The cell nucleus is one of the most well-known, yet poorly understood cellular organelles. It was perceived as a large, disorganized, membrane-bound organelle with DNA and other molecules, wherein all "structures" are only transitory complexes that arise and disperse due to transcription, replication, and RNA processing. However, techniques like transmission electron microscopy shed light on the complexity of nuclear topography. For instance, the perichromatin region (PR) separates the interchromatin compartment from the condensed chromatin domains. The lack of steric hindrance of the PR results in majority of DNA functions to occur within, as enzymes and products freely dock at their targets. Furthermore, RNA processing and certain epigenetic modifications such as DNA and RNA methylation and demethylation may occur in the PR. Consequently,the chromatin organization is a key factor in gene expression regulation. De-regulated metal ion homeostasis is one of the causes of several human diseases, like cancer and other illnesses. Oxidative stress due to imbalance of production and exclusion of free radicals from the cell has been linked to damage to a variety of molecular species, including proteins, lipids, nucleic acids. Reactive oxygen molecules that result from oxidative respiration, Fenton reactions mediated by heavy metals, and redox-cycling processes involving environmental hazards cause damage to DNA. In addition to triggering strand breaks, base oxidation or loss, and DNA-protein crosslinks, metal-generated reactive oxygen species (ROS) can cause lipid peroxidation and protein oxidation, which can lead to abnormal cellular activity. It has been demonstrated that nickel and nickel (Ni) based compounds may cause cancer in humans. When Ni concentrations are high, nickel nanoparticles (NiNPs) can primarily induce cytotoxicity through reactive oxygen species (ROS). Potassium bromate (KBrO3) is a heavy metal and oxidizing agent that is frequently utilized in the production of food and cosmetics. KBrO3 is classified as a Group 2B carcinogen by the International Agency for Research on Cancer, indicating that it is likely carcinogenic to humans. The theory that oxidative stress plays a role in mediating bromate-induced damage is supported by the fact that numerous antioxidants have been shown to be effective in lowering the toxicity of bromate. Despite the possible implications of deepening the studies in this field, to our knowledge only a few studies have deeply investigated the effects of these two heavy metals in human cells, especially at the microscopic level. For these reasons, this work aims at investigating the effects of heavy metals, particularly potassium and nickel, on liver cells with an emphasis on morphological and microscopical alterations. Although the toxicity of heavy metals is widely recognized, little is known about the precise alterations that occur in cellular and subcellular level. Because the liver serves as a vital barrier in the human body, it is especially important to comprehend the effects of heavy metal exposure on hepatocytes. To limit toxic effects, maintain the essential protective function of the liver, and raise awareness of the wider health hazards associated with human exposure to heavy metals, this research strives to advance our understanding of this field. Our data reported significant signs of damage in cell mitochondria, as well as compaction of chromatin in cell exposed to the heavy metals. Furthermore, we observed increment of HP1α levels after potassium exposure. Considering increasing concerns about occupational and environmental exposure to heavy metals, this project has the potential to provide insightful information on the microscopic modifications that occur by elucidating the morphological subtleties of hepatocytes exposed to heavy metals. This information may hopefully help guide public health policies and initiatives.
Il nucleo è uno degli organelli più studiati, tuttavia restano ancora molti aspetti che devono ancora essere investigati. Inizialmente percepito come una miscela disorganizzata di DNA e altre molecole, con "strutture" solo transitorie che sorgono e si disperdono per le operazioni di trascrizione e replicazione, varie tecniche, come la microscopia elettronica a trasmissione, hanno dimostrato un complesso livello di regolazione topografica del nucleo. Ad esempio, la regione pericromatinica (PR) separa il compartimento intercromatinico dai più condensati domini cromatinici. La PR non è caratterizzata dallo stesso ingombro sterico della cromatina condensata, quindi è sede di molte funzioni in cui sono coinvolti DNA ed RNA, e di modificazioni epigenetiche come metilazione e demetilazione, dal momento che i complessi enzimatici possono interagire più facilmente con i loro substrati. Di conseguenza, il livello di organizzazione della cromatina riveste un ruolo centrale nella regolazione dell’espressione genica. La de-regolazione dei livelli di ioni metallici è una delle cause della mancata omeostasi cellulare, con conseguenze patologiche che comprendono il cancro e altre malattie. Lo stress ossidativo, risultante da uno squilibrio tra la produzione di radicali liberi e il sistema di difesa antiossidante di una cellula, può essere causato dalla respirazione ossidativa, da reazioni mediate da metalli pesanti e dai processi di redox, e possono causare danni al DNA, perossidazione lipidica e ossidazione proteica, comportando una proliferazione cellulare non controllata. È stato evidenziato come metalli quali il nichel e i suoi composti possano causare il cancro nell'uomo. In condizioni di elevate concentrazioni di nichel, le nanoparticelle di nichel inducono principalmente citotossicità attraverso le specie reattive dell'ossigeno. Il bromato di potassio (KBrO3) è un metallo pesante e un agente ossidante spesso utilizzato nella produzione di cibi e cosmetici. Il KBrO3 è classificato come un carcinogeno di Gruppo 2B dall'Agenzia Internazionale per la Ricerca sul Cancro, risultando quindi una sostanza “probabilmente cancerogena per l'uomo”. L’idea che lo stress ossidativo giochi un ruolo nella mediazione dei danni indotti dal bromato è supportata dal fatto che numerosi antiossidanti si sono dimostrati efficaci nel ridurne la tossicità. Nonostante le possibili implicazioni, risultano alla nostra attenzione ancora pochi studi che abbiano indagato gli effetti di questi due metalli pesanti su cellule umane, specialmente a livello microscopico. Per tali motivi, questo studio si propone di investigare gli effetti dei metalli pesanti, in particolare del potassio e del nichel, sulle cellule epatiche con un'enfasi sulle alterazioni morfologiche: dato che il fegato svolge una funzione di barriera nel corpo umano, è particolarmente importante comprendere gli effetti dei metalli pesanti. I dati da noi raccolti evidenziano danni ai mitocondri e riorganizzazione della cromatina, nonché un aumento dei livelli di HP1α. Considerando le preoccupazioni riguardo all'esposizione umana ai metalli pesanti, questo progetto ha il potenziale per fornire informazioni a supporto delle conoscenze attualmente disponibili.
Studio dell'effetto dei metalli pesanti: analisi sulla vulnerabilità degli epatociti
SARKAR, MEGHMA
2022/2023
Abstract
The cell nucleus is one of the most well-known, yet poorly understood cellular organelles. It was perceived as a large, disorganized, membrane-bound organelle with DNA and other molecules, wherein all "structures" are only transitory complexes that arise and disperse due to transcription, replication, and RNA processing. However, techniques like transmission electron microscopy shed light on the complexity of nuclear topography. For instance, the perichromatin region (PR) separates the interchromatin compartment from the condensed chromatin domains. The lack of steric hindrance of the PR results in majority of DNA functions to occur within, as enzymes and products freely dock at their targets. Furthermore, RNA processing and certain epigenetic modifications such as DNA and RNA methylation and demethylation may occur in the PR. Consequently,the chromatin organization is a key factor in gene expression regulation. De-regulated metal ion homeostasis is one of the causes of several human diseases, like cancer and other illnesses. Oxidative stress due to imbalance of production and exclusion of free radicals from the cell has been linked to damage to a variety of molecular species, including proteins, lipids, nucleic acids. Reactive oxygen molecules that result from oxidative respiration, Fenton reactions mediated by heavy metals, and redox-cycling processes involving environmental hazards cause damage to DNA. In addition to triggering strand breaks, base oxidation or loss, and DNA-protein crosslinks, metal-generated reactive oxygen species (ROS) can cause lipid peroxidation and protein oxidation, which can lead to abnormal cellular activity. It has been demonstrated that nickel and nickel (Ni) based compounds may cause cancer in humans. When Ni concentrations are high, nickel nanoparticles (NiNPs) can primarily induce cytotoxicity through reactive oxygen species (ROS). Potassium bromate (KBrO3) is a heavy metal and oxidizing agent that is frequently utilized in the production of food and cosmetics. KBrO3 is classified as a Group 2B carcinogen by the International Agency for Research on Cancer, indicating that it is likely carcinogenic to humans. The theory that oxidative stress plays a role in mediating bromate-induced damage is supported by the fact that numerous antioxidants have been shown to be effective in lowering the toxicity of bromate. Despite the possible implications of deepening the studies in this field, to our knowledge only a few studies have deeply investigated the effects of these two heavy metals in human cells, especially at the microscopic level. For these reasons, this work aims at investigating the effects of heavy metals, particularly potassium and nickel, on liver cells with an emphasis on morphological and microscopical alterations. Although the toxicity of heavy metals is widely recognized, little is known about the precise alterations that occur in cellular and subcellular level. Because the liver serves as a vital barrier in the human body, it is especially important to comprehend the effects of heavy metal exposure on hepatocytes. To limit toxic effects, maintain the essential protective function of the liver, and raise awareness of the wider health hazards associated with human exposure to heavy metals, this research strives to advance our understanding of this field. Our data reported significant signs of damage in cell mitochondria, as well as compaction of chromatin in cell exposed to the heavy metals. Furthermore, we observed increment of HP1α levels after potassium exposure. Considering increasing concerns about occupational and environmental exposure to heavy metals, this project has the potential to provide insightful information on the microscopic modifications that occur by elucidating the morphological subtleties of hepatocytes exposed to heavy metals. This information may hopefully help guide public health policies and initiatives.È consentito all'utente scaricare e condividere i documenti disponibili a testo pieno in UNITESI UNIPV nel rispetto della licenza Creative Commons del tipo CC BY NC ND.
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https://hdl.handle.net/20.500.14239/16801