TELOMERES AND TUMORS

Telomere su terminalne strukture linearnih kromosoma u eukariota koji sadrže ponavljajuću sekvencu. Njihova glavna funkcija je zaštita i pružanje stabilnosti kromosomskim krajevima. U većini humanih somatskih stanica sa svakom staničnom diobom, kromosomi kontinuirano postaju kraći i stanica ulazi u proces staničnog starenja. Suprotno tomu, u tumorskim stanicama aktivan je ribonukleoproteinski enzim telomeraza koji produžuje telomere i omogućuje im daljnju proliferaciju. Kod velikog broja tumora kao što su tumor dojke, tumor pluća, neuroblastom i melanom, telomeraza je eksprimirana u gotovo 85% tumorskih stanica, stoga je glavni cilj antitumorskih terapija upravo njena inhibicija. Do sada su razvijene razne metode za supresiju telomerazne aktivnosti, ali postoji potreba daljnjeg razvoja ovih antitumorskih terapija.Telomeres are terminal structures of linear chromosomes in eukaryotes that contain a repetitive sequence. Their main function is to protect and provide stability to chromosome end regions. In most human somatic cells with each cell division, chromosomes continuosly become shorter and cells enter the cellular aging process. In contrast, tumor cells have active ribonucleoprotein enzyme telomerase which prolongs telomeres and allows them further proliferation. Enzyme telomerase is expressed in almost 85% of tumors (breast tumors, lung tumors, neuroblastoma and melanoma), so the main goal of the anticancer treatment is in its inhibition. So far, various methods have been developed to suppress telomerase activity, but there is a need for further development of these anticancer therapies

TELOMERES AND TUMORS

Telomere su terminalne strukture linearnih kromosoma u eukariota koji sadrže ponavljajuću sekvencu. Njihova glavna funkcija je zaštita i pružanje stabilnosti kromosomskim krajevima. U većini humanih somatskih stanica sa svakom staničnom diobom, kromosomi kontinuirano postaju kraći i stanica ulazi u proces staničnog starenja. Suprotno tomu, u tumorskim stanicama aktivan je ribonukleoproteinski enzim telomeraza koji produžuje telomere i omogućuje im daljnju proliferaciju. Kod velikog broja tumora kao što su tumor dojke, tumor pluća, neuroblastom i melanom, telomeraza je eksprimirana u gotovo 85% tumorskih stanica, stoga je glavni cilj antitumorskih terapija upravo njena inhibicija. Do sada su razvijene razne metode za supresiju telomerazne aktivnosti, ali postoji potreba daljnjeg razvoja ovih antitumorskih terapija.Telomeres are terminal structures of linear chromosomes in eukaryotes that contain a repetitive sequence. Their main function is to protect and provide stability to chromosome end regions. In most human somatic cells with each cell division, chromosomes continuosly become shorter and cells enter the cellular aging process. In contrast, tumor cells have active ribonucleoprotein enzyme telomerase which prolongs telomeres and allows them further proliferation. Enzyme telomerase is expressed in almost 85% of tumors (breast tumors, lung tumors, neuroblastoma and melanoma), so the main goal of the anticancer treatment is in its inhibition. So far, various methods have been developed to suppress telomerase activity, but there is a need for further development of these anticancer therapies

Neurotoxic Effect of Flavonol Myricetin in the Presence of Excess Copper

Oxidative stress (OS) induced by the disturbed homeostasis of metal ions is one of the pivotal factors contributing to neurodegeneration. The aim of the present study was to investigate the effects of flavonoid myricetin on copper-induced toxicity in neuroblastoma SH-SY5Y cells. As determined by the MTT method, trypan blue exclusion assay and measurement of ATP production, myricetin heightened the toxic effects of copper and exacerbated cell death. It also increased copper-induced generation of reactive oxygen species, indicating the prooxidative nature of its action. Furthermore, myricetin provoked chromatin condensation and loss of membrane integrity without caspase-3 activation, suggesting the activation of both caspase-independent programmed cell death and necrosis. At the protein level, myricetin-induced upregulation of PARP-1 and decreased expression of Bcl-2, whereas copper-induced changes in the expression of p53, p73, Bax and NME1 were not further affected by myricetin. Inhibitors of ERK1/2 and JNK kinases, protein kinase A and L-type calcium channels exacerbated the toxic effects of myricetin, indicating the involvement of intracellular signaling pathways in cell death. We also employed atomic force microscopy (AFM) to evaluate the morphological and mechanical properties of SH-SY5Y cells at the nanoscale. Consistent with the cellular and molecular methods, this biophysical approach also revealed a myricetin-induced increase in cell surface roughness and reduced elasticity. Taken together, we demonstrated the adverse effects of myricetin, pointing out that caution is required when considering powerful antioxidants for adjuvant therapy in copper-related neurodegeneration

Antioxidative and antiapoptotic effect of flavonol myricetin in cultured SH-SY5Y cells under copper-induced oxidative stress conditions

Jedan od mehanizama u podlozi nastanka neurodegenerativnih promjena je stanje oksidacijskog stresa izazvanog poremećenom homeostazom metalnih iona. Pretpostavlja se da bi antioksidansi prirodnog porijekla mogli pomoći u ublaţavanju štetnih učinaka oksidacijskog stresa, a s obzirom na svoja jaka antioksidacijska svojstva, smatra se da bi spojevi poput flavonoida mogli ostvariti neuroprotektivno djelovanje. Cilj istraţivanja bio je analizirati učinak flavonoida miricetina na stanice SH-SY5Y kod kojih je stanje oksidacijskog stresa izazvano visokim koncentracijama bakra. Miricetin je povećao toksičan učinak bakra i dodatno smanjio preţivljenje stanice SH-SY5Y. TakoĎer, potaknuo je produkciju reaktivnih kisikovih vrsta, ukazujući na svoju prooksidacijsku aktivnost u prisutnosti prijelaznog metala. Iako je miricetin potaknuo kondenzaciju kromatina i gubitak integriteta stanične membrane, aktivnost kaspaza 3 i 7 nije se povećala, što ukazuje na aktivaciju stanične smrti neovisne o kaspazama i smrt nekrozom. Osim toga, nakon tretmana bakrom i miricetina uočen je trend porasta ekspresije proteina PARP-1 i p73, dok je ekspresija TAp73 ostala nepromijenjena. Miricetin je pojačao učinak bakra na smanjenje ekspresije izoforme ΔNp73.One of the main mechanisms leading to the development of neurodegenerative diseases is oxidative stress which is induced by metal ions dyshomeostasis. It is presumed that natural antioxidants could help in reduction of harmful effects of oxidative stress, and considering their strong antioxidative properties, it is believed that compounds like flavonoids could exert neuroprotective effects. The aim of this research was to analyse the effects of flavonoid myricetin in SH-SY5Y cells under copper-induced oxidative stress. Myricetin exacerbated toxic effects of copper and further reduced viability of SH-SY5Y cells. It increased production of reactive oxygen species, thus indicating its prooxidative activity in the presence of transition metal. Although myricetin induced chromatin condensation and loss of membrane integrity, activity of caspases 3 and 7 was not increased, indicating the activation of caspase-independent cell death and death by necrosis. In addition, following exposure to copper and myricetin, a trend towards increased expression of PARP-1 and p53 proteins was observed, while expression of TAp73 remained unchanged. Myricetin potentiated the effect of copper and further reduced the expression of the ΔNp73 isoform

Antioxidative and antiapoptotic effect of flavonol myricetin in cultured SH-SY5Y cells under copper-induced oxidative stress conditions

Jedan od mehanizama u podlozi nastanka neurodegenerativnih promjena je stanje oksidacijskog stresa izazvanog poremećenom homeostazom metalnih iona. Pretpostavlja se da bi antioksidansi prirodnog porijekla mogli pomoći u ublaţavanju štetnih učinaka oksidacijskog stresa, a s obzirom na svoja jaka antioksidacijska svojstva, smatra se da bi spojevi poput flavonoida mogli ostvariti neuroprotektivno djelovanje. Cilj istraţivanja bio je analizirati učinak flavonoida miricetina na stanice SH-SY5Y kod kojih je stanje oksidacijskog stresa izazvano visokim koncentracijama bakra. Miricetin je povećao toksičan učinak bakra i dodatno smanjio preţivljenje stanice SH-SY5Y. TakoĎer, potaknuo je produkciju reaktivnih kisikovih vrsta, ukazujući na svoju prooksidacijsku aktivnost u prisutnosti prijelaznog metala. Iako je miricetin potaknuo kondenzaciju kromatina i gubitak integriteta stanične membrane, aktivnost kaspaza 3 i 7 nije se povećala, što ukazuje na aktivaciju stanične smrti neovisne o kaspazama i smrt nekrozom. Osim toga, nakon tretmana bakrom i miricetina uočen je trend porasta ekspresije proteina PARP-1 i p73, dok je ekspresija TAp73 ostala nepromijenjena. Miricetin je pojačao učinak bakra na smanjenje ekspresije izoforme ΔNp73.One of the main mechanisms leading to the development of neurodegenerative diseases is oxidative stress which is induced by metal ions dyshomeostasis. It is presumed that natural antioxidants could help in reduction of harmful effects of oxidative stress, and considering their strong antioxidative properties, it is believed that compounds like flavonoids could exert neuroprotective effects. The aim of this research was to analyse the effects of flavonoid myricetin in SH-SY5Y cells under copper-induced oxidative stress. Myricetin exacerbated toxic effects of copper and further reduced viability of SH-SY5Y cells. It increased production of reactive oxygen species, thus indicating its prooxidative activity in the presence of transition metal. Although myricetin induced chromatin condensation and loss of membrane integrity, activity of caspases 3 and 7 was not increased, indicating the activation of caspase-independent cell death and death by necrosis. In addition, following exposure to copper and myricetin, a trend towards increased expression of PARP-1 and p53 proteins was observed, while expression of TAp73 remained unchanged. Myricetin potentiated the effect of copper and further reduced the expression of the ΔNp73 isoform

Antioxidative and antiapoptotic effect of flavonol myricetin in cultured SH-SY5Y cells under copper-induced oxidative stress conditions

Jedan od mehanizama u podlozi nastanka neurodegenerativnih promjena je stanje oksidacijskog stresa izazvanog poremećenom homeostazom metalnih iona. Pretpostavlja se da bi antioksidansi prirodnog porijekla mogli pomoći u ublaţavanju štetnih učinaka oksidacijskog stresa, a s obzirom na svoja jaka antioksidacijska svojstva, smatra se da bi spojevi poput flavonoida mogli ostvariti neuroprotektivno djelovanje. Cilj istraţivanja bio je analizirati učinak flavonoida miricetina na stanice SH-SY5Y kod kojih je stanje oksidacijskog stresa izazvano visokim koncentracijama bakra. Miricetin je povećao toksičan učinak bakra i dodatno smanjio preţivljenje stanice SH-SY5Y. TakoĎer, potaknuo je produkciju reaktivnih kisikovih vrsta, ukazujući na svoju prooksidacijsku aktivnost u prisutnosti prijelaznog metala. Iako je miricetin potaknuo kondenzaciju kromatina i gubitak integriteta stanične membrane, aktivnost kaspaza 3 i 7 nije se povećala, što ukazuje na aktivaciju stanične smrti neovisne o kaspazama i smrt nekrozom. Osim toga, nakon tretmana bakrom i miricetina uočen je trend porasta ekspresije proteina PARP-1 i p73, dok je ekspresija TAp73 ostala nepromijenjena. Miricetin je pojačao učinak bakra na smanjenje ekspresije izoforme ΔNp73.One of the main mechanisms leading to the development of neurodegenerative diseases is oxidative stress which is induced by metal ions dyshomeostasis. It is presumed that natural antioxidants could help in reduction of harmful effects of oxidative stress, and considering their strong antioxidative properties, it is believed that compounds like flavonoids could exert neuroprotective effects. The aim of this research was to analyse the effects of flavonoid myricetin in SH-SY5Y cells under copper-induced oxidative stress. Myricetin exacerbated toxic effects of copper and further reduced viability of SH-SY5Y cells. It increased production of reactive oxygen species, thus indicating its prooxidative activity in the presence of transition metal. Although myricetin induced chromatin condensation and loss of membrane integrity, activity of caspases 3 and 7 was not increased, indicating the activation of caspase-independent cell death and death by necrosis. In addition, following exposure to copper and myricetin, a trend towards increased expression of PARP-1 and p53 proteins was observed, while expression of TAp73 remained unchanged. Myricetin potentiated the effect of copper and further reduced the expression of the ΔNp73 isoform