Simultaneous induction of galectin-3 phosphorylated on tyrosine residue, p21(WAF1/Cip1/Sdi1), and the proliferating cell nuclear antigen at a distinctive period of repair of hepatocytes injured by CCl4

Indispensable role of Galectin-3 in promoting quiescence of hematopoietic stem cells

Hematopoietic stem cells (HSCs) in adult bone marrow (BM) are usually maintained in a state of quiescence. The cellular mechanism coordinating the balance between HSC quiescence and differentiation is not fully understood. Here, we report that galactose-binding lectin-3 (galectin-3; Gal-3) is upregulated by Tie2 or Mpl activation to maintain quiescence. Conditional overexpression of Gal-3 in mouse HSCs under the transcriptional control of Tie2 or Vav1 promoters (Gal-3 Tg) causes cell cycle retardation via induction of p21. Conversely, the cell cycle of long-term repopulating HSCs (LT-HSCs) in Gal-3-deficient (Gal-3^-/-) mice is accelerated, resulting in their exhaustion. Mechanistically, Gal-3 regulates p21 transcription by forming a complex with Sp1, thus blocking cell cycle entry. These results demonstrate that Gal-3 is a negative regulator of cell-cycling in HSCs and plays a crucial role in adult hematopoiesis to prevent HSC exhaustion.

Long term haematopoitic stem cells (LT-HSCs) are in a quiescent state during homeostasis, which is critical for their maintenance. Here, the authors show that Gal-3 expression in LT-HSCs is induced in response to Tie2 and Mpl and is both necessary and sufficient for LT-HSC quiescence through regulation of p21.

Acute Myocardial Infarction Biosensor: A Review From Bottom Up

Acute myocardial infarction (AMI) is a cardiovascular disease that is produced due to a deficiency of oxygen generating irreversible damage in the heart muscle. In diagnosis, electrocardiogram (ECG) investigation has been the main method but is insufficient, so approaches like the measurement of biomarkers levels in plasma or saliva have become one of the most commonly applied strategies for prognosis of AMI, as some of them are specifically related to a heart attack. Many tests are carrying on to determine biological markers changes, but usually, they present disadvantages related to time consumption and laborious work. To overcome the issues, researchers around the world have been developing different ways to enhance detection through the use of biosensors. These diagnostic devices have a biological sensing element associated to a physicochemical transducer that can be made from different materials and configurations giving place to different kinds of detection: Electrical/Electrochemical, Optical and Mechanical. In this review, the authors presents relevant investigations related to the most important biomarkers and biosensors used for their detection having in mind the nanotechnology participation in the process through the application of nanostructures as a good choice for device configuration.

[Galectin-3 induces differentiation of rat bone marrow mesenchymal stem cells into hepatocyte-like cells]

OBJECTIVE

To investigate the effect of galectin-3 in inducing the differentiation of rat bone marrow mesenchymal stem cells (BMSCs) into hepatocyte- like cells and explore the involvement of the signaling pathways in the induced cell differentiation.

METHODS

The third passage of cultured rat femoral BMSCs were treated with 0.5 μg/mL galectin-3, 20 ng/mL hepatocyte growth factor (HGF) or both to induce their differentiation, with untreated rat BMSCs and hepatocytes as controls. At 7, 14, 21 and 28 days of induction, the cells were examined for morphological changes followed by glycogen staining, quantitative real-time PCR and Western blotting. Gene microarray technique was used to examine the mRNA expression profile of the BMSCs induced with galectin-3. The BMSCs were also induced with galectin-3 in combination with XMU-MP-1, a Hippo signaling pathway inhibitor, after which Western blotting was performed to detect the expressions of YAP, P-YAP, ALB, AFP and CK-18 in the cells.

RESULTS

The cells isolated from the femoral bone marrow of SD rats showed a consistent surface marker phenotype with the BMSCs. Induction with galectin-3, HGF, or both all resulted in gradual morphological changes of the BMSCs into hepatocyte-like cells, and the cells with a combined induction for 28 days showed the highest morphological similarity with hepatocytes. The cells induced with galectin-3, HGF, or their combination for 28 days all showed increased positivity rate of glycogen staining, which was the highest in the cells with combined induction (P < 0.05) without significant difference between the cells induced with galectin-3 and HGF alone (P > 0.05). Induction with galectin-3 and HGF alone both increased the expressions of AFP, ALB and CK-18 mRNAs in the cells, and their expression levels were similar between the cells at 28 days (P > 0.05). Galectin-3 and HGF did not show an interactive effect on the mRNA expressions of AFP (F=0.236, P=0.640) or ALB (F=50.639, P=0.000), but had a synergistic effect on CK-18 mRNA expression (F=50.639, P=0.000). The protein expressions of AFP, ALB and CK18 were also increased in the induced cells but not detected in the cells without induction. Gene microarray results revealed 27 up-regulated genes and 62 down-regulated genes in galectin-3-induced BMSCs involving TGF-β, PI3K-Akt and Hippo signal pathways. Induction with galectin-3 and galectin-3+XMU-MP-1 increased YAP expression in the cells, and galectin-3+XMU-MP-1 was more efficient to induce the differentiation of the BMSCs.

CONCLUSIONS

Galectin-3 can induce the differentiation of rat BMSCs into hepatocyte-like cells, and the combination with HGF increases the efficiency of induced differentiation of the cells. TGF-β, PI3K-Akt and Hippo pathways are involved in the induced differentiation of the BMSCs, and inhibiting Hippo pathway can improve the induction efficiency.

Cleavage and phosphorylation: important post-translational modifications of galectin-3

As the unique chimeric member of the β-galactoside-binding protein family, galectin-3 is a multivalent and multifunctional oncogenic protein involved in multiple physiological and pathological processes, including cell growth, cell differentiation, cell adhesion, RNA splicing, cell apoptosis, and malignant transformation. Post-translational modifications can effectively increase a protein's functional diversity, either by degradation or adding chemical modifications, thus regulating activity, localization, and ligand interaction. In order to clearly understand the functional mechanisms of galectin-3 involved in normal cell biology and pathogenesis, here, we have summarized the previously reported post-translational modifications of galectin-3, including cleavage and phosphorylation. Cleavage of galectin-3 by MMPs, PSA, and proteases from parasites generated intact carbohydrate-recognition domain and N-terminal peptides of varying lengths that retained lectin binding activity but lost multivalence. Serine and tyrosine phosphorylation of galectin-3 by c-Abl, CKI, and GSK-3β could regulate its localization and associated signal transduction. Accordingly, cleavage and phosphorylation play an important role in regulating galectin-3 function via altering its multivalence, localization, and ligand interaction.

Tissue- and cell-specific localization of galectins, β-galactose-binding animal lectins, and their potential functions in health and disease

Fifteen galectins, β-galactose-binding animal lectins, are known to be distributed throughout the body. We herein summarize current knowledge on the tissue- and cell-specific localization of galectins and their potential functions in health and disease. Galectin-3 is widely distributed in epithelia, including the simple columnar epithelium in the gut, stratified squamous epithelium in the gut and skin, and transitional epithelium and several regions in nephrons in the urinary tract. Galectin-2 and galectin-4/6 are gut-specific, while galectin-7 is found in the stratified squamous epithelium in the gut and skin. The reproductive tract mainly contains galectin-1 and galectin-3, and their expression markedly changes during the estrous/menstrual cycle. The galectin subtype expressed in the corpus luteum (CL) changes in association with luteal function. The CL of women and cows displays a "galectin switch" with coordinated changes in the major galectin subtype and its ligand glycoconjugate structure. Macrophages express galectin-3, which may be involved in phagocytotic activity. Lymphoid tissues contain galectin-3-positive macrophages, which are not always stained with the macrophage marker, F4/80. Subsets of neurons in the brain and dorsal root ganglion express galectin-1 and galectin-3, which may contribute to the regeneration of damaged axons, stem cell differentiation, and pain control. The subtype-specific contribution of galectins to implantation, fibrosis, and diabetes are also discussed. The function of galectins may differ depending on the tissues or cells in which they act. The ligand glycoconjugate structures mediated by glycosyltransferases including MGAT5, ST6GAL1, and C2GnT are important for revealing the functions of galectins in healthy and disease states.

Galectin-3 up-regulation in hypoxic and nutrient deprived microenvironments promotes cell survival

Galectin-3 (gal-3) is a β-galactoside binding protein related to many tumoral aspects, e.g. angiogenesis, cell growth and motility and resistance to cell death. Evidence has shown its upregulation upon hypoxia, a common feature in solid tumors such as glioblastoma multiformes (GBM). This tumor presents a unique feature described as pseudopalisading cells, which accumulate large amounts of gal-3. Tumor cells far from hypoxic/nutrient deprived areas express little, if any gal-3. Here, we have shown that the hybrid glioma cell line, NG97ht, recapitulates GBM growth forming gal-3 positive pseudopalisades even when cells are grafted subcutaneously in nude mice. In vitro experiments were performed exposing these cells to conditions mimicking tumor areas that display oxygen and nutrient deprivation. Results indicated that gal-3 transcription under hypoxic conditions requires previous protein synthesis and is triggered in a HIF-1α and NF-κB dependent manner. In addition, a significant proportion of cells die only when exposed simultaneously to hypoxia and nutrient deprivation and demonstrate ROS induction. Inhibition of gal-3 expression using siRNA led to protein knockdown followed by a 1.7–2.2 fold increase in cell death. Similar results were also found in a human GBM cell line, T98G. In vivo, U87MG gal-3 knockdown cells inoculated subcutaneously in nude mice demonstrated decreased tumor growth and increased time for tumor engraftment. These results indicate that gal-3 protected cells from cell death under hypoxia and nutrient deprivation in vitro and that gal-3 is a key factor in tumor growth and engraftment in hypoxic and nutrient-deprived microenvironments. Overexpression of gal-3, thus, is part of an adaptive program leading to tumor cell survival under these stressing conditions.

Hierarchical and selective roles of galectins in hepatocarcinogenesis, liver fibrosis and inflammation of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) represents a global health problem. Infections with hepatitis B or C virus, non-alcoholic steatohepatitis disease, alcohol abuse, or dietary exposure to aflatoxin are the major risk factors to the development of this tumor. Regardless of the carcinogenic insult, HCC usually develops in a context of cirrhosis due to chronic inflammation and advanced fibrosis. Galectins are a family of evolutionarily-conserved proteins defined by at least one carbohydrate recognition domain with affinity for β-galactosides and conserved sequence motifs. Here, we summarize the current literature implicating galectins in the pathogenesis of HCC. Expression of "proto-type" galectin-1, "chimera-type" galectin-3 and "tandem repeat-type" galectin-4 is up-regulated in HCC cells compared to their normal counterparts. On the other hand, the "tandem-repeat-type" lectins galectin-8 and galectin-9 are down-regulated in tumor hepatocytes. The abnormal expression of these galectins correlates with tumor growth, HCC cell migration and invasion, tumor aggressiveness, metastasis, postoperative recurrence and poor prognosis. Moreover, these galectins have important roles in other pathological conditions of the liver, where chronic inflammation and/or fibrosis take place. Galectin-based therapies have been proposed to attenuate liver pathologies. Further functional studies are required to delineate the precise molecular mechanisms through which galectins contribute to HCC.

Protective effects of silymarin on fumonisin B₁-induced hepatotoxicity in mice

The present study was conducted to investigate the effect of silymarin on experimental liver toxication induced by Fumonisin B₁ (FB₁) in BALB/c mice. The mice were divided into six groups (n = 15). Group 1 served as the control. Group 2 was the silymarin control (100 mg/kg by gavage). Groups 3 and 4 were treated with FB₁ (Group 3, 1.5 mg/kg FB₁, intraperitoneally; and Group 4, 4.5 mg/kg FB₁). Group 5 received FB₁ (1.5 mg/kg) and silymarin (100 mg/kg), and Group 6 was given a higher dose of FB₁ (4.5 mg/kg FB₁) with silymarin (100 mg/kg). Silymarin treatment significantly decreased (p < 0.0001) the apoptotic rate. FB₁ administration significantly increased (p < 0.0001) proliferating cell nuclear antigen and Ki-67 expression. Furthermore, FB₁ elevated the levels of caspase-8 and tumor necrosis factor-alpha mediators while silymarin significantly reduced (p < 0.0001) the expression of these factors. Vascular endothelial growth factor (VEGF) and fibroblast growth factor-2 (FGF-2) expressions were significantly elevated in Group 4 (p < 0.0001). Silymarin administration alleviated increased VEGF and FGF-2 expression levels (p < 0.0001). In conclusion, silymarin ameliorated toxic liver damage caused by FB₁ in BALB/c mice.

Analysis of changes in hepatic gene expression in a murine model of tolerance to acetaminophen hepatotoxicity (autoprotection)

Pretreatment of mice with a low hepatotoxic dose of acetaminophen (APAP) results in resistance to a subsequent, higher dose of APAP. This mouse model, termed APAP autoprotection was used here to identify differentially expressed genes and cellular pathways that could contribute to this development of resistance to hepatotoxicity. Male C57BL/6J mice were pretreated with APAP (400mg/kg) and then challenged 48h later with 600mg APAP/kg. Livers were obtained 4 or 24h later and total hepatic RNA was isolated and hybridized to Affymetrix Mouse Genome MU430_2 GeneChip. Statistically significant genes were determined and gene expression changes were also interrogated using the Causal Reasoning Engine (CRE). Extensive literature review narrowed our focus to methionine adenosyl transferase-1 alpha (MAT1A), nuclear factor (erythroid-derived 2)-like 2 (Nrf2), flavin-containing monooxygenase 3 (Fmo3) and galectin-3 (Lgals3). Down-regulation of MAT1A could lead to decreases in S-adenosylmethionine (SAMe), which is known to protect against APAP toxicity. Nrf2 activation is expected to play a role in protective adaptation. Up-regulation of Lgals3, one of the genes supporting the Nrf2 hypothesis, can lead to suppression of apoptosis and reduced mitochondrial dysfunction. Fmo3 induction suggests the involvement of an enzyme not known to metabolize APAP in the development of tolerance to APAP toxicity. Subsequent quantitative RT-PCR and immunochemical analysis confirmed the differential expression of some of these genes in the APAP autoprotection model. In conclusion, our genomics strategy identified cellular pathways that might further explain the molecular basis for APAP autoprotection.

Deficiency in galectin-3 promotes hepatic injury in CDAA diet-induced nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) is increasingly recognized as a condition in which excess fat accumulates in hepatocytes. Nonalcoholic steatohepatitis (NASH), a severe form of NAFLD in which inflammation and fibrosis in the liver are noted, may eventually progress to end-stage liver disease. Galectin-3, a β-galactoside-binding animal lectin, is a multifunctional protein. This protein is involved in inflammatory responses and carcinogenesis. We investigated whether galectin-3 is involved in the development of NASH by comparing galectin-3 knockout (gal3(-/-)) mice and wild-type (gal3(+/+)) mice with choline-deficient L-amino-acid-defined (CDAA) diet-induced NAFLD/NASH. Hepatic injury was significantly more severe in the gal3(-/-) male mice, as compared to the gal3(+/+) mice. Data generated by microarray analysis of gene expression suggested that galectin-3 deficiency causes alterations in the expression of various genes associated with carcinogenesis and lipid metabolism. Through canonical pathway analysis, involvement of PDGF and IL-6 signaling pathways was suggested in galectin-3 deficiency. Significant increase of CD14, Fos, and Jun, those that were related to lipopolysaccharide-mediated signaling, was candidate to promote hepatocellular damages in galectin-3 deficiency. In conclusion, galectin-3 deficiency in CDAA diet promotes NAFLD features. It may be caused by alterations in the expression profiles of various hepatic genes including lipopolysaccharide-mediated inflammation.

Tyrosine-phosphorylated galectin-3 protein is resistant to prostate-specific antigen (PSA) cleavage

Galectin-3 is a chimeric carbohydrate-binding protein, which interacts with cell surface carbohydrate-containing molecules and extracellular matrix glycoproteins and has been implicated in various biological processes such as cell growth, angiogenesis, motility, and metastasis. It is expressed in a wide range of tumor cells and is associated with tumor progression. The functions of galectin-3 are dependent on its localization and post-translational modifications such as cleavage and phosphorylation. Recently, we showed that galectin-3 Tyr-107 is phosphorylated by c-Abl; concomitantly, it was also shown that galectin-3 can be cleaved at this site by prostate-specific antigen (PSA), a chymotrypsin-like serine protease, after Tyr-107, resulting in loss of galectin-3 multivalency while preserving its carbohydrate binding activity. Galectin-3 is largely a monomer in solution but may form a homodimer by self-association through its carbohydrate recognition domain, whereas, in the presence of a ligand, galectin-3 polymerizes up to pentamers utilizing its N-terminal domain. Oligomerization is a unique feature of secreted galectin-3, which allows its function by forming ordered galectin-glycan structures, i.e. lattices, on the cell surface or through direct engagement of specific cell surface glycoconjugates by traditional ligand-receptor binding. We questioned whether Tyr-107 phosphorylation by c-Abl affects galectin-3 cleavage by PSA. The data suggest a role for galectin-3 in prostate cells associated with increased activity of c-Abl kinase and loss of phosphatase and tensin homologue deleted on chromosome 10 (PTEN) activity. In addition, the ratio of phosphorylated/dephosphorylated galectin-3 might be used as a complementary value to that of PSA for prognosis of prostate cancer and a novel therapeutic target for the treatment of prostate cancer.

Galectin-3: A novel substrate for c-Abl kinase

Galectin-3, a beta-galactoside-binding lectin, is found in cellular and extracellular location of the cell and has pleiotropic biological functions such as cell growth, cell adhesion and cell-cell interaction. It may exhibit anti- or pro-apoptotic activity depending on its localization and post-translational modifications. Two important post-translational modifications of galectin-3 have been reported: its cleavage and phosphorylation. Cleavage of galectin-3 was reported to be involved with angiogenic potential and apoptotic resistance. Phosphorylation of galectin-3 regulates its sugar-binding ability. In this report we have identified novel tyrosine phosphorylation sites in galectin-3 as well as the kinase responsible for its phosphorylation. Our results demonstrate that tyrosines at positions 79, 107 and 118 can be phosphorylated in vitro and in vivo by c-Abl kinase. Tyrosine 107 is the main target of c-Abl. Expression of galectin-3 Y107F mutant in galectin-3 null SK-Br-3 cells leads to morphological changes and increased motility compared to wild type galectin-3. Further investigation is needed to better understand the functional significance of the novel tyrosine phosphorylated sites of galectin-3.

A novel clinically relevant animal model for studying galectin-3 and its ligands during colon carcinogenesis

Galectin-3 (Gal-3) is a multifunctional protein that plays different roles in cancer biology. To better understand the role of Gal-3 and its ligands during colon carcinogenesis, we studied its expression in tumors induced in rats treated with 1,2-dimethylhydrazine (DMH) and in human tissues. Normal colon from untreated rats showed no staining using two specific monoclonal antibodies. In contrast, morphologically normal colon from DMH-treated rats and dysplastic aberrant crypt foci were strongly stained, indicating that increased Gal-3 expression is an early event during the neoplastic transformation in colon cells. Gal-3 was weakly expressed in adenocarcinomas. Overall, the Gal-3 expression pattern observed in the DMH rat model closely resembles that displayed by human colon stained with the same antibodies. We also found that Gal-3 phosphorylation diminishes in serines while increasing in tyrosines during rat colon carcinogenesis. Finally, we showed that Gal-3-ligands expression is strikingly similar in rat and human malignant colon and in non-malignant tissues. In conclusion, the DMH-induced rat colon cancer model displays expression patterns of Gal-3 and its ligands very similar to those observed in human samples. This animal model should contribute to clarifying the role of Gal-3 in colon carcinogenesis and also to finding effective preventive cancer agents based on Gal-3 targeting.

Advances in research on relationship between galectin-3 and liver diseases

Galectin-3, having an apparent molecular weight between 29 and 35 kDa, is a member of a galectin family of mammalian carbohydrate-binding proteins consisting so far of 14 reported members. Galectin-3 is predominantly localized in the cytoplasm and may translocate to the perinuclear membrane, nucleus and get secreted into the extracellular matrix (ECM). It is involved in cell growth, proliferation, differentiation and adhesion, immune responses, angiogenesis, apoptosis, and tumor progression and metastasis. Furthermore, galectin-3 can act as a receptor for advanced glycation end-products. Recent studies have shown that galectin-3 is associated with many hepatic diseases, such as fatty liver disease, hepatic fibrosis, cirrhosis and liver cancer. Here, we will review the relationship between galectin-3 and hepatic diseases.

Nonalcoholic steatohepatitis and hepatocellular carcinoma in galectin-3 knockout mice

AIM

Nonalcoholic fatty liver disease (NAFLD) represents a growing health concern due to its rapidly increasing prevalence worldwide. Nonalcoholic steatohepatitis (NASH) is a progressing form of NAFLD, and recently many studies have reported that it could eventually develop into hepatocellular carcinoma (HCC). We previously reported that 6-month-old male galectin-3 knockout (gal3(-/-)) mice developed clinicopathological features similar to those of NAFLD in humans. Our aim was to investigate the changes in liver histology in gal3(-/-) mice by long-term observation.

METHODS

We initially investigated three 15-month-old gal3(-/-) mice, of which two developed multiple liver nodules with dysplastic changes. Then, we histopathologically examined the liver specimens of the 15-, 20- and 25-month-old gal3(-/-) mice and attempted to evaluate the liver morphology by contrast enhanced computed tomography (CT) before sacrifice.

RESULTS

At the age of 15 months or later, gal3(-/-) mice developed liver nodules with varying degrees of architectural and nuclear atypia based on mild to moderate delicate zone 3 fibrosis. In addition, we successfully confirmed the presence of some of the liver nodules by CT. We report herein that gal3(-/-) mice develop dysplastic liver nodules and HCC.

CONCLUSIONS

We believe that it would be interesting to use this murine model to investigate liver carcinogenesis based on a natural history of NAFLD. Furthermore, CT scanning might be a useful tool for longitudinal evaluation of morphological changes in vivo.

Expression of galectin-3 involved in prognosis of patients with hepatocellular carcinoma

AIMS

Galectins are multifunctional lectins binding to the beta-galactoside of glycoproteins that affect diverse physiological and pathophysiological processes such as development, inflammation and tumor growth. In hepatocellular carcinoma (HCC), the over-expression of galectin-1, 3, and 4 has been reported, although their function and correlation with tumor progression remain unknown. Thus, we aimed to assess the role of galectin-3 during HCC progression.

METHODS

Specimens were obtained during curative operations and used for immunohistochemical analysis of galectin-3 (n = 52), and statistically assessed for correlations with the clinical profiles and the prognoses of the patients. The serum galectin-3 levels from the patients with liver diseases including HCC were assessed by ELISA.

RESULTS

In total, galectin-3 expression was found in 34 of 52 tumors (65%) and was statistically correlated with histological differentiation and vascular invasion. Kaplan-Meier's analysis showed that patients with galectin-3 expression tended to relapse in the earlier phase and had worse overall survival. In particular, a higher expression rate of nuclear galectin-3 showed a markedly worse prognosis, and it was independent in the multivariate analysis for overall survival. Serum galectin-3 levels were significantly increased in HCC compared with chronic liver disease. The sensitivity and specificity of galectin-3 were equivalent to alpha-fetoprotein and Vitamin K absence or antagonist II, and the combination of HCC biomarkers with galectin-3 improved the diagnostic performance.

CONCLUSIONS

Galectin-3 expression was involved in the tumor progression and related to the prognosis of HCC. Our observations suggested that galectin-3 could be a novel tumor marker and therapeutic target.

Disrupted galectin-3 causes non-alcoholic fatty liver disease in male mice

Galectin-3, a beta-galactoside-binding animal lectin, is a multifunctional protein. Previous studies have suggested that galectin-3 may play an important role in inflammatory responses. Non-alcoholic fatty liver disease (NAFLD) is increasingly recognized as a liver condition that may progress to end-stage liver disease and based on the known functions of galectin-3, it was hypothesized that galectin-3 might play a role in the development of NAFLD. Thus, this study investigated the role of galectin-3 in NAFLD by comparing galectin-3 knockout (gal3(-/-)) mice and wild-type (gal3(+/+)) mice. The livers of gal3(-/-) male mice at 6 months of age histologically displayed mild to severe fatty change. The liver weight per body weight ratio, serum alanine aminotransferase levels, liver triglyceride levels, and liver lipid peroxide in gal3(-/-) mice were significantly increased compared with those in gal3(+/+) mice. Furthermore, the hepatic protein levels of advanced glycation end-products (AGE), receptor for AGE (RAGE), and peroxisome proliferator-activated receptor gamma (PPARgamma) were increased in gal3(-/-) mice relative to gal3(+/+) mice. In conclusion, this study suggests that the absence of gal3 can cause clinico-pathological features in male mice similar to those of NAFLD.

Galectin-3: an open-ended story

Galectins, an ancient lectin family, are characterized by specific binding of beta-galactosides through evolutionary conserved sequence elements of carbohydrate-recognition domain (CRD). A structurally unique member of the family is galectin-3; in addition to the CRD it contains a proline- and glycine-rich N-terminal domain (ND) through which is able to form oligomers. Galectin-3 is widely spread among different types of cells and tissues, found intracellularly in nucleus and cytoplasm or secreted via non-classical pathway outside of cell, thus being found on the cell surface or in the extracellular space. Through specific interactions with a variety of intra- and extracellular proteins galectin-3 affects numerous biological processes and seems to be involved in different physiological and pathophysiological conditions, such as development, immune reactions, and neoplastic transformation and metastasis. The review attempts to summarize the existing information on structural, biochemical and intriguing functional properties of galectin-3.

The galectin-3 gene promoter binding proteins in the liver of rats 48-h post-treatment with CCl4

The present study was undertaken to characterize structure-function relationships of the rat galectin-3 gene promoter especially focusing on the promoter binding proteins included in livers injured with CCl4. Transcription start site determination identified a 66-nucleotide-long exon 1 of this gene. Transient expression analysis using a reporter luciferase gene assigned a region between -161 and -15 to the proximal promoter within the 1-kb region flanking the 5'-end of exon 1. The rat galectin-3 gene promoter possesses a Runx2 binding site and inverted repeats of Sp1 binding motifs in separate regions downstream from -117 as structures resembling those of the mouse galectin-3 gene promoter. The -161/-118 region bound two different proteins. One is a novel protein, a rat version of Purbeta that binds to a guanine nucleotide pair at -145 and -144 to modulate constitutive galectin-3 gene transcription. Southwestern blot analysis using the -161/-118 ligand revealed a signal of a 50-kDa protein in liver nuclear extracts from rats 48-h post-treatment with CCl4, but not in those from Ac2F cells and normal rat livers. The inducible nature of this protein suggested its distinctive role in galectin-3 induction in a liver injured with CCl4. E-box and peroxisome proliferator response element-like motifs reside on separate DNA strands from -140 to -135. Contribution of this segment to the regulation of galectin-3 gene transcription under pathological conditions was suggested, since a DNA ligand with the two motifs simultaneously mutagenized at -136 and -137 was not bound by the 50-kDa protein.

Analysis of gene expression in carbon tetrachloride-treated rat livers using a novel bioarray technology

The present study successfully utilizes a new ADME Rat Expression Bioarray, containing 1040 metabolism- and toxicology-linked genes, to monitor gene expression from the livers of rats treated with carbon tetrachloride (CCl(4)). Histopathological analysis, hierarchical clustering methods, and gene expression profiling are compared between the control and CCl(4)-treated animals. A total of 44 transcripts were found to be altered in response to the hepatotoxin, 19 of which were upregulated and 25 were downregulated. Some of these gene expression changes were expected and concurred with previously published data while others were novel findings.

Characterization of human CYP1A1/1A2 induction by DNA microarray and alpha-naphthoflavone

DNA microarrays and real time PCR were used to analyze the mechanism of gene induction by CYP1A1 inducers, beta-naphthoflavone, and omeprazole, in the human hepatocellular carcinoma HepG2 cells. Reproducible and significant inductions were observed in a limited number of genes including CYP1A1 and CYP1A2. Genes induced by omeprazole included several protein tyrosine kinase targets. This result confirmed that omeprazole could modulate gene expressions through protein tyrosine kinase-mediated pathway. Induction ratios were considerably different from CYP1A1 and CYP1A2 (>10-fold) to other induced genes (<5-fold). alpha-Naphthoflavone, which is known as an antagonist to 2,3,7,8-tetrachlorodibenzo-p-dioxin, inhibited the inductions of heme oxygenase 1, glutamate-cysteine ligase (modifier unit), and thioredoxin reductase by beta-naphthoflavone but not those of CYP1A1 and CYP1A2. It unexpectedly enhanced the beta-naphthoflavone-mediated CYP1A1 and CYP1A2 induction. These results suggest that the CYP1A1 and CYP1A2 genes, which share their 5(') enhancer regions, are regulated differently from the other genes.