Elevated Galectin-3 Levels in the Serum of Patients With Alzheimer's Disease

Galectin-3 is required for the microglia-mediated brain inflammation in a model of Huntington's disease

Huntington’s disease (HD) is a neurodegenerative disorder that manifests with movement dysfunction. The expression of mutant Huntingtin (mHTT) disrupts the functions of brain cells. Galectin-3 (Gal3) is a lectin that has not been extensively explored in brain diseases. Herein, we showed that the plasma Gal3 levels of HD patients and mice correlated with disease severity. Moreover, brain Gal3 levels were higher in patients and mice with HD than those in controls. The up-regulation of Gal3 in HD mice occurred before motor impairment, and its level remained high in microglia throughout disease progression. The cell-autonomous up-regulated Gal3 formed puncta in damaged lysosomes and contributed to inflammation through NFκB- and NLRP3 inflammasome-dependent pathways. Knockdown of Gal3 suppressed inflammation, reduced mHTT aggregation, restored neuronal DARPP32 levels, ameliorated motor dysfunction, and increased survival in HD mice. Thus, suppression of Gal3 ameliorates microglia-mediated pathogenesis, which suggests that Gal3 is a novel druggable target for HD.

The authors show that Galectin-3 is up–regulated in brain tissues from patients and a mouse model of Huntington’s disease (HD) and correlates with disease severity. Galectin-3 accumulates at damaged lysosomes in HD microglia, prevents the clearance of damaged lysosomes, and promotes inflammation.

Non-Skeletal Activities of Vitamin D: From Physiology to Brain Pathology

Vitamin D is a secosteroid hormone regulating the expression of almost 900 genes, and it is involved in the regulation of calcium and phosphate metabolism, immune response, and brain development. Low blood vitamin D levels have been reported in patients affected by various diseases. Despite a large amount of literature data, there is uncertainty surrounding the role of vitamin D as a serum biomarker in Alzheimer’s disease (AD) and Parkinson’s disease (PD). Indeed, the lack of internationally recognized 25(OH)D₃ reference measurement procedures and standard materials in the past led to unstandardized serum total 25(OH)D₃ results among research and clinical care laboratories. Thus, most of the literature studies reported unstandardized data, which are of little use and make it difficult to draw conclusions of the role of vitamin D in AD and PD. This review summarizes the extra-skeletal actions of vitamin D, focusing its role in immunomodulation and brain function, and reports the issue of lacking standardized literature data concerning the usefulness of vitamin D as a biomarker in AD and PD.

Vitamin D and the nervous system

Objective: to summarise the activities that Vitamin D (VD) carries out in the brain and to clarify the potential role of VD in neurological diseases. Methods: a literature research has been performed in Pubmed using the following keywords: 'Vitamin D', 'nervous system', 'brain'. Results: the studies reviewed show that VD contributes to cerebral activity in both embryonic and adult brain, helping the connectivity of neural circuits responsible for locomotor, emotional and reward-dependent behavior. Low VD serum levels have been found in patients affected by Alzheimer Disease, Parkinson Disease, Multiple Sclerosis, Autism Spectrum Disorders, Sleep Disorders and Schizophrenia. Discussion: findings are controversial and should be interpreted with caution, since most of the studies performed have observational study set and few interventional studies are available, producing conflicting results. Overall, it can be stated that the potential role of Vitamin D in neurological diseases is mostly unclear and further randomised controlled trials are needed to understand better whether Vitamin D supplementation treatment can be useful in brain disorders.

Galectin-3 promotes Aβ oligomerization and Aβ toxicity in a mouse model of Alzheimer's disease

Amyloid-β (Aβ) oligomers largely initiate the cascade underlying the pathology of Alzheimer's disease (AD). Galectin-3 (Gal-3), which is a member of the galectin protein family, promotes inflammatory responses and enhances the homotypic aggregation of cancer cells. Here, we examined the role and action mechanism of Gal-3 in Aβ oligomerization and Aβ toxicities. Wild-type (WT) and Gal-3-knockout (KO) mice, APP/PS1;WT mice, APP/PS1;Gal-3^+/- mice and brain tissues from normal subjects and AD patients were used. We found that Aβ oligomerization is reduced in Gal-3 KO mice injected with Aβ, whereas overexpression of Gal-3 enhances Aβ oligomerization in the hippocampi of Aβ-injected mice. Gal-3 expression shows an age-dependent increase that parallels endogenous Aβ oligomerization in APP/PS1 mice. Moreover, Aβ oligomerization, Iba1 expression, GFAP expression and amyloid plaque accumulation are reduced in APP/PS1;Gal-3^+/- mice compared with APP/PS1;WT mice. APP/PS1;Gal-3^+/- mice also show better acquisition and retention performance compared to APP/PS1;WT mice. In studying the mechanism underlying Gal-3-promoted Aβ oligomerization, we found that Gal-3 primarily co-localizes with Iba1, and that microglia-secreted Gal-3 directly interacts with Aβ. Gal-3 also interacts with triggering receptor expressed on myeloid cells-2, which then mediates the ability of Gal-3 to activate microglia for further Gal-3 expression. Immunohistochemical analyses show that the distribution of Gal-3 overlaps with that of endogenous Aβ in APP/PS1 mice and partially overlaps with that of amyloid plaque. Moreover, the expression of the Aβ-degrading enzyme, neprilysin, is increased in Gal-3 KO mice and this is associated with enhanced integrin-mediated signaling. Consistently, Gal-3 expression is also increased in the frontal lobe of AD patients, in parallel with Aβ oligomerization. Because Gal-3 expression is dramatically increased as early as 3 months of age in APP/PS1 mice and anti-Aβ oligomerization is believed to protect against Aβ toxicity, Gal-3 could be considered a novel therapeutic target in efforts to combat AD.

The roles of galectin-3 and galectin-4 in the idiopatic Parkinson disease and its progression

OBJECTIVES

Idiopathic Parkinson's Disease is a neurodegenerative disease caused by the loss of cells that secrete dopamine in the basal ganglia. Galectins are multipotent, evolutionarily conserved, cell surface glycoconjugated and crosslinked carbohydrate-binding proteins. The roles of these proteins in the diagnosis of the disease have been investigated.

PATIENT AND METHODS

Patients who were diagnosed with idiopathic Parkinson's disease were classified as early (stage 1-2) and advanced stage (stage 3-5) according to the Hoehn-Yahr classification. In addition, voluntary cases without parkinson disease constituted the control group. Serum samples of consecutive Parkinson patients and age and gender matched healthy controls were used to measure serum galectin-3 and serum galectin-4 levels. The levels were compared between Parkinson's patients and control groups and early and advanced stage Parkinson's groups.

RESULTS

Thirty age and gender-matched healthy controls and 60 parkinson patients were enrolled in the study. Serum galectin-3 levels were lower in controls compared with patients (892.9 (168.2-2416.3) vs. 2271.8 (375.9-9673.4), respectively, P < 0.01). Serum galectin-3 levels were related to Hoehn-Yahr stages and (r: 0.691, P < 0.001). The early stage group (20 patients) had lower serum galectin-4 levels compared with advanced stages (40 patients) (197.97 ± 46.42 vs. 334.263 ± 37, respectively, P < 0.01). Serum galectin-4 levels were also lower in controls compared with patients 185.1 (116.2-313.3) vs. 282.3 (156.9-984.8), respectively, P < 0.01. ROC analysis showed that serum galectin-3 and galectin-4 were statistically significant in the identification of Parkinson disease and advanced stages. The results were significant for galectin-3 (AUC: 0.89, SE: 0.034, P < 0.001 and CI: 0.823-0.958; P < 0.001) and for galectin-4 (AUC: 0.758, SE: 0.05, P < 0.001).

CONCLUSION

Serum galectin-3 and galectin-4 may be potential noninvasive markers for the identification of Parkinson disease and advanced stages.

Vitamin D in malaria: more hypotheses than clues

Vitamin D is a secosteroid hormone regulating calcium and phosphate metabolism, immune response and brain development. Low blood 25(OH)D levels have been reported in patients affected by infectious diseases caused by parasites, including malaria. Despite the high effectiveness of antimalarials, malaria is burdened with high morbidity and mortality, and the search for additional therapies is rapidly growing. Furthermore, available preventive measures have proved to be barely effective so far. Finding new prevention and therapy tools is a matter of urgency. Studies on animal models and humans have hypothesized some mechanisms by which the hormone can influence malaria pathogenesis, and the role of Vitamin D supplementation in preventing and treating this disease has been suggested. Few studies on the association between Vitamin D and malaria are available and disagreeing results have been reported. Studies in humans reporting an association between low 25(OH)D circulating levels and Malaria have a small sample size and observational study-set. Randomized controlled trials are needed in order to understand if Vitamin D administration might play a role in preventing and treating malaria.

Neuroanatomical Quantitative Proteomics Reveals Common Pathogenic Biological Routes between Amyotrophic Lateral Sclerosis (ALS) and Frontotemporal Dementia (FTD)

(1) Background: Amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) are neurodegenerative disorders with an overlap in clinical presentation and neuropathology. Common and differential mechanisms leading to protein expression changes and neurodegeneration in ALS and FTD were studied trough a deep neuroproteome mapping of the spinal cord. (2) Methods: A liquid chromatography tandem mass spectrometry (LC-MS/MS) analysis of the spinal cord from ALS-TAR DNA-binding protein 43 (TDP-43) subjects, ubiquitin-positive frontotemporal lobar degeneration (FTLD-U) subjects and controls without neurodegenerative disease was performed. (3) Results: 281 differentially expressed proteins were detected among ALS versus controls, while 52 proteins were dysregulated among FTLD-U versus controls. Thirty-three differential proteins were shared between both syndromes. The resulting data was subjected to network-driven proteomics analysis, revealing mitochondrial dysfunction and metabolic impairment, both for ALS and FTLD-U that could be validated through the confirmation of expression levels changes of the Prohibitin (PHB) complex. (4) Conclusions: ALS-TDP-43 and FTLD-U share molecular and functional alterations, although part of the proteostatic impairment is region- and disease-specific. We have confirmed the involvement of specific proteins previously associated with ALS (Galectin 2 (LGALS3), Transthyretin (TTR), Protein S100-A6 (S100A6), and Protein S100-A11 (S100A11)) and have shown the involvement of proteins not previously described in the ALS context (Methanethiol oxidase (SELENBP1), Peptidyl-prolyl cis-trans isomerase NIMA-interacting 1 (PIN-1), Calcyclin-binding protein (CACYBP) and Rho-associated protein kinase 2 (ROCK2)).

Galectin-3-Mediated Glial Crosstalk Drives Oligodendrocyte Differentiation and (Re)myelination

Galectin-3 (Gal-3) is the only chimeric protein in the galectin family. Gal-3 structure comprises unusual tandem repeats of proline and glycine-rich short stretches bound to a carbohydrate-recognition domain (CRD). The present review summarizes Gal-3 functions in the extracellular and intracellular space, its regulation and its internalization and secretion, with a focus on the current knowledge of Gal-3 role in central nervous system (CNS) health and disease, particularly oligodendrocyte (OLG) differentiation, myelination and remyelination in experimental models of multiple sclerosis (MS). During myelination, microglia-expressed Gal-3 promotes OLG differentiation by binding glycoconjugates present only on the cell surface of OLG precursor cells (OPC). During remyelination, microglia-expressed Gal-3 favors an M2 microglial phenotype, hence fostering myelin debris phagocytosis through TREM-2b phagocytic receptor and OLG differentiation. Gal-3 is necessary for myelin integrity and function, as evidenced by myelin ultrastructural and behavioral studies from LGALS3^-/- mice. Mechanistically, Gal-3 enhances actin assembly and reduces Erk 1/2 activation, leading to early OLG branching. Gal-3 later induces Akt activation and increases MBP expression, promoting gelsolin release and actin disassembly and thus regulating OLG final differentiation. Altogether, findings indicate that Gal-3 mediates the glial crosstalk driving OLG differentiation and (re)myelination and may be regarded as a target in the design of future therapies for a variety of demyelinating diseases.

Investigation of Gal-3 Expression Pattern in Serum and Cerebrospinal Fluid of Patients Suffering From Neurodegenerative Disorders

We performed this study to investigate the possibility of a definitive pattern of Galectin-3 (Gal-3) expression in the cerebrospinal fluid (CSF) and serum of Alzheimer’s disease (AD) and Amyotrophic Lateral Sclerosis (ALS) patients. In our study, we collected the CSF and serum samples of 31 AD patients, 19 ALS patients and 50 normal healthy subjects (controls). Quantitative ELISA measured Gal-3 concentrations in CSF and serum samples. A comparative analysis was performed to analyze and understand the Gal-3 expression pattern. A number of neuropsychological assessments and statistical analyses were carried out to validate our findings. Recent researches have established the role of galectins in various neurodegenerative disorders (NDDs), but a definitive pattern of galectin expression is still elusive. A significant difference was observed in serum and CSF Gal-3 concentrations between AD patients and healthy controls. The difference in serum and CSF Gal-3 concentrations between ALS patients vs. controls was lesser as compared to AD patients vs. controls. The difference in serum and CSF Gal-3 concentrations of AD vs. ALS patients was not significant. The MMSE score and serum and CSF Gal-3 concentrations in AD and ALS patients, and controls exhibited a significant positive correlation. The findings of the present study are expected to provide an insight into the definitive pattern of Gal-3 expression in AD and ALS patients, and might thus establish Gal-3 as a strong biomarker. This in turn will open up new and promising research avenues targeting the expression of galectins to modulate the progression of NDDs, and pave the way for novel therapeutic options.

IL-33/ST2 Pathway and Galectin-3 as a New Analytes in Pathogenesis and Cardiometabolic Risk Evaluation in Psychosis

Schizophrenia and treatment of this disorder are often accompanied with metabolic syndrome and cardiovascular issues. Alterations in the serum level of innate immune mediators, such as interleukin-33 (IL-33) and its receptor IL-33R (ST2) and Galectin-3 (Gal-3) were observed in these conditions. Moreover, these parameters are potential prognostic and therapeutic markers. There is also accumulating evidence that these molecules play a role in neuroinflammation. Therefore, in this study we have investigated the serum level of Gal-3, IL-33 and soluble ST2 (sST2) in different stages of schizophrenia. Gal-3 levels were elevated in remission and lower in schizophrenia exacerbation in comparison with controls. Levels of IL-33 and sST2 are higher in schizophrenia exacerbation in comparison with controls and patients in remission. This initial analysis of new markers of neuroinflammation suggested their involvement in schizophrenia pathophysiology and/or cardiometabolic comorbidity.

Depression in type 1 diabetes was associated with high levels of circulating galectin-3

OBJECTIVE

Neuroinflammatory responses are implicated in depression. The aim was to explore whether depression in patients with type 1 diabetes (T1D) was associated with high circulating galectin-3, controlling for metabolic variables, s-creatinine, life style factors, medication and cardiovascular complications.

DESIGN

Cross-sectional.

METHODS

Participants were T1D patients (n = 283, 56% men, age 18-59 years, diabetes duration ≥1 year). Depression was assessed by Hospital Anxiety and Depression Scale-depression subscale. Blood samples, anthropometrics and blood pressure were collected, and supplemented with data from medical records and the Swedish National Diabetes Registry. Galectin-3 ≥2.562 µg/l, corresponding to the 85th percentile, was defined as high galectin-3.

RESULTS

Median (quartile₁, quartile₃) galectin-3 (µg/l) was 1.3 (0.8, 2.9) for the 30 depressed patients, and 0.9 (0.5, 1.6) for the 253 non-depressed, P = 0.009. Depression was associated with high galectin-3 in all the 283 patients (adjusted odds ratio (AOR) 3.5), in the 161 men (AOR 3.4), and in the 122 women (AOR 3.9). HbA1c, s-lipids, s-creatinine, blood pressure, obesity, smoking, physical inactivity, cardiovascular complications and drugs (antihypertensive, lipid lowering, oral antidiabetic drugs and antidepressants) were not associated with high galectin-3.

CONCLUSIONS

This is the first study to show an association between depression and galectin-3. Depression was the only explored parameter associated with high circulating galectin-3 levels in 283 T1D patients. High galectin-3 levels might contribute to the increased risk for Alzheimer's disease, cardiovascular and all-cause mortality observed in persons with depression. Potentially, in the future, treatment targeting galactin-3 might improve the prognosis for patients with high galectin-3 levels.

Galectin-3 and incident cognitive impairment in REGARDS, a cohort of blacks and whites

Introduction

The relationship between serum galectin-3 and incident cognitive impairment was analyzed in the Reasons for Geographic and Racial Differences in Stroke study.

Methods

Baseline galectin-3 was measured in 455 cases of incident cognitive impairment and 546 controls. Galectin-3 was divided into quartiles based on the weighted distribution in the control group, and the first quartile was the referent.

Results

There was an increasing odds of cognitive impairment across quartiles of galectin-3 (odds ratios, 1.00 [0.68–1.46], 1.45 [1.01–2.10], and 1.58 [1.10–2.27] relative to the quartile 1; P trend = .003) in an unadjusted model, which persisted after adjusting for age, sex, and race (P = .004). Adjustment for cardiovascular risk factors greatly attenuated this association (odds ratios, 0.97 [0.60–1.57], 1.52 [0.94–2.46], and 1.27 [0.76–2.12]; P = .15). The association differed by diabetes status (P interaction, .007). Among nondiabetics (293 cases, 411 controls), those with galectin-3 in the fourth compared with first quartile had an odds ratio of 1.6 (0.95–2.99; P trend, .02). In diabetics, the odds ratio was 0.23 (0.04–1.33).

Discussion

Serum galectin-3 was associated with increased risk of incident cognitive impairment in a large cohort study of blacks and whites but only in nondiabetics.

A potential impact of Helicobacter pylori-related galectin-3 in neurodegeneration

Neurodegeneration represents a component of the central nervous system (CNS) diseases pathogenesis, either as a disability primary source in the frame of prototype neurodegenerative disorders, or as a secondary effect, following inflammation, hypoxia or neurotoxicity. Galectins are members of the lectin superfamily, a group of endogenous glycan-binding proteins, able to interact with glycosylated receptors expressed by several immune cell types. Glycan-lectin interactions play critical roles in the living systems by involving and mediating a variety of biologically important normal and pathological processes, including cell-cell signaling shaping cell communication, proliferation and migration, immune responses and fertilization, host-pathogen interactions and diseases such as neurodegenerative disorders and tumors. This review focuses in the role of Galectin-3 in shaping responses of the immune system against microbial agents, and concretely, Helicobacter pylori (Hp), thereby potentiating effect of the microbe in areas distant from the ordinary site of colonization, like the CNS. We hereby postulate that gastrointestinal Hp alterations in terms of immune cell functional phenotype, cytokine and chemokine secretion, may trigger systemic responses, thereby conferring implications for remote processes susceptible in immunity disequilibrium, namely, the CNS inflammation and/or neurodegeneration.

Galectin-3 Negatively Regulates Hippocampus-Dependent Memory Formation through Inhibition of Integrin Signaling and Galectin-3 Phosphorylation

Galectin-3, a member of the galectin protein family, has been found to regulate cell proliferation, inhibit apoptosis and promote inflammatory responses. Galectin-3 is also expressed in the adult rat hippocampus, but its role in learning and memory function is not known. Here, we found that contextual fear-conditioning training, spatial training or injection of NMDA into the rat CA1 area each dramatically decreased the level of endogenous galectin-3 expression. Overexpression of galectin-3 impaired fear memory, whereas galectin-3 knockout (KO) enhanced fear retention, spatial memory and hippocampal long-term potentiation. Galectin-3 was further found to associate with integrin α3, an association that was decreased after fear-conditioning training. Transfection of the rat CA1 area with small interfering RNA against galectin-3 facilitated fear memory and increased phosphorylated focal adhesion kinase (FAK) levels, effects that were blocked by co-transfection of the FAK phosphorylation-defective mutant Flag-FAKY397F. Notably, levels of serine-phosphorylated galectin-3 were decreased by fear conditioning training. In addition, blockade of galectin-3 phosphorylation at Ser-6 facilitated fear memory, whereas constitutive activation of galectin-3 at Ser-6 impaired fear memory. Interestingly galectin-1 plays a role in fear-memory formation similar to that of galectin-3. Collectively, our data provide the first demonstration that galectin-3 is a novel negative regulator of memory formation that exerts its effects through both extracellular and intracellular mechanisms.

Desipramine decreases expression of human and murine indoleamine-2,3-dioxygenases

Abundant evidence connects depression symptomology with immune system activation, stress and subsequently elevated levels of kynurenine. Anti-depressants, such as the tricyclic norepinephrine/serotonin reuptake inhibitor desipramine (Desip), were developed under the premise that increasing extracellular neurotransmitter level was the sole mechanism by which they alleviate depressive symptomologies. However, evidence suggests that anti-depressants have additional actions that contribute to their therapeutic potential. The Kynurenine Pathway produces tryptophan metabolites that modulate neurotransmitter activity. This recognition identified another putative pathway for anti-depressant targeting. Considering a recognized role of the Kynurenine Pathway in depression, we investigated the potential for Desip to alter expression of rate-limiting enzymes of this pathway: indoleamine-2,3-dioxygenases (Ido1 and Ido2). Mice were administered lipopolysaccharide (LPS) or synthetic glucocorticoid dexamethasone (Dex) with Desip to determine if Desip alters indoleamine-dioxygenase (DO) expression in vivo following a modeled immune and stress response. This work was followed by treating murine and human peripheral blood mononuclear cells (PBMCs) with interferon-gamma (IFNγ) and Desip. In vivo: Desip blocked LPS-induced Ido1 expression in hippocampi, astrocytes, microglia and PBMCs and Ido2 expression by PBMCs. Ex vivo: Desip decreased IFNγ-induced Ido1 and Ido2 expression in murine PBMCs. This effect was directly translatable to the human system as Desip decreased IDO1 and IDO2 expression by human PBMCs. These data demonstrate for the first time that an anti-depressant alters expression of Ido1 and Ido2, identifying a possible new mechanism behind anti-depressant activity. Furthermore, we propose the assessment of PBMCs for anti-depressant responsiveness using IDO expression as a biomarker.

Increases of Galectin-1 and its S-nitrosylated form in the Brain Tissues of Scrapie-Infected Rodent Models and Human Prion Diseases

Galectin-1 (Gal-1) shows neuroprotective activity in brain ischemia, spinal cord injury, and autoimmune neuroinflammation. To evaluate the Gal-1 situation in the brains of prion disease, the brain levels of Gal-1 in several scrapie-infected experimental rodent models were tested by Western blot, including agents 263K-infected hamsters, 139A-, ME7-, and S15-infected mice. Remarkable increases of brain Gal-1 were observed in all tested scrapie-infected rodents at the terminal stage. The brain levels of Gal-1 showed time-dependent increases along with the prolonging of incubation times. Immunohistochemical assays illustrated much stronger stainings in the brain sections of scrapie-infected rodents. Quantitative RT-PCR of Gal-1 gene demonstrated increased transcription in the brains of scrapie-infected mice. Gal-1 was colocalized with GFAP- and NeuN-positive cells, but not with Iba-1-positive cells in immunofluorescent test. Increases of Gal-1 were also detected in the several postmortem cortex regions of human prion diseases. Moreover, the S-nitrosylated forms of Gal-1 in the brains of scrapie-infected rodents were significantly higher than those of normal ones. Our finding here demonstrates markedly increased brain Gal-1 and S-nitrosylated Gal-1 both in scrapie-infected rodents and human prion diseases.

Vesicular Galectin-3 levels decrease with donor age and contribute to the reduced osteo-inductive potential of human plasma derived extracellular vesicles

Aging results in a decline of physiological functions and in reduced repair capacities, in part due to impaired regenerative power of stem cells, influenced by the systemic environment. In particular osteogenic differentiation capacity (ODC) of mesenchymal stem cells (MSCs) has been shown to decrease with age, thereby contributing to reduced bone formation and an increased fracture risk. Searching for systemic factors that might contribute to this age related decline of regenerative capacity led us to investigate plasma-derived extracellular vesicles (EVs). EVs of the elderly were found to inhibit osteogenesis compared to those of young individuals. By analyzing the differences in the vesicular content Galectin-3 was shown to be reduced in elderly-derived vesicles. While overexpression of Galectin-3 resulted in an enhanced ODC of MSCs, siRNA against Galectin-3 reduced osteogenesis. Modulation of intravesicular Galectin-3 levels correlated with an altered osteo-inductive potential indicating that vesicular Galectin-3 contributes to the biological response of MSCs to EVs. By site-directed mutagenesis we identified a phosphorylation-site on Galectin-3 mediating this effect. Finally, we showed that cell penetrating peptides comprising this phosphorylation-site are sufficient to increase ODC in MSCs. Therefore, we suggest that decrease of Galectin-3 in the plasma of elderly contributes to the age-related loss of ODC.

Galectin-3 induces cell migration via a calcium-sensitive MAPK/ERK1/2 pathway

The presence and level of circulating galectin-3 (Gal-3), a member of the galectin family, is associated with diverse diseases ranging from heart failure, immune disorders to cancer metastasis and serves as a biomarker of diagnosis and treatment response. However, the mechanisms by which exogenous Gal-3 affects pathobiology events remain elusive. In the current study, we found that exogenous Gal-3 slightly delays, while prolonging tyrosine phosphorylation of extracellular signal-regulated kinase 1/2 (ERK1/2) in HeLa cells through a calcium-sensitive and PKC-dependent signaling pathway. The activation was dependent on the sugar-binding properties of Gal-3, since the antagonist lactose could inhibit it. The sugar-binding motif of Gal-3 was required for the activation of ERK1/2. The activation of ERK1/2 was necessary for the initiation and induction of cell migration associated with the phosphorylation of paxillin. All the results presented in this study suggest a novel calcium-sensitive and PKC-dependent pathway through which circulating Gal-3 promotes cell migration and activating the ERK1/2. Taken together, the data depicted here propose a biological function and a target for the diseases' associated circulating Gal-3.