Target engagement and intracellular delivery of mono- and bivalent LDL receptor-binding peptide-cargo conjugates: Implications for the rational design of new targeted drug therapies

Targeted delivery to specific tissues and subcellular compartments is of paramount importance to optimize therapeutic or diagnostic interventions while minimizing side-effects. Using recently identified LDL receptor (LDLR) -targeting small synthetic peptide-vectors conjugated to model cargos of different nature and size, we investigated in LDLR-expressing cells the impact of vector-cargo molecular engineering and coupling valency, as well as the cellular exposure duration on their target engagement and intracellular trafficking and delivery profiles. All vector-cargo conjugates evaluated were found to be delivered to late compartments together with the natural ligand LDL, although to varying extents and with different kinetics. Partial recycling together with the LDLR was also consistently observed. Under continuous cellular exposure, the extent of intracellular vector-cargo delivery primarily relies on their endosomal unloading potential. In this condition, the highest intracellular delivery potential was observed with a monovalent conjugate displaying a rather high LDLR dissociation rate. On the contrary, under transient cellular exposure followed by chase, low dissociation-rate bivalent conjugates revealed a higher intracellular delivery potential than the monovalent conjugate. This was shown to rely on their ability to undergo multiple endocytosis-recycling rounds, with limited release in the ligand-free medium. The absence of reciprocal competition with the natural ligand LDL on their respective intracellular trafficking was also demonstrated, which is essential in terms of potential safety liabilities. These results demonstrate that not only molecular engineering of new therapeutic conjugates of interest, but also the cellular exposure mode used during in vitro evaluations are critical to anticipate and optimize their delivery potential.

Experimental study of carbon sequestration reactions controlled by the percolation of CO2-rich brine through peridotites

Carbonation of ultramafic rocks in geological reservoirs is, in theory, the most efficient way to trap CO2 irreversibly; however, possible feedback effects between carbonation reactions and changes in the reservoir permeability must be considered to realistically assess the efficiency and sustainability of this process. We investigated changes in the hydrodynamic properties of sintered dunite samples by means of percolation experiments, under conditions analogous to that of in situ carbonation. Our results show that carbonation efficiency is controlled by the local renewal of the reactants and the heterogeneity of the pore structure. Preferential flow zones are characterized by the formation of magnetite and of a silica-rich layer at the olivine surfaces, which eventually inhibits olivine dissolution. Conversely, sustainable olivine dissolution together with coprecipitation of magnesite, siderite, and minor Mg-TOT-phyllosilicates, occur in reduced-flow zones. Thus carbonate precipitation only decreases porosity in zones where diffusion-controlled transport is dominant. Consequently, while high flow rates will decrease the carbonation efficiency of the reservoir and low flow rates may reduce the permeability irreversibly close to the injection point, moderate injection rates will ensure a partial carbonation of the rock and maintain the reservoir permeability.

[Transfusion in elderly patients]

The frequency of anemia is responsible of a frequent use of transfusion in elderly patients. However, transfusion in elderly patients requires several warnings. First, semiology of elderly patients is characterized with atypical clinical signs, and anemia tolerance is often difficult to appreciate. Second, numerous comorbidities make of elderly patients an heterogeneous population, in which guidelines are poorly applicable. Last, elderly patients are particularly sensitive to iatrogenic events, and the haemodynamic overload related to transfusion has to be carefully managed. All these difficulties raise the need of prospective studies on transfusion in elderly patients to validate clinical practice.

[Removal of a tracheostomy in ventilator-dependent patients with neuromuscular disease]

BACKGROUND

Ventilation via a tracheostomy is effective but very restricting in patients with neuromuscular disease. Return to non-invasive ventilation (NIV) is possible but this is not common practice, partly for want of standardised procedures ensuring a safe transition.

METHODS

A procedure for transfer of ventilation via a tracheostomy to a mask has been developed based on the literature and local experience (feasibility of NIV, absence of laryngo-tracheal lesions, adequate leak compensation, effective cough). It has been tested in three patients with severe but stable neuromuscular disorders (chronic polyneuropathy in two cases and progressive spinal amyotrophy on one).

RESULTS

The three patients were able to be extubated and established on domiciliary ventilation in 6,7 and 10 days, at the end of which all were discharged home. After 4 months in two cases and 6 months in the other no significant complications developed, the respiratory status under NIV was comparable to that previously under tracheostomy and the patients were satisfied with the change.

CONCLUSION

The proposed algorithm seems to permit a rapid and safe transition from a tracheostomy to a mask. Large scale studies are needed to verify this concept and subsequently to identify within which group a similar approach may be correctly applied.

Resistance training improves single muscle fiber contractile function in older women

The purpose of this study was to 1) examine single cell contractile mechanics of skeletal muscle before and after 12 wk of progressive resistance training (PRT) in older women (n = 7; 74 +/- 2 yr) and 2) to compare these results to our previously completed single cell PRT work with older men (n = 7; 74 +/- 2 yr) (Trappe S, Williamson D, Godard M, Porter D, Rowden G, and Costill D. J Applied Physiol 89:143--152, 2000). Knee extensor PRT was performed 3 days/wk at 80% of one-repetition maximum. Muscle biopsies were obtained from the vastus lateralis before and after the PRT. Chemically skinned single muscle fibers (n = 313) were studied at 15 degrees C for peak tension (P(o)), unloaded shortening velocity (V(o)), and power. Due to the low number of hybrid fibers identified post-PRT, direct comparisons were limited to MHC I and IIa fibers. Muscle fiber diameter increased 24% (90 +/- 2 to 112 +/- 6 microm; P < 0.05) in MHC I fibers with no change in MHC IIa fibers. P(o) increased (P < 0.05) 33% in MHC I (0.76 +/- 0.04 to 1.01 +/- 0.09 mN) and 14% in MHC IIa (0.73 +/- 0.04 to 0.83 +/- 0.05 mN) fibers. Muscle fiber V(o) was unaltered in both fiber types with PRT. MHC I and IIa fiber power increased (P < 0.05) 50% [11 +/- 2 to 17 +/- 2 microN. fiber length (FL). s(-1)] and 25% (40 +/- 8 to 51 +/- 6 microN. FL. s(-1)), respectively. However, when peak power was normalized to cell size, no pre- to postimprovements were observed. These data indicate that PRT in elderly women increases muscle cell size, strength, and peak power in both slow and fast muscle fibers, which was similar to the older men. However, in contrast to the older men, no change in fiber V(o) or normalized power was observed in the older women. These data suggest that older men and women respond differently at the muscle cell level to the same resistance-training stimulus.

Effect of resistance training on single muscle fiber contractile function in older men

The purpose of this study was to examine single cell contractile mechanics of skeletal muscle before and after 12 wk of progressive resistance training (PRT) in older men (n = 7; age = 74 +/- 2 yr and weight = 75 +/- 5 kg). Knee extensor PRT was performed 3 days/wk at 80% of one-repetition maximum. Muscle biopsy samples were obtained from the vastus lateralis before and after PRT (pre- and post-PRT, respectively). For analysis, chemically skinned single muscle fibers were studied at 15 degrees C for peak tension [the maximal isometric force (P(o))], unloaded shortening velocity (V(o)), and force-velocity parameters. In this study, a total of 199 (89 pre- and 110 post-PRT) myosin heavy chain (MHC) I and 99 (55 pre- and 44 post-PRT) MHC IIa fibers were reported. Because of the minimal number of hybrid fibers identified post-PRT, direct comparisons were limited to MHC I and IIa fibers. Muscle fiber diameter increased 20% (83 +/- 1 to 100 +/- 1 microm) and 13% (86 +/- 1 to 97 +/- 2 microm) in MHC I and IIa fibers, respectively (P < 0.05). P(o) was higher (P < 0.05) in MHC I (0.58 +/- 0.02 to 0.90 +/- 0.02 mN) and IIa (0.68 +/- 0.02 to 0.85 +/- 0.03 mN) fibers. Muscle fiber V(o) was elevated 75% (MHC I) and 45% (MHC IIa) after PRT (P < 0.05). MHC I and IIa fiber power increased (P < 0.05) from 7.7 +/- 0.5 to 17.6 +/- 0.9 microN. fiber lengths. s(-1) and from 25.5 to 41.1 microN. fiber lengths. s(-1), respectively. These data indicate that PRT in elderly men increases muscle cell size, strength, contractile velocity, and power in both slow- and fast-twitch muscle fibers. However, it appears that these changes are more pronounced in the MHC I muscle fibers.

Familial lipoprotein lipase deficiency in infancy: clinical, biochemical, and molecular study

OBJECTIVES

To describe the characteristics of lipoprotein lipase (LPL)-deficient patients seen in infancy and to evaluate the safety and efficacy of severe fat restriction.

METHODS

Children <1 year old presenting with chylomicronemia between 1972 and 1995 were identified, and their clinical courses were reviewed retrospectively.

RESULTS

LPL deficiency was demonstrated in 16 infants who presented with irritability (n = 7), lower intestinal bleeding (n = 2), pallor, anemia, or splenomegaly (n = 5), and a family history or fortuitous discovery (n = 2). All plasma samples were lactescent at presentation. Chylomicronemia responded rapidly to dietary fat restriction, and it was possible to maintain satisfactory metabolic control for a prolonged period of time. Only 1 adolescent girl had an episode of pancreatitis associated with the use of oral contraceptives. No persistent adverse effects on growth were seen. We obtained abnormal values for serum iron, alkaline phosphatase, and total calcium.

CONCLUSIONS

The presentation of LPL deficiency is heterogeneous during infancy. Close dietary monitoring is required to avoid nutritional deficiencies. Estrogen therapy should be avoided in LPL-deficient patients.

Improvement of hematologic recovery after high-dose intensification using peripheral blood progenitor cells (PBPC) mobilized by chemotherapy and GM-CSF

We have tested the efficiency of GM-CSF to mobilize peripheral blood progenitor cells (PBPC) and evaluated the hematological reconstitution after GM-CSF primed-PBPC infusion following myeloablative therapy. Twenty three patients suffering from hematological malignancies were included in this study. Starting 24 hours after completion of a standard dose chemotherapy including vindesine, cyclophosphamide, adriblastine, prednisone, (VCAP), 5 micrograms/kg sub-cutaneous daily dose GM-CSF was given for a median time of 14 days followed by three consecutives cycles of leukapheresis. Fifteen of these 23 patients underwent GM-CSF primed-PBPC autotransplantation following high dosed intensification regimen. PBPC collection and hematopoietic recovery were compared with a 15 patients control group who did not receive GM-CSF. No marrow or growth factors were administered after PBPC reinfusion in the two groups. VCAP/GM-CSF mobilization induced significantly higher yields of CFU-GM (3.8 fold) than did VCAP mobilization alone, 19 x 10(4)/kg (2-73) vs 5 x 10(4)/kg (2-27), (p < 0.005). The median number of days to achieve 1.10(9)/l neutrophils, platelet count > 20.10(9)/l and > 50.10(9)/l was significantly lower in the GM-CSF group than in the control group, respectively 13 vs 19 days (p = 0.04), 15.5 vs 27 days (p < 0.02), 19 vs 51 days (p < 0.01). When compared with the control group, transfusion requirements and median of hospital stay were both significantly decreased for the patients receiving GM-CSF primed-PBPC. Our study confirms that infusion of GM-CSF primed-PBPC as a sole source of hematopoietic support improves hematopoietic reconstitution following myeloablative therapy.

Beneficial effects of fish-oil supplements on lipids, lipoproteins, and lipoprotein lipase in patients with glycogen storage disease type I

Glycogen storage disease type I (GSD-I) is frequently complicated by severe hyperlipoproteinemia and the increased potential risk of premature atherosclerosis. The effects of fish-oil supplementation [MaxEPA, 10 g.(1.73 m2)-1 for 3 mo] were investigated prospectively in seven hyperlipoproteinemic patients with GSD-I. Hypertriglyceridemia and hypercholesterolemia improved after 3 mo of fish-oil treatment, decreasing 49% (P < 0.005) and 23%, respectively. This was accompanied by a reduction in both low-density-lipoprotein (LDL) cholesterol (25%, P < 0.03) and apolipoprotein B (40%) and by increased high-density-lipoprotein increased (HDL) cholesterol (30%, P < 0.002) and apolipoprotein A-I (31%, P < 0.05). Low pretreatment ratios of HDL to total cholesterol and HDL to LDL, indicators of elevated atherosclerosis risk, increased significantly (P < 0.05). Plasma lipoprotein profile as well as lipoprotein composition [triglyceride (TG) enrichment and cholesteryl depletion] improved. Reduced TG concentrations were due to enhanced fat catabolism, as evidenced by the significantly increased hepatic and extrahepatic lipoprotein lipase activity (P < 0.05). Withdrawal of fish oil for 3 mo was associated with a return to pretreatment abnormalities in plasma lipids and lipoproteins. Fish-oil supplementation thus improves the hyperlipoproteinemia in GSD-I and may significantly reduce the risk of premature atherosclerotic cardiovascular disease.