Per- and polyfluoroalkyl substances (PFAS) are a group of chemicals containing stable per- or polyfluoroalkyl groups. Recent epidemiological studies have shown that PFAS cause health risks even at low concentrations. This review outlines the toxicokinetics, exposure and health risks of PFAS, with a focus on perfluorooctane sulfonic acid (PFOS), perfluorooctanoic acid (PFOA), and long-chain perfluoroalkyl carboxylic acids (LC-PFCAs). These compounds are known to interact with various proteins in vivo, including the peroxisomal proliferator-activated receptor-α (PPARα). PFOA and PFOS have been identified as carcinogenic. It is known that PFOA and PFOS are transported by transporters such as organic anion transporter. Significant species differences in the behavior of these compounds exist, with much longer half-lives in humans than in mice and rats. One of the reasons that the half-lives of PFOA and PFOS are long in humans is that their renal clearance is low in humans. For animal toxicity experiments, it is essential that the doses in animal experiments are converted to equivalent doses in humans using pharmacokinetic models. Compared with PFOA, some LC-PFCAs have longer half-lives and accumulate more in the liver. Although tap water is a source of exposure to PFAS, the most common exposure source is food, with seafood being an important source for exposure to PFAS in Japan. PFOS and PFOA concentrations in human blood in Japan have been decreasing in recent years. However, according to clinical guidance published in 2022 by the United States National Academies, most Japanese residents are still in the medium risk group (PFAS concentration in plasma or serum is greater than 2 ng/mL and less than 20 ng/mL) or above. Further research is needed to help reduce exposure, and further risk assessments are required.

Hypoxia induces the expression of nuclear factor kappa B (NF-kappa-B). NF-kappa-B functions by forming dimers from five main subunits: p65 (RelA), RelB, p52, p50, and c-Rel. In the classical pathway, NF-kappa-B activity is regulated by the degradation-inducing factor I kappa B kinase (IKK). IKK is composed of an α/β isomer and essential modulator NEMO (γ) subunits in the classical pathway, which may be the major pathway for NF-kappa-B signaling. In the present study, we focused on factor-inhibiting HIF-1 (FIH-1) and Prolyl hydroxylase domain enzyme (PHD), which have been identified as oxygen concentration-dependent regulators of HIF-1α. PHD has three isoforms: PHD1, PHD2, and PHD3, which have different affinities towards HIF-1α. We examined the interactions between IKKα/β and PHD1-3 by immunoprecipitation. PHDs efficiently interacted with IKKα/β. Furthermore, the overexpression of PHDs decreased the mRNA level of IL-1β, a downstream factor of NF-kappa-B activated by LPS. The overexpression of PHD1 and PHD2 markedly reduced IKKα/β protein levels; however, the effects of PHD3 were weaker than those of PHD1 and PHD2. Mutants of the active sites of PHD1 and PHD2 did not decrease IKKα/β protein levels, and a mutation in the active site of PHD3 did not affect IKKα/β protein levels. We also attempted to investigate the interactions of FIH-1 with IKKα/β and IκBα by immunoprecipitation, but found none. Moreover, IKKα/β and p65 protein levels were not affected by the overexpression of FIH-1. Collectively, these results suggest that PHDs directly regulated IKK protein levels, while FIH-1 did not affect the NF-kappa-B classical pathway.

Prolongation of QRS duration (prolonged QRS) is associated with severe outcomes in non-tricyclic antidepressant poisoning. However, factors other than xenobiotics affecting QRS duration have not yet been investigated. Hence, this study aimed to identify factors contributing to prolonged QRS. This study was a single-center retrospective case control study. Patients who had overdosed on drugs or orally ingested xenobiotics that they would not normally ingest orally were included in the study. Patients were divided into two groups: prolonged QRS and normal QRS. Subsequently, these groups were compared. We performed a logistic regression analysis with the factors extracted by comparison as explanatory variables and prolonged QRS as the objective variable. In total, 108 patients were analyzed; 19 belonged to the prolonged QRS group. In the prolonged QRS group, factors such as male sex, low level of potassium, and xenobiotic ingestion resulted in prolonged QRS. In a logistic regression analysis, significant differences were observed in terms of male sex (odds ratio [OR], 27.00; 95% confidence interval [CI], 5.93-123.00; p<0.001), xenobiotics ingested that resulted in prolonged QRS (OR, 8.55; 95% CI, 1.84-39.70; p<0.001), and potassium levels (OR, 0.15; 95% CI, 0.03-0.88; p=0.035). Ingestion of sodium channel blockers, male sex, and low level of potassium may contribute to prolonged QRS.

In a 3-month repeated oral dose toxicity study of DS-1971a, a selective inhibitor of the Nav1.7 voltage-gated sodium channel, fatty change of hepatocytes was observed only in male rats at doses of 100 mg/kg and above. However, this change was not observed in female rats even at the highest dose of 1500 mg/kg. Furthermore, fatty change was not observed in mice and monkeys administered the highest dose of 1000 mg/kg for 6 and 9 months, respectively. To further investigate species differences of this fatty change, lipid accumulation was evaluated by staining with the LipidTOX dye in primary cultured hepatocytes derived from male and female rats, male monkeys, and male and female humans. After exposure to DS-1971a for 72 hr, the staining showed an increase in intensity specifically in male rat-derived hepatocytes in a concentration-dependent manner. Metabolomic analysis using rat-derived primary cultured hepatocytes exposed to DS-1971a for 24 and 72 hr revealed that phospholipids, not neutral lipids like triacylglycerols, and adenosine were elevated in the male-derived hepatocytes. These results suggest that the elevation of phospholipids and adenosine in the hepatocytes may contribute to the specific fatty change observed in male rats.

Cholestatic drug-induced liver injury (DILI) is caused by the aberrant excretion of bile acids (BAs) from hepatocytes via bile canaliculus-like structures (BCLSs) into the bile ducts. The precise in vitro evaluation method for cholestatic DILI has not been established due to a lack of specific markers and cell resources. We previously reported that HepG2-NIAS cells cultured on a collagen vitrigel (CV) membrane formed BCLSs with high protein expression of transporters involved in the excretion of BAs, including bile salt export pump (BSEP). In this study, the potential of connexin (Cx) 32, a component of gap junction, as a predictive marker for cholestatic DILI was investigated using a CV-culture model of HepG2-NIAS cells. The cells were treated with 7 drugs with different DILI-risk levels, and cell toxicity and Cx32 expression were evaluated. Cell toxicity was significantly increased not only by high DILI-risk drugs (troglitazone and cyclosporine A) but also by chlorpromazine with low DILI-risk. Furthermore, cell toxicity of troglitazone was not enhanced by a co-treatment with taurocholate, suggesting the low involvement of inhibition of BA excretion via BSEP in cholestatic DILI. In contrast, the total protein expression of Cx32 and co-localization of Cx32 and F-actin, which is composed of BCLSs, were significantly increased only by high DILI-risk drugs. Treatment with high DILI-risk drugs also induced the increased protein expression of zonula occludens (ZO)-1, which supports BCLSs concerted with Cx32. These results suggest that Cx32 expression in the CV-culture model of HepG2-NIAS cells may be a prominent predictive marker for cholestatic DILI.

Exposure to fine particulate matter (PM_2.5) has been epidemiologically reported to worsen the prognosis of ischemic stroke; however, the details have not been investigated. One of the major toxic mechanisms of PM_2.5 inhalation is oxidative stress, which is mediated by reactive oxygen species generated by PM_2.5 components such as metals and polycyclic aromatic hydrocarbons. In this study, we examined the effects of long-term exposure to urban particulate matter, focusing on oxidative stress, on prognosis after ischemic stroke in mice. When mice were intranasally exposed for 28 days to an urban aerosol collected in Beijing, China (CRM28), microglial activation was observed in the cerebral cortex, indicating that CRM28 induced neuroinflammation. CRM28 exposure resulted in increased serum levels of brain natriuretic peptide and troponin I, suggesting that cardiac injury was elicited by CRM28. Lung inflammation was also observed following CRM28 exposure; however, systemic inflammation was not detected. Mice exposed to CRM28 showed an exacerbation of mortality after ischemic stroke induction compared with vehicle mice. A vitamin E-rich diet suppressed CRM28-induced lipid peroxidation in the heart and lungs but not in the brain. A vitamin E-rich diet also attenuated cardiac injury and lung inflammation induced by CRM28 exposure, whereas neuroinflammation was not affected. Mortality after ischemic stroke improved with the administration of a vitamin E-rich diet. Considering that systemic inflammation did not occur, cardiac injury induced by oxidative stress under exposure to urban particulate matter may be involved in increased mortality after ischemic stroke. Antioxidation under air pollution is fundamental for protection against ischemic stroke.