Project description:BackgroundDysfunctional humoral and cellular innate immunity are key components in the development and progression of age-related macular degeneration (AMD). Specifically, chronically activated microglia and their disturbed regulatory system contribute to retinal degeneration. Galectin-3, a β-galactose binding protein, is a potent driver of macrophage and microglia activation and has been implicated in neuroinflammation, including neurodegenerative diseases of the brain. Here, we hypothesized that genetic deficiency of galectin-3 or its modulation via TD139 dampens mononuclear phagocyte reactivity and delays retinal degeneration.MethodsGalectin-3 expression in AMD patients was analyzed by immunohistochemical stainings. Galectin-3 knockout and BALB/cJ mice were exposed to white bright light with an intensity of 15,000 lux for 1 h and Cx3cr1GFP/+ mice to focal blue light of 50,000 lux for 10 min. BALB/cJ and Cx3cr1GFP/+ mice received intraperitoneal injections of 15 mg/kg TD139 or vehicle for five consecutive days, starting one day prior to light exposure. The effects of galectin-3 deficiency or inhibition on microglia were analyzed by immunohistochemical stainings and in situ hybridization of retinal sections and flat mounts. Pro-inflammatory cytokine levels in the retina and retinal pigment epithelium (RPE) were quantified by qRT-PCR and transcriptomic changes were analyzed by RNA-sequencing. Retinal thickness and structure were evaluated by optical coherence tomography.ResultsWe found that galectin-3 expression was strongly upregulated in reactive retinal mononuclear phagocytes of AMD patients and in the two related mouse models of light-induced retinal degeneration. The experimental in vivo data further showed that specific targeting of galectin-3 by genetic knockout or administration of the small-molecule inhibitor TD139 reduced microglia reactivity and delayed retinal damage in both light damage conditions.ConclusionThis study defines galectin-3 as a potent driver of retinal degeneration and highlights the protein as a drug target for ocular immunomodulatory therapies.

Project description:Background: Galectin-3 is upregulated in heart disease, and its inhibition has been reported to confer benefits on cardiac remodeling and dysfunction. It remains unknown whether galectin-3 plays a biological role in a setting of dilated cardiomyopathy (DCM). We determined galectin-3 expression in transgenic (TG) mice with cardiac-restricted overexpression of mammalian sterile 20-like kinase 1 (Mst1-TG), and studied the effects of pharmacological and genetic inhibition of galectin-3 on the DCM phenotype. Methods and results: The DCM phenotype of male Mst1-TG mice was assessed at 2, 3 and 6 months of age. Galectin-3 deletion in Mst1-TG mice was achieved by cross-breeding Mst1-TG with galectin-3 knockout (KO) mice to produce genotypes of non-TG (nTG), KO, Mst1-TG, and Mst1-TG mice with partial or complete deletion of the galectin-3 gene. Pharmacological inhibition of galectin-3 was tested by treating Mst1-TG mice with modified citrus pectin for 4 months. Changes in the DCM phenotype were assessed by serial echocardiography, ECG recording and biochemical assays. Mst1-TG mice exhibited upregulated levels of cardiac galectin-3 expression by 40~50-fold, atrial dilatation, reduced left ventricular (LV) ejection fraction, increased LV volume at systole and diastole, atrial conduction delay, severe cardiac fibrosis, and upregulated fibrosis-related genes. Galectin-3 gene deletion in Mst1-TG mice attenuates increased LV volume at systole and diastole, atrial conduction delay and cardiac fibrogenesis. Treatment with modified citrus pectin in Mst1-TG mice did not confer benefit on the DCM phenotype, possibly due to the very high expression of galectin-3. Conclusion: Galectin-3 expression is markedly increased in Mst1-TG hearts exhibiting DCM. Galectin-3 gene deletion effectively suppressed cardiac fibrotic signaling and LV dilatation, and was associated with better function. Thus, suppression of galectin-3 expression may represent a potential therapeutic approach in DCM. The development of new galectin-3 inhibitors are warranted.

Project description:Pharmacological activation of the activating transcription factor 6 (ATF6) arm of the Unfolded Protein Response (UPR) has proven useful for ameliorating proteostasis deficiencies in a variety of etiologically diverse diseases. Previous high-throughput screening efforts identified the small molecule AA147 as a potent and selective ATF6 activating compound that operates through a mechanism involving metabolic activation of its 2-amino- p -cresol substructure affording a quinone methide, which then covalently modifies a subset of ER protein disulfide isomerases (PDIs). Intriguingly, another compound identified in this screen, AA132, also contains a 2-amino- p -cresol moiety; however, this compound showed less transcriptional selectivity, instead globally activating all three arms of the UPR. Here, we show that AA132 activates global UPR signaling through a mechanism analogous to that of AA147, involving metabolic activation and covalent PDI modification. Chemoproteomic-enabled analyses show that AA132 covalently modifies PDIs to a greater extent than AA147. Paradoxically, activated AA132 reacts slower with PDIs, indicating it is less reactive than activated AA147. This suggests that the higher labeling of PDIs observed with activated AA132 can be attributed to its lower reactivity, which allows this activated compound to persist longer in the cellular environment prior to quenching by endogenous nucleophiles. Collectively, these results suggest that AA132 globally activates the UPR through increased engagement of ER PDIs. Consistent with this, reducing the cellular concentration of AA132 decreases PDI modifications and allows for selective ATF6 activation. Our results highlight the relationship between metabolically activatable-electrophile stability, ER proteome reactivity, and the transcriptional response observed with the enaminone chemotype of ER proteostasis regulators, enabling continued development of next-generation ATF6 activating compounds.

Project description:The goal of this study was to examine differences in gene expression of tumor specific CD8 T cells in an in vivo tumor mouse model after inhibition of galectin-3 protein expression by genetic knockout. Galectin-3 is thought to modulate CD8 T cell response by cross-linking cell surface glycoproteins Galectin-3 is a 31 kD carbohydrate-binding lectin that is over-expressed by many human malignancies. It also modulates T cell responses through a diverse array of mechanisms including induction of apoptosis, TCR cross linking in CD8+ T cells, and T cell receptor (TCR) down regulation in CD4+ T cells. We found that patients responding to a granulocyte-macrophage colony-stimulating factor (GM-CSF) secreting allogeneic pancreatic tumor vaccine developed post immunization antibody responses to galectin-3 on a proteomic screen. We used the HER-2/neu (neu-N) transgenic mouse model to study galectin-3 binding on adoptively transferred high avidity neu-specific CD8+ T cells derived from TCR transgenic mice. Here, we show that galectin-3 binds preferentially to activated antigen-committed CD8+ T cells only in the tumor microenvironment (TME). Galectin-3 deficient mice exhibit improved CD8+ T cell effector function and increased expression of several inflammatory genes when compared with wild type (WT) mice. We also show that galectin-3 binds to LAG-3, and LAG-3 expression is necessary for galectin-3 mediated suppression of CD8+ T cells in vitro. Lastly, galectin-3 deficient mice have significantly elevated levels of circulating plasmacytoid dendritic cells (pDCs), which are superior to conventional dendritic cells (cDCs) in activating CD8+ T cells. Binding of galectin-3 to cell-surface glycoproteins on immune cells suppresses a pro-inflammatory immune response. Thus, inhibiting galectin-3 in conjunction with CD8+ T cell directed immunotherapies should enhance the tumor specific immune response. 3 different experimental groups were studied. Galectin-3 WT CD8 T cells adoptively transferred into Galectin-3 WT mice, galectin-3 WT CD8 T cells transferred into galectin-3 KO mice, and finally galectin-3 KO CD8 T cells transferred into galectin-3 KO mice. Galectin-3 WT CD8 T cells transferred into Galectin-3 WT mice were used as the reference group. Four biological replicates were submitted for each group, and adoptively transfered CD8 T cells were isolated 5 days post-adoptive transfer into tumor-bearing mice treated with a whole cell GM-CSF secreting vaccine. Cells were purified by cell sorting on the Thy1.2 surface marker.

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Genetic targeting or pharmacological inhibition of galectin-3 dampens microglia reactivity and delays retinal degeneration

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