Hydrogen peroxide-induced cellular apoptosis is mediated by TGF-beta2 signaling pathway in cultured human lens epithelial cells

Relationship between expression levels of TDRD7 and CRYBB3 and development of age-related cortico-nuclear cataracts

Background

The human lens develops age-related cataracts (ARCs) because of the complicated effects of aging and stressful conditions. Under conditions involving oxidative stress, cells form stress granules (SGs). TDRD7 has been identified as an RNA granule component and an important component of SGs. TDRD7 plays a role in the post-transcriptional expression of genes, such as the crystallin gene CRYBB3. Therefore, the present study investigated TDRD7 and CRYBB3 mRNA expressions in relation to age-related cortico-nuclear cataracts.

Methods

Quantitative real-time PCR was used to determine the expression levels of TDRD7 and CRYBB3 in 52 patients with ARC and 52 healthy controls. Anterior lens capsules and peripheral blood samples from patients with ARC were included in the patient group, and peripheral blood samples from healthy subjects and human lens epithelial cells (HLE-B3) were included in the control group. Gene expression levels in the different age groups were compared. Correlation analysis was used to assess the gene expression levels and age.

Results

The expression of TDRD7 and CRYBB3 was significantly up-regulated (P < 0.0001) in anterior lens capsules compared to that in HLE-B3 cells. Similarly, the expression of TDRD7 (P = 0.0004) and CRYBB3 (P < 0.0001) was higher in the peripheral blood samples of patients with ARC than in those of healthy subjects. Significant upregulation (P < 0.05) was observed in the 71–81-year age group of patients. No correlation was found between gene expression levels and age.

Conclusion

Significantly higher expression levels of TDRD7 and CRYBB3 in patients with ARC than in controls suggest that TDRD7 and CRYBB3 are associated with the development of age-related cortico-nuclear cataracts and the aging process under chronic stress.

The role of TGF-β2 in cartilage development and diseases

Transforming growth factor-beta2 (TGF-β2) is recognized as a versatile cytokine that plays a vital role in regulation of joint development, homeostasis, and diseases, but its role as a biological mechanism is understood far less than that of its counterpart, TGF-β1. Cartilage as a load-resisting structure in vertebrates however displays a fragile performance when any tissue disturbance occurs, due to its lack of blood vessels, nerves, and lymphatics. Recent reports have indicated that TGF-β2 is involved in the physiological processes of chondrocytes such as proliferation, differentiation, migration, and apoptosis, and the pathological progress of cartilage such as osteoarthritis (OA) and rheumatoid arthritis (RA). TGF-β2 also shows its potent capacity in the repair of cartilage defects by recruiting autologous mesenchymal stem cells and promoting secretion of other growth factor clusters. In addition, some pioneering studies have already considered it as a potential target in the treatment of OA and RA. This article aims to summarize the current progress of TGF-β2 in cartilage development and diseases, which might provide new cues for remodelling of cartilage defect and intervention of cartilage diseases.

All-trans-retinoic acid inhibits mink hair follicle growth via inhibiting proliferation and inducing apoptosis of dermal papilla cells through TGF-β2/Smad2/3 pathway

Dermal papilla cells (DPCs), an important component of hair follicles, its proliferation and apoptosis directly regulate and maintain the growth of hair follicles. All-trans-retinoic acid (ATRA) plays a critical role in hair growth. In this study, the effects of ATRA on cultured mink hair follicle growth were studied by administration of different concentrations of ATRA for 12 days in vitro. In addition, the proliferation and apoptosis of DPCs were measured after treating with ATRA. The mRNA and protein levels of hair follicle growth associated factor transforming growth factor-β2 (TGF-β2) and the phosphorylation levels of Smad2/3 were determined. Moreover, TGF-β type I and type II receptor inhibitor LY2109761 and specific inhibitor of Smad3 (SIS3) were administered to investigate the underlying molecular mechanism. The results showed that ATRA inhibited hair follicle growth, promoted TGF-β2 expression and activated phosphorylation of Smad2/3. In addition, ATRA inhibited cell proliferation by arresting the cell cycle at G1 phase and induced apoptosis of DPCs by enhancing the ratio of Bax/Bcl-2 and promoted the cleavage of caspase-3. Furthermore, LY2109761 or SIS3 partially reversed the decreased cell viability, increased apoptosis that were induced by ATRA. In conclusion, ATRA could inhibit hair follicle growth via inhibiting proliferation and inducing apoptosis of DPCs partially through the TGF-β2/Smad2/3 pathway.

Sumoylation of SMAD 4 ameliorates the oxidative stress-induced apoptosis in osteoblasts

Oxidative stress-induced mitochondrial function and cell apoptosis to osteoblasts, plays a critical role in the pathophysiology of osteoporosis. However, mechanisms underlying such process remain not yet clear. We aims in this study to investigate a possible role of SMAD (the mothers against decapentaplegic homolog 4 (SMAD4) in the oxidative stress-induced apoptosis, in homo sapiens osteoblast hFOB1.19 cells. Results demonstrated that the treatment with more than 100μM H₂O₂ significantly downregulated the cellular viability, whereas markedly induced apoptosis in hFOB1.19 cells. The SMAD4 was markedly reduced in both mRNA and protein levels in the H₂O₂ -treated hFOB1.19 cells, along with the reduction of Small ubiquitin-related modifier 1 (SUMO 1) and SUMO 2/3. The immunoprecipitation assay confirmed indicated the interaction between SUMO 1 (or SUMO 2/3) and SMAD4. Moreover, the SMAD4 overexpression markedly ameliorated the H₂O₂-resulted viability reduction and apoptosis induction in hFOB1.19 cells. Interestingly, such amelioration was blocked by the knockdown of SUMO 2/3. Taken together, we conclued that SMAD4 inhibits the H₂O₂-induced apoptosis in osteoblast hFOB1.19 cells; such inhibition might depend on the SUMOylation by SUMO 2/3. It implies a promising role of SMAD4 in oxidative stress-promoted damage to osteoblasts.