Role of Galectin 3 in the pathogenesis of experimental autoimmune myocarditis

Miokarditis je inflamatorno oboljenje srčanog mišića, koje se karakteriše degeneracijom i/ili nekrozom kardiomiocita i prisustvom ćelijskog infiltrata u intersticijumu miokarda. Miokarditis se može manifestovati kao akutno, subakutno ili hronično zapaljenje miokarda, sa fokalnim ili difuznim ćelijskim infiltratom i može progredirati do fibroze, remodelovanja tkiva i gubitka kontraktilne funkcije. Najčešći uzročnici miokarditisa su virusi, bakterije i paraziti,međutim brojni dokazi ukazuju da ovo oboljenje može biti i autoimunske prirode. Eksperimentalni autoimunski miokarditis (EAM) predstavlja animalni model postinfektivnog miokarditisa i dilatacione kardiomiopatije. Galektin 3 (Gal-3) pripada familiji β-galaktozid-vezujućih lektina i eksprimiran je na mnogim ćelijama imunskog sistema i ima važnu ulogu u regulaciji inflamacije. Uloga Gal-3 jeispitivana u različitim autoimunskim i inflamatornim bolestima i pokazano je da Gal-3 može dvojako regulisati imunski odgovor, što zavisi od više faktora, kao što su specifični uslovi inflamacije, vrsta tkiva i nivo ekspresije ovog molekula kako u fiziološkim tako i u patološkim stanjima. Nema podtaka o ulozi i značaju Gal-3 u patogenezi EAM kod C57BL/6 miševa, koji su relativno rezistentni na peptidom indukovani EAM. Da bi se utvrdilo da li i na koji način delecija gena za Gal-3 utiče na patogenezu EAM korišćeni su miševi čistog soja WT- C57BL/6 i Gal-3KO miševi. Svi WT i Gal- 3KO miševi imunizovani su MyHCα334-352 peptidom 0. i 7. dana. Težina EAM određivana je 21-og dana eksperimenta, odnosno prilikom žrtvovanja životinja. Gal-3KO miševi su imali značajno veću hipertrofiju srca i veći patohistološki skor u poređenju sa WT miševima 21. dana nakon imunizacije. Gal-3KO miševi imali su značajno veću infiltraciju srčanog mišića CD45+ mononuklearnim ćelijama posebno F4/80+ makrofagama i CD3+ T limfocitima, kao i veću zastupljenost eozinofila u poređenju sa WT miševima. Serumske koncentracije Th2 citokina (IL-4 i IL-33) su bile više u serumima Gal-3KO u poređenju sa kontrolnim obolelim WT miševima. Delecija gena za Gal-3 je indukovala značajno veći influks Th1 i Th2 ćelija u srcu imunizovanih Gal-3KO u odnosu na WT miševe. Odsustvo ekspresije gena za Gal-3 značajno povećava ukupan broj F4/80+ ćelija i olakšava alternativnu aktivaciju makrofaga u srcu. U obolelom miokardu Gal-3KO miševa registrovana je značajno veća procentualna zastupljenost i ukupan broj: mijeloidnih CD11b+Ly6Chi makrofaga; i CD11c+ ćelija koje produkuju IL-13. U miokardu Gal-3KO miševa detektovan je veći broj IgG pozitivnih ćelija i veća količina IgG depozita u poređenju sa WT miševima. Delecija gena za Gal-3 povećava broj antifibrotskih ćelija koje produkuju IL-10 što se manifestuje značajno slabijim deponovanjem kolagena u srcu obolelih miševa. Delecija gena za Gal-3 povećava oštećenje tkiva u animalnom modelu autoimunskog miokarditisa indukovanog aplikacijom MyHCα334-352 peptida i ukida rezistenciju C57BL/6 miševa na indukciju bolesti.Myocarditis is an inflammatory heart muscle disease characterized by degeneration and necrosis of cardiomyocytes with presence of cellular infiltrates in the interstitium. Myocarditis can be manifested as acute, subacute or chronic myocardial inflammation with focal or diffuse cell infiltrates, it can progress to fibrosis, tissue remodeling and loss of contractile function. The most common causes of myocarditis are viruses, bacteria and parasites, however numerous evidence suggests that this disease can also be autoimmune. Experimental autoimmune myocarditis (EAM) is an animal model of postinfective myocarditis and dilated cardiomyopathy. Galectin 3 (Gal-3), which belongs to the family of β- galactoside-binding lectins is expressed on many cells of the immune system and plays an important role in regulation of inflammation. The role of Gal-3 was studied in various autoimmune and inflammatory diseases and it has been shown that Gal-3 can have a different effect on the immune response. Its role depends on several factors, such as the specific conditions of inflammation, the type of tissue, and the expression level of this molecule in pathological as well as in physiological conditions. There are no precise data on the role and significance of Gal-3 in the pathogenesis of EAM in C57BL/6 mice, which are relatively resistant to EAM-induced by peptide. Mice of the pure strain WT-C57BL/6 and Gal-3KO mice were used in order to determine whether and how the deletion of the Gal-3 gene affects the EAM pathogenesis. WT and Gal-3KO mice were immunized with the MyHCα334-352 peptide on day zero and day seven. Severity of EAM was determined on the 21st day of the experiment, during the sacrifice of animals. Gal-3KO mice had significantly higher cardiac hypertrophy and higher histopathological score compared to WT mice on the 21st day after immunization. Gal-3KO mice also had a significantly higher infiltration of heart muscle by CD45+ mononuclear cells, particulary with F4/80+ macrophages and CD3+T lymphocytes, and higher number of eosinophils compared to WT mice.Serum concentrations of Th2 cytokine (IL-4 and IL-33) were higher in Gal-3KO mice than in control diseased WT mice. The deletion of the Gal-3 gene also induced significantly higher influx Th1 and Th2 cells at the heart of the immunized Gal-3KO compared to WT mice. The absence of gene expression for Gal-3 significantly increases the total number of F4/80+ cells and facilitates alternative macrophage activation in the heart. In myocardium of Gal-3KO mice were significantly higher percentage of distribution and total number of: myeloid CD11b+Ly6Chi macrophages and CD11c+ cells producing IL-13. In the myocardium of Gal-3KO mice were detected a higher number of IgG positive cells and a larger amount of IgG deposits compared to WT mice. The deletion of Gal-3 gene increases the number of antifibrotic cells that produce IL-10, which is manifested by significantly less collagen storage in the heart of diseased mice. Gal-3 gene deletion increases tissue damage in animal model of autoimmune myocarditis induced by application of the MyHCα334-352 peptide and eliminates the resistance of C57BL/6 mice to induction of the disease