Apoptotic and bioenergetic changes in pancreatic cells after exposure to individual toxicants and their mixtures

Pancreatic cancer has one of the worst fatality rates in oncology. Despite advances in treatment and recovery rates for other cancers, pancreatic cancer's lack of early symptomology culminates in a dismal five-year survival rate of 3-9% that has remained unchanged for decades. Cadmium has been implicated in the initiation of pancreatic cancer. Its prevalence in the environment make it a candidate for interactions with pesticides that have gone relatively unexplored. In this study, we examined the role of cadmium, pesticides, and their mixtures on the p53 apoptotic pathway and in the adaptive bioenergetics that foretell transition to a cancer state. We used 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) to establish a No Observable Adverse Effect Limit (NOAEL) which allowed us to identify sub-toxic chronic exposure concentrations to emulate realistic combination exposures for molecular evaluation of biological endpoints. These concentrations were used to examine p53 recruitment and downstream apoptotic markers phosphatidylserine (PS) and caspase 3/7 activity. Bioenergetic shifts were assessed by mitochondrial toxicity assays in the presence of glucose or galactose and evaluated in conjunction with mitochondrial membrane potential (MMP), oxygen consumption rates, and reactive oxygen species (ROS) production. Non-linear regression analysis led to the employment of 500nM Cd and 1uM Atrazine and Glyphosate test concentrations. Cadmium drove p53 response in HPNE cells while glyphosate and both mixtures increased p53 expression in tumor cells. Interestingly, only cadmium exhibited increased PS by annexin labeling, but mixtures showed significantly less PS, indicating a potential reinforcement of membrane integrity. No treatment groups in either cell line responded to treatment by increases in caspase activity. Taken together, we can surmise that the p53 apoptotic pathway is not initiated by exposure to these toxicants. Although ROS production was elevated in all groups and glutathione response was unaffected, it is unlikely the mild increase is responsible for differences in mitochondrial health. Summation of mitochondrial health using ATP production with cell membrane analysis is the lone parameter where mixtures behaved differently from their parts. Both mixtures distinctly presented as mitochondrial toxins and remodeled metabolism in a manner similar to that found in tumorigenic cells, indicating a potential pathway to carcinogenicity

Cadmium Exposure as a Putative Risk Factor for the Development of Pancreatic Cancer: Three Different Lines of Evidence

Although profoundly studied, etiology of pancreatic cancer (PC) is still rather scant. Exposure to cadmium (Cd), a ubiquitous metal associated with well-established toxic and carcinogenic properties, has been hypothesized to one putative cause of PC. Hence, we analyzed recently published observational studies, meta-analyses, and experimental animal and in vitro studies with the aim of summarizing the evidence of Cd involvement in PC development and describing the possible mechanisms. Consolidation of epidemiological data on PC and exposure to Cd indicated a significant association with an elevated risk of PC among general population exposed to Cd. Cadmium exposure of laboratory animals was showed to cause PC supporting the findings suggested by human studies. The concordance with human and animal studies is buttressed by in vitro studies, although in vitro data interpretation is problematic. In most instances, only significant effects are reported, and the concentrations of Cd are excessive, which would skew interpretation. Previous reports suggest that oxidative stress, apoptotic changes, and DNA cross-linking and hypermethylation are involved in Cd-mediated carcinogenesis. Undoubtedly, a significant amount of work is still needed to achieve a better understanding of the Cd involvement in pancreatic cancer which could facilitate prevention, diagnosis, and therapy of this fatal disease

Potential interaction of cadmium chloride with pancreatic mitochondria: Implications for pancreatic cancer

Pancreatic cancer (PC) is insidious with a high mortality rate due to the lack of symptomology prior to diagnosis. Mitochondrial involvement in PC development is becoming accepted, and exposure to cadmium (Cd) is suspected of being a risk factor for the development of PC; however, the mechanisms involved remain unclear. In this study, we examined the role of Cd as a mitochondrial toxicant and whether alterations in mitochondrial function may be an underlying cause for the development of PC. In this study, cadmium chloride (CdCl2)-mediated toxicity in hTERT-HPNE and AsPC-1 pancreatic cell lines was determined by MTT assay. We also investigated the release of LDH and the generation of free radicals. Mitochondrial toxicity assays were performed in media containing glucose (25 mM) or galactose (10 mM) and following exposure to CdCl2 (0-100 M) followed by MTT assay. For the confirmation of mitochondrial toxicity, we measured the release of ATP following exposure to CdCl2. Initial experiments confirmed that exposure to CdCl2 did not reduce the viability of either cell line until a concentration of >10 M was used. Non-linear analysis of the response curves revealed lethal concentration 50% (LC50) values for CdCl2 in the HPNE cells of 77 M compared to 42 M in the AsPC-1 cells (P lt 0.01). The CdCl2-mediated mitochondrial toxic effects were greater in the HPNE cells, suggesting a heightened sensitivity to the effects of CdCl2, not due to elevated oxidative stress. Increased mitochondrial toxic sensitivity was indicated by a 73.4% reduction in IC50 values in the HPNE cells cultured in galactose compared to culture in glucose media, whereas the AsPC-1 cells exhibited a 58.8% reduction in IC50 values. In addition, the higher concentration of CdCl2 elicited a significant cell-dependent effect on ATP release in both cell lines, suggestive of CdCl2 being a mitochondrial toxicant. Cell survival was unaffected following exposure to low concentrations of CdCl2; however, exposure did alter mitochondrial function (control cells > tumor cells). Therefore, the findings of this study indicate that the mitochondria may be a site of action for cadmium in promoting tumor development

Overview of Cadmium Thyroid Disrupting Effects and Mechanisms

Humans are exposed to a significant number of chemicals that are suspected to produce disturbances in hormone homeostasis. Hence, in recent decades, there has been a growing interest in endocrine disruptive chemicals. One of the alleged thyroid disrupting substances is cadmium (Cd), a ubiquitous toxic metal shown to act as a thyroid disruptor and carcinogen in both animals and humans. Multiple PubMed searches with core keywords were performed to identify and evaluate appropriate studies which revealed literature suggesting evidence for the link between exposure to Cd and histological and metabolic changes in the thyroid gland. Furthermore, Cd influence on thyroid homeostasis at the peripheral level has also been hypothesized. Both in vivo and in vitro studies revealed that a Cd exposure at environmentally relevant concentrations results in biphasic Cd dose-thyroid response relationships. Development of thyroid tumors following exposure to Cd has been studied mainly using in vitro methodologies. In the thyroid, Cd has been shown to activate or stimulate the activity of various factors, leading to increased cell proliferation and a reduction in normal apoptotic activity. Evidence establishing the association between Cd and thyroid disruption remains ambiguous, with further studies needed to elucidate the issue and improve our understanding of Cd-mediated effects on the thyroid gland

Environmental cadmium exposure and pancreatic cancer: Evidence from case control, animal and in vitro studies

Although profoundly studied, etiology of pancreatic cancer (PC) is still rather scarce. Some of established risk factors of PC are connected to an increased cadmium (Cd) body burden. Hence, the aim of this study was to investigate the role of this environmental pollutant in PC development by conducting human observational, experimental and in vitro studies. The case-control study included 31 patients with a histologically based diagnosis of exocrine PC subjected to radical surgical intervention as cases and 29 accidental fatalities or subjects who died of a nonmalignant illness as controls. Animal study included two treated groups of Wistar rats (15 and 30 mg Cd/kg b.w) and untreated control group, sacrificed 24 h after single oral exposure. In in vitro study pancreas hTERT-HPNE and AsPC-1 cells were exposed to different Cd concentrations corresponding to levels measured in human cancerous pancreatic tissue. Cd content in cancer tissue significantly differed from the content in healthy controls. Odds ratio levels for PC development were 2.79 (95% CI 0.91-8.50) and 3.44 (95% CI 1.19-9.95) in the third and fourth quartiles of Cd distribution, respectively. Animal study confirmed Cd deposition in pancreatic tissue. In vitro studies revealed that Cd produces disturbances in intrinsic pathway of apoptotic activity and the elevation in oxidative stress in pancreatic cells. This study presents three different lines of evidence pointing towards Cd as an agent responsible for the development of PC

Analysis of Outcomes in Ischemic vs Nonischemic Cardiomyopathy in Patients With Atrial Fibrillation A Report From the GARFIELD-AF Registry

IMPORTANCE Congestive heart failure (CHF) is commonly associated with nonvalvular atrial fibrillation (AF), and their combination may affect treatment strategies and outcomes