A role for the age-dependent loss of α(E)-catenin in regulation of N-cadherin expression and cell migration

Colostrum-Induced Temporary Changes in the Expression of Proteins Regulating the Epithelial Barrier Function in the Intestine

The intestinal wall and epithelial cells are interconnected by numerous intercellular junctions. Colostrum (Col), in its natural form, is a secretion of the mammary gland of mammals at the end of pregnancy and up to 72 h after birth. Recently, it has been used as a biologically active dietary supplement with a high content of lactoferrin (Lf). Lf, a glycoprotein with a broad spectrum of activity, is becoming more popular in health-promoting supplements. This study aims to investigate whether Col supplementation can affect small and large intestine morphology by modulating the expression of selected proteins involved in tissue integrity. We examined the thickness of the epithelium, and the length of the microvilli, and assessed the expression of CDH1, CDH2, CTNNB, CX43, VCL, OCLN, HP, MYH9, and ACTG2 gene levels using qRT-PCR and at the protein level using IHC. Additionally, to evaluate whether the effect of Col supplementation is temporary or persistent, we performed all analyses on tissues collected from animals receiving Col for 1, 3, or 6 months. We noticed a decrease in CDH1 and CDH2 expression, especially after 3 months of supplementation in the large intestine and in CTNNB in the small intestine as well as increased levels of CX43 and CTNNB1 in the small intestine. The present data indicate that Col can temporarily alter some components of the cell adhesion molecules involved in the formation of the cellular barrier.

The renoprotective effects of soy protein in the aging rat kidney

Aging is a risk factor for chronic kidney disease (CKD) and is itself associated with alterations in renal structure and function. There are no specific interventions to attenuate age-dependent renal dysfunction and the mechanism(s) responsible for these deficits have not been fully elucidated. In this study, male Fischer 344 rats, which develop age-dependent nephropathy, were feed a casein- or soy protein diet beginning at 16 mon (late life intervention) and renal structure and function was assessed at 20 mon. The soy diet did not significantly affect body weight, but was renoprotective as assessed by decreased proteinuria, increased glomerular filtration rate (GFR) and decreased urinary kidney injury molecule-1 (Kim-1). Renal fibrosis, as assessed by hydroxyproline content, was decreased by the soy diet, as were several indicators of inflammation. RNA sequencing identified several candidates for the renoprotective effects of soy, including decreased expression of Twist2, a basic helix-loop-helix transcription factor that network analysis suggest may regulate the expression of several genes associated with renal dysfunction. Twist2 expression is upregulated in the aging kidney and the unilateral ureteral obstruction of fibrosis; the expression is limited to distal tubules of mice. Taken together, these data demonstrate the renoprotective potential of soy protein, putatively by reducing inflammation and fibrosis, and identify Twist2 as a novel mediator of renal dysfunction that is targeted by soy.

MicroRNA-30a increases tight junction protein expression to suppress the epithelial-mesenchymal transition and metastasis by targeting Slug in breast cancer

The epithelial-to-mesenchymal (EMT) transition is a prerequisite for conferring metastatic potential during tumor progression. microRNA-30a (miR-30a) expression was significantly lower in aggressive breast cancer cell lines compared with non-invasive breast cancer and non-malignant mammary epithelial cell lines. In contrast, miR-30a overexpression reversed the mesenchymal appearance of cancer cells to result in a cobblestone-like epithelial phenotype. We identified Slug, one of the master regulators of EMT, as a target of miR-30a using in silico prediction. Reporter assays indicated that miR-30a could bind to the 3'-untranslted region of Slug mRNA. Furthermore, we linked miR-30a to increased expression of claudins, a family of tight junction transmembrane proteins. An interaction between Slug and E-box in the claudin promoter sequences was reduced upon miR-30a overexpression, further leading to reduction of filopodia formation and decreased invasiveness/metastasis capabilities of breast cancer cells. Consistently, delivery of miR-30a in xenografted mice decreased tumor invasion and migration. In patients with breast cancer, a significantly elevated risk of the miR-30alow/CLDN2low/FSCNhigh genotype was observed, linking to a phenotypic manifestation of larger tumor size, lymph node metastasis, and advanced tumor stage among patients. In conclusion, the miR-30a/Slug axis inhibits mesenchymal tumor development by interfering with metastatic cancer cell programming and may be a potential target for therapy in breast cancer.

The impact of aging on epithelial barriers

The epithelium has many critical roles in homeostasis, including an essential responsibility in establishing tissue barriers. In addition to the fundamental role in separating internal from external environment, epithelial barriers maintain nutrient, fluid, electrolyte and metabolic waste balance in multiple organs. While, by definition, barrier function is conserved, the structure of the epithelium varies across organs. For example, the skin barrier is a squamous layer of cells with distinct structural features, while the lung barrier is composed of a very thin single cell to minimize diffusion space. With the increased focus on age-dependent alterations in organ structure and function, there is an emerging interest in the impact of age on epithelial barriers. This review will focus on the impact of aging on the epithelial barrier of several organs, including the skin, lung, gastrointestinal tract and the kidney, at a structural and functional level.

Twist2 Is Upregulated in Early Stages of Repair Following Acute Kidney Injury

The aging kidney is a marked by a number of structural and functional changes, including an increased susceptibility to acute kidney injury (AKI). Previous studies from our laboratory have shown that aging male Fischer 344 rats (24 month) are more susceptible to apoptosis-mediated injury than young counterparts. In the current studies, we examined the initial injury and early recovery phases of mercuric chloride-induced AKI. Interestingly, the aging kidney had decreased serum creatinine compared to young controls 1 day following mercuric chloride injury, but by day 4, serum creatinine was significantly elevated, suggesting that the aging kidney did not recover from injury. This conclusion is supported by the findings that serum creatinine and kidney injury molecule-1 (Kim-1) gene expression remain elevated compared to young controls at 10 days post-injury. To begin to elucidate mechanism(s) underlying dysrepair in the aging kidney, we examined the expression of Twist2, a helix-loop-helix transcription factor that may mediate renal fibrosis. Interestingly, Twist2 gene expression was elevated following injury in both young and aged rats, and Twist2 protein expression is elevated by mercuric chloride in vitro.

Fascin2 regulates cisplatin-induced apoptosis in NRK-52E cells

Previous studies have shown that the aging kidney has a marked loss of α(E)-catenin in proximal tubular epithelium. α-Catenin, a key regulator of the actin cytoskeleton, interacts with a variety of actin-binding proteins. Cisplatin-induced loss of fascin2, an actin bundling protein, was observed in cells with a stable knockdown of α(E)-catenin (C2 cells), as well as in aging (24 mon), but not young (4 mon), kidney. Fascin2 co-localized with α-catenin and the actin cytoskeleton in NRK-52E cells. Knockdown of fascin2 increased the susceptibility of tubular epithelial cells to cisplatin-induced injury. Overexpression of fascin2 in C2 cells restored actin stress fibers and attenuated the increased sensitivity of C2 cells to cisplatin-induced apoptosis. Interestingly, fascin2 overexpression attenuated cisplatin-induced mitochondrial dysfunction and oxidative stress in C2 cells. These data demonstrate that fascin2, a putative target of α(E)-catenin, may play important role in preventing cisplatin-induced acute kidney injury.

Loss of α(E)-catenin promotes Fas mediated apoptosis in tubular epithelial cells

The aging kidney undergoes structural and functional alterations which make it more susceptible to drug-induced acute kidney injury (AKI). Previous studies in our lab have shown that the expression of α(E)-catenin is decreased in aged kidney and loss of α(E)-catenin potentiates AKI-induced apoptosis, but not necrosis, in renal tubular epithelial cells (NRK-52E cells). However, the specific apoptotic pathway underlying the increased AKI-induced cell death is not yet understood. In this study, cells were challenged with nephrotoxicant cisplatin to induce AKI. A ~5.5-fold increase in Fas expression in C2 (stable α(E)-catenin knockdown) relative to NT3 (non-targeted control) cells was seen. Increased caspase-8 and -9 activation was induced by cisplatin in C2 as compared to NT3 cells. In addition, decreased Bcl-2 expression and increased BID cleavage and cytochrome C release were detected in C2 cells after cisplatin challenge. Treating the cells with cisplatin, in combination with a Bcl-2 inhibitor, decreased the viability of NT3 cells to the same level as C2 cells after cisplatin. Furthermore, caspase-3/-7 activation is blocked by Fas, caspase-8, caspase-9 and pan-caspase inhibitors. These inhibitors also completely abolished the difference in viability between NT3 and C2 cells in response to cisplatin. These results demonstrate a Fas-mediated apoptotic signaling pathway that is enhanced by the age-dependent loss of α(E)-catenin in renal tubule epithelial cells.

The aging kidney: increased susceptibility to nephrotoxicity

Three decades have passed since a series of studies indicated that the aging kidney was characterized by increased susceptibility to nephrotoxic injury. Data from these experimental models is strengthened by clinical data demonstrating that the aging population has an increased incidence and severity of acute kidney injury (AKI). Since then a number of studies have focused on age-dependent alterations in pathways that predispose the kidney to acute insult. This review will focus on the mechanisms that are altered by aging in the kidney that may increase susceptibility to injury, including hemodynamics, oxidative stress, apoptosis, autophagy, inflammation and decreased repair.

Loss of α(E)-catenin potentiates cisplatin-induced nephrotoxicity via increasing apoptosis in renal tubular epithelial cells

Cisplatin is one of the most potent and widely used antitumor drugs. However, the use of cisplatin is limited by its side effect, nephrotoxicity. Evidence has shown an increased incidence and severity of acute kidney injury (AKI) in the elderly. Previous studies from our laboratory demonstrate a decrease in α(E)-catenin expression in aged kidney. In this study, we investigated whether the loss of α(E)-catenin may increase cisplatin nephrotoxicity. To study the effects of reduced α(E)-catenin, a cell line with stable knockdown of α(E)-catenin (C2 cells) was used; NT3 is nontargeted control. C2 cells exhibited a significant loss of viability as determined by MTT assay compared with NT3 cells after cisplatin challenge, but showed no difference in lactate dehydrogenase (LDH) leakage. Increased caspase 3/7 activation and PARP cleavage was observed in C2 cells after cisplatin treatment. Z-VAD, a pan-caspase inhibitor, abolished the difference in susceptibility between NT3 and C2 cells. Interestingly, the expression of α(E)-catenin was further decreased after cisplatin treatment. Furthermore, in vivo data demonstrated a significant increase in serum creatinine at 72 h after a single dose of cisplatin in 24-month-old rats, but not in 4-month-old rats. Increased expression of KIM-1 and in situ apoptosis were also detected in aged kidney after cisplatin challenge. Taken together, these data suggest that loss of α(E)-catenin increases apoptosis of tubular epithelial cells which may contribute to the increased nephrotoxicity induced by cisplatin in aged kidney.