Induction of a senescent like phenotype and loss of gap junctional intercellular communication by carbon nanoparticle exposure of lung epithelial cells

Analysis of the function and therapeutic strategy of connexin 43 from its subcellular localization

Connexins (Cxs) are a family of transmembrane proteins located in the plasma membrane of human cells, among which connexin 43 (Cx43) is abundantly expressed in various types of human cells. Cx43, encoded by the gap junction protein alpha 1 (GJA1) gene, assembles into a hexameric structure in the Golgi apparatus and translocates to the plasma membrane to form hemichannels (Hcs), which pair with those of the cells in contact with each other and form gap junction intercellular communication (GJIC). The role of Cx43 as a connexin localized at the plasma membrane to perform channel functions is well recognized in previous studies, but recent studies have found that it can also be localized in the nucleus, mitochondria, or present in extracellular vesicles (EVs) and tunneling nanotubes (TNTs). Cx43 in the nucleus is involved in gene transcription regulation, cytoskeleton formation, cell migration and adhesion. Cx43 in mitochondria is involved in mitochondrial respiration-related functions, and Cx43 in extracellular vesicles and tunneling nanotubes is involved in distant cellular information exchange. It is because of the diverse distribution of subcellular localization of Cx43 that it is possible to explore the corresponding functions by analyzing its localization. In this review, we summarize the important roles of Cx43 in disease development from the perspective of subcellular localization, and provide new ideas for Cx43 as a therapeutic target and the search for related pathological mechanisms.

Effects of nanomaterial exposure on telomere dysfunction, hallmarks of mammalian and zebrafish cell senescence, and zebrafish mortality

Environmental and occupational exposure to hazardous substances accelerates biological aging. However, the toxic effects of nanomaterials on telomere and cellular senescence (major hallmarks of the biological aging) remained controversial. This study was to synthesize all published evidence to explore the effects of nanomaterial exposure on the telomere change, cellular senescence and mortality of model animals. Thirty-five studies were included by searching electronic databases (PubMed, Embase and Web of Science). The pooled analysis by Stata 15.0 software showed that compared with the control, nanomaterial exposure could significantly shorten the telomere length [measured as kbp: standardized mean difference (SMD) = -1.88; 95% confidence interval (CI) = -3.13 - - 0.64; % of control: SMD = -1.26; 95%CI = -2.11- - 0.42; < 3 kbp %: SMD = 5.76; 95%CI = 2.92 - 8.60), increase the telomerase activity (SMD = -1.00; 95%CI = -1.74 to -0.26), senescence-associated β-galactosidase levels in cells (SMD = 8.20; 95%CI = 6.05 - 10.34) and zebrafish embryos (SMD = 7.32; 95%CI = 4.70 - 9.94) as well as the mortality of zebrafish (SMD = 3.83; 95%CI = 2.94 - 4.72)]. The expression levels of telomerase TERT, shelterin components (TRF1, TRF2 and POT1) and senescence biomarkers (p21, p16) were respectively identified to be decreased or increased in subgroup analyses. In conclusion, this meta-analysis demonstrates that nanomaterial exposure is associated with telomere attrition, cell senescence and organismal death.

Targeting gap junctional intercellular communication by hepatocarcinogenic compounds

Gap junctions in liver, as in other organs, play a critical role in tissue homeostasis. Inherently, these cellular constituents are major targets for systemic toxicity and diseases, including cancer. This review provides an overview of chemicals that compromise liver gap junctions, in particular biological toxins, organic solvents, pesticides, pharmaceuticals, peroxides, metals and phthalates. The focus in this review is placed upon the mechanistic scenarios that underlie these adverse effects. Further, the potential use of gap junctional activity as an in vitro biomarker to identify non-genotoxic hepatocarcinogenic chemicals is discussed.