Apoptosis of human endothelial cells is accompanied by proteolytic processing of latent TGF-beta binding proteins and activation of TGF-beta

Understanding and targeting anoikis in metastasis for cancer therapies

The development of effective treatments for cancers requires investigations for a more detailed and comprehensive understanding of the basic cellular mechanisms involved in carcinogenesis, cancer progression, and metastasis. One of those driving mechanisms is anoikis, a special type of apoptosis, which is induced by losing anchorage from the extracellular matrix (ECM). In other words, resisting death in detached cells (cells without ECM) forms an anoikis-resistant phenotype. Since the anoikis-resistance state compensates for the initial steps of cancer metastasis, this review aimed to discuss mechanisms of gaining anoikis/anoikis resistance phenotype in tumor cells. Finally, we highlighted the significance of anoikis in malignancies so as to provide clear insight into cancer diagnosis and therapy development.

Classical epithelial-mesenchymal transition (EMT) and alternative cell death process-driven blebbishield metastatic-witch (BMW) pathways to cancer metastasis

Metastasis is a pivotal event that accelerates the prognosis of cancer patients towards mortality. Therapies that aim to induce cell death in metastatic cells require a more detailed understanding of the metastasis for better mitigation. Towards this goal, we discuss the details of two distinct but overlapping pathways of metastasis: a classical reversible epithelial-to-mesenchymal transition (hybrid-EMT)-driven transport pathway and an alternative cell death process-driven blebbishield metastatic-witch (BMW) transport pathway involving reversible cell death process. The knowledge about the EMT and BMW pathways is important for the therapy of metastatic cancers as these pathways confer drug resistance coupled to immune evasion/suppression. We initially discuss the EMT pathway and compare it with the BMW pathway in the contexts of coordinated oncogenic, metabolic, immunologic, and cell biological events that drive metastasis. In particular, we discuss how the cell death environment involving apoptosis, ferroptosis, necroptosis, and NETosis in BMW or EMT pathways recruits immune cells, fuses with it, migrates, permeabilizes vasculature, and settles at distant sites to establish metastasis. Finally, we discuss the therapeutic targets that are common to both EMT and BMW pathways.

Molecular signaling in pancreatic ductal metaplasia: emerging biomarkers for detection and intervention of early pancreatic cancer

Pancreatic ductal metaplasia (PDM) is the transformation of potentially various types of cells in the pancreas into ductal or ductal-like cells, which eventually replace the existing differentiated somatic cell type(s). PDM is usually triggered by and manifests its ability to adapt to environmental stimuli and genetic insults. The development of PDM to atypical hyperplasia or dysplasia is an important risk factor for pancreatic intraepithelial neoplasia (PanIN) and pancreatic ductal adenocarcinoma (PDA). Recent studies using genetically engineered mouse models, cell lineage tracing, single-cell sequencing and others have unraveled novel cellular and molecular insights in PDM formation and evolution. Those novel findings help better understand the cellular origins and functional significance of PDM and its regulation at cellular and molecular levels. Given that PDM represents the earliest pathological changes in PDA initiation and development, translational studies are beginning to define PDM-associated cell and molecular biomarkers that can be used to screen and detect early PDA and to enable its effective intervention, thereby truly and significantly reducing the dreadful mortality rate of PDA. This review will describe recent advances in the understanding of PDM biology with a focus on its underlying cellular and molecular mechanisms, and in biomarker discovery with clinical implications for the management of pancreatic regeneration and tumorigenesis.

The leaving group in Au(I)-phosphine compounds dictates cytotoxic pathways in CEM leukemia cells and reactivity towards a Cys2His2 model zinc finger

Gold(i)-phosphine "auranofin-like" compounds have been extensively explored as anticancer agents in the past decade. Although potent cytotoxic agents, the lack of selectivity towards tumorigenic vs. non-tumorigenic cell lines often hinders further application. Here we explore the cytotoxic effects of a series of (R3P)AuL compounds, evaluating both the effect of the basicity and bulkiness of the carrier phosphine (R = Et or Cy), and the leaving group L (Cl-vs. dmap). [Au(dmap)(Et3P)]+ had an IC50 of 0.32 μM against the CEM cell line, with good selectivity in relation to HUVEC. Flow cytometry indicates reduced G1 population and slight accumulation in G2, as opposed to auranofin, which induces a high population of cells with fragmented DNA. Protein expression profile sets [Au(dmap)(Et3P)]+ further apart from auranofin, with proteolytic degradation of caspase-3 and poly(ADP-ribose)-polymerase (PARP), DNA strand-break induced phosphorylation of Chk2 Thr68 and increased p53 ser15 phosphorylation. The cytoxicity and observable biological effects correlate directly with the reactivity trend observed when using the series of gold(i)-phosphine compounds for targeting a model zinc finger, Sp1 ZnF3.

Potential Effects of Nonadherent on Adherent Human Umbilical Venous Endothelial Cells in Cell Culture

The adherence and shear-resistance of human umbilical venous endothelial cells (HUVEC) on polymers is determined in vitro in order to qualify cardiovascular implant materials. In these tests, variable fractions of HUVEC do not adhere to the material but remain suspended in the culture medium. Nonadherent HUVEC usually stop growing, rapidly lose their viability and can release mediators able to influence the growth and function of the adherent HUVEC. The aim of this study was the investigation of the time dependent behaviour of HUVEC under controlled nonadherent conditions, in order to gain insights into potential influences of these cells on their surrounding environment in particular adherent HUVEC in the context of in vitro biofunctionality assessment of cardiovascular implant materials. Data from adherent or nonadherent HUVEC growing on polystyrene-based cell adhesive tissue culture plates (TCP) or nonadhesive low attachment plates (LAP) allow to calculate the number of mediators released into the culture medium either from adherent or nonadherent cells. Thus, the source of the inflammatory mediators can be identified. For nonadherent HUVEC, a time-dependent aggregation without further proliferation was observed. The rate of apoptotic/dead HUVEC progressively increased over 90% within two days. Concomitant with distinct blebbing and loss of membrane integrity over time, augmented releases of prostacyclin (PGI2, up to 2.91 ± 0.62 fg/cell) and platelet-derived growth factor BB (PDGF-BB, up to 1.46 ± 0.42 fg/cell) were detected. The study revealed that nonadherent, dying HUVEC released mediators, which can influence the surrounding microenvironment and thereby the results of in vitro biofunctionality assessment of cardiovascular implant materials. Neglecting nonadherent HUVEC bears the risk for under- or overestimation of the materials endothelialization potential, which could lead to the loss of relevant candidates or to uncertainty with regard to their suitability for cardiac applications. One approach to minimize the influence from nonadherent endothelial cells could be their removal shortly after observing initial cell adhesion. However, this would require an individual adaptation of the study design, depending on the properties of the biomaterial used.

Modulation of TGF‑β activity by latent TGF‑β‑binding protein 1 in human osteoarthritis fibroblast‑like synoviocytes

Osteoarthritis (OA) is a common degenerative joint disease; however, its underlying pathogenesis remains to be elucidated. Previous studies have demonstrated that the transforming growth factor‑β (TGF‑β) signaling pathway has a role in the initiation and development of OA. Additionally, latent TGF‑β‑binding protein‑1 (LTBP‑1) modulates the activity of the TGF‑β‑mothers against decapentaplegic (Smad) signaling pathway in numerous diseases, including malignant glioma. The present study demonstrated that expression of LTBP‑1 is increased in OA synovial tissues compared with normal synovial tissues. The effect of TGF‑β was identified to be mediated by phosphorylated(p)‑(Smad)2/3, which may activate activin‑like kinase (ALK)5 receptor, and by p‑Smad1/5/8, which may induce ALK1, thereby stimulating expression of matrix metalloproteinase‑(MMP)‑13 in OA fibroblast‑like synoviocytes (FLS). Compared with normal FLS, OA FLS demonstrated an increased p‑Smad1/5/8:p‑Smad2 ratio, which led to elevated MMP‑13 expression and aggravation of OA. Furthermore, knockdown of the LTBP‑1 gene by siRNA transfection in OA FLS reduced p‑Smad1/5/8 expression without affecting TGF‑β mRNA levels, although p‑Smad2 expression increased. It was also demonstrated that OA FLS exhibited increased proliferation compared with normal FLS in vitro. Furthermore, siRNA‑mediated downregulation of LTBP‑1 reduced proliferation of OA FLS. In conclusion, the present study demonstrated that an alteration in the p‑Smad1/5/8:p‑Smad2 ratio as well as association between p‑Smad1/5/8 and MMP‑13 expression in human OA FLS, may contribute to the development of OA. The results of the present study suggested that LTBP‑1 is a modulator of the TGF‑β signaling pathway in human OA FLS, which may aid in elucidating the mechanism underlying the pathology of OA.

RETRACTED ARTICLE: High Pulsatility Flow Promotes Vascular Fibrosis by Triggering Endothelial EndMT and Fibroblast Activation

Vascular fibrosis, the formation of excess fibrous tissue on the blood vessel wall, is characterized by unmitigated proliferation of fibroblasts or myofibroblast-like cells exhibiting α-smooth-muscle-actin in vessel lumen and other vascular layers. It likely contributes to vascular unresponsiveness to conventional therapies. This paper demonstrates a new flow-induced vascular fibrosis mechanism. Using our developed flow system which simulates the effect of vessel stiffening and generates unidirectional high pulsatility flow (HPF) with the mean shear flow at a physiological level, we have shown that HPF caused vascular endothelial dysfunction. Herein, we further explored the role of HPF in vascular fibrosis through endothelial-to-mesenchymal transdifferentiation (EndMT). Pulmonary arterial endothelial cells (ECs) were exposed to steady flow and HPF, which have the same physiological mean fluid shear but different in flow pulsatility. Cells were analyzed after being conditioned with flows for 24 or 48 h. HPF was found to induce EndMT of cells after 48 h stimulation; cells demonstrated drastically decreased expression in EC marker CD31, as well as increased transforming growth factor β, α-SMA, and collagen type-I, in both gene and protein expression profiles. Using the flow media from HPF-conditioned endothelial culture to cultivate arterial adventitial fibroblasts (AdvFBs) and ECs respectively, we found that the conditioned media respectively enhanced migration, proliferation and α-SMA expression of AdvFBs, and induced EndMT of ECs. It was further revealed that cells exposed to HPF exhibited much higher percentage of caspase-positive cells compared to those exposed to steady flow. Apoptotic cells together with remaining, caspase-negative cells suggested the presence of apoptosis-resistant dysfunctional ECs which likely underwent EndMT process and perpetuated fibrosis throughout vascular tissues. Therefore, our results indicate that prolonged HPF stimuli induce vascular fibrosis through triggering EndMT and EC-mediated AdvFB activation and migration, which follows initial endothelial inflammation, dysfunction and apoptosis.

Evasion of immune responses by Trypanosoma cruzi, the etiological agent of Chagas disease

Infection with the protozoan parasite Trypanosoma cruzi leads to Chagas disease, which affects millions of people in Latin America. Infection with T. cruzi cannot be eliminated by the immune system. A better understanding of immune evasion mechanisms is required in order to develop more effective vaccines. During the acute phase, parasites replicate extensively and release immunomodulatory molecules that delay parasite-specific responses mediated by T cells. This immune evasion allows the parasite to spread in the host. In the chronic phase, parasite evasion relies on its replication strategy of hijacking the TGF-β signaling pathway involved in inflammation and tissue regeneration. In this article, the mechanisms of immune evasion described for T. cruzi are reviewed.

Modulation of TGF-beta activity by latent TGF-beta-binding protein 1 in human malignant glioma cells

High biological activity of the transforming growth factor (TGF)-beta-Smad pathway characterizes the malignant phenotype of malignant gliomas and confers poor prognosis to glioma patients. Accordingly, TGF-beta has become a novel target for the experimental treatment of these tumors. TGF-beta is processed by furin-like proteases (FLP) and secreted from cells in a latent complex with its processed propeptide, the latency-associated peptide (LAP). Latent TGF-beta-binding protein 1 (LTBP-1) covalently binds to this small latent TGF-beta complex (SLC) and regulates its function, presumably via interaction with the extracellular matrix (ECM). We report here that the levels of LTBP-1 protein in vivo increase with the grade of malignancy in gliomas. LTBP-1 is associated with the ECM as well as secreted into the medium in cultured malignant glioma cells. The release of LTBP-1 into the medium is decreased by the inhibition of FLP activity. Gene-transfer mediated overexpression of LTBP-1 in glioma cell lines results in an increase inTGF-beta activity. Accordingly, Smad2 phosphorylation as an intracellular marker of TGF-beta activity is enhanced. Conversely, LTBP-1 gene silencing reduces TGF-beta activity and Smad2 phosphorylation without affecting TGF-beta protein levels. Collectively, we identify LTBP-1 as an important modulator of TGF-beta activation in glioma cells, which may contribute to the malignant phenotype of these tumors.

Transforming growth factor-beta1 causes pulmonary microvascular endothelial cell apoptosis via ALK5

We have previously shown that transforming growth factor (TGF)-beta1 protected against main pulmonary artery endothelial cell (PAEC) apoptosis induced by serum deprivation and VEGF receptor blockade through a mechanism associated with ALK5-mediated Bcl-2 upregulation. In the current study, we investigated the effect of TGF-beta1 on pulmonary microvascular endothelial cell (PMVEC) apoptosis. We found that, in contrast to the results seen in conduit PAEC, TGF-beta1 caused apoptosis of PMVEC, an effect that was also dependent on ALK5 activity. We noted that non-SMAD signaling pathways did not play a role in TGF-beta1-induced apoptosis. Both SMAD2 and SMAD1/5 were activated upon exposure to TGF-beta1. TGF-beta1-induced activation of SMAD2, but not SMAD1/5, was abolished by ALK5 inhibition, an effect that associated with prevention of TGF-beta1-induced apoptosis. These results suggest that SMAD2 is important in TGF-beta1-induced apoptosis of PMVEC. While caspase-12 activity was not altered, caspase-8 was activated by TGF-beta1, an effect that correlated with a reduction of cFLIP protein levels. Additionally, TGF-beta1 decreased Bcl-2 protein levels and induced cytochrome c cytosolic redistribution. These results suggest that TGF-beta1 caused apoptosis of PMVEC likely through both caspase-8-dependent extrinsic pathway and mitochondria-mediated intrinsic pathway. We noted that inhibition of ALK5 attenuated serum deprivation-induced apoptosis, an effect that correlated with increased expression and activation of CREB and its potential target genes, Bcl-2 and cFLIP. These results suggest that CREB may be important in mediating apoptosis resistance of PMVEC upon ALK5 inhibition perhaps through upregulation of Bcl-2 and cFLIP. Finally, we noted that SMAD1/5 were activated upon ALK5 inhibition in the presence of low levels of TGF-beta1, an effect associated with enhanced endothelial proliferation. We speculate that imbalance of ALK1 and ALK5 may contribute to the development of pulmonary artery hypertension.

Glyphosate formulations induce apoptosis and necrosis in human umbilical, embryonic, and placental cells

We have evaluated the toxicity of four glyphosate (G)-based herbicides in Roundup formulations, from 10(5) times dilutions, on three different human cell types. This dilution level is far below agricultural recommendations and corresponds to low levels of residues in food or feed. The formulations have been compared to G alone and with its main metabolite AMPA or with one known adjuvant of R formulations, POEA. HUVEC primary neonate umbilical cord vein cells have been tested with 293 embryonic kidney and JEG3 placental cell lines. All R formulations cause total cell death within 24 h, through an inhibition of the mitochondrial succinate dehydrogenase activity, and necrosis, by release of cytosolic adenylate kinase measuring membrane damage. They also induce apoptosis via activation of enzymatic caspases 3/7 activity. This is confirmed by characteristic DNA fragmentation, nuclear shrinkage (pyknosis), and nuclear fragmentation (karyorrhexis), which is demonstrated by DAPI in apoptotic round cells. G provokes only apoptosis, and HUVEC are 100 times more sensitive overall at this level. The deleterious effects are not proportional to G concentrations but rather depend on the nature of the adjuvants. AMPA and POEA separately and synergistically damage cell membranes like R but at different concentrations. Their mixtures are generally even more harmful with G. In conclusion, the R adjuvants like POEA change human cell permeability and amplify toxicity induced already by G, through apoptosis and necrosis. The real threshold of G toxicity must take into account the presence of adjuvants but also G metabolism and time-amplified effects or bioaccumulation. This should be discussed when analyzing the in vivo toxic actions of R. This work clearly confirms that the adjuvants in Roundup formulations are not inert. Moreover, the proprietary mixtures available on the market could cause cell damage and even death around residual levels to be expected, especially in food and feed derived from R formulation-treated crops.

Alveolar cell apoptosis is dependent on p38 MAP kinase-mediated activation of xanthine oxidoreductase in ventilator-induced lung injury

Signaling via p38 MAP kinase has been implicated in the mechanotransduction associated with mechanical stress and ventilator-induced lung injury (VILI). However, the critical downstream mediators of alveolar injury remain incompletely defined. We provide evidence that high-tidal volume mechanical ventilation (HVt MV) rapidly activates caspases within the lung, resulting in increased alveolar cell apoptosis. Antagonism of MV-induced p38 MAP kinase activity with SB-203580 suppresses both MV-induced caspase activity and alveolar apoptosis, placing p38 MAP kinase upstream of MV-induced caspase activation and programmed cell death. The reactive oxygen species (ROS)-producing enzyme xanthine oxidoreductase (XOR) is activated in a p38 MAP kinase-dependent manner following HVt MV. Allopurinol, a XOR inhibitor, also suppresses HVt MV-induced apoptosis, implicating HVt MV-induced ROS in the induction of alveolar cell apoptosis. Finally, systemic administration of the pan-caspase inhibitor, z-VAD-fmk, but not its inactive peptidyl analog, z-FA-fmk, blocks ventilator-induced apoptosis of alveolar cells and alveolar-capillary leak, indicating that caspase-dependent cell death is necessary for VILI-associated barrier dysfunction in vivo.

Transforming growth factor-beta1 protects against pulmonary artery endothelial cell apoptosis via ALK5

Transforming growth factor (TGF)-beta1 has been reported to cause endothelial cell apoptosis. However, conflicting data have also demonstrated that TGF-beta1 promotes endothelial cell survival. In this study, the effect of TGF-beta1 on apoptosis of cultured bovine pulmonary artery endothelial cells (PAEC) induced by multiple stimuli was investigated. TGF-beta1 protected against apoptosis of bovine PAEC induced by serum deprivation or the VEGF receptor inhibitor SU-5416, but not by UV light exposure or TNFalpha. Neither caspase-8 nor caspase-12 was activated by serum deprivation or the VEGF receptor blocker. However, blockade of VEGF receptors activated caspase-9, an effect that was abolished by TGF-beta1. Furthermore, serum deprivation and inhibition of VEGF receptors significantly decreased the protein level of Bcl-2, an effect that was also abrogated by TGF-beta1. In addition, the baseline level of Bcl-2 was enhanced by TGF-beta1 and reduced by inhibition of activin receptor-like kinase 5 (ALK5), a TGF-beta1 type I receptor. Furthermore, inhibition of ALK5 caused apoptosis of bovine PAEC. These results suggest that TGF-beta1 signaling is critical for maintenance of bovine PAEC survival. Finally, the protective effects of TGF-beta1 on bovine PAEC apoptosis and Bcl-2 reduction were abolished by ALK5 inhibition, but not by inhibition of non-SMAD signaling pathways. Also, TGF-beta1 activated SMAD2 and SMAD1/5, an effect that was abolished by ALK5 inhibition. The results of this study suggest that TGF-beta1 protects against bovine PAEC apoptosis, possibly through ALK5-mediated Bcl-2 induction and subsequent inhibition of the mitochondria-mediated intrinsic pathway of apoptosis. Understanding the mechanism by which TGF-beta1 promotes endothelial cell survival may provide a better treatment for apoptosis-dependent vascular diseases, such as emphysema.

Lack of association between leukocyte telomere length and genetic variants in two ageing-related candidate genes

BACKGROUND

Leukocyte telomere length, a putative marker of ageing, is a highly variable and heritable complex trait. In order to determine the possible underlying genetic variants for leukocyte telomere length variation, we conducted an association study of leukocyte telomere length and two candidate genes for ageing-related traits, TGFB1 and KLOTHO, in a female Caucasian dizygotic twin population.

METHODS AND MATERIALS

Terminal restriction fragment (TRF) length, an index of telomere length, was measured using Southern Blotting. Six and four single nucleotide polymorphisms (SNP) were genotyped in TGFB1 and KLOTHO gene, respectively, and tested for association. When there is strong LD between SNPs (r(2) > 0.5), haplotypic association was investigated using haplotype trend regression approach.

RESULTS

All SNPs were in Hardy-Weinberg equilibrium (p > 0.05). No significant association was detected for individual SNPs (p > 0.101), or two-locus haplotypes (p = 0.7497) with TRF variation.

CONCLUSION

We failed to find any significant association between leukocyte telomere length and 10 SNPs in two ageing-related candidate genes, TGFB1 and KLOTHO. This result suggests that while we could not exclude minor effects, none of 10 SNPs in these two candidate genes showed significant association with the variation of leukocyte telomere length in our cohort. But as it is unclear whether telomere length dynamics is the cause or the effect of the ageing process, it is still possible the genes are associated with ageing via alternate mechanisms.

Blockade of p38 mitogen-activated protein kinase and TGF-beta1/Smad signaling pathways rescues bone marrow-derived peritubular capillary endothelial cells in adriamycin-induced nephrosis

The peritubular capillary (PTC) network is a component of the tubulointerstitium of the kidney with important roles in renal function and hemodynamics. Bone marrow (BM)-derived cells can contribute to repair of the renal PTC network after ischemic injury. However, the cell fate and the regulation of renal BM-derived cell engraftment in comparison with somatic cells during disease progression are unclear. This study characterized the time course and regulation of PTC endothelial cell injury in adriamycin (ADR)-induced nephropathy in mice, a model of chronic, irreversible, progressive renal disease. Enhanced green fluorescence protein-positive BM cells that coexpressed two endothelial cell markers, von Willebrand factor and CD31, were found to engraft into the PTC of chimeric ADR-injected mice in a time-dependent manner. The number of BM-derived PTC endothelial cells peaked 2 wk after ADR injection, then declined dramatically thereafter. In these mice, apoptosis was evident in BM-derived PTC endothelial cells, and the p38 mitogen-activated protein kinase (MAPK) and TGF-beta1/Smad signaling pathways were activated. Blocking both the p38 MAPK and TGF-beta1/Smad signaling pathways by administration of a p38 MAPK inhibitor (SB203580) and a TGF-beta receptor 1 inhibitor (ALK5I) to ADR-injected mice rescued BM-derived PTC endothelial cells from apoptosis, reduced the loss of PTC, and restored kidney function. Investigation into the signaling pathways that regulate the differentiation and survival of BM-derived cells that engraft into the kidney in the proinflammatory setting of progressive renal disease is vital for the successful development of cell-based therapies to promote renal regeneration and repair.

Proteolytic activation of latent TGF-beta precedes caspase-3 activation and enhances apoptotic death of lung epithelial cells

Transforming growth factors beta (TGF-betas) are multifunctional cytokines, which are secreted in latent forms in large latent TGF-beta complexes (LL-TGF-beta) with subsequent deposition to the extracellular matrix (ECM). While a variety of mechanisms capable of activating latent TGF-beta in vitro have been described, the physiological conditions, which promote the activation of TGF-beta in vivo are poorly understood. Mink lung epithelial cells (Mv1Lu) are a widely used model for evaluation of the effects of exogenous TGF-beta both in transcriptional and growth inhibitor assays. We find here that apoptosis of Mv1Lu cells, induced either by staurosporine or serum deprivation, is accompanied by proteolytic processing of LL-TGF-beta and the activation of endogenous TGF-beta. Activation of TGF-beta preceded caspase-3 activation and was almost completely suppressed by the serine protease inhibitor, AEBSF. Both exogenous and endogenously activated TGF-betas were able to enhance the apoptotic response of Mv1Lu cells leading to potentiation of cell death. Potentiation of cell death by activated TGF-beta was associated with downregulation of Akt and p38 MAPK, which were both activated at the initial stages of Mv1Lu apoptosis and were suppressed by exogenous TGF-beta. Pharmacological interruption of either phosphoinositide-3-kinase (PI-3K)/Akt or p38 MAPK signaling by the specific inhibitors mimicked the effect of TGF-beta leading to potentiation of cell death. Current results suggest that proteolytic activation of endogenous TGF-beta is a component of the apoptotic response, capable of modulating the death of Mv1Lu cells by inhibition of both PI-3K/Akt and p38 MAPK-dependent survival pathways.