tLyp-1: A peptide suitable to target NRP-1 receptor.

Targeting vascular endothelial growth factor receptor (VEFGR) and its co-receptor neuropilin-1 (NRP-1) is an interesting vascular strategy. tLyp-1 is a tumor-homing and penetrating peptide of 7 amino acids (CGNKRTR). It is a truncated form of Lyp-1 (CGNKRTRGC), which is known to target NRP-1 receptor, with high affinity and specificity. It is mediated by endocytosis via C-end rule (CendR) internalization pathway. The aim of this study is to evaluate the importance of each amino acid in the tLyp-1 sequence through alanine-scanning (Ala-scan) technique, during which each of the amino acid in the sequence was systematically replaced by alanine to produce 7 different analogues. In silico approach through molecular docking and molecular dynamics are employed to understand the interaction between the peptide and its analogues with the NRP-1 receptor, followed by in vitro ligand binding assay study. The C-terminal Arg is crucial in the interaction of tLyp-1 with NRP-1 receptor. Substituting this residue dramatically reduces the affinity of this peptide which is clearly seen in this study. Lys-4 is also important in the interaction, which is confirmed via the in vitro study and the MM-PBSA analysis. The finding in this study supports the CendR, in which the presence of R/K-XX-R/K motif is essential in the binding of a ligand with NRP-1 receptor. This presented work will serve as a guide in the future work pertaining the development of active targeting agent towards NRP-1 receptor.

Clickable C-Glycosyl Scaffold for the Development of a Dual Fluorescent and [18F]fluorinated Cyanine-Containing Probe and Preliminary In Vitro/Vivo Evaluation by Fluorescence Imaging.

Considering the individual characteristics of positron emission tomography (PET) and optical imaging (OI) in terms of sensitivity, spatial resolution, and tissue penetration, the development of dual imaging agents for bimodal PET/OI imaging is a growing field. A current major breakthrough in this field is the design of monomolecular agent displaying both a radioisotope for PET and a fluorescent dye for OI. We took advantage of the multifunctionalities allowed by a clickable C-glycosyl scaffold to gather the different elements. We describe, for the first time, the synthesis of a cyanine-based dual PET/OI imaging probe based on a versatile synthetic strategy and its direct radiofluorination via [18F]F-C bond formation. The non-radioactive dual imaging probe coupled with two c(RGDfK) peptides was evaluated in vitro and in vivo in fluorescence imaging. The binding on αvß3 integrin (IC50 = 16 nM) demonstrated the efficiency of the dimeric structure and PEG linkers in maintaining the affinity. In vivo fluorescence imaging of U-87 MG engrafted nude mice showed a high tumor uptake (40- and 100-fold increase for orthotopic and ectopic brain tumors, respectively, compared to healthy brain). In vitro and in vivo evaluations and resection of the ectopic tumor demonstrated the potential of the conjugate in glioblastoma cancer diagnosis and image-guided surgery.

Preliminary Study of New Gallium-68 Radiolabeled Peptide Targeting NRP-1 to Detect Brain Metastases by Positron Emission Tomography.

Due to their very poor prognosis and a fatal outcome, secondary brain tumors are one of the biggest challenges in oncology today. From the point of view of the early diagnosis of these brain micro- and macro-tumors, the sensitivity and specificity of the diagnostic tools constitute an obstacle. Molecular imaging, such as Positron Emission Tomography (PET), is a promising technique but remains limited in the search for cerebral localizations, given the commercially available radiotracers. Indeed, the [18F]FDG PET remains constrained by the physiological fixation of the cerebral cortex, which hinders the visualization of cerebral metastases. Tumor angiogenesis is recognized as a crucial phenomenon in the progression of malignant tumors and is correlated with overexpression of the neuropilin-1 (NRP-1) receptor. Here, we describe the synthesis and the photophysical properties of the new gallium-68 radiolabeled peptide to target NRP-1. The KDKPPR peptide was coupled with gallium-68 anchored into a bifunctional NODAGA chelating agent, as well as Cy5 for fluorescence detection. The Cy5 absorbance spectra did not change, whereas the molar extinction coefficient (ε) decreased drastically. An enhancement of the fluorescence quantum yield (φF) could be observed due to the better water solubility of Cy5. [68Ga]Ga-NODAGA-K(Cy5)DKPPR was radiosynthesized efficiently, presented hydrophilic properties (log D = -1.86), and had high in vitro stability (>120 min). The molecular affinity and the cytotoxicity of this new chelated radiotracer were evaluated in vitro on endothelial cells (HUVEC) and MDA-MB-231 cancer cells (hormone-independent and triple-negative line) and in vivo on a brain model of metastasis in a nude rat using the MDA-MB-231 cell line. No in vitro toxicity has been observed. The in vivo preliminary experiments showed promising results, with a high contrast between the healthy brain and metastatic foci for [68Ga]Ga-NODAGA-K(Cy5)DKPPR.

Design of a Targeting and Oxygen-Independent Platform to Improve Photodynamic Therapy: A Proof of Concept.

Photodynamic therapy (PDT) is a promising technique to treat different kinds of disease especially cancer. PDT requires three elements: molecular oxygen, a photoactivatable molecule called the photosensitizer (PS), and appropriate light. Under illumination, the PSs generate, in the presence of oxygen, the formation of reactive oxygen species including singlet oxygen, toxic, which then destroys the surrounding tissues. Even if PDT is used with success to treat actinic keratosis or prostate cancer for example, PDT suffers from two major drawbacks: the lack of selectivity of most of the PSs currently used clinically as well as the need for oxygen to be effective. To remedy the lack of selectivity, targeting the tumor neovessels is a promising approach to destroy the vascularization and cause asphyxia of the tumor. KDKPPR peptide affinity for the neuropilin-1 (NRP-1) receptor overexpressed on endothelial cells has already been proven. To compensate for the lack of oxygen, we focused on photoactivatable alkoxyamines (Alks), molecules capable of generating toxic radicals by light activation. In this article, we describe the synthesis of a multifunctional platform combining three units: a PS for an oxygen-dependent PDT, a peptide to target tumor neovessels, and an Alk for an oxygen-independent activity. The synthesis of the compound was successfully carried out, and the study of its photophysical properties showed that the PS retained its capacity to form singlet oxygen and the affinity tests confirmed the affinity of the compound for NRP-1. Thanks to the electron paramagnetic resonance spectroscopy, a technique of choice for radical investigation, the radicals generated by the illumination of the Alk could be detected. The proof of concept was thus successfully established.

Synthesis of a DOTA-C-glyco bifunctional chelating agent and preliminary in vitro and in vivo study of [68Ga]Ga-DOTA-C-glyco-RGD.

The design of bifunctional chelating agents (BFCA) allowing straightforward radiometal labelling of biomolecules is a current challenge. We report herein the development of a bifunctional chelating agent based on a DOTA chelator linked to a C-glycosyl compound, taking advantage of the robustness and hydrophilicity of this type of carbohydrate derivative. This new BFCA was coupled with success by CuAAC with c(RGDfK) for αvß3 integrin targeting. As attested by in vitro evaluation, the conjugate DOTA-C-glyco-c(RGDfC) demonstrated high affinity for αvß3 integrins (IC50 of 42 nM). [68Ga]Ga-DOTA-C-glyco-c(RGDfK) was radiosynthesized straightforwardly and showed high hydrophilic property (log D 7.4 = -3.71) and in vitro stability (>120 min). Preliminary in vivo PET study of U87MG engrafted mice gave evidence of an interesting tumor-to-non-target area ratio. All these data indicate that [68Ga]Ga-DOTA-C-glyco-c(RGDfK) allows monitoring of αvß3 expression and could thus be used for cancer diagnosis. The DOTA-C-glycoside BFCA reported here could also be used with various ligands and chelating other (radio)metals opening a broad scope of applications in imaging modalities and therapy.

Multiscale Selectivity and in vivo Biodistribution of NRP-1-Targeted Theranostic AGuIX Nanoparticles for PDT of Glioblastoma.

BACKGROUND: Local recurrences of glioblastoma (GBM) after heavy standard treatments remain frequent and lead to a poor prognostic. Major challenges are the infiltrative part of the tumor tissue which is the ultimate cause of recurrence. The therapeutic arsenal faces the difficulty of eradicating this infiltrating part of the tumor tissue while increasing the targeting of tumor and endogenous stromal cells such as angiogenic endothelial cells. In this aim, neuropilin-1 (NRP-1), a transmembrane receptor mainly overexpressed by endothelial cells of the tumor vascular system and associated with malignancy, proliferation and migration of GBM, highlighted to be a relevant molecular target to promote the anti-vascular effect of photodynamic therapy (VTP). METHODS: The multiscale selectivity was investigated for KDKPPR peptide moiety targeting NRP-1 and a porphyrin molecule as photosensitizer (PS), both grafted onto original AGuIX design nanoparticle. AGuIX nanoparticle, currently in Phase II clinical trials for the treatment of brain metastases with radiotherapy, allows to achieve a real-time magnetic resonance imaging (MRI) and an accumulation in the tumor area by EPR (enhanced permeability and retention) effect. Using surface-plasmon resonance (SPR), we evaluated the affinities of KDKPPR and scramble free peptides, and also peptides-conjugated AGuIX nanoparticles to recombinant rat and human NRP-1 proteins. For in vivo selectivity, we used a cranial window model and parametric maps obtained from T2*-weighted perfusion MRI analysis. RESULTS: The photophysical characteristics of the PS and KDKPPR molecular affinity for recombinant human NRP-1 proteins were maintained after the functionalization of AGuIX nanoparticle with a dissociation constant of 4.7 µM determined by SPR assays. Cranial window model and parametric maps, both revealed a prolonged retention in the vascular system of human xenotransplanted GBM. Thanks to the fluorescence of porphyrin by non-invasive imaging and the concentration of gadolinium evaluated after extraction of organs, we checked the absence of nanoparticle in the brains of tumor-free animals and highlighted elimination by renal excretion and hepatic metabolism. CONCLUSION: Post-VTP follow-ups demonstrated promising tumor responses with a prolonged delay in tumor growth accompanied by a decrease in tumor metabolism.

Inclusion complex vs. conjugation of hydrophobic photosensitizers with ß-cyclodextrin: Improved disaggregation and photodynamic therapy efficacy against glioblastoma cells.

Self-aggregation of hydrophobic porphyrin-based photosensitizers (PSs) in aqueous biological environment decreases their bioavailability and in vivo therapeutic efficacy, which hampers their clinical use in photodynamic therapy (PDT). In the current study, we explore three new supramolecular systems based of hydrophobic PSs (i.e. 5,10,15,20-tetrakis(3-hydroxyphenyl)porphyrin (mTHPP) or 5-(4-carboxyphenyl)-10,15,20-triphenylporphyrin (P1COOH)) non-covalently or covalently attached to ß-CD. The two non-covalent solid inclusion complexes (ß-CD)2/mTHPP and [(ß-CD)/P1COOH]4 are prepared by a new co-precipitation@lyophilization combined method and the covalent conjugate ß-CD-P1 by click chemistry. The binding type effect and effectiveness on the disaggregation in aqueous medium and in vitro PDT efficacy against glioblastoma cancer cells of PSs are investigated for the three ß-CD/PS systems. The findings reveal a remarkable improvement of the disaggregation and in vitro PDT activity of these ß-CD/PS systems compared to the free PSs, except for [(ß-CD)/P1COOH]4 inclusion complex caused by J-type self-aggregation of the inclusion complex in tetrameric form. ß-CD-P1 conjugate shows the higher in vitro PDT efficacy compared to the other ß-CD/PS systems. Overall, the results indicate that the disaggregation in aqueous medium and in vitro PDT activity of hydrophobic PSs can be improved by their binding to ß-CD and the covalent binding is the best approach.

Overcoming the diverse mechanisms of multidrug resistance in lung cancer cells by photodynamic therapy using pTHPP-loaded PLGA-lipid hybrid nanoparticles.

Multidrug resistance (MDR) and the spread of cancer cells (metastasis) are major causes leading to failure of cancer treatment. MDR can develop in two main ways, with differences in their mechanisms for drug resistance, first drug-selected MDR developing after chemotherapeutic treatment, and metastasis-associated MDR acquired by cellular adaptation to microenvironmental changes during metastasis. This study aims to use a nanoparticle-mediated photodynamic therapy (NPs/PDT) approach to overcome both types of MDR. A photosensitizer, 5,10,15,20-Tetrakis(4-hydroxy-phenyl)-21H,23H-porphine (pTHPP) was loaded into poly(D,L-lactide-co-glycolide) (PLGA)-lipid hybrid nanoparticles. The photocytotoxic effect of the nanoparticles was evaluated using two different MDR models established from one cell line, A549 human lung adenocarcinoma, including (1) A549RT-eto, a MDR cell line derived from A549 cells by drug-selection, and (2) detachment-induced MDR acquired by A549 cells when cultured as floating cells under non-adherent conditions, which mimic metastasizing cancer cells in the blood/lymphatic circulation. In the drug-selected MDR model, A549RT-eto cells displayed 17.4- and 1.8-fold resistance to Etoposide and Paclitaxel, respectively, compared to the A549 parental cells. In contrast to treatment with anticancer drugs, NPs/PDT with pTHPP-loaded nanoparticles resulted in equal photocytotoxic effect in A549RT-eto and parental cells. Intracellular pTHPP accumulation and light-induced superoxide anion generation were observed at similar levels in the two cell lines. The NPs/PDT killed A549RT-eto and parental cells through apoptosis as revealed by flow cytometry. In the metastasis-associated MDR model, A549 floating cells exhibited resistance to Etoposide (11.6-fold) and Paclitaxel (57.8-fold) compared to A549 attached cells, but the floating cells failed to show resistance against the photocytotoxic effect of the NPs/PDT. The MDR overcoming activity of NPs/PDT is mainly due to delivery ability of the PLGA-lipid hybrid nanoparticles. In conclusion, this work suggests that PLGA-lipid hybrid nanoparticles have potential in delivering photosensitizer or chemotherapeutic drug for treating both drug-selected and metastasis-associated MDR lung cancer cells.

New Targeted Gold Nanorods for the Treatment of Glioblastoma by Photodynamic Therapy.

This study describes the employment of gold nanorods (AuNRs), known for their good reputation in hyperthermia-based cancer therapy, in a hybrid combination of photosensitizers (PS) and peptides (PP). We report here, the design and the synthesis of this nanosystem and its application as a vehicle for the selective drug delivery and the efficient photodynamic therapy (PDT). AuNRs were functionalized by polyethylene glycol, phototoxic pyropheophorbide-a (Pyro) PS, and a "KDKPPR" peptide moiety to target neuropilin-1 receptor (NRP-1). The physicochemical characteristics of AuNRs, the synthesized peptide and the intermediate PP-PS conjugates were investigated. The photophysical properties of the hybrid AuNRs revealed that upon conjugation, the AuNRs acquired the characteristic properties of Pyro concerning the extension of the absorption profile and the capability to fluoresce (Φf = 0.3) and emit singlet oxygen (ΦΔ = 0.4) when excited at 412 nm. Even after being conjugated onto the surface of the AuNRs, the molecular affinity of "KDKPPR" for NRP-1 was preserved. Under irradiation at 652 nm, in vitro assays were conducted on glioblastoma U87 cells incubated with different PS concentrations of free Pyro, intermediate PP-PS conjugate and hybrid AuNRs. The AuNRs showed no cytotoxicity in the absence of light even at high PS concentrations. However, they efficiently decreased the cell viability by 67% under light exposure. This nanosystem possesses good efficiency in PDT and an expected potential effect in a combined photodynamic/photothermal therapy guided by NIR fluorescence imaging of the tumors due to the presence of both the hyperthermic agent, AuNRs, and the fluorescent active phototoxic PS.

Titania and silica nanoparticles coupled to Chlorin e6 for anti-cancer photodynamic therapy.

In this study, light-sensitive photosensitizers (Chlorin e6, Ce6) were linked to TiO2 and SiO2 nanoparticles (NPs) in order to develop new kinds of NP-based drug delivery systems for cancer treatment by PDT. TiO2 or SiO2 NPs were modified either by the growth of a polysiloxane layer constituted of two silane reagents ((3-aminopropyl)triethoxysilane (APTES) and tetraethyl orthosilicate (TEOS)) around the core (PEGylated NPs: TiO2@4Si-Ce6-PEG, SiO2@4Si-Ce6-PEG) or simply modified by APTES alone (APTES-modified NPs: TiO2-APTES-Ce6, SiO2-APTES-Ce6). Ce6 was covalently attached onto the modified TiO2 and SiO2 NPs via an amide bond. The absorption profile of the hybridized NPs was extended to the visible region of the light. The physicochemical properties of these NPs were explored by TEM, HR-TEM, XRD, FTIR and zeta potential. The photophysical characteristics including the light absorption, the fluorescence properties and the production reactive oxygen species (1O2 and HO) were also addressed. In vitro experiments on glioblastoma U87 cells were performed to evaluate the photodynamic efficiency of the new hybridized NPs. The cells were exposed to different concentrations of NPs and illuminated (λexc = 652 nm, fluence rate 10 J/cm2). In contrast to the PEGylated NPs, the APTES-modified nanosystems were found to be more efficient for PDT. An interesting photodynamic effect was observed in the case of TiO2-APTES-Ce6 NPs. After illumination, the viability of U87 was decreased by 89% when they were exposed to 200 µg/mL of TiO2-APTES-Ce6 NPs, which corresponds to 0.22 µM of Ce6. The same effect can be obtained with free photosensitizer but using a higher concentration of 10 µM of Ce6.

Polymer-lipid-PEG hybrid nanoparticles as photosensitizer carrier for photodynamic therapy.

Polymer-lipid-PEG hybrid nanoparticles were investigated as carriers for the photosensitizer (PS), 5,10,15,20-Tetrakis(4-hydroxy-phenyl)-21H,23H-porphine (pTHPP) for use in photodynamic therapy (PDT). A self-assembled nanoprecipitation technique was used for preparing two types of core polymers poly(d,l-lactide-co-glycolide) (PLGA) and poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV) with lipid-PEG as stabilizer. The resulting nanoparticles had an average particle size of 88.5±3.4nm for PLGA and 215.0±6.3nm for PHBV. Both nanoparticles exhibited a core-shell structure under TEM with high zeta potential and loading efficiency. X-ray powder diffraction analysis showed that the encapsulated pTHPP molecules in polymeric nanoparticles no longer had peaks of free pTHPP in the crystalline state. The pTHPP molecules encapsulated inside the polymeric core demonstrated improved photophysical properties in terms of singlet oxygen generation and cellular uptake rate in a FTC-133 human thyroid carcinoma cell line, compared to non-encapsulated pTHPP. The pTHPP-loaded polymer-lipid-PEG nanoparticles showed better in vitro phototoxicity compared to free pTHPP, in both time- and concentration-dependent manners. Overall, this study provides detailed analysis of the photophysical properties of pTHPP molecules when entrapped within either PLGA or PHBV nanoparticle cores, and demonstrates the effectiveness of these systems for delivery of photosensitizers. The two polymeric systems may have different potential benefits, when used with cancer cells. For instance, the pTHPP-loaded PLGA system requires only a short time to show a PDT effect and may be suitable for topical PDT, while the delayed photo-induced cytotoxic effect of the pTHPP-loaded PHBV system may be more suitable for cancer solid tumors. Hence, both pTHPP-encapsulated polymer-lipid-PEG nanoparticles can be considered promising delivery systems for PDT cancer treatment.

Monte Carlo simulations guided by imaging to predict the in vitro ranking of radiosensitizing nanoparticles.

This article addresses the in silico-in vitro prediction issue of organometallic nanoparticles (NPs)-based radiosensitization enhancement. The goal was to carry out computational experiments to quickly identify efficient nanostructures and then to preferentially select the most promising ones for the subsequent in vivo studies. To this aim, this interdisciplinary article introduces a new theoretical Monte Carlo computational ranking method and tests it using 3 different organometallic NPs in terms of size and composition. While the ranking predicted in a classical theoretical scenario did not fit the reference results at all, in contrast, we showed for the first time how our accelerated in silico virtual screening method, based on basic in vitro experimental data (which takes into account the NPs cell biodistribution), was able to predict a relevant ranking in accordance with in vitro clonogenic efficiency. This corroborates the pertinence of such a prior ranking method that could speed up the preclinical development of NPs in radiation therapy.

Design, synthesis and biological evaluation of new classes of thieno[3,2-d]pyrimidinone and thieno[1,2,3]triazine as inhibitor of vascular endothelial growth factor receptor-2 (VEGFR-2).

Driven by a multidisciplinary approach combination (Structure-Based (SB) Three-Dimensional Quantitative Structure-Activity Relationships (3-D QSAR), molecular modeling, organic chemistry and various biological evaluations) here is reported the disclosure of new thienopyrimidines 1-3 as inhibitors of KDR activity and human umbilical vein endothelial cell (HUVEC) proliferation. More specifically, compound 2f represents a new lead compound that inhibits VEGFR-2 and HUVEC at µM concentration. Moreover by the mean of an endothelial cell tube formation in vitro model 2f tartaric acid salt proved to block angiogenesis of HUVEC at µM level.

Modulation of endothelial cell network formation in vitro by molecular signaling of head and neck squamous cell carcinoma (HNSCC) exposed to cetuximab.

Overexpression of EGFR plays a key-role in head and neck squamous cell carcinoma (HNSCC) and justifies the extensive use of cetuximab, a monoclonal anti-EGFR antibody, as well as EGFR-tyrosine kinase inhibitors (EGFR-TKI), which have been reported to inhibit tumor cell growth and the secretion of pro-angiogenic factors by tumor cells, such as VEGF and IL-8. Moreover, vessel normalization in tumors, suggesting a more complex mediation of endothelial cell growth control has also been observed in vivo. The present study was designed to investigate the angiogenic consequences of exposure of HNSCC tumor cell lines to cetuximab and intercellular signaling between tumor and endothelial cells by secretion of pro- and anti-angiogenic mediators in the conditioned media (CM). The results achieved showed that cetuximab decreased the secretion of VEGF by HNSCC cells and that exposure of human umbilical vein endothelial cells (HUVEC) to CM from HNSCC cells exposed to cetuximab induced an increase in endothelial cell network formation. Angiogenesis proteome profiling showed that cetuximab induced a complex alteration of the secretion of pro- and anti-angiogenic factors by HNSCC cells without enabling to identify a unique molecular marker. Expression of endothelial membrane receptors (VEGFR-2, EGFR, PECAM-1 and Notch-4) was investigated and only EGFR expression was found influenced when HUVEC were exposed to CM from cetuximab-exposed HNSCC cells. These results showed that the decrease in the secretion of pro-angiogenic agents like VEGF by HNSCC cells exposed to cetuximab could not be sufficient to justify its anti-angiogenic activity in vitro.

Immunoadsorption of alloantibodies onto erythroid membrane antigens encapsulated into polymeric microparticles.

PURPOSE: Classical immunoadsorbents used for the removal of deleterious molecules in blood such as auto-antibodies are prepared by covalent coupling of antigens onto previously chemically activated supports. Such a chemical treatment may induce a potential toxicity which can be reduced if new immunoadsorbents are prepared by encapsulating erythrocytes-ghosts carrying antigens inside polymeric and porous microparticles. MATERIALS AND METHODS: Erythrocyte-ghosts obtained by hemolysis in hypotonic buffer were encapsulated into ethylcellulose microparticles by w/o/w emulsification. The porosity of microparticles was evaluated by mercury porosimetry. The adsorption ability of encapsulated antigens was evaluated by hemagglutination after contact in tube or elution in column with polyclonal antibody solutions or human blood-plasma. RESULTS: The encapsulation process did not significantly alter the evaluated antigens since a significant decrease in anti-A (from 256 to 4) as well as anti-Kell (from 64 to 2) antibody titer has been observed in column after eight chromatographic runs (2 h). The higher the ghost concentration (total protein content of 6 mg/ml), the higher the adsorption capacity. CONCLUSION: Encapsulation, currently used for drug delivery purposes, may consequently also be applied to the design of new immunoadsorbents as biomaterials.

A comparison of epinephrine only, arginine vasopressin only, and epinephrine followed by arginine vasopressin on the survival rate in a rat model of anaphylactic shock.

BACKGROUND: Epinephrine and more recently arginine vasopressin (AVP) alone or in combination have been proposed in patients with anaphylactic shock, but few experimental data exist. The authors investigated the effects of epinephrine only, AVP only, or epinephrine followed by AVP in a model of anaphylactic shock. METHODS: Ovalbumin-sensitized Brown Norway rats were anesthetized, intubated, and shock induced with ovalbumin. Rats (n = 6/group) were randomly allocated to receive 5 min after shock onset: (1) saline (no-treatment group); (2) two boluses of epinephrine followed by continuous infusion (epinephrine group); (3) AVP bolus followed by continuous infusion (AVP group); (4) epinephrine bolus followed by AVP continuous infusion (epinephrine + AVP group). Mean arterial pressure (MAP) and skeletal muscle oxygen pressure (PtiO2) were measured. Continuous infusion rates were titrated to reach MAP values of 60 mmHg. Survival was analyzed. RESULTS: Without treatment, MAP and PtiO2 decreased rapidly with 0% survival. In the epinephrine group, MAP and PtiO2 recovered after an initial decrease, with 84% survival. In the AVP group, MAP was partially restored and subsequently decreased; PtiO2 values decreased to values similar to those in the no-treatment group; survival was 0%. In the epinephrine + AVP group, MAP and PtiO2 values increased more slowly as compared with the epinephrine group; survival was 100%. CONCLUSIONS: In this model of anaphylactic shock, early treatment with epinephrine followed by continuous epinephrine or vasopressin infusion resulted in an excellent survival rate, whereas vasopressin only resulted in a 100% death rate. These experimental results suggest that epinephrine must still be considered as the first-line drug to treat anaphylactic shock.

Effects of a new perfluorocarbon emulsion on human plasma and whole-blood viscosity in the presence of albumin, hydroxyethyl starch, or modified fluid gelatin: an in vitro rheologic approach.

BACKGROUND: Artificial oxygen carriers such as perfluorocarbon (PFC) emulsions have reached Phase III clinical trials as alternatives to homologous blood, but their rheologic effects have not been characterized. In this study, the rheologic effects of PFC emulsion in the presence of clinically used volume expanders were investigated. STUDY DESIGN AND METHODS: The effects of a new PFC emulsion (small droplet size with narrow size distribution) at two PFC concentrations (4 and 8 g/dL) on plasma and whole-blood viscosity in the presence of human albumin solution (HAS), hydroxyethyl starch (HES), or modified fluid gelatin (MFG) were investigated. Three hematocrit (Hct) levels were investigated: 30, 20, and 13 percent. Plasma, PFC emulsions, and whole-blood viscosity, with a Couette viscometer, and RBC elongation, with an ektacytometer, were measured for shear rates of 0.2 to 128 per second. RESULTS: The two PFC concentrations increased plasma and whole-blood viscosities. Viscosity values similar to physiologic ones (Hct level, 40%) were observed at: 1) Hct level of 13 percent, with 4 or 8 g per dL MFG-PFC; 2) Hct level of 20 percent, with 4 g per dL MFG-PFC; and 3) Hct level of 30 percent, with 4 g per dL HES-PFC and 4 and 8 g per dL HAS-PFC. RBC deformability was unchanged. CONCLUSION: It is concluded that this new PFC emulsion increases plasma and blood viscosity and that among the three studied volume expanders, the interaction with MFG can result in viscosity values above the physiologic one even at low Hct values. The possible consequences of the increased viscosity at low Hct values are discussed.

Comparison of arginine vasopressin, terlipressin, or epinephrine to correct hypotension in a model of anaphylactic shock in anesthetized brown Norway rats.

BACKGROUND: Arginine vasopressin (AVP) and terlipressin were proposed as alternatives to catecholamines in shock states characterized by decreased plasma AVP concentrations. The endogenous plasma AVP profile in anaphylactic shock is unknown. In an ovalbumin-sensitized anesthetized anaphylactic shock rat model, the authors investigated (1) plasma AVP concentrations and (2) the dose versus mean arterial pressure response for exogenous AVP and terlipressin and compared them with those of epinephrine. METHODS: In a first series of rats (n = 12), endogenous plasma AVP concentrations were compared with a model of pharmacologically induced hypotension (nicardipine, n = 12). A second series was randomly assigned to three groups (AVP, n = 7; terlipressin, n = 7; epinephrine, n = 7) and dose (AVP: 8 doses, 0.03-100 U/kg; terlipressin: 7 doses, 0.03-30 microg/kg; epinephrine: 7 doses, 0.3-300 microg/kg)-response mean arterial pressure curves were plotted. Data are expressed as mean +/- SD. RESULTS: Endogenous plasma AVP concentrations were significantly lower in anaphylactic shock (57 +/- 26 pg/ml) than in the nicardipine group (91 +/- 43 pg/ml; P < 0.05). The ED50 was 10.6 microg/kg (95% confidence interval, 7.1-15.9) for epinephrine and 4.1 U/kg (95% confidence interval, 3.0-5.6) for AVP. Terlipressin did not change mean arterial pressure, regardless of the dose used. CONCLUSIONS: In a rat model, anaphylactic shock is associated with inadequately low plasma AVP concentrations. For clinically relevant doses, AVP and epinephrine had comparable effects on mean arterial pressure and heart rate values, whereas, unexpectedly, terlipressin was ineffective. These results are consistent with reports in humans experiencing anaphylaxis where AVP injection restored arterial pressure.

Anaphylactic shock: a form of distributive shock without inhibition of oxygen consumption.

BACKGROUND: The pathophysiology of anaphylactic shock during anesthesia is incompletely characterized. It is described as distributive by analogy with septic shock (anaerobic metabolism, high tissue oxygen pressure [Ptio2] values). The Ptio2 profile and its metabolic consequences during anaphylaxis are not known. METHODS: Ovalbumin-sensitized anaphylactic shock rats (n = 11) were compared to nicardipine-induced hypotension rats (n = 12) for systemic hemodynamics, Ptio2, sympathetic nervous system activation, skeletal muscle blood flow, and interstitial lactate and pyruvate concentrations using combined microdialysis and polarographic Clark-type oxygen probes. RESULTS: In both groups, the time course and the magnitude of arterial hypotension were similar. The ovalbumin group but not the nicardipine group displayed decreased skeletal muscle blood flow (from 45 +/- 6.2 ml x 100 g(-1) x min(-1) to 24.3 +/- 5 ml x 100 g(-1) x min(-1); P < 0.0001) and Ptio2 values (from 42 +/- 5 to 5 +/- 2; P < 0.0001). The ovalbumin group had more intense sympathetic nervous system activation with higher plasma epinephrine and interstitial norepinephrine concentrations. For the ovalbumin group, there was skeletal muscle anaerobic metabolism (lactate concentration increased from 0.446 +/- 0.105 to 1.741 +/- 0.459 mm; P < 0.05) and substrate depletion (pyruvate concentration decreased from 0.034 +/- 0.01 mm to 0.006 +/- 0.002 mm; P < 0.05) leading to increased interstitial lactate/pyruvate ratios (from 17 +/- 6 to 311 +/- 115; P < 0.05). CONCLUSIONS: This profile suggests decreased skeletal muscle blood flow and oxygen delivery. Persistent energy consumption results in decreased Ptio2 and substrate depletion through anaerobic glycolysis leading to complete failure of cellular energy production. This could explain rapid organ dysfunction and resuscitation difficulties.