Autophagy is a tightly regulated catabolic mechanism that degrades proteins and organelles. Autophagy mediates programmed cell death under certain conditions. To determine the role of autophagy in T cells, we examined, in mouse CD4+ T cells, conditions under which autophagy is induced and alterations of the cell fate when autophagy is blocked. We have found that resting naive CD4+ T cells do not contain detectable autophagosomes. Autophagy can be observed in activated CD4+ T cells upon TCR stimulation, cytokine culturing, and prolonged serum starvation. Induction of autophagy in T cells requires JNK and the class III PI3K. Autophagy is inhibited by caspases and mammalian target of rapamycin in T cells. Interestingly, more Th2 cells than Th1 cells undergo autophagy. Th2 cells become more resistant to growth factor-withdrawal cell death when autophagy is blocked using either chemical inhibitors 3-methyladenine, or by RNA interference knockdown of beclin 1 and Atg7. Therefore, autophagy is an important mechanism that controls homeostasis of CD4+ T cells.

The growth arrest and DNA damage-inducible 45␤ (GADD45␤) gene product has been implicated in the stress response, cell cycle arrest, and apoptosis. Here we demonstrated the unexpected expression of GADD45␤ in the embryonic growth plate and uncovered its novel role as an essential mediator of matrix metalloproteinase-13 (MMP-13) expression during terminal chondrocyte differentiation. We identified GADD45␤ as a prominent early response gene induced by bone morphogenetic protein-2 (BMP-2) through a Smad1/Runx2-dependent pathway. Because this pathway is involved in skeletal development, we examined mouse embryonic growth plates, and we observed expression of Gadd45␤ mRNA coincident with Runx2 protein in pre-hypertrophic chondrocytes, whereas GADD45␤ protein was localized prominently in the nucleus in late stage hypertrophic chondrocytes where Mmp-13 mRNA was expressed. In Gadd45␤ ؊/؊ mouse embryos, defective mineralization and decreased bone growth accompanied deficient Mmp-13 and Col10a1 gene expression in the hypertrophic zone. Transduction of small interfering RNA-GADD45␤ in epiphyseal chondrocytes in vitro blocked terminal differentiation and the associated expression of Mmp-13 and Col10a1 mRNA in vitro. Finally, GADD45␤ stimulated MMP-13 promoter activity in chondrocytes through the JNK-mediated phosphorylation of JunD, partnered with Fra2, in synergy with Runx2. These observations indicated that GADD45␤ plays an essential role during chondrocyte terminal differentiation.Growth arrest and DNA damage-inducible (GADD) 4 45␤ is a member of the GADD45 family of small (18 kDa) proteins, also including GADD45␣ and GADD45␥. The GADD45 family is known to be associated with cell growth control, apoptotic cell death, and the cellular response to DNA damage (1, 2). Initially, GADD45␤, encoded by MyD118, was identified as a myeloid differentiation primary response gene activated by IL-6 in murine myeloid leukemia cells upon induction of terminal differentiation (1, 3). More recently, GADD45␤, which is induced by TGF-␤ in a SMAD-dependent manner, has been identified as a positive regulator of TGF-␤-induced apoptosis (4). Although GADD45␣ has been identified on DNA microarrays as prominently expressed genes in chondrocytes from adult articular cartilage and in chondrosarcoma or immortalized chondrocyte cell lines (5, 6), a role for GADD45 family members, including GADD45␤, during cartilage development has not been reported previously.Formation of the vertebrate skeleton through endochondrial ossification, involving progressive differentiation of proliferating chondrocytes to growth-arrested hypertrophic cells, is one of the most complex processes in biology. In the embryonic or postnatal growth plate, terminal chondrocyte differentiation occurs during conversion of cartilage to a vascularized tissue that supports matrix remodeling, cartilage calcification, and recruitment of osteogenic precursors. Cascades of growth and differentiation factors act through positive and negative signaling kinases and transcription factors to t...

Mononuclear phagocyte recognition of apoptotic cells triggering suppressive cytokine signaling is a key event in inflammation resolution from injury. Mice deficient in thrombospondin-1 (thbs1−/−), an extracellular matrix glycoprotein that bridges cell-cell interactions, are prone to LPS-induced lung injury and show defective macrophage IL-10 production during the resolution phase of inflammation. Reconstitution of IL-10 rescues thbs1−/− mice from persistent neutrophilic lung inflammation and injury and thbs1−/− alveolar macrophages show defective IL-10 production following intratracheal instillation of apoptotic neutrophils despite intact efferocytosis. Following co-culture with apoptotic neutrophils, thbs1−/− macrophages show a selective defect in IL-10 production whereas PGE2 and TGF-β1 responses remain intact. Full macrophage IL-10 responses require the engagement of thrombospondin-1 structural repeat 2 domain and the macrophage scavenger receptor CD36 LIMP-II Emp sequence homology (CLESH) domain in vitro. Although TSP-1 is not essential for macrophage engulfment of apoptotic neutrophils in vivo, TSP-1 aids in the curtailment of inflammatory responses during the resolution phase of injury in the lungs by providing a means by which apoptotic cells are recognized and trigger optimal IL-10 production by macrophages.

Our aim is to investigate the cytobiological effects of autologous platelet-rich fibrin (PRF) on dental pulp stem cells (DPSCs) and to explore the ectopic and orthotopic possibilities of dental pulp revascularization and pulp-dentin complex regeneration along the root canal cavities of the tooth by using a novel tissue-engineered transplant composed of cell-sheet fragments of DPSCs and PRF granules. Canine DPSCs were isolated and characterized by assaying their colony-forming ability and by determining their cell surface markers and osteogenic/adipogenic differentiation potential. The biological effects of autologous PRF on DPSCs, including cell proliferation, alkaline phosphatase (ALP) activity and odonto-/osteogenic gene expression, were then investigated and quantified. A novel transplant consisting of cell-sheet fragments of DPSCs and PRF granules was adopted to regenerate pulp-dentin-like tissues in the root canal, both subcutaneously in nude mice and in the roots of canines. PRF promoted the proliferation of DPSCs in a dose- and time-dependent manner and induced the differentiation of DPSCs to odonto-/osteoblastic fates by increasing the expression of the Alp, Dspp, Dmp1 and Bsp genes. Transplantation of the DPSC/PRF construct led both to a favorable regeneration of homogeneous and compact pulp-like tissues with abundantly distributed blood capillaries and to the deposition of regenerated dentin along the intracanal walls at 8 weeks post-operation. Thus, the application of DPSC/PRF tissue constructs might serve as a potential therapy in regenerative endodontics for pulp revitalization or revascularization.

Silybin was effective in preventing the MCD-induced increases in hepatic steatosis, fibrosis and inflammation. The effect was related to alteration of lipid metabolism-related gene expression, activation of the Nrf2 pathway and inhibition of the NF-κB signaling pathway in the NASH liver.