A therapeutic chemical chaperone inhibits cholera intoxication and unfolding/translocation of the cholera toxin A1 subunit

Cholera toxin (CT) travels as an intact AB(5) protein toxin from the cell surface to the endoplasmic reticulum (ER) of an intoxicated cell. In the ER, the catalytic A1 subunit dissociates from the rest of the toxin. Translocation of CTA1 from the ER to the cytosol is then facilitated by the quality control mechanism of ER-associated degradation (ERAD). Thermal instability in the isolated CTA1 subunit generates an unfolded toxin conformation that acts as the trigger for ERAD-mediated translocation to the cytosol. In this work, we show by circular dichroism and fluorescence spectroscopy that exposure to 4-phenylbutyric acid (PBA) inhibited the thermal unfolding of CTA1. This, in turn, blocked the ER-to-cytosol export of CTA1 and productive intoxication of either cultured cells or rat ileal loops. In cell culture studies PBA did not affect CT trafficking to the ER, CTA1 dissociation from the holotoxin, or functioning of the ERAD system. PBA is currently used as a therapeutic agent to treat urea cycle disorders. Our data suggest PBA could also be used in a new application to prevent or possibly treat cholera.

Transfer factor and allergy

Although various mechanisms involving antibodies and various cell types participate, a Thl and Th2 cells imbalance seems to play a central role for allergy development. Other lymphocyte subpopulations, such as Th17, CD4 FOXP3, and Th9 positive regulatory T lymphocytes may also be involved in the allergic response. Regulatory processes are an appealing target for therapeutic approaches aiming to solve allergic reactions by restoring the delicate balance within the immune system. Transfer factor (TF) or dialyzable leukocyte extract is meant to transfer cell-mediated immunity from immune competent donors to unsensitized or deficient recipients. A PubMed search on the current knowledge on TF indicates that TF may restore the Th1/Th2 balance and improve immune regulatory mechanisms of patients receiving it. Our preliminary results demonstrate that TF induces mRNA expression of IFN-g, osteopontin, RANTES, and hBD-2 in human healthy subjects. TF has been used to treat a variety of immune dysfunction related-pathologies, such as allergy, autoimmunity, immunodeficiencies, infectious diseases and tumors. Patients receiving TF together with their conventional treatment often have better clinical evolution than without it, as we have witnessed, adding TF to the usual medical treatment of allergic diseases as an attempt to provide allergic patients with those regulatory elements that they apparently lack but require to achieve properly regulated immune responses and thus obtain a faster and better resolution of allergic reactions.

Hsp90 is required for transfer of the cholera toxin A1 subunit from the endoplasmic reticulum to the cytosol

Cholera toxin (CT) is an AB(5) toxin that moves from the cell surface to the endoplasmic reticulum (ER) by retrograde vesicular transport. In the ER, the catalytic A1 subunit dissociates from the rest of the toxin and enters the cytosol by exploiting the quality control system of ER-associated degradation (ERAD). The driving force for CTA1 dislocation into the cytosol is unknown. Here, we demonstrate that the cytosolic chaperone Hsp90 is required for CTA1 passage into the cytosol. Hsp90 bound to CTA1 in an ATP-dependent manner that was blocked by geldanamycin (GA), an established Hsp90 inhibitor. CT activity against cultured cells and ileal loops was also blocked by GA, as was the ER-to-cytosol export of CTA1. Experiments using RNA interference or N-ethylcarboxamidoadenosine, a drug that inhibits ER-localized GRP94 but not cytosolic Hsp90, confirmed that the inhibitory effects of GA resulted specifically from the loss of Hsp90 activity. This work establishes a functional role for Hsp90 in the ERAD-mediated dislocation of CTA1.

The immunogenic SigA enterotoxin of Shigella flexneri 2a binds to HEp-2 cells and induces fodrin redistribution in intoxicated epithelial cells

Background

We have previously shown that the enterotoxin SigA which resides on the she pathogenicity island (PAI) of S. flexneri 2a is an autonomously secreted serine protease capable of degrading casein. We have also demonstrated that SigA is cytopathic for HEp-2 cells and plays a role in the intestinal fluid accumulation associated with S. flexneri infections.

Methods/Principal Findings

In this work we show that SigA binds specifically to HEp-2 cells and degrades recombinant human αII spectrin (α-fodrin) in vitro, suggesting that the cytotoxic and enterotoxic effects mediated by SigA are likely associated with the degradation of epithelial fodrin. Consistent with our data, this study also demonstrates that SigA cleaves intracellular fodrin in situ, causing its redistribution within cells. These results strongly implicate SigA in altering the cytoskeleton during the pathogenesis of shigellosis. On the basis of these findings, cleavage of fodrin is a novel mechanism of cellular intoxication for a Shigella toxin. Furthermore, information regarding immunogenicity to SigA in infected patients is lacking. We studied the immune response of SigA from day 28 post-challenge serum of one volunteer from S. flexneri 2a challenge studies. Our results demonstrate that SigA is immunogenic following infection with S. flexneri 2a.

Conclusions

This work shows that SigA binds to epithelial HEp-2 cells as well as being able to induce fodrin degradation in vitro and in situ, further extending its documented role in the pathogenesis of Shigella infections.

Structural characteristics of the plasmid-encoded toxin from enteroaggregative Escherichia coli

Intoxication by the plasmid-encoded toxin (Pet) of enteroaggregative Escherichia coli requires toxin translocation from the endoplasmic reticulum (ER) to the cytosol. This event involves the quality control system of ER-associated degradation (ERAD), but the molecular details of the process are poorly characterized. For many structurally distinct AB-type toxins, ERAD-mediated translocation is triggered by the spontaneous unfolding of a thermally unstable A chain. Here we show that Pet, a non-AB toxin, engages ERAD by a different mechanism that does not involve thermal unfolding. Circular dichroism and fluorescence spectroscopy measurements demonstrated that Pet maintains most of its secondary and tertiary structural features at 37 degrees C, with significant thermal unfolding only occurring at temperatures >or=50 degrees C. Fluorescence quenching experiments detected the partial solvent exposure of Pet aromatic amino acid residues at 37 degrees C, and a cell-based assay suggested that these changes could activate an ERAD-related event known as the unfolded protein response. We also found that HEp-2 cells were resistant to Pet intoxication when incubated with glycerol, a protein stabilizer. Altogether, our data are consistent with a model in which ERAD activity is triggered by a subtle structural destabilization of Pet and the exposure of Pet hydrophobic residues at physiological temperature. This was further supported by computer modeling analysis, which identified a surface-exposed hydrophobic loop among other accessible nonpolar residues in Pet. From our data it appears that Pet can promote its ERAD-mediated translocation into the cytosol by a distinct mechanism involving partial exposure of hydrophobic residues rather than the substantial unfolding observed for certain AB toxins.

Effects of intermittent ozone exposure on peak expiratory flow and respiratory symptoms among asthmatic children in Mexico City

In a panel study of Mexican children (5-13 y of age) with mild asthma, the authors studied the relationship between ozone exposure and the course of childhood asthma. Decrements in peak expiratory flow rate were associated with ozone, and respiratory symptoms were associated with both ozone level and ambient particulate matter (< 10 microm) level. After the authors adjusted for minimum temperature and autocorrelation in the data, they determined that an increase of 50 ppb in a daily ozone 1-h maximum was related to an 8% increase in cough (95% confidence interval = 2, 15); a 24% increase in phlegm (95% confidence interval = 13, 35); and an 11% increase in low respiratory symptoms index (95% confidence interval = 5, 19). The authors concluded that children with mild asthma who resided in the south of Mexico City were affected adversely by the high ozone ambient levels observed in this area.

Effects of air pollution on the respiratory health of asthmatic children living in Mexico City

The relation between air pollution and the exacerbation of childhood asthma was studied in a panel of 71 children (aged 5 to 7 yr) with mild asthma who resided in the northern part of mexico City. During the follow-up, ambient measures of particulate matter less than 10 microns (PM10, 24-h average) and ozone (1-h maximum) frequently exceeded the Mexican standards for these contaminants. The peak expiratory flow rate (PEFR) was strongly associated with PM10 levels and marginally with ozone levels. Respiratory symptoms (coughing, phlegm production, wheezing, and difficulty breathing) were associated with both PM10 and ozone levels. An increase of 20 micrograms/m3 of PM10 was related to an 8% increase in lower respiratory illness (LRI) among children on the same day (95% confidence interval [CI] = 1.04-1.15), and an increase of 10 micrograms/m3 in the weekly mean of particulate matter less than 2.5 microns (PM2.5) was related to a 21% increase in LRI (95% CI = 1.08-1.35). A 50 parts per billion (ppb) increase in ozone was associated with a 9% increase in LRI (95% CI = 1.03-1.15) on the same day. We concluded that children with mild asthma are affected by the high ambient levels of particulate matter and ozone observed in the northern part of Mexico City.

[Frequency of allergens in immediate, late, and dual allergic skin response at the National Institute of Pediatrics]

We studied 126 children with allergic illness in Instituto Nacional de Pediatria. We applied cutaneous test to determine the early, late and dual response. The results were 68% for the early response, 6% late response and 26% dual response. The allergens more frequently found in the early and late response were Dermatophagoides pteronyssinus, Dermatophagoides farinae and house dust. Approximately the third part of the children studied presented late cutaneous response (dual response more isolated late response). It is important to make the evaluation of the late response in patients with allergy disease for a good etiologic diagnosis.

Effects of urban air pollutants on emergency visits for childhood asthma in Mexico City

The metropolitan area of Mexico City, Mexico, has serious air pollution problems. Although air contaminants may contribute to clinical asthma, there are at present no data on the relation between air pollution exposure and childhood asthma in Mexico City. The authors reviewed data on emergency visits from January to June 1990 at one major pediatric hospital in Mexico City. They used a Poisson regression model to study the relation between the number of daily emergency visits for asthma and air pollutant levels. The levels of ozone and sulfur dioxide-exposure were significantly associated with the number of emergency visits for asthma. After adjustment for potential confounding factors, the multivariate regression model predicted that an increase of 50 ppb in the 1-hour maximum ozone level would lead to a 43% increase in the number of emergency visits for asthma on the following day. Exposure to high ozone levels (> 110 ppb) for 2 consecutive days increased the number of asthma-related emergency visits by 68 percent. The results of this study suggest that ozone exposure is positively associated with the number of children's emergency visits for asthma in Mexico City.

[Retrospective analysis of prognostic factors in patients with primary lymphoma of the intestine]

Forty-six patients with stage IE and IIE malignant lymphoma of the intestine were analyzed to assess the efficacy of prognostic factors to predict the course and therapeutic approach in these patients. Because the lesion was considered unresectable in all cases, chemotherapy was given after surgery. Using Cox's univariate regression analysis, survival was found to correlate with stage (IE vs IIE) and high levels of lactic dehidrogenase, nevertheless in the multivariate analysis only beta 2 microglobulin levels were associated with a shorter survival. We believe that treatment of extranodal lymphomas, like nodal presentations, as those of the intestine, could be based in the determinations of prognostic factors and that beta 2 microglobulin would be considered the most powerful prognostic factor. Most studies on patients with malignant lymphoma of the intestine are necessary to define the role of beta 2 microglobulin as therapeutic prognostic index.

The role of maintenance therapy in the treatment of large-cell non-Hodgkin's lymphoma

Eighty-one patients with large-cell non-Hodgkin's lymphoma achieving complete restaging verified remission after induction chemotherapy (CHOP-Bleo or m-BACOD) were randomized to the following 3 arms: 1. No further treatment (observation). 2. Early consolidation therapy with 6 courses of CVP (cyclophosphamide, vincristine, prednisone) given monthly. 3. Maintenance therapy with cyclophosphamide and prednisone given every 6 weeks for 2 years. The relapse-free survival was better in the maintenance and consolidation arms than in the observation arm. The additional therapy given after the initial complete remission produced lasting disease control in a considerable number of patients and with acceptable toxicity. The authors feel that patients with large-cell lymphoma do not need more aggressive and toxic initial management because the use of maintenance therapy can increase the number of patients remaining in complete remission by more conventional, less toxic chemotherapy.

[CHOP-bleo versus m-BACOD in the treatment of intermediate and high-grade malignant lymphomas]

Eighty-three patients with malignant lymphoma of intermediate and high histologic subtypes were randomly assigned to receive induction chemotherapy with either of two intensive regimens: CHOP-Bleo (cyclophosphamide, adriamycin, vincristine, prednisone and bleomycin) or m-BACOD (low-dose methotrexate, bleomycin adriamycin, cyclophosphamide, vincristine and dexamethasone). The median follow-up study is 5 years. The two therapies were not significantly different in regard to response rates (52 to 59%), duration of complete remission (27 months vs 24 months) and survival, but m-BACOD was significantly more toxic than CHOP-Bleo. The relative small proportion of long-term disease free-survivors with both regimens underscores the need for other therapeutic approaches.

[Age of menarche and genetic blood markers]

In 160 girls from low and middle socio-economic class of Santiago we correlated the age at menarque with genetic markers such as ABO blood group, Rh, MN, Xg, haptoglobins, Esterase D and Phosphoglucomutase. No significant association of these markers and age at menarque was found.

[Ecology of the oral biosystem]

The present work is a Literature review about the Ecologycal Concepts that can be applied to the host-parasite relationship that generates in the oral cavity. These concepts let understand us, much of the phenomena presents in the mouth, that explain pathologies that affects organs and tissues of it, in its morphophysiological aspects.

[Analysis of the in vitro antibacterial action of a fluoridated amalgam]

To a conventional silver amalgam alloy was added 1% of stanous fluoride, to prove in vitro, if it presents any antibacteria actions against S. mutans and Lactobacillus acidophilus. Thirteen Petri plate were seeded with S. mutans and 12 Petri plate with Lactobacillus, in both cases, was disposited fluoride containing amalgam and conventional amalgam. The average of inhibition signs in the Petri plates with S. mutans was 1.7 mm in the Petri plates with Lactobacillus the average was 2.4 mm. Is demonstrated that the fluoride containing amalgam has in vitro antibacteria action in comparison with conventional amalgam, that has none.

[Growth of girls and boys at puberty]

Growth at puberty varies according to age and individual maturity. Changes in height and weight of girls (aged 10 to 16 years) and boys (aged 11 to 17 years) which participate in a follow-up study at northern metropolitan Santiago, Chile, are described. Sexual maturity seems more determinant than chronological age on weight and height at puberty. For instance height of the whole sample of boys from 12 to 15.5 years of age ranged from 141 to 164 cm in contrast to 147 to 160 for those of the same age range but in the third stage of public hair development (Tanner). Sexual maturity should be taken into account for appropriate growth evaluation at puberty.

Two myeloma globulins, IgG1-kappa and IgG1-lambda, from a single patient (Im). I. Purification and immunochemical characterization

Electrophoretic analysis of the serum from a patient Im suffering from a multiple myeloma revealed the existence of two abnormal bands. Purification of these two fractions on a DEAE—cellulose column showed that both fractions had the same sedimentation coefficient (7S), belonged to the same class (IgG), and subclass (γl) and bore the same allotype (Gm₁). However, the heavy (H) chains of one immunoglobulin were associated with type κ light (L) chains whereas those of the other were associated with type λ L chains.

Three individual antigenic determinants were found in these two proteins. One was common to the H chains of both proteins and the other two were each specific to one of the L chains. These results suggest that the myeloma cells of patient (Im) were able to produce at least three polypeptide chains, one H chain and two different types of L chains.