Reduction of the allergenicity of cow's milk α-lactalbumin under heat-treatment and enzymatic hydrolysis in Moroccan population.

Summary: The aim of the present study is to evaluate the effect of heat-treatment and enzymatic hydrolysis on the allergenicity of cow's milk α-lactalbumin (α-LA) in a Moroccan population. A total of 557 patients were recruited from the University Hospital Complex and the Ibn El Khatib Hospital of Fez city. This population consented to realize a dosage of IgE levels to raw cow milk and then to α-LA native and treated with the studied treatments. The results revealed that 54.4% of the studied subjects presented positive values of serial IgE to raw cow milk. The effect of treatments on the allergenicity of α-LA showed that heat-treatment at 90°C and pepsin hydrolysis at 37°C, for 1 hour each, caused an important decrease in the IgE binding with an average of reduction of 59% and 74%, respectively.

Effect of industrial processing on the IgE reactivity of three commonly consumed Mo-roccan fish species in Fez region.

Summary: Objectives. The aim of this work was to study the effect of industrial processing on the allergenicity of three commonly consumed Moroccan fish species in Fez region (sardine, common pandora, and shrimp). Methods. This work was conducted by a sera-bank obtained from 1248 patients recruited from Fez Hospitals. Their sera were analyzed for specific IgE binding to raw fish extracts. Among them, 60 patients with higher specific IgE levels were selected, and used to estimate the binding variation of IgE to these products under several processing (frying, cooking, canning, marinade, and fermentation) using ELISA analysis. Results. ELISA results demonstrated that all the studied processing cause a reduction in the immunoreactivity of human IgE to fish products, with a high action with marinade and fermentation compared to other processing. This alteration was also observed with rabbit IgG in all processed products, showing that the maximum reduction was marked in fermented sardine with 64.5%, in cooked common pandora with 58%, and in fermented shrimp with 69.2%. Conclusion. In conclusion, our study has shown that the allergenicity of the three studied fish could be reduced by different industrial processes with different degrees.

Modulation of IgE immunoreactivity to broad bean proteins after food processing in a Moroccan population

BACKGROUND: The aim of this study was to assess the sensitivity profile of the population of Fez and Casablanca in Morocco to dry broad bean (Vicia faba), and to investigate the effect of food processing (heat and/or enzymatic hydrolysis by pepsin) on the human IgE binding capacity to broad bean proteins (BBP). METHODS: Sera samples from 146 patients with atopic hypersensitivity were recruited in order to evaluate specific IgE levels to native and processed broad bean proteins by ELISA. Under the same conditions, we assessed the immunoreactivity of rabbit IgG obtained by immunisation with native BBP. RESULTS: High IgE levels to BBP were found; in fact, 79.3% of children and 80.4% of adults had positive values. The heat treatment (70 °C during 60 min) of dry beans proteins showed slight reduction in recognition of these antigens by rabbit IgG (22%) and by human IgE (12%). Pepsin hydrolysis decreased rabbit-IgG recognition by 55% in the first 30 min of treatment. In contrast, and under the same conditions, pepsin increased human-IgE recognition with an average of 143% for all patients. However, the combination of the two treatments (heating and pepsin digestion) showed a decrease of 16% in BBP recognition for all patients. CONCLUSIONS: This study demonstrates a high sensitivity of a Moroccan population to broad bean proteins which was resistant to heat and digestion by pepsin

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Modulation of IgE immunoreactivity to broad bean proteins after food processing in a Moroccan population.

BACKGROUND: The aim of this study was to assess the sensitivity profile of the population of Fez and Casablanca in Morocco to dry broad bean (Vicia faba), and to investigate the effect of food processing (heat and/or enzymatic hydrolysis by pepsin) on the human IgE binding capacity to broad bean proteins (BBP). METHODS: Sera samples from 146 patients with atopic hypersensitivity were recruited in order to evaluate specific IgE levels to native and processed broad bean proteins by ELISA. Under the same conditions, we assessed the immunoreactivity of rabbit IgG obtained by immunisation with native BBP. RESULTS: High IgE levels to BBP were found; in fact, 79.3% of children and 80.4% of adults had positive values. The heat treatment (70°C during 60 min) of dry beans proteins showed slight reduction in recognition of these antigens by rabbit IgG (22%) and by human IgE (12%). Pepsin hydrolysis decreased rabbit-IgG recognition by 55% in the first 30 min of treatment. In contrast, and under the same conditions, pepsin increased human-IgE recognition with an average of 143% for all patients. However, the combination of the two treatments (heating and pepsin digestion) showed a decrease of 16% in BBP recognition for all patients. CONCLUSIONS: This study demonstrates a high sensitivity of a Moroccan population to broad bean proteins which was resistant to heat and digestion by pepsin.

Cellular localization of type 5 and type 6 ACs in collecting duct and regulation of cAMP synthesis.

The cellular distribution of Ca(2+)-inhibitable adenylyl cyclase (AC) type 5 and type 6 mRNAs in rat outer medullary collecting duct (OMCD) was performed by in situ hybridization. Kidney sections were also stained with specific antibodies against either collecting duct intercalated cells or principal cells. The localization of type 5 AC in H(+)-ATPase-, but not aquaporin-3-, positive cells demonstrated that type 5 AC mRNA is expressed only in intercalated cells. In contrast, type 6 AC mRNA was observed in both intercalated and principal cells. In microdissected OMCDs, the simultaneous superfusion of carbachol and PGE(2) elicited an additive increase in the intracellular Ca(2+) concentration, suggesting that the Ca(2+)-dependent regulation of these agents occurs in different cell types. Glucagon-dependent cAMP synthesis was inhibited by both a pertussis toxin-sensitive PGE(2) pathway (63.7 +/- 4.6% inhibition, n = 5) and a Ca(2+)-dependent carbachol pathway (48.6 +/- 3.3%, n = 5). The simultaneous addition of both agents induced a cumulative inhibition of glucagon-dependent cAMP synthesis (78.2 +/- 3.3%, n = 5). The results demonstrate a distinct cellular localization of type 5 and type 6 AC mRNAs in OMCD and the functional expression of these Ca(2+)-inhibitable enzymes in intercalated cells.

[Regulation of intracellular cAMP content in kidney tubules: role of adenylyl cyclases inhibitable by calcium]. / Régulation du contenu intracellulaire d'AMPc dans le tubule rénal: rôle des adénylyl cyclases inhibables par le calcium.

Adenylyl cyclase (AC) isoforms 5 and 6 can be inhibited by submicromolar concentrations of Ca2+. Quantitative RT-PCR allowed to study the corresponding messengers (mRNA) along the rat nephron. The results demonstrate a significant expression of AC 6 mRNA all along the nephron and of AC 5 mRNA in the glomerulus and the collecting tubule located in the cortex and the outer medulla. Regulation of cAMP synthesis and of intracellular cAMP content in defined renal cell types established the functional expression of AC 5 and AC 6. In particular, adenylyl cyclase activity is strongly stimulated by hormones and can be inhibited by several factors which either increase intracellular Ca2+ concentration or are coupled to G alpha 1. In each renal cell studied, the expression of 5 and 6 isoforms allow to integrate specific, multiple and independent inhibitory pathways which contribute to decrease intracellular cAMP content.

Cell-specific coupling of PGE2 to different transduction pathways in arginine vasopressin- and glucagon-sensitive segments of the rat renal tubule.

1. The aim of the present study was to investigate the transduction pathways elicited by prostaglandin E2 (PGE2) to inhibit hormone-stimulated adenosine 3':5'-cyclic monophosphate (cyclic AMP) accumulation in the outer medullary collecting duct (OMCD) and medullary thick ascending limb (MTAL) microdissected from the rat nephron. 2. In the OMCD, 0.3 microM PGE2 and low concentrations of Ca2+ ionophores (10 nM ionomycin or 50 nM A23187) inhibited by about 50% a same pool of arginine vasopressin (AVP)-stimulated cyclic AMP content through a same process insensitive to Bordetella pertussis toxin (PTX). 3. Sulprostone, an agonist of the EP1/EP3 subtypes of the PGE2 receptor, decreased AVP-dependent cyclic AMP accumulation in OMCD and MTAL samples. The concentration eliciting half-maximal inhibition was of about 50 nM in OMCD and 0.1 nM in MTAL. 4. In MTAL, 1 nM sulprostone and PGE2 inhibited by about 90% a same pool of AVP-dependent cyclic AMP content through a PTX-sensitive, Ca2+ -independent pathway. 5. In the OMCD, PGE2 decreased by about 50% glucagon-dependent cyclic AMP synthesis by a process sensitive to PTX and Ca2+ -independent. Sulprostone 1 nM induced the same level of inhibition. 6. These results demonstrate that PGE2 decrease hormone-dependent cyclic AMP accumulation through a G(alpha)i-mediated inhibition of adenylyl cyclase activity in MTAL cells and glucagon-sensitive cells of the OMCD or through a PTX-insensitive increase of intracellular Ca2+ concentration in AVP-sensitive cells of the OMCD.

Localization of mRNAs encoding Ca2+-inhibitable adenylyl cyclases along the renal tubule. Functional consequences for regulation of the cAMP content.

Expression of Ca2+-inhibitable types V and VI adenylyl cyclases was studied by reverse transcription-polymerase chain reaction in rat renal glomeruli and nephron segments isolated by microdissection. Quantitation of each mRNA was achieved using a mutant cRNA which differed from the wild type by substituting two bases to create a new restriction site in the corresponding cDNA. Type VI mRNA was present all along the nephron but was more abundant in distal than in proximal segments. The expression of type V mRNA was restricted to the glomerulus and to the initial portions of the collecting duct. Expression of the Ca2+-insensitive type IV mRNA studied on the same samples was evidenced only in the glomerulus. The functional relevance of the expression of Ca2+-inhibitable isoforms was studied by measuring cAMP content in the microdissected outer medullary collecting duct which expressed both type V mRNA (2367 +/- 178 molecules/mm tubular length; n = 8) and type VI mRNA (5658 +/- 543 molecules/mm, n = 8). Agents known to increase intracellular Ca2+ in this segment induced a Ca2+-dependent inhibition on either arginine vasopressin- or glucagon-stimulated cAMP level. The characteristics of these inhibitions suggest a functional and differential expression of types V and VI adenylyl cyclases in two different cell types of the rat outer medullary collecting duct.

Arachidonic acid inhibits hormone-stimulated cAMP accumulation in the medullary thick ascending limb of the rat kidney by a mechanism sensitive to pertussis toxin.

The possible regulation of adenosine 3',5'-cyclic monophosphate (cAMP) accumulation by arachidonic acid (AA) was studied in segments, microdissected from the rat kidney, which are sensitive to arginine vasopressin (AVP). In the presence of 5 microM indomethacin, the addition of 5 microM AA did not impair AVP-dependent cAMP accumulation (measured during 4 min at 35 degrees C) in the cortical or outer medullary collecting tubule, but decreased this response in the thick ascending limb with an inhibition much more pronounced in the medullary portion (MTAL) than in the cortical portion. In MTAL, the response to 10 nM AVP was inhibited by 34.4 +/- 9.6% (SEM) and 65.8 +/- 5.4% with 1 microM and 5 microM AA, respectively, N = 5 experiments. AVP-, glucagon- and calcitonin-sensitive cAMP levels in MTAL were inhibited by 5 microM AA to a similar extent. AA-induced inhibition was unaffected by the presence of inhibitors of AA metabolism: (1) either 10 microM indomethacin or 50 microM ibuprofen added to all media; (2) a 10-min pre-incubation and a 4-min incubation of MTAL samples with 10 microM eicosa-5,8,11,14-tetrayonic acid, (3) a 1-h preincubation with either 30 microM SKF-525A, 20 microM ketoconazole, or 20 microM nordihydroguariaretic acid. In contrast to AA, 11 other saturated or unsaturated fatty acids had no inhibitory effect on the AVP-dependent cAMP level. In fura-2-loaded MTAL samples, AA induced a slow increase of the intracellular calcium concentration ([Ca2+]i) which reached 21.0 +/- 3.8 nM and 92.9 +/- 21.4 nM over basal values (n = 11) at 2 min and 4 min, respectively, after the beginning of the superfusion of 5 microM AA. AA-induced inhibition of AVP-dependent cAMP accumulation was due neither to the increase in [Ca2+]i elicited by AA, nor to an activation of protein kinase C because this inhibition: (1) was not blocked when MTAL samples were incubated either in zero Ca2+ medium, or in the presence of 1,2-bis(2-aminophenoxy)ethane-N, N, N', N'-tetraacetic acid (BAPTA) to chelate [Ca2+]i, and (2) it was not reproduced by a pre-treatment of MTAL segments with a phorbol ester. Pre-incubation of MTAL (6 h at 35 degrees C) with 500 ng/ml pertussis toxin (PTX) prevented AA-induced inhibition: in the presence of PTX inhibition was 24.7 +/- 6.6% vs 10 nM AVP, as compared to 81.6 +/- 4.0% in control groups, i.e in the absence of PTX, N = 6.(ABSTRACT TRUNCATED AT 400 WORDS)

The activation of protein kinase C prevents PGE2-induced inhibition of AVP-dependent cAMP accumulation in the rat outer medullary collecting tubule.

Previous studies have demonstrated that prostaglandin E2 (PGE2) inhibits arginine vasopressin-(AVP)dependent adenosine 3',5'-cyclic monophosphate (cAMP) accumulation in microdissected rat outer medullary collecting tubules (OMCD), by a mechanism unrelated to the inhibition of cAMP synthesis. The potential role of the activation of protein kinase C (PKC) to explain the negative regulation elicited by PGE2 was investigated in this study. Single OMCD samples were pre-incubated (10 min, 30 degrees C) in the presence or absence of either activators of PKC, phorbol 12-myristate 13-acetate (PMA), 1-oleoyl-2-acetyl-glycerol (OAG), dioctanoylglycerol (DOG) or an inhibitor of PKC, staurosporine (SSP). These compounds were present also with the agonists tested during the incubation period (4 min, 35 degrees C). In contrast to PGE2, activators of PKC did not decrease AVP-dependent cAMP accumulation (mean +/- SEM): 1 nM AVP = 47.1 +/- 6.8 fmol.mm-1 x 4 min-1; AVP+0.3 microM PGE2 = 20.1 +/- 2.7, P < 0.01 versus AVP; AVP + 10 nM PMA = 42.0 +/- 4.7, NS versus AVP; AVP + 50 micrograms/ml OAG = 44.1 +/- 4.8. NS versus AVP, N = 5 experiments. However, 10 nM PMA prevented PGE2-induced inhibition: AVP + PGE2 = 44.2 +/- 3.5% of the response to AVP and 90.3 +/- 3.2% without and with PMA respectively, N = 16. Similar results were obtained with either 50 micrograms/ml OAG or 25 micrograms/ml DOG (AVP + PGE2 + OAG = 92.9 +/- 6.6% of the response to AVP, N = 8; AVP + PGE2 + DOG = 94.1 +/- 5.3%, N = 7).(ABSTRACT TRUNCATED AT 250 WORDS)

PGE2-induced inhibition of AVP-dependent cAMP accumulation in the OMCD of the rat kidney is cumulative with respect to the effects of alpha 2-adrenergic and alpha 1-adenosine agonists, insensitive to pertussis toxin and dependent on extracellular calcium.

The accumulation of cyclic adenosine 3',5'-phosphate (cAMP) elicited by antidiuretic hormone (arginine vasopressin, AVP) in the medullary collecting tubule (OMCD) microdissected from the rat kidney is inhibited by different factors: the A1 agonist of adenosine (-)-N6-(R-phenylisopropyl) adenosine (PIA), an alpha 2-adrenergic agonist clonidine (CLO), and prostaglandin E2 (PGE2). The negative regulation elicited by PGE2 was further characterized by measuring summation of inhibition with other inhibitors, by testing the effect of pertussis toxin and by studying the part played by extracellular calcium. Inhibitors were used at concentrations inducing maximum effects. The simultaneous addition of 0.3 microM PGE2 with either 0.1 microM PIA or 1 microM CLO led to an inhibition of the response to AVP (80.0 +/- 3.5%, SEM, N = 7 and 92.6 +/- 0.8%, N = 5, respectively) greater than those elicited by each agent alone. In contrast, PIA and CLO added together induced an inhibition similar to that due to CLO alone. The action of PGE2 in combination with either PIA or CLO corresponded to a partial summation fitting with the values calculated by assuming a cumulative inhibition. Preincubation of OMCD samples with pertussis toxin (100 ng/ml or 1 micrograms/ml) relieved the inhibitory effects of CLO and PIA but did not affect the action of PGE2. PGE2-induced inhibition was prevented in a calcium-free medium [0 Ca2+ + 0.1 mM [ethylene-bis (oxyethylene-nitrilo)] tetraacetate (EGTA)]: values were 67.0 +/- 2.1% and 5.8 +/- 8.7% (+/- SEM) in 2 mM Ca2+ and 0 Ca2+ medium, respectively, N = 7.(ABSTRACT TRUNCATED AT 250 WORDS)