Peroxiredoxin 1 promotes proliferation and inhibits differentiation of MC3T3-E1 cells via AKT1 / NF-κB signaling pathway

OBJECTIVES

Osteoporosis is the most common metabolic bone disease worldwide. The decrease in bone mass is primarily accompanied by a decrease in the number and activity of osteoblasts. Peroxiredoxins (PRDXs) are proteins that detect extremely low peroxide levels and act as sensors that regulate oxidation signals, thereby regulating various cellular functions. This study aimed to evaluate the effects of PRDX1 and estrogen on the biological behavior of osteoblasts, including their proliferation and differentiation.

METHODS

Ovariectomized (OVX) mice were used to establish a model of osteoporosis and perform morphological and immunohistochemical analyses. Prdx1 gene knockout and overexpression were performed in mouse MC3T3-E1 pre-osteoblasts to assess proliferation and osteogenic differentiation using the cell counting kit-8, quantitative reverse transcription polymerase chain reaction, western blotting (WB), Alizarin Red S staining, etc. RESULTS: The OVX mice exhibited osteoporosis and PRDX1 expression increased. In vitro experiments showed that during the osteogenic differentiation of osteoblasts, PRDX1 expression decreased, while the expression of COL1 and RUNX2 increased. After Prdx1 knockout, the proliferation of osteoblasts decreased; expression of Runx2, ALP, and COL1 increased; and mineralization increased. However, after Prdx1 overexpression, osteoblast proliferation was enhanced, whereas osteogenic differentiation and mineralization were inhibited. Estrogen inhibits the H2O2-induced decrease in osteoblastic differentiation and increase in PRDX1 expression. WB revealed that when LY294002 inhibited the AKT signaling pathway, the levels of p-AKT1, p-P65, and PRDX1 protein in MC3T3-E1 cells decreased. However, when pyrrolidine dithiocarbamate (PDTC) inhibited the NF-κB signaling pathway, the expression of p-AKT1 and PRDX1 did not change except for a significant reduction of p-P65 expression. Furthermore, PDTC reversed the decreased expression of RUNX2, ALP, and COL1 caused by PRDX1 overexpression.

CONCLUSIONS

PRDX1 promotes the proliferation of osteoblasts and inhibits osteogenic differentiation. Estrogen regulated osteoblastic differentiation by affecting the expression of PRDX1 in osteoblasts, and the effect is related to the AKT1/NF-κB signaling pathway.

The Role of the Thioredoxin System in Brain Diseases

The thioredoxin system, consisting of thioredoxin (Trx), thioredoxin reductase (TrxR), and NADPH, plays a fundamental role in the control of antioxidant defenses, cell proliferation, redox states, and apoptosis. Aberrations in the Trx system may lead to increased oxidative stress toxicity and neurodegenerative processes. This study reviews the role of the Trx system in the pathophysiology and treatment of Alzheimer's, Parkinson's and Huntington's diseases, brain stroke, and multiple sclerosis. Trx system plays an important role in the pathophysiology of those disorders via multiple interactions through oxidative stress, apoptotic, neuro-immune, and pro-survival pathways. Multiple aberrations in Trx and TrxR systems related to other redox systems and their multiple reciprocal relationships with the neurodegenerative, neuro-inflammatory, and neuro-oxidative pathways are here analyzed. Genetic and environmental factors (nutrition, metals, and toxins) may impact the function of the Trx system, thereby contributing to neuropsychiatric disease. Aberrations in the Trx and TrxR systems could be a promising drug target to prevent and treat neurodegenerative, neuro-inflammatory, neuro-oxidative stress processes, and related brain disorders.

Peroxiredoxin I deficiency increases pancreatic β‑cell apoptosis after streptozotocin stimulation via the AKT/GSK3β signaling pathway

Apoptosis of pancreatic β-cells is involved in the pathogenesis of type I and II diabetes. Peroxiredoxin I (Prx I) serves an important role in regulating cellular apoptosis; however, the role of Prx I in pancreatic β-cell apoptosis is not completely understood. In the present study, the role of peroxiredoxin 1 (Prx I) during streptozotocin (STZ)-induced apoptosis of pancreatic β-cells was investigated. The expression level of Prx I was decreased by STZ treatment in a time-dependent manner, and apoptosis of Prx I knockdown MIN6 cells was increased by STZ stimulation, compared with untransduced MIN6 cells. Furthermore, an intraperitoneal injection of STZ increased pancreatic islet damage in Prx I knockout mice, compared with wild-type and Prx II knockout mice. AKT and glycogen synthase kinase (GSK)-3β phosphorylation significantly decreased following Prx I knockdown in MIN6 cells. However, phosphorylated β-catenin and p65 levels significantly increased after STZ stimulation, compared with untransduced cells. The results of the present study indicate that deletion of Prx I mediated STZ-induced pancreatic β-cell death in vivo and in vitro by regulating the AKT/GSK-3β/β-catenin signaling pathway, as well as NF-κB signaling. These findings provide a theoretical basis for treatment of pancreatic damage.

Stearate-Induced Apoptosis in Human Pancreatic β-Cells is Associated with Changes in Membrane Protein Expression and These Changes are Inhibited by Oleate

PURPOSE

Lipotoxicity is implicated in type 2 diabetes pathogenesis. Its molecular mechanisms are not completely understood. The aim of this study is to identify new suspect proteins involved in pancreatic β-cell death induction by saturated fatty acids and its inhibition by unsaturated fatty acids.

EXPERIMENTAL DESIGN

Employing 2DE analysis and subsequent western blot confirmation, the differences in membrane/membrane-associated protein expression in human β-cell line NES2Y are assessed during cell death induction by stearate and its inhibition by oleate.

RESULTS

Induction of apoptosis by stearate is associated with significantly increased levels of Hsp90β, peroxiredoxin-1, and 14-3-3γ in the membrane fraction of NES2Y cells and significantly decreased levels of annexin A2, annexin A4, and reticulocalbin-2. All these changes are significantly inhibited by oleate co-application. No expression changes are detected after application of stearate together with oleate. Furthermore, the expression of reticulocalbin-2 is significantly decreased after stearate application also in the whole cell lysate.

CONCLUSIONS AND CLINICAL RELEVANCE

Several membrane-associated proteins that could be related to pro- and anti-apoptotic signaling initiated by fatty acids in human pancreatic β-cells are identified. As far as we know, annexin A4, reticulocalbin-2, and 14-3-3γ represent novel molecules related to the effect of fatty acids on β-cell viability.

Oleate protects beta-cells from the toxic effect of palmitate by activating pro-survival pathways of the ER stress response

Long-term exposure of beta cells to saturated fatty acids impairs insulin secretion and increases apoptosis. In contrast, unsaturated fatty acids protect beta-cells from the long-term negative effects of saturated fatty acids. We aimed to identify the mechanisms underlying this protective action of unsaturated fatty acids. To address the aim, insulin-secreting MIN6 cells were exposed to palmitate in the absence or presence of oleate and analyzed by using nano-LC MS/MS based proteomic approach. Important findings were validated by using alternative approaches. Proteomic analysis identified 34 proteins differentially expressed in the presence of palmitate compared to control samples. These proteins play a role in insulin processing, mitochondrial function, metabolism of biomolecules, calcium homeostasis, exocytosis, receptor signaling, ER protein folding, antioxidant activity and anti-apoptotic function. When oleate was also present during culture, expression of 15 proteins was different from the expression in the presence of palmitate alone. Most of the proteins affected by oleate are targets of the ER stress response and play a pro-survival role in beta cells such as protein folding and antioxidative defence. We conclude that restoration of pro-survival pathways of the ER stress response is a major mechanism underlying the protective effect of unsaturated fatty acids in beta-cells treated with saturated fatty acids.

Peroxiredoxin 1 has an anti-apoptotic role via apoptosis signal-regulating kinase 1 and p38 activation in mouse models with oral precancerous lesions

Peroxiredoxin 1 (Prx1) is important in the protection of cells from oxidative damage and the regulation of cell proliferation and apoptosis. Prx1 is overexpressed in oral precancerous lesions of oral leukoplakia (OLK) and oral cancer; however, the association between Prx1 expression and OLK pathogenesis remains unknown. The present study investigated the role of Prx1 and its molecular mechanisms in oxidative stress-induced apoptosis during the pathogenesis of OLK. Wild-type and Prx1 knockout mice were treated with 50 µg/ml 4-nitroquinoline-1-oxide (4NQO) or 4NQO + H₂O₂ for 16 weeks to establish mouse models with tongue precancerous lesions. Apoptotic cells were detected using terminal deoxynucleotidyl transferase dUTP nick-end labeling assay. The expression of Prx1, apoptosis signal-regulating kinase 1 (ASK1), phosphor-ASK1, p38 and phosphor-p38 was analyzed using immunohistochemical staining, and their mRNA expression levels were evaluated by reverse transcription quantitative polymerase chain reaction. The present results demonstrated that 4NQO or 4NQO + H₂O₂ induced the development of tongue precancerous lesions in Prx1 knockout and wild-type mice. Prx1 was overexpressed in tongue precancerous lesions compared with normal tongue mucosa. There was a significant decrease in the degree of moderate or severe epithelial dysplasia, and mild epithelial dysplasia was clearly elevated, in Prx1 knockout mice treated with 4NQO + H₂O₂ compared with wild-type mice treated with 4NQO + H₂O₂. Prx1 suppressed apoptosis and upregulated phosphor-ASK1 and phosphor-p38 expression in tongue precancerous lesions. The present results suggest that Prx1 suppresses oxidative stress-induced apoptosis via the ASK1/p38 signalling pathway in mouse tongue precancerous lesions. In conclusion, Prx1 and H₂O₂ have a coordination role in promoting the progression of tongue precancerous mucosa lesions. The present findings provide novel insight into Prx1 function and the mechanisms of Prx1 in OLK pathogenesis.