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Research paper thumbnail of The role of gut microbiota in shaping the immune response in relapse-remitting and chronic-progressive mouse models of multiple sclerosis

The Journal of Immunology

In this study, we used a mouse model of multiple sclerosis (MS), experimental autoimmune encephal... more In this study, we used a mouse model of multiple sclerosis (MS), experimental autoimmune encephalitis (EAE), to evaluate the role of gut microbiota in modulating T helper cell function in chronic-progressive (CP) versus relapse-remitting (RR) forms of the disease. We hypothesized that encephalitogenic T cell function in RR-EAE and CP-EAE is differentially shaped by gut microbiota. Metagenomic sequencing of the variable V4 region of the prokaryotic 16S ribosomal RNA gene present in feces derived from naïve mice and mice exhibiting CP-EAE or RR-EAE revealed significantly diverse microbial populations, which may be responsible for differing disease courses. Specifically, the order Bacteroidales was dominantly represented by RR-EAE mice, with very little or no detection in naive or CP-EAE mice, suggesting a potential role for bacteria in this order in shaping tolerant or remittance-favoring conditions. Additionally, Akkermansia and rc4-4, of phyla Verrucomicrobia and Firmicutes, respect...

Research paper thumbnail of Skin Mast Cell-Driven Ceramides Drive Early Apoptosis in Pre-Symptomatic Eczema in Mice

International Journal of Molecular Sciences, 2021

Atopic dermatitis (AD or eczema) is the most common chronic inflammatory skin disorder worldwide.... more Atopic dermatitis (AD or eczema) is the most common chronic inflammatory skin disorder worldwide. Ceramides (Cer) maintain skin barrier functions, which are disrupted in lesional skin of AD patients. However, Cer status during the pre-lesional phase of AD is not well defined. Using a variation of human AD-like preclinical model consisting of a 7-day topical exposure to ovalbumin (OVA), or control, we observed elevation of Cer C16 and C24. Skin mRNA quantification of enzymes involved in Cer metabolism [Cer synthases (CerS) and ceramidases (Asah1/Asah2)], which revealed augmented CerS 4, 5 and 6 and Asah1. Given the overall pro-apoptotic nature of Cer, local apoptosis was assessed, then quantified using novel morphometric measurements of cleaved caspase (Casp)-3-restricted immunofluorescence signal in skin samples. Apoptosis was induced in response to OVA. Because apoptosis may occur downstream of endoplasmic reticulum (ER) stress, we measured markers of ER stress-induced apoptosis an...

Research paper thumbnail of Effects of Acute 2,3,7,8-Tetrachlorodibenzo-p-Dioxin Exposure on the Circulating and Cecal Metabolome Profile

International Journal of Molecular Sciences, 2021

2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) is a polyhalogenated planar hydrocarbon belonging to a... more 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) is a polyhalogenated planar hydrocarbon belonging to a group of highly toxic and persistent environmental contaminants known as “dioxins”. TCDD is an animal teratogen and carcinogen that is well characterized for causing immunosuppression through activation of aryl hydrocarbon receptor (AHR). In this study, we investigated the effect of exposure of mice to an acute dose of TCDD on the metabolic profile within the serum and cecal contents to better define the effects of TCDD on host physiology. Our findings demonstrated that within the circulating metabolome following acute TCDD exposure, there was significant dysregulation in the metabolism of bioactive lipids, amino acids, and carbohydrates when compared with the vehicle (VEH)-treated mice. These widespread changes in metabolite abundance were identified to regulate host immunity via modulating nuclear factor-kappa B (NF-κB) and extracellular signal-regulated protein kinase (ERK1/2) activi...

Research paper thumbnail of Resveratrol (3, 5, 4′-Trihydroxy-trans-Stilbene) Attenuates a Mouse Model of Multiple Sclerosis by Altering the miR-124/Sphingosine Kinase 1 Axis in Encephalitogenic T Cells in the Brain

Journal of Neuroimmune Pharmacology, 2019

Research paper thumbnail of The role of gut microbiota in shaping the relapse-remitting and chronic-progressive forms of multiple sclerosis in mouse models

Research paper thumbnail of CD44 deletion leading to attenuation of experimental autoimmune encephalomyelitis results from alterations in gut microbiome in mice

European journal of immunology, Jul 23, 2017

Dysbiosis in gut microbiome has been shown to be associated with inflammatory and autoimmune dise... more Dysbiosis in gut microbiome has been shown to be associated with inflammatory and autoimmune diseases. Previous studies from our laboratory demonstrated the pivotal role played by CD44 in the regulation of experimental autoimmune encephalomyelitis (EAE), a murine model of multiple sclerosis. In the current study, we determined whether these effects resulted from an alteration in gut microbiota and the short-chain fatty acid (SCFA) production in CD44KO mice. Fecal transfer from naïve CD44KO but not CD44WT mice, into EAE-induced CD44WT mice, led to significant amelioration of EAE. High-throughput bacterial 16S rRNA gene sequencing, followed by clustering sequences into operational taxonomic units (OTUs) and biochemical analysis, revealed that EAE-induced CD44KO mice showed significant diversity, richness, and evenness when compared to EAE-induced CD44WT mice at the phylum level, with dominant Bacteroidetes (68.5%) and low Firmicutes (26.8%). Further, data showed a significant change i...

Research paper thumbnail of Epidermal growth factor-induced cellular invasion requires sphingosine-1-phosphate/sphingosine-1-phosphate 2 receptor-mediated ezrin activation

Research paper thumbnail of Sphingosine kinase: Role in regulation of bioactive sphingolipid mediators in inflammation

Research paper thumbnail of Sphingosine 1-phosphate induces filopodia formation through S1PR2 activation of ERM proteins

Biochemical Journal, 2013

Previously we demonstrated that the sphingolipids ceramide and S1P (sphingosine 1-phosphate) regu... more Previously we demonstrated that the sphingolipids ceramide and S1P (sphingosine 1-phosphate) regulate phosphorylation of the ERM (ezrin/radixin/moesin) family of cytoskeletal proteins [Canals, Jenkins, Roddy, Hernande-Corbacho, Obeid and Hannun (2010) J. Biol. Chem. 285, 32476–3285]. In the present article, we show that exogenously applied or endogenously generated S1P (in a sphingosine kinase-dependent manner) results in significant increases in phosphorylation of ERM proteins as well as filopodia formation. Using phosphomimetic and non-phosphorylatable ezrin mutants, we show that the S1P-induced cytoskeletal protrusions are dependent on ERM phosphorylation. Employing various pharmacological S1PR (S1P receptor) agonists and antagonists, along with siRNA (small interfering RNA) techniques and genetic knockout approaches, we identify the S1PR2 as the specific and necessary receptor to induce phosphorylation of ERM proteins and subsequent filopodia formation. Taken together, the resul...

Research paper thumbnail of Targeting the sphingosine kinase/sphingosine 1-phosphate pathway in disease: Review of sphingosine kinase inhibitors

Biochimica et Biophysica Acta (BBA) - Molecular and Cell Biology of Lipids, 2013

Research paper thumbnail of Regulation of the Sphingosine Kinase/Sphingosine 1-Phosphate Pathway

Handbook of Experimental Pharmacology, 2013

Sphingolipids have emerged as pleiotropic signaling molecules with roles in numerous cellular and... more Sphingolipids have emerged as pleiotropic signaling molecules with roles in numerous cellular and biological functions. Defining the regulatory mechanisms governing sphingolipid metabolism is crucial in order to develop a complete understanding of the biological functions of sphingolipid metabolites. The sphingosine kinase/ sphingosine 1-phosphate pathway was originally thought to function in the irreversible breakdown of sphingoid bases; however, in the last few decades it has materialized as an extremely important signaling pathway involved in a plethora of cellular events contributing to both normal and pathophysiological events. Recognition of the SK/S1P pathway as a second messaging system has aided in the identification of many mechanisms of its regulation; however, a cohesive, global understanding of the regulatory mechanisms controlling the SK/S1P pathway is lacking. In this chapter, the role of the SK/S1P pathway as a second messenger is discussed, and its role in mediating TNF-α- and EGF-induced biologies is examined. This work provides a comprehensive look into the roles and regulation of the sphingosine kinase/ sphingosine 1-phosphate pathway and highlights the potential of the pathway as a therapeutic target.

Research paper thumbnail of Differential epigenetic regulation of encephalitogenic T cells in relapse-remitting and chronic-progressive mouse models of multiple sclerosis

Journal of Immunology, 2016

In this study, we used a mouse model of multiple sclerosis (MS), experimental autoimmune encephal... more In this study, we used a mouse model of multiple sclerosis (MS), experimental autoimmune encephalitis (EAE), to evaluate the role of microRNA (miRNA) in modulating T helper cell function in chronic-progressive (CP) versus relapse-remitting (RR) forms of the disease. We hypothesized that encephalitogenic T cell function in RR-EAE and CP-EAE is differentially regulated my microRNA. Microarray analysis of brain-derived CD4+ T cells revealed significant up-regulation of 106 and down-regulation of 42 miRNAs in the chronic-progressive (relative to relapse-remitting) form of disease. In silico analysis of the top up-regulated miRNAs and their target genes revealed significant overlap with signaling pathways imperative for the generation and maintenance of immune tolerance. Specifically miRNA-34, -148, -326 and -6691 were found to be up-regulated in the chronic-progressive form of disease. These miRNAs were predicted to target genes required for TGF-β signaling (ITGB8, ITGAV, NOTCH1, NOTCH2...

Research paper thumbnail of The role of gut microbiota in shaping the immune response in relapse-remitting and chronic-progressive mouse models of multiple sclerosis

The Journal of Immunology

In this study, we used a mouse model of multiple sclerosis (MS), experimental autoimmune encephal... more In this study, we used a mouse model of multiple sclerosis (MS), experimental autoimmune encephalitis (EAE), to evaluate the role of gut microbiota in modulating T helper cell function in chronic-progressive (CP) versus relapse-remitting (RR) forms of the disease. We hypothesized that encephalitogenic T cell function in RR-EAE and CP-EAE is differentially shaped by gut microbiota. Metagenomic sequencing of the variable V4 region of the prokaryotic 16S ribosomal RNA gene present in feces derived from naïve mice and mice exhibiting CP-EAE or RR-EAE revealed significantly diverse microbial populations, which may be responsible for differing disease courses. Specifically, the order Bacteroidales was dominantly represented by RR-EAE mice, with very little or no detection in naive or CP-EAE mice, suggesting a potential role for bacteria in this order in shaping tolerant or remittance-favoring conditions. Additionally, Akkermansia and rc4-4, of phyla Verrucomicrobia and Firmicutes, respect...

Research paper thumbnail of Skin Mast Cell-Driven Ceramides Drive Early Apoptosis in Pre-Symptomatic Eczema in Mice

International Journal of Molecular Sciences, 2021

Atopic dermatitis (AD or eczema) is the most common chronic inflammatory skin disorder worldwide.... more Atopic dermatitis (AD or eczema) is the most common chronic inflammatory skin disorder worldwide. Ceramides (Cer) maintain skin barrier functions, which are disrupted in lesional skin of AD patients. However, Cer status during the pre-lesional phase of AD is not well defined. Using a variation of human AD-like preclinical model consisting of a 7-day topical exposure to ovalbumin (OVA), or control, we observed elevation of Cer C16 and C24. Skin mRNA quantification of enzymes involved in Cer metabolism [Cer synthases (CerS) and ceramidases (Asah1/Asah2)], which revealed augmented CerS 4, 5 and 6 and Asah1. Given the overall pro-apoptotic nature of Cer, local apoptosis was assessed, then quantified using novel morphometric measurements of cleaved caspase (Casp)-3-restricted immunofluorescence signal in skin samples. Apoptosis was induced in response to OVA. Because apoptosis may occur downstream of endoplasmic reticulum (ER) stress, we measured markers of ER stress-induced apoptosis an...

Research paper thumbnail of Effects of Acute 2,3,7,8-Tetrachlorodibenzo-p-Dioxin Exposure on the Circulating and Cecal Metabolome Profile

International Journal of Molecular Sciences, 2021

2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) is a polyhalogenated planar hydrocarbon belonging to a... more 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) is a polyhalogenated planar hydrocarbon belonging to a group of highly toxic and persistent environmental contaminants known as “dioxins”. TCDD is an animal teratogen and carcinogen that is well characterized for causing immunosuppression through activation of aryl hydrocarbon receptor (AHR). In this study, we investigated the effect of exposure of mice to an acute dose of TCDD on the metabolic profile within the serum and cecal contents to better define the effects of TCDD on host physiology. Our findings demonstrated that within the circulating metabolome following acute TCDD exposure, there was significant dysregulation in the metabolism of bioactive lipids, amino acids, and carbohydrates when compared with the vehicle (VEH)-treated mice. These widespread changes in metabolite abundance were identified to regulate host immunity via modulating nuclear factor-kappa B (NF-κB) and extracellular signal-regulated protein kinase (ERK1/2) activi...

Research paper thumbnail of Resveratrol (3, 5, 4′-Trihydroxy-trans-Stilbene) Attenuates a Mouse Model of Multiple Sclerosis by Altering the miR-124/Sphingosine Kinase 1 Axis in Encephalitogenic T Cells in the Brain

Journal of Neuroimmune Pharmacology, 2019

Research paper thumbnail of The role of gut microbiota in shaping the relapse-remitting and chronic-progressive forms of multiple sclerosis in mouse models

Research paper thumbnail of CD44 deletion leading to attenuation of experimental autoimmune encephalomyelitis results from alterations in gut microbiome in mice

European journal of immunology, Jul 23, 2017

Dysbiosis in gut microbiome has been shown to be associated with inflammatory and autoimmune dise... more Dysbiosis in gut microbiome has been shown to be associated with inflammatory and autoimmune diseases. Previous studies from our laboratory demonstrated the pivotal role played by CD44 in the regulation of experimental autoimmune encephalomyelitis (EAE), a murine model of multiple sclerosis. In the current study, we determined whether these effects resulted from an alteration in gut microbiota and the short-chain fatty acid (SCFA) production in CD44KO mice. Fecal transfer from naïve CD44KO but not CD44WT mice, into EAE-induced CD44WT mice, led to significant amelioration of EAE. High-throughput bacterial 16S rRNA gene sequencing, followed by clustering sequences into operational taxonomic units (OTUs) and biochemical analysis, revealed that EAE-induced CD44KO mice showed significant diversity, richness, and evenness when compared to EAE-induced CD44WT mice at the phylum level, with dominant Bacteroidetes (68.5%) and low Firmicutes (26.8%). Further, data showed a significant change i...

Research paper thumbnail of Epidermal growth factor-induced cellular invasion requires sphingosine-1-phosphate/sphingosine-1-phosphate 2 receptor-mediated ezrin activation

Research paper thumbnail of Sphingosine kinase: Role in regulation of bioactive sphingolipid mediators in inflammation

Research paper thumbnail of Sphingosine 1-phosphate induces filopodia formation through S1PR2 activation of ERM proteins

Biochemical Journal, 2013

Previously we demonstrated that the sphingolipids ceramide and S1P (sphingosine 1-phosphate) regu... more Previously we demonstrated that the sphingolipids ceramide and S1P (sphingosine 1-phosphate) regulate phosphorylation of the ERM (ezrin/radixin/moesin) family of cytoskeletal proteins [Canals, Jenkins, Roddy, Hernande-Corbacho, Obeid and Hannun (2010) J. Biol. Chem. 285, 32476–3285]. In the present article, we show that exogenously applied or endogenously generated S1P (in a sphingosine kinase-dependent manner) results in significant increases in phosphorylation of ERM proteins as well as filopodia formation. Using phosphomimetic and non-phosphorylatable ezrin mutants, we show that the S1P-induced cytoskeletal protrusions are dependent on ERM phosphorylation. Employing various pharmacological S1PR (S1P receptor) agonists and antagonists, along with siRNA (small interfering RNA) techniques and genetic knockout approaches, we identify the S1PR2 as the specific and necessary receptor to induce phosphorylation of ERM proteins and subsequent filopodia formation. Taken together, the resul...

Research paper thumbnail of Targeting the sphingosine kinase/sphingosine 1-phosphate pathway in disease: Review of sphingosine kinase inhibitors

Biochimica et Biophysica Acta (BBA) - Molecular and Cell Biology of Lipids, 2013

Research paper thumbnail of Regulation of the Sphingosine Kinase/Sphingosine 1-Phosphate Pathway

Handbook of Experimental Pharmacology, 2013

Sphingolipids have emerged as pleiotropic signaling molecules with roles in numerous cellular and... more Sphingolipids have emerged as pleiotropic signaling molecules with roles in numerous cellular and biological functions. Defining the regulatory mechanisms governing sphingolipid metabolism is crucial in order to develop a complete understanding of the biological functions of sphingolipid metabolites. The sphingosine kinase/ sphingosine 1-phosphate pathway was originally thought to function in the irreversible breakdown of sphingoid bases; however, in the last few decades it has materialized as an extremely important signaling pathway involved in a plethora of cellular events contributing to both normal and pathophysiological events. Recognition of the SK/S1P pathway as a second messaging system has aided in the identification of many mechanisms of its regulation; however, a cohesive, global understanding of the regulatory mechanisms controlling the SK/S1P pathway is lacking. In this chapter, the role of the SK/S1P pathway as a second messenger is discussed, and its role in mediating TNF-α- and EGF-induced biologies is examined. This work provides a comprehensive look into the roles and regulation of the sphingosine kinase/ sphingosine 1-phosphate pathway and highlights the potential of the pathway as a therapeutic target.

Research paper thumbnail of Differential epigenetic regulation of encephalitogenic T cells in relapse-remitting and chronic-progressive mouse models of multiple sclerosis

Journal of Immunology, 2016

In this study, we used a mouse model of multiple sclerosis (MS), experimental autoimmune encephal... more In this study, we used a mouse model of multiple sclerosis (MS), experimental autoimmune encephalitis (EAE), to evaluate the role of microRNA (miRNA) in modulating T helper cell function in chronic-progressive (CP) versus relapse-remitting (RR) forms of the disease. We hypothesized that encephalitogenic T cell function in RR-EAE and CP-EAE is differentially regulated my microRNA. Microarray analysis of brain-derived CD4+ T cells revealed significant up-regulation of 106 and down-regulation of 42 miRNAs in the chronic-progressive (relative to relapse-remitting) form of disease. In silico analysis of the top up-regulated miRNAs and their target genes revealed significant overlap with signaling pathways imperative for the generation and maintenance of immune tolerance. Specifically miRNA-34, -148, -326 and -6691 were found to be up-regulated in the chronic-progressive form of disease. These miRNAs were predicted to target genes required for TGF-β signaling (ITGB8, ITGAV, NOTCH1, NOTCH2...