Age-associated temporal decline in butyrate-producing bacteria plays a key pathogenic role in the onset and progression of neuropathology and memory deficits in 3×Tg-AD mice.

Alterations in the gut-microbiome-brain axis are increasingly being recognized to be involved in Alzheimer's disease (AD) pathogenesis. However, the functional consequences of enteric dysbiosis linking gut microbiota and brain pathology in AD progression remain largely undetermined. The present work investigated the causal role of age-associated temporal decline in butyrate-producing bacteria and butyrate in the etiopathogenesis of AD. Longitudinal metagenomics, neuropathological, and memory analyses were performed in the 3×Tg-AD mouse model. Metataxonomic analyses showed a significant temporal decline in the alpha diversity marked by a decrease in butyrate-producing bacterial communities and a concurrent reduction in cecal butyrate production. Inferred metagenomics analysis identified the bacterial acetyl-CoA pathway as the main butyrate synthesis pathway impacted. Concomitantly, there was an age-associated decline in the transcriptionally permissive acetylation of histone 3 at lysines 9 and 14 (H3K9/K14-Ac) in hippocampal neurons. Importantly, these microbiome-gut-brain changes preceded AD-related neuropathology, including oxidative stress, tau hyperphosphorylation, memory deficits, and neuromuscular dysfunction, which manifest by 17-18 months. Initiation of oral administration of tributyrin, a butyrate prodrug, at 6 months of age mitigated the age-related decline in butyrate-producing bacteria, protected the H3K9/K14-Ac status, and attenuated the development of neuropathological and cognitive changes associated with AD pathogenesis. These data causally implicate age-associated decline in butyrate-producing bacteria as a key pathogenic feature of the microbiome-gut-brain axis affecting the onset and progression of AD. Importantly, the regulation of butyrate-producing bacteria and consequent butyrate synthesis could be a significant therapeutic strategy in the prevention and treatment of AD.

Fibroblast-derived conditioned media promotes lung cancer progression.

Lung cancer is the leading cause of cancer death in men and women in the United States. Recent studies have implicated the tumor microenvironment as a new chemotherapeutic target by demonstrating the importance of tumor cell-stromal interactions in cancer progression. However, the exact mechanisms by which tumor cell-stromal interactions drive lung cancer progression remain undefined, particularly in the lung. We suspect host fibroblasts represent an important component of the tumor microenvironment that drives tumor progression. We found that human non-small cell lung carcinoma cell lines show alterations in cell morphology, proliferation, migration, and colony formation on soft agar when exposed to fibroblast-conditioned media (FCM). Interestingly, FCM also promoted tumor cell resistance to cisplatin-induced apoptosis. These effects varied depending on the cancer cell line used. Similar observations were made when exposing murine Lewis Lung Carcinoma cells to conditioned media harvested from primary murine lung fibroblasts. Certain effects of FCM, but not all, could be prevented by using a cMET inhibitor. In vivo, we observed enhanced growth of the primary tumors when treated with FCM, but no changes in metastatic behavior. Although the identity of the stimulating agent(s) in the fibroblast-conditioned media was not unveiled, further studies revealed that the activity is more than one factor with a high-molecular weight (over 100 kDa). These studies implicate lung fibroblast-derived factors in lung cancer progression. These data suggest that targeting the lung tumor stroma alone, or in combination with other interventions, is a promising concept that warrants further study in the setting of lung cancer.

Interplay between aging, lung inflammation/remodeling, and fibronectin EDA in lung cancer progression.

Lung cancer remains the leading cause of cancer death in the United States. Since most lung cancers occur in aged individuals with chronic lung disorders characterized by inflammation and/or fibrosis, we hypothesized that aging and tissue inflammation/remodeling act in concert to promote lung cancer progression. To test this, we engaged in studies using young and aged C57BL/6 mice in conjunction with bleomycin treatment in a syngeneic model of lung cancer. Wildtype young (3 months) and aged (9 months) C57BL/6 mice were injected with Lewis Lung Carcinoma (LLC) cells at day 14 after injection with phosphate-buffered saline or bleomycin. Untreated aged mice were found to develop more lung metastases than young mice. Bleomycin induced weight loss and lung inflammation/remodeling in both young and aged mice, and it increased the number of lung metastases in aged lungs, but not in young lungs. Since aged lungs show alterations in the expression of fibronectin EDA, we repeated studies in aged WT and aged FN EDA KO mice. In the absence of tissue remodeling/inflammation, WT and FN EDA KO mice developed the same number of metastases when injected with LLC cells. However, the increase in lung metastasis due to bleomycin treatment was abolished in FN EDA KO mice, but only in aged and injured lungs. Together, these studies show increased lung cancer metastasis in aging animals and point to the influence of FN EDA and injury in this process.

Impact of sex, age and diet on the cysteine/cystine and glutathione/glutathione disulfide plasma redox couples in mice.

Age, sex and diet are well-established risk factors for several diseases. In humans, each of these variables has been linked to differences in plasma redox potentials (Eh) of the glutathione/glutathione disulfide (GSH/GSSG) and cysteine/cystine (Cys/CySS) redox couples. Mice have been very useful for modeling human disease processes, but it is unknown if age, sex and diet affect redox couples in mice as they do in humans. The purpose of the present study was to examine the effects of these factors on plasma redox potentials in C57BL/6J mice. We found that age had no effect on either redox couple in either sex. Plasma Eh Cys/CySS and Eh GSH/GSSG were both more oxidized (more positive) in females than in males. A 24-hour fast negated the sex differences in both redox potentials by oxidizing both redox couples in male mice, while having no effect on Eh Cys/CySS and a smaller effect on Eh GSH/GSSG in female mice. A diet with excess sulfur amino acids reduced the plasma Eh Cys/CySS in females to a level comparable to that seen in male mice. Thus, sex-specific differences in plasma Eh Cys/CySS could be normalized by two different dietary interventions. Some of these findings are consistent with reported human studies, while others are not. Most strikingly, mice do not exhibit age-dependent oxidation of plasma redox potentials. Care must be taken when designing and interpreting mouse studies to investigate redox regulation in humans.