AP-1 activation attenuates the arsenite-induced apoptotic response in human bronchial epithelial cells by up-regulating HO-1 expression

Pathways involved in pony body size development

BACKGROUND

The mechanism of body growth in mammals is poorly understood. Here, we investigated the regulatory networks involved in body growth through transcriptomic analysis of pituitary and epiphyseal tissues of smaller sized Debao ponies and Mongolian horses at the juvenile and adult stages.

RESULTS

We found that growth hormone receptor (GHR) was expressed at low levels in long bones, although growth hormone (GH) was highly expressed in Debao ponies compared with Mongolian horses. Moreover, significant downregulated of the GHR pathway components m-RAS and ATF3 was found in juvenile ponies, which slowed the proliferation of bone osteocytes. However, WNT2 and PLCβ2 were obviously upregulated in juvenile Debao ponies, which led to premature mineralization of the bone extracellular matrix. Furthermore, we found that the WNT/Ca²⁺ pathway may be responsible for regulating body growth. GHR was demonstrated by q-PCR and Western blot analyses to be expressed at low levels in long bones of Debao ponies. Treatment with WNT antagonistI decreased the expression of WNT pathway components (P < 0.05) in vitro. Transduction of ATDC5 cells with a GHR-RNAi lentiviral vector decreased the expression of the GHR pathway components (P < 0.05). Additionally, the expression of the IGF-1 gene in the liver was lower in Debao ponies than in Mongolian horses at the juvenile and adult stages. Detection of plasma hormone concentrations showed that Debao ponies expressed higher levels of IGF-1 as juveniles and higher levels of GH as adults than Mongolian horses, indicating that the hormone regulation in Debao ponies differs from that in Mongolian horses.

CONCLUSION

Our work provides insights into the genetic regulation of short stature growth in mammals and can provide useful information for the development of therapeutic strategies for small size.

Club Cell Heme Oxygenase-1 Deletion: Effects in Hyperoxia-Exposed Adult Mice

Thioredoxin reductase-1 (TXNRD1) inhibition activates nuclear factor (erythroid-derived 2)-like 2 (Nrf2) responses and prevents acute lung injury (ALI). Heme oxygenase-1 (HO-1) induction following TXNRD1 inhibition is Nrf2-dependent in airway epithelial (club) cells in vitro. The influence of club cell HO-1 on lung development and lung injury responses is poorly understood. The present studies characterized the effects of hyperoxia on club cell-specific HO-1 knockout (KO) mice. These mice were generated by crossing Hmox1 flox mice with transgenic mice expressing cre recombinase under control of the club cell-specific Scgb1a1 promoter. Baseline analyses of lung architecture and function performed in age-matched adult wild-type and KO mice indicated an increased alveolar size and airway resistance in HO-1 KO mice. In subsequent experiments, adult wild-type and HO-1 KO mice were either continuously exposed to >95% hyperoxia or room air for 72 h or exposed to >95 hyperoxia for 48 h followed by recovery in room air for 48 h. Injury was quantitatively assessed by calculating right lung/body weight ratios (g/kg). Analyses indicated an independent effect of hyperoxia but not genotype on right lung/body weight ratios in both wild-type and HO-1 KO mice. The magnitude of increases in right lung/body weight ratios was similar in mice of both genotypes. In the recovery model, an independent effect of hyperoxia but not genotype was also detected. In contrast to the continuous exposure model, right lung/body weight ratio mice were significantly elevated in HO-1 KO but not wild-type mice. Though club cell HO-1 does not alter hyperoxic sensitivity in adult mice, it significantly influences lung development and resolution of lung injury following acute hyperoxic exposure.

Role of mitochondrial DNA in oxidative damage induced by sodium arsenite in human bronchial epithelial cells

Long-term exposure to sodium arsenite was found to induce malignant transformation in human bronchial epithelial (HBE) cell line as evidenced by elevated ROS levels. Although chronic sodium arsenite-induced HBE cell line transformation was associated with elevated ROS generation, it was of interest to determine whether acute sodium arsenite exposure also initiated pulmonary damage. Thus, the aim of this study was to investigate oxidative-stress-related pulmonary damage using a human bronchial epithelial (HBE) cell line. Incubation of ρ⁺-HBE (in the presence of mitochondrial DNA) cells with various concentrations of sodium arsenite, significantly increased ROS and MDA levels accompanied by decreased SOD activity in a concentration-dependent manner. In contrast, treatment of ρ^-HBE (without mitochondrial DNA) cells various concentrations of sodium arsenite a reduction in ROS and MDA levels were noted. However, the SOD activity remained decreased in ρ^-HBE cells. This was accompanied by a significant rise in HO-1 protein expressions levels in both cell types with greater changes ρ^-HBE cells at the lower sodium arsenite concentrations. Data indicate that acute sodium arsenite exposure exerted a greater effect ρ^-HBE cells suggesting that absence of mitochondrial DNA appears to enhance sensitivity to the oxidant actions of inorganic As.

The thioredoxin reductase inhibitor auranofin induces heme oxygenase-1 in lung epithelial cells via Nrf2-dependent mechanisms

Thioredoxin reductase-1 (TXNRD1) inhibition effectively activates nuclear factor (erythroid-derived 2)-like 2 (Nrf2) responses and attenuates lung injury in acute respiratory distress syndrome (ARDS) and bronchopulmonary dysplasia (BPD) models. Upon TXNRD1 inhibition, heme oxygenase-1 (HO-1) is disproportionally increased compared with Nrf2 target NADPH quinone oxidoreductase-1 (Nqo1). HO-1 has been investigated as a potential therapeutic target in both ARDS and BPD. TXNRD1 is predominantly expressed in airway epithelial cells; however, the mechanism of HO-1 induction by TXNRD1 inhibitors is unknown. We tested the hypothesis that TXNRD1 inhibition induces HO-1 via Nrf2-dependent mechanisms. Wild-type (WT), Nrf2KO1.3, and Nrf2KO2.2 cells were morphologically indistinguishable, indicating that Nrf2 can be deleted from murine-transformed club cells (mtCCs) using CRISPR/Cas9 gene editing. Hemin, a Nrf2-independent HO-1-inducing agent, significantly increased HO-1 expression in WT, Nrf2KO1.3, and Nrf2KO2.2. Auranofin (AFN) (0.5 µM) inhibited TXNRD1 activity by 50% and increased Nqo1 and Hmox1 mRNA levels by 6- and 24-fold, respectively, in WT cells. Despite similar levels of TXNRD1 inhibition, Nqo1 mRNA levels were not different between control and AFN-treated Nrf2KO1.3 and Nrf2KO2.2. AFN slightly increased Hmox1 mRNA levels in Nrf2KO1.3 and Nrf2KO2.2 cells compared with controls. AFN failed to increase HO-1 protein in Nrf2KO1.3 and Nrf2KO2.2 compared with a 36-fold increase in WT mtCCs. Our data indicate that Nrf2 is the primary mechanism by which TXNRD1 inhibitors increase HO-1 in lung epithelia. Future studies will use ARDS and BPD models to define the role of HO-1 in attenuation of lung injury by TXNRD1 inhibitors.

A systematic review and meta-analysis of bidirectional effect of arsenic on ERK signaling pathway

Arsenic is a toxic metal, which ultimately leads to cell apoptosis. ERK is considered a key transcriptional regulator of arsenic‑induced apoptosis. Due to a few controversial issues about arsenic‑mediated extracellular signal‑regulated MAP kinases (ERK) signaling, a meta‑analysis was performed. Subgroup analyses demonstrated that high doses (≥2 µmol/l) of arsenic increased the expression of Ras, ERK, ERK1, ERK2, phosphorylated (p)‑ERK, p‑ERK1, and p‑ERK2, while low doses (<2 µmol/l) decreased the expression of Ras, ERK1, p‑ERK, and p‑ERK2 when compared to control groups. Long term exposure (>24 h) to arsenic led to inhibition of expression of ERK1, p‑ERK1, and p‑ERK2, whereas short‑term exposure (≤24 h) triggered the expression of ERK1, ERK2, p‑ERK, p‑ERK1, and p‑ERK2. Furthermore, normal cells exposed to arsenic exhibited higher production levels of Ras and p‑ERK. Conversely, exposure of cancer cells to arsenic showed a lower level of production of Ras and p‑ERK as well as higher level of p‑ERK1 and p‑ERK2 as compared to control group. Short‑term exposure of normal cells to high doses of arsenic may promote ERK signaling pathway. In contrast, long‑term exposure of cancer cells to low doses of arsenic may inhibit ERK signaling pathway. This study may be helpful in providing a theoretical basis for the diverging result of arsenic adverse effects on one hand and therapeutic mechanisms on the other concerning arsenic‑induced apoptosis.

Geniposide improves insulin production and reduces apoptosis in high glucose-induced glucotoxic insulinoma cells

Our previous work revealed that in the pancreatic β cell line, geniposide modulated ATP production and glucose-stimulated insulin secretion (GSIS) induced by the acute stimulation of high glucose concentration. However, the effects of geniposide on functional impairment and the mass of β-cells exposed to elevated levels of glucose remains unknown. In the present study, impaired GSIS and restrained proliferation were observed in the prolonged culture of insulinoma INS-1 cells with 33mM of glucose (high glucose). Our results indicate that the glucose-induced impairment of insulin release was significantly reverted by the inclusion of 1 or 10μM of geniposide. Moreover, induction of the phosphorylation of AMP-activated protein kinase (AMPK) was observed, which promoted the utilization of nutrient stores for energy production. AMPK phosphorylation was enhanced by an increased number of INS-1 cells, and the increased expression of AMPK downstream target heme oxygenase 1 (HO-1), under high glucose concentration. Furthermore, geniposide protected rat insulinoma cells from apoptosis in high-glucose concentrations. We have shown that these effects were associated with an increased apoptosis-related Bcl-2/BAX protein ratio. In conclusion, geniposide dose dependently improves β-cell function and increases the proliferation of β-cells exposed to prolonged hyperglycemia.