ALDH7A1 is a protein that protects Atlantic salmon against Aeromonas salmonicida at the early stages of infection

Aldehyde dehydrogenases (ALDHs) belong to a super-family of detoxifying proteins and perform a significant role in developing epithelial homeostasis, protecting cells from toxic aldehydes and drug resistance. However, the activity and function of these detoxifying proteins remain unknown, especially in fish. In our research, we aimed to study functions of aldehyde dehydrogenase 7A1 (ALDH7A1) in Atlantic salmon infected by Aeromonas salmonicida. Recombinant ALDH7A1 (rALDH7A1) was verified by SDS-PAGE and western blot. The molecular mass of the deduced amino acid sequence of rALDH7A1 is 58.9 kDa with an estimated pI of 7.09. Only a low complexity region (¹⁴¹yvegvgevqeyvdv¹⁵³) without a signal peptide existed in rALDH7A1. Results of ELISA indicated that rALDH7A1 exhibited apparent binding activities with A. salmonicida and its expression was highest in fish kidney. A Real-Time PCR (qRT-PCR) assay in kidneys confirmed that fish in this experiment were authentically infected and bacterial loads in rALDH7A1-adminsitered fish were significantly reduced at an early stage of infection. Meanwhile, we found the mRNA expression of NF-kβ, P-38 MAPK, caspase-3 and TNF-α were mainly up-regulated at 72 h in the kidneys and livers of highly infected fish injected with rALDH7A1, and the same variation trend existed in fish spleens at 12 h. Consistent with these observations, neutralization experiments in vivo indicated that rALDH7A1 could obviously reduce the death rate compared to the BSA and control group. Taken together, we concluded that rALDH7A1 could act in host immune defense against bacterial infection and decrease the mortality rate of Atlantic salmon at early stages of infection with A. salmonicida.

MicroRNA-33-dependent regulation of macrophage metabolism directs immune cell polarization in atherosclerosis

Cellular metabolism is increasingly recognized as a controller of immune cell fate and function. MicroRNA-33 (miR-33) regulates cellular lipid metabolism and represses genes involved in cholesterol efflux, HDL biogenesis, and fatty acid oxidation. Here, we determined that miR-33-mediated disruption of the balance of aerobic glycolysis and mitochondrial oxidative phosphorylation instructs macrophage inflammatory polarization and shapes innate and adaptive immune responses. Macrophage-specific Mir33 deletion increased oxidative respiration, enhanced spare respiratory capacity, and induced an M2 macrophage polarization-associated gene profile. Furthermore, miR-33-mediated M2 polarization required miR-33 targeting of the energy sensor AMP-activated protein kinase (AMPK), but not cholesterol efflux. Notably, miR-33 inhibition increased macrophage expression of the retinoic acid-producing enzyme aldehyde dehydrogenase family 1, subfamily A2 (ALDH1A2) and retinal dehydrogenase activity both in vitro and in a mouse model. Consistent with the ability of retinoic acid to foster inducible Tregs, miR-33-depleted macrophages had an enhanced capacity to induce forkhead box P3 (FOXP3) expression in naive CD4(+) T cells. Finally, treatment of hypercholesterolemic mice with miR-33 inhibitors for 8 weeks resulted in accumulation of inflammation-suppressing M2 macrophages and FOXP3(+) Tregs in plaques and reduced atherosclerosis progression. Collectively, these results reveal that miR-33 regulates macrophage inflammation and demonstrate that miR-33 antagonism is atheroprotective, in part, by reducing plaque inflammation by promoting M2 macrophage polarization and Treg induction.

Slc5a8, a Na+-coupled high-affinity transporter for short-chain fatty acids, is a conditional tumour suppressor in colon that protects against colitis and colon cancer under low-fibre dietary conditions

Mammalian colon harbours trillions of bacteria under physiological conditions; this symbiosis is made possible because of a tolerized response from the mucosal immune system. The mechanisms underlying this tolerogenic phenomenon remain poorly understood. In the present study we show that Slc5a8 (solute carrier gene family 5a, member 8), a Na(+)-coupled high-affinity transporter in colon for the bacterial fermentation product butyrate, plays a critical role in this process. Among various immune cells in colon, dendritic cells (DCs) are unique not only in their accessibility to luminal contents but also in their ability to induce tolerogenic phenotype in T-cells. We found that DCs exposed to butyrate express the immunosuppressive enzymes indoleamine 2,3-dioxygenase 1 (IDO1) and aldehyde dehydrogenase 1A2 (Aldh1A2), promote conversion of naive T-cells into immunosuppressive forkhead box P3(+) (FoxP3(+)) Tregs (regulatory T-cells) and suppress conversion of naive T-cells into pro-inflammatory interferon (IFN)-γ-producing cells. Slc5a8-null DCs do not induce IDO1 and Aldh1A2 and do not generate Tregs or suppress IFN-γ-producing T-cells in response to butyrate. We also provide in vivo evidence for an obligatory role for Slc5a8 in suppression of IFN-γ-producing T-cells. Furthermore, Slc5a8 protects against colitis and colon cancer under conditions of low-fibre intake but not when dietary fibre intake is optimal. This agrees with the high-affinity nature of the transporter to mediate butyrate entry into cells. We conclude that Slc5a8 is an obligatory link between dietary fibre and mucosal immune system via the bacterial metabolite butyrate and that this transporter is a conditional tumour suppressor in colon linked to dietary fibre content.

Proteomic analysis of human nasal mucosa: different expression profile in rhino-pathologic states

BACKGROUND

Rhinitis comprises several diseases with varying causes and different clinical manifestations and pathological features, but treated as a single clinical disorder. As heterogeneous disease, proper differential diagnosis is useful to delineate appropriate therapeutic intervention. Comparative proteomic investigation was aimed to provide information for specific differentially expressed proteins in rhino pathologic state, that could be used for diagnostic purpose and therapeutic monitoring.

METHODS

Proteins extracted from nasal mucosa cells of patients with different features of rhinitis and from control subjects, were separated by 2-DE. Proteins differentially expressed were identified by mass spectrometry (MS).

RESULTS

Comparative proteomic analyses led to the identification of eighteen proteins differentially expressed in patients with rhinitis, mainly related to cell defense and innate and acquired immunity. From that, at least one protein can be a possible candidate as biomarker of disease.

Measles virus-derived peptide/food antigen adducts facilitate the establishment of antigen specific oral tolerance

Allergy is a skewed T helper (Th)2 polarization response in the body; its treatment is not satisfactory currently. Oral tolerance dysfunction plays a critical role in the pathogenesis of allergy. The present study aims to restore the breached intestinal tolerance with an artificial adduct of a measles virus C protein-derived small peptide (MVCP) and a model antigen, ovalbumin (MOA), and to observe the effect of MOA on inhibition of intestinal allergy in a mouse model. The MOA was formed by the MVCP and ovalbumin. The effect of MOA on regulation of the properties of dendritic cells (DC) and CD4(+) T cells was observed with a cell culture model and a mouse model of the gut Th2 pattern inflammation. After treatment with MOA, mouse intestinal DCs showed high levels of aldehyde dehydrogenase (ALDH) activity and expressed transforming growth factor (TGF)-beta; the frequency of Treg in the intestine was also significantly increased. The treatment with MOA efficiently suppressed the antigen-specific Th2 pattern inflammation in the intestine. Administration with the MOA can induce the development of antigen-specific oral tolerance and inhibit the antigen-specific allergic reaction in the intestine. The adduct of MOA has the therapeutic potential for the allergen related immune inflammation.

From the diet to the nucleus: vitamin A and TGF-beta join efforts at the mucosal interface of the intestine

The vitamin A metabolites, including retinoic acid (RA), form ligands for retinoic acid-related nuclear receptors and together they play pleiotropic roles in various biological processes. Recently, we described that RA also functions as a key modulator of transforming growth factor-beta (TGF-beta)-driven immune deviation, capable of suppressing the differentiation of interleukin-17 secreting T helper cells (T(H)17) and conversely promoting the generation of Foxp3(+) T regulatory (Treg) cells. This review will focus on the role of RA in the reciprocal TGF-beta-driven differentiation of T(H)17 and Treg and on the importance of such regulatory mechanism to control a functional immune system, in particular at the mucosal interface of the intestine.

Isolation of bone marrow-derived stem cells using density-gradient separation

OBJECTIVE

Our laboratory has established two unique methods to isolate murine hematopoietic stem cells on the basis of functional characteristics such as the ability of stem cells to home to bone marrow and aldehyde dehydrogenase (ALDH) activity. An essential component of both protocols is the separation of whole bone marrow into small-sized cells by counter-flow elutriation. We sought to provide the scientific community with an alternate approach to acquire our stem cells by replacing elutriation with the use of density-gradient centrifugation.

METHODS

The elutriated fraction 25 population was characterized based on density using a discontinuous gradient. The long-term reconstituting potential of whole bone marrow cells collected at each density interface was determined by subjecting the fractions to the two-day homing protocol, transplanting them into lethally irradiated recipient mice, and assessing peripheral blood chimerism. We also investigated the ability of high-density bone marrow cells isolated in conjunction with the ALDH protocol to repopulate the hematopoietic system of myeloablated recipients.

RESULTS

Bone marrow cells collected at the high-density interface of 1.081/1.087 g/mL (fraction 3) had the capacity for homing to marrow and the ability to provide long-term hematopoietic reconstitution. Fraction three lineage-depleted ALDH-bright cells could also engraft and provide long-term hematopoiesis at limiting dilutions.

CONCLUSIONS

Density-gradient centrifugation can be used in conjunction with either of our stem cell isolation protocols to obtain cells with long-term reconstitution ability. We anticipate that this strategy will encourage and enable investigators to study the biology of HSCs isolated using functional characteristics.

Inhibition of mitochondrial aldehyde dehydrogenase by nitric oxide-mediated S-nitrosylation

Mitochondrial aldehyde dehydrogenase (ALDH2) is responsible for the metabolism of acetaldehyde and other toxic lipid aldehydes. Despite many reports about the inhibition of ALDH2 by toxic chemicals, it is unknown whether nitric oxide (NO) can alter the ALDH2 activity in intact cells or in vivo animals. The aim of this study was to investigate the effects of NO on ALDH2 activity in H4IIE-C3 rat hepatoma cells. NO donors such as S-nitrosoglutathione (GSNO), S-nitroso-N-acetylpenicillamine, and 3-morpholinosydnonimine significantly increased the nitrite concentration while they inhibited the ALDH2 activity. Addition of GSH-ethylester (GSH-EE) completely blocked the GSNO-mediated ALDH2 inhibition and increased nitrite concentration. To directly demonstrate the NO-mediated S-nitrosylation and inactivation, ALDH2 was immunopurified from control or GSNO-treated cells and subjected to immunoblot analysis. The anti-nitrosocysteine antibody recognized the immunopurified ALDH2 only from the GSNO-treated samples. All these results indicate that S-nitrosylation of ALDH2 in intact cells leads to reversible inhibition of ALDH2 activity.

Human aldehyde dehydrogenase 3A1 (ALDH3A1): biochemical characterization and immunohistochemical localization in the cornea

ALDH3A1 (aldehyde dehydrogenase 3A1) is expressed at high concentrations in the mammalian cornea and it is believed that it protects this vital tissue and the rest of the eye against UV-light-induced damage. The precise biological function(s) and cellular distribution of ALDH3A1 in the corneal tissue remain to be elucidated. Among the hypotheses proposed for ALDH3A1 function in cornea is detoxification of aldehydes formed during UV-induced lipid peroxidation. To investigate in detail the biochemical properties and distribution of this protein in the human cornea, we expressed human ALDH3A1 in Sf9 insect cells using a baculovirus vector and raised monoclonal antibodies against ALDH3A1. Recombinant ALDH3A1 protein was purified to homogeneity with a single-step affinity chromatography method using 5'-AMP-Sepharose 4B. Human ALDH3A1 demonstrated high substrate specificity for medium-chain (6 carbons and more) saturated and unsaturated aldehydes, including 4-hydroxy-2-nonenal, which are generated by the peroxidation of cellular lipids. Short-chain aliphatic aldehydes, such as acetaldehyde, propionaldehyde and malondialdehyde, were found to be very poor substrates for human ALDH3A1. In addition, ALDH3A1 metabolized glyceraldehyde poorly and did not metabolize glucose 6-phosphate, 6-phosphoglucono-delta-lactone and 6-phosphogluconate at all, suggesting that this enzyme is not involved in either glycolysis or the pentose phosphate pathway. Immunohistochemistry in human corneas, using the monoclonal antibodies described herein, revealed ALDH3A1 expression in epithelial cells and stromal keratocytes, but not in endothelial cells. Overall, these cumulative findings support the metabolic function of ALDH3A1 as a part of a corneal cellular defence mechanism against oxidative damage caused by aldehydic products of lipid peroxidation. Both recombinant human ALDH3A1 and the highly specific monoclonal antibodies described in the present paper may prove to be useful in probing biological functions of this protein in ocular tissue.

Distinct functions for Aldh1 and Raldh2 in the control of ligand production for embryonic retinoid signaling pathways

During vertebrate embryogenesis retinoic acid (RA) synthesis must be spatiotemporally regulated in order to appropriately stimulate various retinoid signaling pathways. Various forms of mammalian aldehyde dehydrogenase (ALDH) have been shown to oxidize the vitamin A precursor retinal to RA in vitro. Here we show that injection of Xenopus embryos with mRNAs for either mouse Aldh1 or mouse Raldh2 stimulates RA synthesis at low and high levels, respectively, while injection of human ALDH3 mRNA is unable to stimulate any detectable level of RA synthesis. This provides evidence that some members of the ALDH gene family can indeed perform RA synthesis in vivo. Whole-mount immunohistochemical analyses of mouse embryos indicate that ALDH1 and RALDH2 proteins are localized in distinct tissues. RALDH2 is detected at E7.5-E10.5 primarily in trunk tissue (paraxial mesoderm, somites, pericardium, midgut, mesonephros) plus transiently from E8.5-E9.5 in the ventral optic vesicle and surrounding frontonasal region. ALDH1 is first detected at E9.0-E10. 5 primarily in cranial tissues (ventral mesencephalon, dorsal retina, thymic primordia, otic vesicles) and in the mesonephros. As previous findings indicate that embryonic RA is more abundant in trunk rather than cranial tissues, our findings suggest that Raldh2 and Aldh1 control distinct retinoid signaling pathways by stimulating high and low RA biosynthetic activities, respectively, in various trunk and cranial tissues.

Surface localization, regulation, and biologic properties of the 96-kDa alcohol/aldehyde dehydrogenase (EhADH2) of pathogenic Entamoeba histolytica

The 96-kDa surface antigen of Entamoeba histolytica was demonstrated through extensive immunologic evaluation with monoclonal and monospecific antibodies to be identical to or an isoform of the amebic alcohol/aldehyde dehydrogenase (EhADH2). EhADH2 was secreted, excreted, or shed into the culture medium in quantities commensurate with amebic growth when studied in a novel culture system. Of importance, using RNase protection assays, specific mRNA coding for the EhADH2 gene product(s) was up-regulated by treatment of viable trophozoites with the enzyme substrate ethanol. These data provide insight into the biology of this enzyme and its regulation by appropriate stressors.

Identification of protein-receptor components required for the import of prealdehyde dehydrogenase into rat liver mitochondria

Mitochondrial aldehyde dehydrogenase is synthesized as a high-molecular-weight precursor in cytosol and transported into mitochondrial matrix space where it is processed to the mature enzyme. To identify components of the transport machinery on liver mitochondria, anti-idiotypic antibodies against the rabbit anti-prealdehyde dehydrogenase signal peptide antibodies were produced in chicken eggs and rabbit. Both anti-idiotypic antibodies inhibited the import of prealdehyde dehydrogenase (pALDH) into isolated rat liver mitochondria. The rabbit anti-idiotypic antibody could recognize by Western blotting five mitochondrial membrane proteins with apparent molecular weights of 66, 60, 42, 34, and 29 kDa. The anti-idiotypic antibodies were cross-linked to mitochondrial membrane proteins using sulfosuccinimidyl 2-(p-azidosalicylamido)ethyl-1,3'-dithiopropionate which is an iodinatable, heterofunctional, and photoreactive cross-linker. Mitochondrial proteins with apparent molecular weights of 66, 60, and 42 kDa were identified using the chicken antibody. The 66- and 34-kDa proteins were cross-linked to the rabbit antibody as the major components and the 42-kDa protein as a minor one. Antibodies against the 60- and 42-kDa proteins, as well as Fab fragments, inhibited the import of pALDH, suggesting that these proteins are receptor/translocator components for pALDH import.

Immunohistochemical study of hepatocellular carcinoma-specific aldehyde dehydrogenase

Tumor-associated aldehyde dehydrogenase (ALDH) was reported in cases of human hepatocellular carcinoma and animal hepatoma models. This ALDH isozyme is similar to ALDH3 which exists in the stomach and lung; however, the biochemical and clinical significance of this unique ALDH isozyme have not been established. Human tumor-associated ALDH was purified, and polyclonal antibodies prepared. Using these antibodies, specific development of tumor-associated ALDH was confirmed by immunohistochemical techniques. It was found that about 50% of hepatocellular carcinomas reacted with the antibody. This unique ALDH isozyme may be a novel tumor marker of hepatocellular carcinoma.

Direct demonstration of elevated aldehyde dehydrogenase in human hematopoietic progenitor cells

Relative levels of cytoplasmic aldehyde dehydrogenase (ALDH) were determined in selected subpopulations of normal human bone marrow cells using a flow cytometric assay that simultaneously detects a cell surface antigen (as a marker of cell lineage and developmental stage) and the level of ALDH. The intracellular level of this enzyme has been shown to be directly related to cellular resistance to activated cyclophosphamide and is believed to be important in the survival of cells capable of repopulating marrow in autologous bone marrow transplant procedures. Western blot analysis and flow cytometric analysis of four murine cell lines with known ALDH levels were used to establish the relation between ALDH content and fluorescence with an affinity-purified anti-mouse ALDH antibody. An affinity purified anti-human ALDH antibody, characterized by immunoblotting of cytosolic extracts of cell lines with known ALDH content, was used to determine relative ALDH levels in the marrow subpopulations. We found that hematopoietic progenitor cells express the highest level of ALDH, while lymphocytes express the lowest level. Immature erythroid cells express ALDH at a level intermediate between progenitor cells and lymphocytes.

Some comparisons of pig and sheep liver cytosolic aldehyde dehydrogenases

1. The pig enzyme was purified to homogeneity and was found to be a tetramer of apparently identical subunits. 2. The pig enzyme was found to contain 1 mol NADH/mol enzyme which is tightly bound, which is not directly involved in catalysis and which so far has not been removed from the enzyme so as to produce an active apoenzyme. 3. The pig enzyme seems to contain only one functioning active site/tetramer. 4. The pig and sheep enzymes are compared in respect of NADH binding, substrate specificity, immunological response and surface charge.

Presence of cytosolic aldehyde dehydrogenase isozymes in adult and fetal rat liver

A colony of Wistar-strain rats bred at Purdue University was composed of animals with two different isozyme patterns of liver cytosolic aldehyde dehydrogenase (EC 1.2.1.3, ALDH) as determined by isoelectric focusing. One cytosolic isozyme pattern had a major activity band with a pI = 5.8 and a minor activity band at pI = 6.2. The other pattern contained three major isozymes with pI values of 5.3, 5.4 and 5.6 along with the pI 6.2 isozyme and a trace of the 5.8 one. The 5.8 and 6.2 isozymes were recognized by antibodies produced against horse and beef liver cytosolic ALDH, whereas the set of three (5.3-5.6) were not. The cytosolic isozymes were inhibited by low levels of disulfiram and had Km values for acetaldehyde in the 100 microM range, properties typical for cytosolic ALDHs. All animals contained the same isozymes of liver mitochondrial ALDH. These were a major activity with a pI = 5.2 and minor activities associated with isozymes of pI = 6.4 and 6.6. These isozymes were recognized by antibodies produced against pure horse and beef liver mitochondrial ALDHs. Both cytosolic and mitochondrial ALDHs were found in fetal liver as early as day 15 of gestation. The total activity for mitochondrial ALDH increased between day 15 and day 21 whereas that for cytosolic ALDHs remained relatively constant during development. It appeared that both cytosolic and mitochondrial ALDH were present by at least the third trimester and could afford the fetus some protection against the toxic action of endogenous or exogenous aldehydes.

Identification and selective precipitation of human aldehyde dehydrogenase isozymes using antibodies raised to horse liver aldehyde dehydrogenase isozymes

Aldehyde dehydrogenase (ALDH) enzymes from human liver homogenates were recognized in immunoblotting experiments and precipitated in Ouchterlony double diffusion gels by antibodies raised to the horse liver mitochondrial and cytosolic ALDH isozymes. The antibody raised to the cytosolic horse liver ALDH (alpha HC) has been shown to be specific for cytosolic ALDH isozymes, while the antibody raised to the horse liver mitochondrial ALDH (alpha HM) precipitated both mitochondrial and cytosolic ALDH isozymes. It was possible to selectively remove the cytosolic ALDH from a homogenate of a liver sample from a Caucasian by preincubation with alpha HC; the remaining mitochondrial enzyme was then precipitated by alpha HM in double diffusion gels. The experiments were repeated with a liver sample from an Oriental, presumed to have been alcohol sensitive since no active mitochondrial ALDH was found. The precipitation of a relatively inactive mitochondrial enzyme by alpha HM from a cytosolic ALDH-free sample confirmed previous reports of the existence of a mitochondrial ALDH in tissue from an alcohol-sensitive Oriental. The results of immunoblotting experiments confirm the co-migration, in electrophoresis, of the cytosolic and mitochondrial ALDHs from the liver of an alcohol-sensitive Oriental. The results reported here, together with previous observations, indicate that the antibodies raised to horse liver ALDH isozymes can be used to determine the subcellular location of ALDH isozymes in various human tissues, including frozen tissue samples which are not amenable to subcellular fractionation.

Identification of hepatocarcinogenesis-associated aldehyde dehydrogenase in normal rat urinary bladder

An aldehyde dehydrogenase (ALDH) with properties identical to those of the NADP+-dependent, tumor-associated aldehyde dehydrogenase appearing during rat hepatocarcinogenesis has been identified in normal rat urinary bladder. Like the tumor-associated aldehyde dehydrogenase, bladder NADP+-ALDH is cytosolic and preferentially oxidizes benzaldehyde-like aromatic aldehydes. Bladder ALDH is also extremely sensitive to the aldehyde dehydrogenase inhibitor disulfiram. Additionally, the electrophoretic mobility of bladder ALDH is identical to that of the NADP+-dependent, tumor-associated aldehyde dehydrogenase. Finally, antibodies to the tumor-associated ALDH cross-react with bladder aldehyde dehydrogenase. Histochemically, bladder aldehyde dehydrogenase is localized to the very active epithelial lining and to the inner and outer smooth muscle layers. The observation that normal urinary bladder possesses an enzyme activity very similar to one expressed during hepatocarcinogenesis, but not in normal liver, is consistent with the hypothesis that derepression of a gene normally repressed in liver is responsible for expression of the tumor-associated aldehyde dehydrogenase phenotype.

Enzymatic activity of atypical Oriental types of aldehyde dehydrogenases

Catalytic activity of the atypical Oriental-type aldehyde dehydrogenase-2 (ALDH2) was considered to be null or severely diminished. Recently it was suggested that the atypical ALDH2(2) retained about 30% of the specific activity of the usual ALDH2(1). We reexamined the problem by two-dimensional crossed immunoelectrophoresis. The usual Caucasian livers exhibited two distinctive precipitin peaks, one corresponding to the cytosolic ALDH1 and the other corresponding to the usual mitochondrial ALDH2(1), in both protein stain and enzyme activity stain. In contrast, the atypical Oriental livers exhibited two precipitin peaks in protein stain, but only one peak, corresponding to ALDH1, in enzyme activity stain. These results support the original notion that the atypical ALDH2(2) is enzymatically inactive or far less active than the usual enzyme, refuting the idea of the atypical ALDH2(2) with substantial enzyme activity.