Stem cells and inflammation in the intestine

Current Status and Challenges of Stem Cell Treatment for Alzheimer's Disease

Neurodegenerative diseases called tauopathies, such as Alzheimer's disease (AD), frontotemporal dementia, progressive supranuclear palsy, and Parkinson's disease, among others, are characterized by the pathological processing and accumulation of tau protein. AD is the most prevalent neurodegenerative disease and is characterized by two lesions: neurofibrillary tangles (NFTs) and neuritic plaques. The presence of NFTs in the hippocampus and neocortex in early and advanced stages, respectively, correlates with the patient's cognitive deterioration. So far, no drugs can prevent, decrease, or limit neuronal death due to abnormal pathological tau accumulation. Among potential non-pharmacological treatments, physical exercise has been shown to stimulate the development of stem cells (SCs) and may be useful in early stages. However, this does not prevent neuronal death from the massive accumulation of NFTs. In recent years, SCs therapies have emerged as a promising tool to repopulate areas involved in cognition in neurodegenerative diseases. Unfortunately, protocols for SCs therapy are still being developed and the mechanism of action of such therapy remains unclear. In this review, we show the advances and limitations of SCs therapy. Finally, we provide a critical analysis of its clinical use for AD.

p53 dependent LGR5 inhibition and caspase 3 activation are critically involved in apoptotic effect of compound K and its combination therapy potential in HCT116 cells

Though ginsenoside metabolite compound K was known to have antitumor effect in several cancers, its underlying apoptotic mechanism still remains unclear so far. Thus, in the present study, the apoptotic mechanism of compound K was explored in colorectal cancer cells (CRCs) in association with leucine rich repeat containing G protein-coupled receptor 5 (LGR5) that was overexpressed in colorectal cancers with poor survival rate. Here compound K significantly reduced viability of HCT116^p53+/+ cells better than that of HCT116^p53-/- cells. Consistently, compound K increased sub G1 population and attenuated the expression of LGR5, c-Myc, procaspase3, Pin1 in HCT116^p53+/+ cells more than in HCT116^p53-/- cells. Conversely, caspase 3 inhibitor Z-DEVD-FMK reversed inhibitory effect of compound K on LGR5, c-Myc and procaspase3 in HCT116 cells. Consistently, inhibition of LGR5 using transfection method enhanced suppression of pro-PARP, Bcl-x_L c-Myc, Snail and Pin1 in compound K treated HCT116^p53+/+ cells. Furthermore, compound K synergistically potentiated antitumor effect of 5-fluorouracil (5-FU) or Doxorubicin to reduce the survival genes and cytotoxicity in HCT116^p53+/+ cells. Overall, our findings provide scientific insight that compound K induces apoptosis in colon cancer cells via caspase and p53 dependent LGR5 inhibition with combination therapy potential with 5-FU or doxorubicin.

Refining the role for adult stem cells as cancer cells of origin

Significant progress has been made to identify the cells at the foundation of tumorigenesis, the cancer cell of origin (CCO). The majority of data points towards resident adult stem cells (ASCs) or primitive progenitors as the CCO for those cancers studied, highlighting the importance of stem cells not only as propagators but also as initiators of cancer. Recent data suggest tumor initiation at the CCOs can be regulated through both intrinsic and extrinsic signals and that the identity of the CCOs and their propensity to initiate tumorigenesis is context dependent. In this review, we summarize some of the recent findings regarding CCOs and solid tumor initiation and highlight its relation with bona fide human cancer.

Antioxidant properties of mesalamine in colitis inhibit phosphoinositide 3-kinase signaling in progenitor cells

BACKGROUND

Mesalamine, 5-aminosalicylic acid (5-ASA), is a potent antioxidant and is known to enhance peroxisome proliferator-activated receptor γ activity in the intestine. Our previous studies suggested reduced Phosphoinositide 3-Kinase (PI3K)/β-catenin signaling as a mechanism for 5-ASA chemoprevention in chronic ulcerative colitis (CUC). We now hypothesize that 5-ASA mediates changes in intestinal epithelial cell (IEC) reactive oxygen species during colitis to affect phosphatase and tensin homolog (PTEN), PI3K, and β-catenin signaling.

METHODS

Here, we examined effects of 5-ASA on oxidant-induced cell signaling pathways in HT-29 cells, IECs from mice, and biopsy tissue from control and CUC patients. Samples were selected to control for inflammation between untreated and 5-ASA-treated CUC patients.

RESULTS

Direct evaluation of IEC in H2O2-stimulated whole colonic crypts indicated that 5-ASA reduces reactive oxygen species levels in lower crypt IECs where long-lived progenitor cells reside. Analysis of biopsies from patient samples revealed that 5-ASA increases expression of the antioxidant catalase in CUC patients. Also, 5-ASA increased nuclear peroxisome proliferator-activated receptor γ protein and target gene expression. Data showed 5-ASA-induced peroxisome proliferator-activated receptor γ DNA binding to the PTEN promoter (chromatin immunoprecipitation) and reduced both phosphorylated and oxidized (inactive) PTEN protein levels. Analysis of patient samples revealed 5-ASA that also reduced levels of active phosphorylated Akt in inflamed colitis tissue. Reduced PI3K/Akt signaling and expression of β-catenin target genes in 5-ASA-treated CUC patients additionally suggests enhanced PTEN activity as well.

CONCLUSIONS

Therefore, 5-ASA reduces CUC-induced reactive oxygen species in colonic progenitor cells and enhances PTEN activity, thus attenuating PI3K/Akt signaling. These data suggest that the antioxidant properties of 5-ASA may be the predominant mechanism for 5-ASA chemoprevention.

The benefits and risks of stem cell technology

The potential impact of stem cell technology on medical and dental practice is vast. Stem cell research will not only provide the foundation for future therapies, but also reveal unique insights into basic disease mechanisms. Therefore, an understanding of stem cell technology will be necessary for clinicians in the future. Herein, we give a basic overview of stem cell biology and therapeutics for the practicing clinician.