/liter) and copper (0.05, 0.10, and 0.15 mg/liter). During copper exposure, this heavy metal did not accumulate in zebrafish kidney. Unlike copper, a small amount of zinc accumulated in kidneys of fish exposed at 0.25 mg/liter. To estimate the effects of this heavy metal on listerial infection, the mortality of fish and the number of viable bacteria in fish kidney were determined at various times (1, 4, 7, and 10 days) after ip challenge with Listeria monocytogenes (strain 31386, serotype 4b). The results indicate that the number of colony-forming units in zinc-exposed fish decreased at 4, 7, and 10 days after challenge with 0.2 x LD50 of viable bacteria. In contrast, copper-exposed fish indicated both decreases and increases in the number of colony-forming units depending on the concentration of L. monocytogenes used.

Human bone marrow fibroblasts--an overview of their characterization, proliferation and inflammatory mediator production.

Bone marrow fibroblasts regulate hematopoiesis by interacting directly (cell-to-cell contact) with hematopoietic cells and by secreting regulatory molecules (such as GM-CSF, M-CSF, IL6 and LIF) that modulate hematopoiesis either in a positive or a negative manner. Several cytokines (such as bFGF, EGF, PDGF and TGF-beta) affect the growth of human marrow fibroblasts in vitro. Further in vivo studies are still required to clarify the role of marrow fibroblasts and their interactions with hematopoietic progenitors during myelofibrosis and leukemic diseases.

Platelet-activating factor and haematopoiesis. XI. Platelet-activating factor has no effect on the production of interleukin-6 and tumor necrosis factor-alpha by human bone marrow stromal cells.

PAF is a phospholipid mediator of inflammation with stimulates IL-6 production by murine skin fibroblasts. Although PAF is present in human bone marrow, its role in haematopoiesis is unknown. We have assessed whether PAF stimulates IL-6 and TNF-alpha production by human bone marrow stromal cells (mostly fibroblast-like cells). We report that PAF (1 nM to 10 microM) has no effect on the synthesis of IL-6 and TNF-alpha by human bone marrow stromal cells. This difference may be due to the widely accepted concept "tissue-specific fibroblasts". The role of PAF in the regulation of human haematopoiesis remains to be elucidated.

In vitro effects of substance P and somatostatin on lymphoproliferation in rainbow trout (Salmo gairdneri).

Lymphocytes from peripheral blood of rainbow trout are put in the presence of increasing concentrations of substance P (SP) and somatostatin (SOM). We have shown that SP stimulates and SOM inhibits lymphoproliferation and that the effects are dose dependent. These results suggest that SP and SOM receptors may exist on fish peripheral blood lymphocytes. When cells are stimulated by PHA or LPS, the presence of SP enhances the response to PHA whereas it only modifies the response to LPS to a slight extent. The presence of SOM inhibits PHA- or LPS-induced stimulation. The inhibition of the proliferation is higher in the case of LPS-stimulated cells. These results suggest that there is an unequal distribution of neuropeptide receptors among the various lymphocyte subpopulations.