Increased Mitochondrial Fragmentation Mediated by Dynamin-Related Protein 1 Contributes to Hexavalent Chromium-Induced Mitochondrial Respiratory Chain Complex I-Dependent Cytotoxicity

Targeted Redox Balancing through Pulmonary Nanomedicine Delivery Reverses Oxidative Stress Induced Lung Inflammation

Non-invasive delivery of drugs is important for the reversal of respiratory diseases essentially by-passing metabolic pathways and targeting large surface area of drug absorption. Here, we study the inhalation of a redox nano medicine namely citrate functionalized Mn3O4 (C-Mn3O4) duly encapsulated in droplet evaporated aerosols for the balancing of oxidative stress generated by the exposure of Chromium (VI) ion, a potential lung carcinogenic agent. Our optical spectroscopic in-vitro experiments demonstrates the efficacy of redox balancing of the encapsulated nanoparticles (NP) for the maintenance of a homeostatic condition. The formation of Cr-NP complex as an excretion of the heavy metal is also demonstrated through optical spectroscopic and high resolution transmission optical microscopy (HRTEM). Our studies confirm the oxidative stress mitigation activity of the Cr-NP complex. A detailed immunological assay followed by histopathological studies and assessment of mitochondrial parameters in pre-clinical mice model with chromium (Cr) induced lung inflammation establishes the mechanism of drug action to be redox-buffering. Thus, localised delivery of C-Mn3O4 NPs in the respiratory tract via aerosols can act as an effective nanotherapeutic agent against oxidative stress induced lung inflammation.

Chronic low-dose chromium VI exposure induces oxidative stress and apoptosis with altered expressions of DNA repair genes and promoter hypermethylation in the liver of Swiss albino mice

The present investigation dealt with harmful effects of hexavalent chromium (Cr [VI]) on liver of Swiss albino mice. This variant exhibited cytotoxicity, mutagenicity, and carcinogenicity. Our study focused on elucidating the hepatotoxic effects of chronic low-dose exposure to Cr (VI) (2, 5, and 10 ppm) administered via drinking water for 4 and 8 months. The observed elevation in SGPT, ALP, and SGOT and increased oxidative stress markers unequivocally confirmed the severe disruption of liver homeostasis at these low treatment doses. Noteworthy alterations in histoarchitecture, body weight, and water intake provided further evidences of the harmful effects of Cr (VI). Production of reactive oxygen species (ROS) during metabolism led to DNA damages. Immunohistochemistry and qRT-PCR analyses revealed that chronic low-dose exposure of Cr (VI) induced apoptosis in liver tissue. Our study exhibited alterations in the expression pattern of DNA repair genes (Rad51, Mutyh, Mlh1, and Ogg1), coupled with promoter hypermethylation of Mutyh and Rad51, leading to transcriptional inhibition. Our findings underscored the potential of low-dose Cr (VI) exposure on hepatotoxicity by the intricate interplay between apoptosis induction and epigenetic alterations of DNA repair genes.

Effects of hexavalent chromium on mitochondria and their implications in carcinogenesis

Hexavalent chromium (Cr(VI)) is a well-known occupational and environmental human carcinogen. The cellular effect of Cr(VI) is complex and often nonspecific due to its ability to modulate multiple cellular targets. The toxicity of Cr(VI) is strongly linked to the generation of reactive oxygen species (ROS) during its reduction process. ROS can cause oxidation of cellular macromolecules, such as proteins, lipids, and DNA, thereby altering their functions. A major genotoxic effect of Cr(VI) that contributes to carcinogenesis is the formation of DNA adducts, which can lead to DNA damage. Modulations of cellular signaling pathways and epigenetics may also contribute to the carcinogenic effects of Cr(VI). Cr(VI) has a major impact on many aspects of mitochondrial biology, including oxidative phosphorylation, mitophagy, and mitochondrial biogenesis. These effects have the potential to alter the trajectory of Cr(VI)-induced carcinogenic process. This perspective article summarizes current understandings of the effect of Cr(VI) on mitochondria and discusses the future directions of research in this area, particularly with regard to carcinogenesis.

Toxic and carcinogenic effects of hexavalent chromium in mammalian cells in vivo and in vitro: a recent update

Chromium VI (Cr (VI)) can cross cell membranes readily and causes the formation of Cr-DNA adducts, genomic damages, elevation of reactive oxygen species (ROS) and alteration of survival signaling pathways, as evidenced by the modulation in p53 signaling pathway. Mammals, including humans are exposed to Cr, including Cr (VI), frequently through inhalation, drinking water, and food. Several studies demonstrated that Cr (VI) induces cellular death through apoptosis and autophagy, genotoxicity, functional alteration of mitochondria, endocrine and reproductive impairments. In the present review, studies on deleterious effects of Cr (VI) exposure to mammalian cells (in vivo and in vitro) have been documented. Special attention is paid to the underlying molecular mechanism of Cr (VI) toxicity.