mTOR inhibition prevents epithelial stem cell senescence and protects from radiation-induced mucositis

The integrity of the epidermis and mucosal epithelia is highly dependent on resident self-renewing stem cells, which makes them vulnerable to physical and chemical insults compromising the repopulating capacity of the epithelial stem cell compartment. This is frequently the case in cancer patients receiving radiation or chemotherapy, many of whom develop mucositis, a debilitating condition involving painful and deep mucosal ulcerations. Here, we show that inhibiting the mammalian target of rapamycin (mTOR) with rapamycin increases the clonogenic capacity of primary human oral keratinocytes and their resident self-renewing cells by preventing stem cell senescence. This protective effect of rapamycin is mediated by the increase in expression of mitochondrial superoxide dismutase (MnSOD), and the consequent inhibition of ROS formation and oxidative stress. mTOR inhibition also protects from the loss of proliferative basal epithelial stem cells upon ionizing radiation in vivo, thereby preserving the integrity of the oral mucosa and protecting from radiation-induced mucositis.

Biomarkers of chemotherapy-induced diarrhoea: a clinical study of intestinal microbiome alterations, inflammation and circulating matrix metalloproteinases

PURPOSE

A common side effect of chemotherapy treatment is diarrhoea. Unfortunately, the underlying mechanisms of chemotherapy-induced diarrhoea (CD) are poorly understood. We aimed to determine if faecal microbes of CD patients were displaced, if faecal calprotectin increased during CD and if there were alterations in circulating matrix metalloproteinases, nuclear factor kappa B (NF-κB), IL-1β and TNF.

PATIENTS AND METHODS

Twenty-six cancer patients receiving chemotherapy were enrolled and requested to provide stool samples and blood samples at various times during their chemotherapy cycle. Stool samples were analysed using conventional culture techniques and qRT-PCR. ELISA kits determined faecal calprotectin levels, levels of circulating matrix metalloproteinases and circulating NF-κB, IL-1β and TNF.

RESULTS

The majority of patients with CD showed decreases in Lactobacillus spp., Bifidobacterium spp., Bacteroides spp. and Enterococcus spp. Increases were observed in Escherichia coli and Staphylococcus spp. Methanogenic archaea were also quantified, with all patients except one showing a decrease. Faecal calprotectin levels were increased in 81.25 % of patients with CD. Circulating MMP-3 and MMP-9 significantly increased following chemotherapy. Circulating levels of NF-κB, IL-1β and TNF were increased following chemotherapy, although this did not reach significance.

CONCLUSIONS

We demonstrated that CD is associated with marked changes in intestinal microflora, methanogenic archaea, matrix metalloproteinase and serum levels of NF-κB, IL-1β and TNF. These changes may result in diminished bacterial functions within the gut, altering gut function and initiating intestinal damage, resulting in the onset of diarrhoea. More importantly, these changes may provide clinicians with a possible new target for biomarkers of toxicity.

A novel animal model to investigate fractionated radiotherapy-induced alimentary mucositis: the role of apoptosis, p53, nuclear factor-kappaB, COX-1, and COX-2

Radiation-induced mucositis is a common and serious side effect of radiotherapy. Molecular mechanisms of mucosal injury, however, are still poorly understood and extremely difficult to study in humans. A novel Dark Agouti rat model using fractionated radiotherapy to induce mucositis has been developed to investigate the occurrence of alimentary mucosal injury. Twenty-four Dark Agouti rats were randomly assigned to receive either fractionated radiotherapy or no radiotherapy. The irradiated rats received a fractionated course of abdominal radiotherapy at 45 Gy/18 fractions/6 weeks treating thrice weekly (i.e., at a radiation dose of 2.5 Gy per fraction). After each week of radiation, a group of irradiated rats was killed. Histomorphology and mucin distribution in the alimentary tract was investigated. The terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling assay was used to examine apoptosis in the colon and jejunum, and intestinal morphometry was used to assess villus length, crypt length, and mitotic crypt count. Immunohistochemistry of p53, nuclear factor-kappaB, cyclooxygenase (COX)-1, and COX-2 was also done. The fractionated radiotherapy course induced alimentary mucositis from week 1, with more severe injury seen in the small intestine. The hallmark appearance of apoptosis was present in the crypts of the small and large intestine. In the jejunum and colon, goblet cell disorganization and degeneration was obvious and crypt mitotic counts were severely depleted throughout the treatment. Expression of p53, nuclear factor-kappaB, COX-1, and COX-2 was increased in the irradiated intestinal sections. Fractionated radiation-induced alimentary mucositis has been effectively documented in the Dark Agouti rat for the first time. Further studies investigating the molecular mechanisms underlying radiation-induced mucositis are planned to ultimately achieve anti-mucotoxic-targeted therapies.

Grape seed extract dose-responsively decreases disease severity in a rat model of mucositis; concomitantly enhancing chemotherapeutic effectiveness in colon cancer cells

OBJECTIVE

Mucositis is a serious disorder of the gastrointestinal tract that results from cancer chemotherapy. We investigated the effects of increasing grape seed extract doses on the severity of chemotherapy in a rat model and its coincident impact on chemotherapeutic effectiveness in colon cancer cells.

DESIGN

Female Dark Agouti rats were gavaged with grape seed extract (400-1000 mg/kg) or water (day 3-11) and were injected intraperitoneally with 5-Fluorouracil (150 mg/kg) or saline (control) on day 9 to induce mucositis. Daily metabolic data were collected and rats were sacrificed on day 12. Intestinal tissues were collected for histological and myeloperoxidase analyses. Caco-2 cell viability was examined in response to grape seed extract in combination with 5-Fluorouracil by 3-(4,5-Dimethylthiazol-2yl)-2,5-diphenyl-tetrazolium bromide) assay.

RESULTS

Compared with 5-Fluorouracil controls, grape seed extract (400-1000 mg/kg) significantly decreased the histological damage score (P<0.05) in the jejunum. Grape seed extract (1000 mg/kg) increased jejunal crypt depth by 25% (P<0.05) in 5-Fluorouracil treated rats compared to 5-Fluorouracil controls, and attenuated the 5-Fluorouracil -induced reduction of mucosal thickness (25%, P<0.05). Grape seed extract (600 mg/kg) decreased myeloperoxidase activity by 55% (P<0.01) compared to 5-Fluorouracil controls. Grape seed extract was more effective at ameliorating 5-Fluorouracil induced intestinal injury, with effects most pronounced in the proximal jejunum. Grape seed extract (10-25 ug/mL) significantly enhanced the growth-inhibitory effects of 5-Fluorouracil by 26% (P<0.05) in Caco-2 cells and was more potent than 5-Fluorouracil at 50-100 µg/mL.

CONCLUSION

Grape seed extract may represent a new therapeutic option to decrease the symptoms of intestinal mucositis while concurrently impacting on the viability of colon cancer cells.

p38 MAPK signaling in oral-related diseases

Multiple dental diseases are characterized by chronic inflammation, due to the production of cytokines, chemokines, and prostanoids by immune and non-immune cells. Membrane-bound receptors provide a link between the extracellular environment and the initiation of intracellular signaling events that activate common signaling components, including p38 mitogen-activated protein kinase (MAPK), extracellular signal-regulated kinase (ERK), c-Jun N-terminal kinase (JNK), and nuclear factor (NF)-kappaB. Although ERK pathways regulate cell survival and are responsive to extracellular mitogens, p38 MAPK, JNK, and NF-kappaB are involved in environmental stress responses, including inflammatory stimuli. Over the past decade, significant advances have been made relative to our understanding of the fundamental intracellular signaling mechanisms that govern inflammatory cytokine expression. The p38 MAPK pathway has been shown to play a pivotal role in inflammatory cytokine and chemokine gene regulation at both the transcriptional and the post-transcriptional levels. In this review, we present evidence for the significance of p38 MAPK signaling in diverse dental diseases, including chronic pain, desquamative disorders, and periodontal diseases. Additional information is presented on the molecular mechanisms whereby p38 signaling controls post-transcriptional gene expression in inflammatory states.

Neutrophil elastase inhibitor (MPH-966) improves intestinal mucosal damage and gut microbiota in a mouse model of 5-fluorouracil-induced intestinal mucositis

BACKGROUND

5-Fluorouracil (5-FU)-based chemotherapy is first-line chemotherapy for colorectal cancer. However, 5-FU-induced intestinal mucositis (FUIIM) is a common adverse effect that severely impairs drug tolerance and results in poor patient health.

METHODS

Male C57BL/6 mice were given 5-FU (50 mg/kg/day, i.p.) and treated with MPH-966 (5 and 7.5 mg/kg/day, p.o.) for five days. The body weight loss and the amount of food intake, and histopathological findings were recorded and analyzed. In addition, the neutrophil infiltration, levels of neutrophil serine proteases and pro-inflammatory cytokines, and tight junction proteins expression in intestinal tissues were determined. The ecology of gut microbiota was performed through next-generation sequencing technologies.

RESULTS

Neutrophil elastase (NE) overexpression is a key feature in FUIIM. This study showed that treatment with the specific NE inhibitor MPH-966 (7.5 mg/kg/day, p.o.) significantly reversed 5-FU-induced loss in body weight and food intake; reversed villous atrophy; significantly suppressed myeloperoxidase, NE, and proteinase 3 activity; and reduced pro-inflammatory cytokine expression in an FUIIM mouse model. In addition, MPH-966 prevented 5-FU-induced intestinal barrier dysfunction, as indicated by the modulated expression of the tight junction proteins zonula occludin-1 and occludin. MPH-966 also reversed 5-FU-induced changes in gut microbiota diversity and abundances, specifically the Firmicutes-to-Bacteroidetes ratio; Muribaculaceae, Ruminococcaceae, and Eggerthellaceae abundances at the family level; and Candidatus Arthromitus abundance at the genus level.

CONCLUSION

These data indicate that NE inhibitor is a key treatment candidate to alleviate FUIIM by regulating abnormal inflammatory responses, intestinal barrier dysfunction, and gut microbiota imbalance.

Chemotherapy-induced mucositis is associated with changes in proteolytic pathways

Mucositis, a common toxic side effect of chemotherapy, is characterized by an arrest of cell proliferation and a loss of gut barrier function, which may cause treatment reduction or withdrawal. Gut integrity depends on nutritional and metabolic factors, including the balance between protein synthesis and proteolysis. The effects of methotrexate (MTX; a frequently used chemotherapeutic agent) on intestinal proteolysis and gut barrier function were investigated in rats. Male Sprague-Dawley rats received 2.5 mg/kg of MTX subcutaneously during 3 days and were euthanized at Day 4 (D4) or Day 7 (D7). We observed at D4 that MTX induced mucosal damage and increased intestinal permeability (7-fold) and the mucosal concentration of interleukin (IL)-1beta and IL-6 (4- to 6-fold). In addition, villus height and glutathione content significantly decreased. Intestinal proteolysis was also affected by MTX as cathepsin D activity increased at D4, whereas chymotrypsin-like proteasome activity decreased and calpain activities remained unaffected. At D7, cathepsin D activity was restored to control levels, but proteasome activity remained reduced. This disruption of proteolysis pathways strongly contributed to mucositis and requires further study. Lysosomal proteolytic activity may be considered the main proteolytic pathway responsible for alteration of mucosal integrity and intestinal permeability during mucositis, as cathepsin D activity was found to be correlated with mucosal atrophy and intestinal permeability. Proteasome regulation could possibly be an adaptive process for survival. Future investigation is warranted to target proteolytic pathways with protective nutritional or pharmacological therapies during mucositis.

Puerarin Ameliorates 5-Fluorouracil-Induced Intestinal Mucositis in Mice by Inhibiting JAKs

Intestinal mucositis resulting from 5-fluorouracil (5-FU)-based chemotherapy subjects patients to great pain and hampers cancer treatment progress. Puerarin, the major active ingredient in Pueraria lobata, exerts anti-inflammatory and antioxidative effects. However, whether puerarin has an effect on 5-FU-induced intestinal mucositis remains unknown. We established a mice model of intestinal mucositis through the intraperitoneal injection of 5-FU and then injected puerarin (50 and 100 mg/kg) intraperitoneally for 7 consecutive days. Routine parameters, such as body weight, food intake, and diarrheal incidence, were examined to evaluate the effects of puerarin on intestinal mucositis in mice. The intestinal barrier's functions were also evaluated by measuring the serum recovery of fluorescein isothiocyanate-4kD dextran in this study. The expression levels of inflammatory cytokines, inflammatory mediators, oxidative reactions, as well as apoptotic marker proteins were determined to elucidate the underlying mechanisms of puerarin on intestinal mucositis. The model mice presented symptoms and histopathological changes typical of 5-FU-induced intestinal mucositis. In addition to vigorous inflammatory reactions, oxidative reactions, and cell apoptosis, Janus kinase (JAK) was markedly activated. Puerarin decreased the expression levels of those of inflammatory mediators, oxidative reactions, and apoptosis-related proteins in 5-FU-induced mucositis by blocking the activation of JAK. Puerarin decreased inflammation, oxidative reactions, and apoptosis and protected intestinal barrier functions to ameliorate 5-FU-induced intestinal mucositis by inhibiting the activation of JAK. This study provides novel insights into the pathologic mechanisms of (and treatment alternatives for) 5-FU-induced intestinal mucositis. SIGNIFICANCE STATEMENT: This study reveals the mechanism responsible for the protective effects of puerarin in 5-fluorouracil-induced intestinal mucositis. Puerarin inhibits the activation of JAK, thereby suppressing inflammation, oxidative reactions, cell apoptosis, and protected intestinal barrier functions to ameliorate 5-FU-induced intestinal mucositis. Overall, our results suggest that puerarin can serve as a potential natural JAK inhibitor in the treatment of 5-FU-induced intestinal mucositis.

Activation of G protein coupled estrogen receptor prevents chemotherapy-induced intestinal mucositis by inhibiting the DNA damage in crypt cell in an extracellular signal-regulated kinase 1- and 2- dependent manner

Chemotherapy-induced intestinal mucositis (CIM) is a common adverse reaction to antineoplastic treatment with few appropriate, specific interventions. We aimed to identify the role of the G protein coupled estrogen receptor (GPER) in CIM and its mechanism. Adult male C57BL/6 mice were intraperitoneally injected with 5-fluorouracil to establish the CIM model. The selective GPER agonist G-1 significantly inhibited weight loss and histological damage in CIM mice and restored mucosal barrier dysfunction, including improving the expression of ZO-1, increasing the number of goblet cells, and decreasing mucosal permeability. Moreover, G-1 treatment did not alter the antitumor effect of 5-fluorouracil. In the CIM model, G-1 therapy reduced the expression of proapoptotic protein and cyclin D1 and cyclin B1, reversed the changes in the number of TUNEL+ cells, Ki67+ and bromodeoxyuridine+ cells in crypts. The selective GPER antagonist G15 eliminated all of the above effects caused by G-1 on CIM, and application of G15 alone increased the severity of CIM. GPER was predominantly expressed in ileal crypts, and G-1 inhibited the DNA damage induced by 5-fluorouracil in vivo and vitro, as confirmed by the decrease in the number of γH2AX+ cells in the crypts and the comet assay results. Referring to the data from GEO dataset we verified GPER activation restored ERK1/2 activity in CIM and 5-fluorouracil-treated IEC-6 cells. Once the effects of G-1 on ERK1/2 activity were abolished with the ERK1/2 inhibitor PD0325901, the effects of G-1 on DNA damage both in vivo and in vitro were eliminated. Correspondingly, all of the manifestations of G-1 protection against CIM were inhibited by PD0325901, such as body weight and histological changes, the mucosal barrier, the apoptosis and proliferation of crypt cells. In conclusion, GPER activation prevents CIM by inhibiting crypt cell DNA damage in an ERK1/2-dependent manner, suggesting GPER might be a target preventing CIM.