Mutated p21/WAF/CIP transgene overexpression reduces smooth muscle cell proliferation, macrophage deposition, oxidation-sensitive mechanisms, and restenosis in hypercholesterolemic apolipoprotein E knockout mice

Estrogen Receptor Subtypes Elicit a Distinct Gene Expression Profile of Endothelial-Derived Factors Implicated in Atherosclerotic Plaque Vulnerability

In the presence of established atherosclerosis, estrogens are potentially harmful. MMP-2 and MMP-9, their inhibitors (TIMP-2 and TIMP-1), RANK, RANKL, OPG, MCP-1, lysyl oxidase (LOX), PDGF-β, and ADAMTS-4 play critical roles in plaque instability/rupture. We aimed to investigate (i) the effect of estradiol on the expression of the abovementioned molecules in endothelial cells, (ii) which type(s) of estrogen receptors mediate these effects, and (iii) the role of p21 in the estrogen-mediated regulation of the aforementioned factors. Human aortic endothelial cells (HAECs) were cultured with estradiol in the presence or absence of TNF-α. The expression of the aforementioned molecules was assessed by qRT-PCR and ELISA. Zymography was also performed. The experiments were repeated in either ERα- or ERβ-transfected HAECs and after silencing p21. HAECs expressed only the GPR-30 estrogen receptor. Estradiol, at low concentrations, decreased MMP-2 activity by 15-fold, increased LOX expression by 2-fold via GPR-30, and reduced MCP-1 expression by 3.5-fold via ERβ. The overexpression of ERα increased MCP-1 mRNA expression by 2.5-fold. In a low-grade inflammation state, lower concentrations of estradiol induced the mRNA expression of MCP-1 (3.4-fold) and MMP-9 (7.5-fold) and increased the activity of MMP-2 (1.7-fold) via GPR-30. Moreover, p21 silencing resulted in equivocal effects on the expression of the abovementioned molecules. Estradiol induced different effects regarding atherogenic plaque instability through different ERs. The balance of the expression of the various ER subtypes may play an important role in the paradoxical characterization of estrogens as both beneficial and harmful.

Identification of Potential Ferroptosis-Related Biomarkers and Immune Infiltration in Human Coronary Artery Atherosclerosis

Objective

Ferroptosis is a specific subtype of programmed cell death, which plays an essential role in the immune-associated disease, atherosclerosis (AS). The purpose of this study was to identify potential ferroptosis-related gene biomarkers and its association with immune infiltration characteristics in atherosclerosis with bioinformatics methods.

Methods

Differentially expressed genes (DEGs) between AS and control groups were screened from GSE40231, analyzed for functional enrichment and then intersected with ferroptosis-related genes. Then, a random forest model was constructed based on these differentially expressed ferroptosis-related genes (DE-FRGs) and validated with dataset GSE132651. The performance of the models was evaluated with the area under receiver operating characteristic curves (AUC). Finally, we analyzed the correlation between DE-FRGs above and the characteristics of immune infiltration via CIBERSORT method.

Results

Six DE-FRGs (IL6, ANGPTL7, CDKN1A, AKR1C3, NOX4 and VLDLR) were detected based on dataset of GSE40231. Furthermore, a random forest model was constructed based on them with a compelling diagnostic performance of AUC = 0.8974 in the validation dataset GSE132651. In addition, the proportion of follicular helper T (Tfh) cells was significantly higher in AS group (P < 0.001). And we found significant correlation relationship between Tfh and expression level of ANGPTL7 (R = 0.35, P < 0.01), CDKN1A (R = 0.4, P < 0.0001), AKR1C3 (R = 0.64, P < 0.0001), NOX4 (R = 0.32, P < 0.01) and VLDLR (R = −0.43, P < 0.0001).

Conclusion

This study identified 6 DE-FRGs and validated a predicted model for the early prediction of AS, which also proved the close relationship between ferroptosis and immunity in the pathogenesis of AS.

Evidence of an Epigenetic Modification in Cell-cycle Arrest Caused by the Use of Ultra-highly-diluted Gonolobus Condurango Extract

Objectives:

Whether the ultra-highly-diluted remedies used in homeopathy can effectively bring about modulations of gene expressions through acetylation/deacetylation of histones has not been explored. Therefore, in this study, we pointedly checked if the homeopathically-diluted anti-cancer remedy Condurango 30C (ethanolic extract of Gonolobus condurango diluted 10^-60 times) was capable of arresting the cell cycles in cervical cancer cells HeLa by triggering an epigenetic modification through modulation of the activity of the key enzyme histone deacetylase 2 vis-a-vis the succussed alcohol (placebo) control.

Methods:

We checked the activity of different signal proteins (like p21^WAF, p53, Akt, STAT3) related to deacetylation, cell growth and differentiation by western blotting and analyzed cell-cycle arrest, if any, by fluorescence activated cell sorting. After viability assays had been performed with Condurango 30C and with a placebo, the activities of histone de-acetylase (HDAC) enzymes 1 and 2 were measured colorimetrically.

Results:

While Condurango 30C induced cytotoxicity in HeLa cells in vitro and reduced HDAC2 activity quite strikingly, it apparently did not alter the HDAC1 enzyme; the placebo had no or negligible cytotoxicity against HeLa cells and could not alter either the HDAC 1 or 2 activity. Data on p21^WAF, p53, Akt, and STAT3 activities and a cell-cycle analysis revealed a reduction in DNA synthesis and G1-phase cell-cycle arrest when Condurango 30C was used at a 2% dose.

Conclusion:

Condurango 30C appeared to trigger key epigenetic events of gene modulation in effectively combating cancer cells, which the placebo was unable to do.

EPO gene expression promotes proliferation, migration and invasion via the p38MAPK/AP-1/MMP-9 pathway by p21WAF1 expression in vascular smooth muscle cells

The use of recombinant human erythropoietin (rHuEpo) can lead to hypertrophy and hyperplasia, and has induced the proliferation of vascular smooth muscle cells (VSMCs). The effect of the EPO gene in the migration and invasion of VSMCs remains unclear. In this study, overexpression of the EPO gene increased the DNA synthesis and phosphorylation of ERK1/2 and p38MAPK in VSMCs. In addition, EPO gene expression induced the migration and invasion of VSMCs via the expression of MMP-9 by the activation of NF-κB and AP-1 binding. A blockade of p38MAPK by specific p38MAPK inhibitor SB203580 led to a suppression of the increased DNA synthesis, migration, and invasion of VSMCs that was induced by the EPO gene. SB203580 treatment blocked the increased expression of MMP-9 through the binding activity of AP-1. Transfection of the EPO gene with VSMCs was associated with the up-regulation of cyclin D1/CDK4, cyclin E/CDK2, and p21WAF1, and with the down-regulation of p27KIP1. The specific suppression of p21WAF1 expression by siRNA rescued the enhancement of DNA synthesis via the phosphorylation of p38MAPK and the increase in migration and invasion through AP-1-mediated MMP-9 expression in EPO gene transfectants. These novel findings demonstrate that p21WAF1 regulates the proliferation, migration and invasion of VSMC induced by EPO gene.

Atherosclerosis and tumor suppressor molecules (review)

Atherosclerosis, the major cause of heart attack and stroke, is a chronic inflammatory disease characterized by the formation of atherosclerotic plaque. Oxidized low-density lipoprotein through increased oxidative stress has been identified as one of the primary factors responsible for atherogenesis. Cell proliferation and death are key processes in the progression of atherosclerosis. The oxidative environment in areas of lipid accumulation is mainly created by the production of reactive oxygen species, which are assumed to mediate vascular tissue injury. Oxidative DNA damage and levels of DNA repair are reduced during dietary lipid lowering. The tumor suppressor molecules play a pivotal role in regulating cell proliferation, DNA repair and cell death, which are important processes in regulating the composition of atherosclerotic plaque. Accordingly, in this review, we discuss the fundamental role of tumor suppressor molecules in regulating atherogenesis. In particular, we discuss how tumor suppressor molecules are activated in the complex environment of atherosclerotic plaque, and regulate growth arrest, cell senescence and the apoptosis of vascular smooth muscle cells, which may protect against the progression of atherosclerosis. In addition, we discuss promising alternatives to the use of medications (such as statin) against atherosclerosis, namely diet, with the use of plant-derived supplements to modulate the expression and/or activity of tumor suppressor molecules. We also summarize the progress of research made on herbs with a focus on the modulatory roles of tumor suppressors, and on the molecular mechanisms underlying the prevention if atherosclerosis, supporting designs for further research in this field.

Effects of nitric oxide on cell proliferation: novel insights

Nitric oxide (NO) has been suggested to be a pathophysiological modulator of cell proliferation, cell cycle arrest, and apoptosis. In this context, NO can exert opposite effects under diverse conditions. Indeed, several studies have indicated that low relative concentrations of NO seem to favor cell proliferation and antiapoptotic responses and higher levels of NO favor pathways inducing cell cycle arrest, mitochondria respiration, senescence, or apoptosis. Here we report the effects of NO on both promotion and inhibition of cell proliferation, in particular in regard to cardiovascular disease, diabetes, and stem cells. Moreover, we focus on molecular mechanisms of action involved in the control of cell cycle progression, which include both cyclic guanosine monophosphate-dependent and -independent pathways. This growing field may lead to broad and novel targeted therapies against cardiovascular diseases, especially concomitant type 2 diabetes, as well as novel bioimaging NO-based diagnostic tools.

Interaction between resistin and adiponectin in the proliferation of rat vascular smooth muscle cells

We investigated the effect between resistin and adiponectin on the proliferation of vascular smooth muscle cells (VSMCs). We confirmed that resistin significantly increases the number of rat VSMCs as well as thymidine incorporation with them, whereas adiponectin diminishes resistin-induced cell proliferation. Resistin significantly increased p42/44 mitogen-activated protein kinase (MAPK) phosphorylation within rat VSMCs, whereas adiponectin inhibited resistin-induced MAPK phosphorylation. Moreover, resistin significantly increased c-fos expression, whereas adiponectin suppressed resistin-induced c-fos expression. Cell cycle progression is a tightly controlled event that is negatively regulated by cyclin-dependent kinases inhibitors (CDKIs) such as p53, p21, and p27. Resistin significantly decreased the expression of these CDKIs, whereas adiponectin restored the resistin-induced decrease in CDKIs expression. These effects were abolished in the MAPK inhibitors. In conclusion, resistin plays a role in the development of atherosclerosis, whereas adiponectin may be an important in its prevention in insulin-resistant patients.

HDAC2 phosphorylation-dependent Klf5 deacetylation and RARα acetylation induced by RAR agonist switch the transcription regulatory programs of p21 in VSMCs

Abnormal proliferation of vascular smooth muscle cells (VSMCs) occurs in hypertension, atherosclerosis and restenosis after angioplasty, leading to pathophysiological vascular remodeling. As an important growth arrest gene, p21 plays critical roles in vascular remodeling. Regulation of p21 expression by retinoic acid receptor (RAR) and its ligand has important implications for control of pathological vascular remodeling. Nevertheless, the mechanism of RAR-mediated p21 expression in VSMCs remains poorly understood. Here, we show that, under basal conditions, RARα forms a complex with histone deacetylase 2 (HDAC2) and Krüppel-like factor 5 (Klf5) at the p21 promoter to inhibit its expression. Upon RARα agonist stimulation, HDAC2 is phosphorylated by CK2α. Phosphorylation of HDAC2, on the one hand, promotes its dissociation from RARα, thus allowing the liganded-RARα to interact with co-activators; on the other hand, it increases its interaction with Klf5, thus leading to deacetylation of Klf5. Deacetylation of Klf5 facilitates its dissociation from the p21 promoter, relieving its repressive effect on the p21 promoter. Interference with HDAC2 phosphorylation by either CK2α knockdown or the use of phosphorylation-deficient mutant of HDAC2 prevents the dissociation of Klf5 from the p21 promoter and impairs RAR agonist-induced p21 activation. Our results reveal a novel mechanism involving a phosphorylation-deacetylation cascade that functions to remove the basal repression complex from the p21 promoter upon RAR agonist treatment, allowing for optimum agonist-induced p21 expression.

Early inflammatory reactions in atherosclerosis are induced by proline-rich tyrosine kinase/reactive oxygen species-mediated release of tumor necrosis factor-alpha and subsequent activation of the p21Cip1/Ets-1/p300 system

OBJECTIVE

Reactive oxygen species (ROS) are involved in the initial process of atherosclerosis, whereas it remains to be determined how atherogenic stimulus causes ROS-mediated proinflammatory reactions. Here, we focused on proline-rich tyrosine kinase (PYK2)-mediated ROS generation and examined how atherogenic stimulus causes early proinflammatory reactions.

METHODS AND RESULTS

PYK2-deficient (knockout [KO]) (PYK2-KO) mice were crossbred with apolipoprotein E (ApoE)-deficient (PYK2-KO/ApoE-KO) mice. PYK2-KO/ApoE-KO mice and endothelial cells (EC) were used for the study. Aortic atherogenic lesions in PYK2-KO/ApoE-KO mice were markedly decreased (55% versus ApoE-KO) after 8 weeks of a Western diet. Aortic PYK2 was activated as early as 7 days after the Western diet, when inflammatory cells were not yet activated. Addition of the proatherogenic oxidized phospholipid lysophosphatidylcholine caused activation of endothelial PYK2. Lysophosphatidylcholine-activated PYK2 induced NADPH oxidase-mediated ROS generation and ROS-mediated synthesis of tumor necrosis factor-α (TNFα), vascular cell adhesion molecule-1 (VCAM-1), monocyte chemotactic protein-1 (MCP-1), and p21Cip1/Ets-1. Neutralizing anti-TNFα antibody or knockdown of p21Cip1/Ets-1 system blocked the induction of VCAM-1 and MCP-1. PYK2 deficiency abolished these ROS-mediated proinflammatory reactions. Further analysis revealed that PYK2/ROS-mediated p21Cip1/Ets-1 activation upregulated the transcription of the MCP-1 gene in collaboration with p300 transcription coactivator.

CONCLUSIONS

PYK2 is a key tyrosine kinase activated by high cholesterol exposure, which causes ROS-mediated TNFα release and induces TNFα-dependent expression of proinflammatory molecules via the p21Cip1/Ets-1/p300 transcription system.

Effect of endothelial cell proliferation on atherogenesis: a role of p21(Sdi/Cip/Waf1) in monocyte adhesion to endothelial cells

OBJECTIVE

Uniform laminar shear stress (LS) and disturbed turbulent shear stress (DS) are thought to play opposite roles in preventing or inducing atherosclerosis. Endothelial cell (EC) growth and monocyte adhesion to ECs, an early event in atherosclerosis, are also oppositely regulated by LS and DS. However, how atherogenesis is affected by the regulation of growth by blood flow is unknown. Here we examined the role of p21(Sdi/Cip/Waf1) (p21), a growth inhibitor induced by LS, in monocyte adhesion to ECs.

METHODS

p21 was overexpressed by transfecting a p21-expressing adenoviral vector into ECs. Factors linking EC growth, monocyte adhesion, and p21 were examined by microarray analysis, PCR and Western blotting.

RESULTS

Compared with DS, in the presence or absence of TNFalpha, LS significantly inhibited EC growth and monocyte adhesion to ECs. Both EC proliferation and monocyte adhesion induced by DS were inhibited by p21-overexpression. LS suppressed the expression of thioredoxin-interacting protein (TXNIP). Thioredoxin (TRX) activity, which is suppressed by TXNIP, was therefore higher under LS than DS, as reported previously. p21-overexpression significantly suppressed the DS-induced TXNIP expression, and inhibited the expression of vascular cell adhesion molecule 1 and chemokine (C-C motif) ligand 5 (CCL5/RANTES), which stimulates leukocyte recruitment and is downregulated by ROS scavenging.

CONCLUSION

p21 may function to prevent atherogenesis by regulating the redox balance, which leads to the inhibition of adhesion molecule and chemokine expression in ECs under LS.

Deficiency of cyclin-dependent kinase inhibitors p21Cip1 and p27Kip1 accelerates atherogenesis in apolipoprotein E-deficient mice

Cyclin-dependent kinase inhibitors, p21(Cip1) and p27(Kip1), are upregulated during vascular cell proliferation and negatively regulate growth of vascular cells. We hypothesized that absence of either p21(Cip1) or p27(Kip1) in apolipoprotein E (apoE)-deficiency may increase atherosclerotic plaque formation. Compared to apoE(-/-) aortae, both apoE(-/-)/p21(-/-) and apoE(-/-)/p27(-/-) aortae exhibited significantly more atherosclerotic plaque following a high-cholesterol regimen. This increase was particularly observed in the abdominal aortic regions. Deficiency of p27(Kip1) accelerated plaque formation significantly more than p21(-/-) in apoE(-/-) mice. This increased plaque formation was in parallel with increased intima/media area ratios. Deficiency of p21(Cip1) and p27(Kip1) accelerates atherogenesis in apoE(-/-) mice. These findings have significant implications for our understanding of the molecular basis of atherosclerosis associated with excessive proliferation of vascular cells.

Identification of an up-regulated anti-apoptotic network in the internal thoracic artery

BACKGROUND

The radial artery (RA) is known as an atherosclerosis-prone vessel in contrast to the atherosclerosis-resistant internal thoracic artery (ITA). The purpose of the present study was to compare the gene expression profile of these arteries from the same patient in order to identify genes involved in atherogenesis or intimal hyperplasia.

METHODS

Paired specimens of RA and ITA (n=6) were analyzed by histomorphometry and whole genome microarray. The microarray data underwent pathway analysis to identify biological networks. Laser microdissection (LMD) was used to identify the cellular expression of candidate genes in the intimal or medial layer of the ITA and RA.

RESULTS

Histomorphometric analyses revealed a significantly higher degree of intimal hyperplasia in the RA compared to the ITA. 552 genes were differentially expressed in the ITA and RA. qRT-PCR confirmed a significant up-regulation of six anti-apoptotic genes. p21 (11.8-fold, p=0.011), CCL2 (5.4-fold, p=0.034), SOCS3 (7.2-fold, p=0.002), IER3 (4.1-fold, p=0.048), MCL-1 (2.6-fold, p=0.025) and IL-6 (17.8-fold, p=0.046) were up-regulated in the ITA. LMD confirmed that cells of the intimal layer of the ITA consistently expressed higher levels of all six candidate genes than those of the RA.

CONCLUSIONS

Microarray analysis and qRT-PCR identified significantly up-regulated genes in the ITA involved in an anti-apoptotic network. LMD revealed a higher expression of all anti-apoptotic genes in the intimal area of the ITA. These genes may play an important role in protecting the intima of the ITA from developing hyperplasia and atherosclerosis.

Enhanced susceptibility of cyclin kinase inhibitor p21 knockout mice to high fat diet induced atherosclerosis

Cyclin kinase inhibitor p21 is one of the most potent inhibitors of aortic smooth muscle cell proliferation, a key mediator of atherosclerosis. This study tests if p2l deficiency will result in severe atherosclerosis in a mouse model. p21-/- and strain matched wild type mice were fed with high fat diet for 21 weeks. Analysis for biochemical parameters (cholesterol, triglycerides) in serum and mRNA expression of CD36, HO-1, TGF-beta, IFN-gamma, TNF-alpha, PPAR-gamma and NADPH oxidase components (p22phox, NOX-1 and Rac-1) was performed in aortic tissues by Real Time PCR. p21-/- mice gained significantly (p < 0.01) more weight than wild type mice, triglycerides (p < 0.05) and cholesterol levels (p < 0.01) were more pronounced in the sera of p21-/- compared to wild type mice fed with high fat diet. High fat diet resulted in significantly decreased TGF-beta (p < 0.02), HO-l (p < 0.02) and increased CD36 (p < 0.03) mRNA expression in aortic tissues of p21-/- mice compared to animal fed with regular diet. IFN-gamma mRNA expression (235 +/- 11 folds) increased significantly in high fat diet fed p21-/- mice and a multifold modulation of PPAR-gamma(136 +/- 7), p22phox, NOX-1 and Rac-1 (15-35-folds) mRNA in aortic tissues from p21-/- mice compared to the wild type mice. Severity of atherosclerotic lesions was significantly higher in p21-/- compared to wild type mice. The results demonstrate that the deficiency of p21 leads to altered expression of pro-atherogenic genes, and severe atherosclerosis in mice fed with high fat diet. This opens the possibility of p21 protein as a therapeutic tool to control progression of atherosclerosis.

Activation of transcription factors and gene expression by oxidized low-density lipoprotein

It is well recognized that oxidized LDL (OxLDL) plays a crucial role in the initiation and progression of atherosclerosis. Many biological effects of OxLDL are mediated through signaling pathways, especially via the activation of transcription factors, which in turn stimulate the expression of genes involved in the inflammatory and oxidative stress response or in cell cycle regulation. In this review, we will discuss the various transcription factors activated by OxLDL, the studied cell types, the active compounds of the OxLDL particle, and the downstream genes when identified. Identification of the transcription factors and some of the downstream genes regulated by OxLDL has helped us understand the molecular mechanism involved in generation of the atherosclerotic plaque.

p21Cip1 modulates arterial wound repair through the stromal cell-derived factor-1/CXCR4 axis in mice

Cyclin-dependent kinase inhibitors, including p21Cip1, are implicated in cell turnover and are active players in cardiovascular wound repair. Here, we show that p21Cip1 orchestrates the complex interactions between local vascular and circulating immune cells during vascular wound repair. In response to femoral artery mechanical injury, mice with homozygous deletion of p21Cip1 displayed accelerated proliferation of VSMCs and increased immune cell infiltration. BM transplantation experiments indicated that local p21Cip1 plays a pivotal role in restraining excessive proliferation during vascular wound repair. Increased local vascular stromal cell-derived factor-1 (SDF-1) levels were observed after femoral artery injury in p21+/+ and p21-/- mice, although this was significantly greater in p21-/- animals. In addition, disruption of SDF-1/CXCR4 signaling inhibited the proliferative response during vascular remodeling in both p21+/+ and p21-/- mice. We provide evidence that the JAK/STAT signaling pathway is an important regulator of vascular SDF-1 levels and that p21Cip1 inhibits STAT3 binding to the STAT-binding site within the murine SDF-1 promoter. Collectively, these results suggest that p21Cip1 activity is essential for the regulation of cell proliferation and inflammation after arterial injury in local vascular cells and that the SDF-1/CXCR4 signaling system is a key mediator of vascular proliferation in response to injury.

Evidence of COX-1 and COX-2 expression in Kaposi's sarcoma tissues

Cyclooxygenases (COXs) are enzymes catalysing prostaglandin synthesis and are implicated in the carcinogenesis of some cancer types. In addition, an important role of these enzymes in herpesvirus infections was demonstrated and it has recently been proposed that COX-2 may participate in herpesvirus-induced neoplasia such as Kaposi's sarcoma (KS). To date no immunohistochemical study has been performed to determine the identification of COX-1 and COX-2 in KS. We have investigated 35 cases of classic KS and 27 cases of epidemic KS form in order to study the distribution and localisation of COXs. We have examined by immunohistochemistry the expression of COX-1 and COX-2 in classic and epidemic forms of KS also in relationship to the characteristic morphological phases (patch, plaque and nodular stage) of KS and cell localisation by double immunostaining. Moreover, we have obtained COX-1 and COX-2 expression by Western blot analysis. Our results establish that (a) COX-1 and COX-2 are overexpressed significantly in classic and epidemic KS compared with control skin tissues (P<0.01 and P>0.03, respectively, for COX-1; P<0.01 and P>0.03, respectively, for COX-2); (b) the extent and intensity staining for both COXs were higher in classic than in epidemic form of KS. Our data support the hypothesis that both COXs may be involved in the pathogenesis of KS.

Novel challenges in exploring peptide ligands and corresponding tissue-specific endothelial receptors

The structural and molecular diversity of vascular endothelium may depend on the functional state and tissue localisation of its cells. Tumour vasculature expresses a number of molecular markers that distinguish it from normal vasculature. In cancer, the determinant of specific tumour vasculature heterogeneity is, in part, dictated by dysregulated expression of tumour-derived angiogenic factors. The identification of molecular 'addresses' on the surface of tumour vasculature has significantly contributed to the selection of targets, which have been used for delivering therapeutic and imaging agents in cancer. Cytotoxic drug, pro-apoptotic peptides, protease inhibitors, and gene therapy vectors have been successfully linked to peptides and delivered to tumour sites with an improved experimental therapy. Different diagnostic and therapeutic compounds can be efficiently targeted to specific receptors on vascular endothelial cells; the development of ligand-directed vector tools may promote systemic targeted gene delivery. Here, we review the very recent advances in the identification of peptide ligands and their corresponding tissue-specific endothelial receptors through the phage display technology with emphasis on ligand-directed delivery of therapeutic agents and targeted gene therapy.

Gene therapy for restenosis: biological solution to a biological problem

Coronary artery disease remains a significant health threat afflicting millions of individuals worldwide. Despite the development of a variety of technologies and catheter based interventions, post-procedure restenosis is still a significant concern. Gene therapy has emerged as a promising approach aimed at modification of cellular processes that give rise to restenosis. When juxtaposed alongside the failure of traditional pharmacotherapeutics to eliminate restenosis, gene therapy has engendered great expectations for cubing coronary restenosis. In this review we have discussed an overview of gene therapy approaches that hve been utilized to reduce restenosis in preclinical and clinical studies, current status of anti-restenosis gene therapy and perspectives on its future application. For brevity, we have limited our discussion on anti-restenosis gene therapy to the introduction of a nucleic acid to the cell, tissue, organ or organism in order to give rise to the expression of a protein, the function of which will confer therapeutic effect. For the purpose of this review, we have focused ou discussion on two relevant anti-restenosis strategies, anti-proliferative and pro-endothelialization.

G1 cell cycle arrest by amlodipine, a dihydropyridine Ca2+ channel blocker, in human epidermoid carcinoma A431 cells

We demonstrated previously that amlodipine, a dihydropyridine Ca(2+) channel blocker, exhibits antitumor effects on human epidermoid carcinoma A431 cells both in vitro and in vivo, in part through inhibition of capacitative Ca(2+) entry. In this study, we examined the effects of amlodipine on cell cycle distribution and cell cycle regulatory molecules in A431 cells, since a rise in intracellular Ca(2+) is required at several points during cell cycle progression. Flow cytometric analysis revealed that treatment with amlodipine (20-30muM, for 24h) induced G1 phase cell accumulation. The amlodipine-induced G1 arrest was associated with a decrease in phosphorylation of retinoblastoma protein (pRB), a regulator of G1 to S phase transition, reduction of protein levels of cyclin D1 and cyclin dependent kinase 4 (CDK4), G1 specific cell cycle proteins, and increased expression of p21(Waf1/Cip1), an inhibitory protein of CDK/cyclin complexes. In vitro kinase assay revealed that amlodipine significantly decreased CDK2-, CDK4-, and their partners cyclin E- and cyclin D1-associated kinase activities. The amlodipine-induced reductions in cyclin D1 protein expression and in CDK2 kinase activity were reproduced by a dihydropyridine derivative, nicardipine, having an inhibitory effect on A431 cell growth, but not by nifedipine, lacking the antiproliferative activity. Our results demonstrate that amlodipine caused G1 cell cycle arrest and growth inhibition in A431 cells through induction of p21(Waf1/Cip1) expression, inhibition of CDK/cyclin-associated kinase activities, and reduced phosphorylation of pRB.

Mechanism by which avenanthramide-c, a polyphenol of oats, blocks cell cycle progression in vascular smooth muscle cells

Previously, we reported that avenanthramide-c (Avn-c), one of the major avenanthramides, polyphenols of oats, inhibited the serum-induced proliferation of vascular smooth muscle cells (SMC), which is an important process in the initiation and development of atherosclerosis. In the present study, we further investigated its cell cycle inhibitory mechanism. Rat embryonic aortic smooth muscle cell line A10 was used in this study. Flow cytometry analysis revealed that treatment of A10 cells with 80 muM Avn-c arrested the cell cycle in G1 phase as indicated by an increase in the number of cells in G1 phase and a decrease in the number of cells in S phase. This cell cycle arrest was associated with a decrease in the phosphorylation of retinoblastoma protein (pRb), whose hyperphosphorylation is a hallmark of the G1 to S transition in the cell cycle. The inhibition of pRb phosphorylation with Avn-c was accompanied by a decrease in cyclin D1 expression and an increase in cyclin-dependent kinase inhibitor p21cip1 expression, without significant changes in p27kip1 expression. Furthermore, Avn-c treatment increased the expression level and stability of p53 protein, which could account for the increase of p21cip1 expression. Our results demonstrate for the first time that Avn-c, which is a unique polyphenol found in oats, arrests SMC proliferation at G1 phase by upregulating the p53-p21cip1 pathway and inhibiting pRB phosphorylation. This inhibitory effect of Avn-c on SMC proliferation is an additional indication for the potential health benefit of oat consumption in the prevention of coronary heart disease beyond its known effect through lowering blood cholesterol.

Therapeutic effects of concurrent autologous bone marrow cell infusion and metabolic intervention in ischemia-induced angiogenesis in the hypercholesterolemic mouse hindlimb

Lower-limb ischemia is a major health problem especially when associated to hypercholesterolemia. Because of the absence of effective treatment in the advanced stages of the disease, amputation is undertaken to alleviate unbearable symptoms. Since tissue ischemia and hypercholesterolemia are associated with an overwhelming generation of oxygen radicals, metabolic intervention with antioxidants and l-arginine can induce beneficial effects beyond those achieved by a novel therapeutic approach represented by the use of autologous bone marrow cells (BMCs). The protective effect of BMCs and vascular protection by metabolic cotreatment (1.0% vitamin E added to the chow, 0.05% vitamin C and 6% l-arginine added to the drinking water) were examined in ischemia-induced angiogenesis in the hypercholesterolemic mouse hindlimb. Intravenous BMC therapy improved blood flow and increased capillary densities. This beneficial effect was amplified by metabolic cotreatment, an intervention inducing vascular protection, at least in part, through the nitric oxide pathway, reduction of systemic oxidative stress and macrophage activation.

Regulation of proliferation and gene expression in cultured human aortic smooth muscle cells by resveratrol and standardized grape extracts

Epidemiologic studies suggest that low to moderate consumption of red wine is inversely associated with the risk of coronary heart disease; the protection is in part attributed to grape-derived polyphenols, notably trans-resveratrol, present in red wine. It is not clear whether the cardioprotective effects of resveratrol can be reproduced by standardized grape extracts (SGE). In the present studies, we determined, using cultured human aortic smooth muscle cells (HASMC), growth and specific gene responses to resveratrol and SGE provided by the California Table Grape Commission. Suppression of HASMC proliferation by resveratrol was accompanied by a dose-dependent increase in the expression of tumor suppressor gene p53 and heat shock protein HSP27. Using resveratrol affinity chromatography and biochemical fractionation procedures, we showed by immunoblot analysis that treatment of HASMC with resveratrol increased the expression of quinone reductase I and II, and also altered their subcellular distribution. Growth of HASMC was significantly inhibited by 70% ethanolic SGE; however, gene expression patterns in various cellular compartments elicited in response to SGE were substantially different from those observed in resveratrol-treated cells. Further, SGE also differed from resveratrol in not being able to induce relaxation of rat carotid arterial rings. These results indicate that distinct mechanisms are involved in the regulation of HASMC growth and gene expression by SGE and resveratrol.

Adenosine monophosphate-activated protein kinase suppresses vascular smooth muscle cell proliferation through the inhibition of cell cycle progression

Vascular smooth muscle cell (VSMC) proliferation is a critical event in the development and progression of vascular diseases, including atherosclerosis. We investigated whether the activation of adenosine monophosphate-activated protein kinase (AMPK) could suppress VSMC proliferation and inhibit cell cycle progression. Treatment of human aortic smooth muscle cells (HASMCs) or isolated rabbit aortas with the AMPK activator 5-Aminoimidazole-4-carboxamide ribonucleoside (AICAR) induced phosphorylation of AMPK and acetyl Co-A carboxylase. AICAR significantly inhibited HASMC proliferation induced by both platelet-derived growth factor-BB (PDGF-BB) and fetal calf serum (FCS). Treatment with AICAR inhibited the phosphorylation of retinoblastoma gene product (Rb) induced by PDGF-BB or FCS, and increased the expression of cyclin-dependent kinase inhibitor p21(CIP) but not that of p27(KIP). Pharmacological inhibition of AMPK or overexpression of dominant negative-AMPK inhibited both the suppressive effect of AICAR on cell proliferation and the phosphorylation of Rb, suggesting that the effect of AICAR is mediated through the activation of AMPK. Cell cycle analysis in HASMCs showed that AICAR significantly increased cell population in G0/G1-phase and reduced that in S- and G2/M-phase, suggesting AICAR induced cell cycle arrest. AICAR increased both p53 protein and Ser-15 phosphorylated p53 in HASMCs, which were blocked by inhibition of AMPK. In isolated rabbit aortas, AICAR also increased Ser-15 phosphorylation and protein expression of p53 and inhibited Rb phosphorylation induced by FCS. These data suggest for the first time that AMPK suppresses VSMC proliferation via cell cycle regulation by p53 upregulation. Therefore, AMPK activation in VSMCs may be a therapoietic target for the prevention of vascular diseases.

Absence of p21 Waf1/Cip1/Sdi1 Modulates Macrophage Differentiation and Inflammatory Response and Protects Against Atherosclerosis

BACKGROUND

The tumor suppressor p53 protects against atherosclerosis progression in several different mouse models. A major target of p53 is p21, the cyclin-dependent kinase inhibitor that regulates entry into the cell cycle of different types of cells, including stem cells. p21 is also involved in the maturation and differentiation of monocytes into macrophages.

METHODS AND RESULTS

We studied the effect of p21Waf1 inactivation on atherosclerosis development in apolipoprotein E-deficient mice (apoE-/-). Contrary to previous data suggesting a protective role for p21, we found that absence of p21, either globally or in bone marrow-derived cells, protects against atherosclerosis. Atherosclerotic lesions of p21-/-/apoE-/- mice exhibit a more stable phenotype, with increased apoptosis and reduced inflammatory vascular cell adhesion molecule-1 immunostaining but no difference in cellular proliferation compared with lesions of p21+/+/apoE-/- mice. Because bone marrow-derived cells mediate many of the effects of p21, we examined the expression profile of 23 genes in macrophages using real-time polymerase chain reaction. Compared with their p21+/+ counterparts, peritoneal macrophages of p21-/- mice express lower levels of proinflammatory markers, including macrophage inflammatory proteins 1 and 2 and interleukin-1alpha, and higher levels of putative protective genes, such as scavenger receptor type B-I and LDL receptor-related protein. Furthermore, we found that, in comparison with p21+/+ macrophages, p21-/- macrophages displayed increased phagocytic activity toward fluorescent latex microspheres as well as apoptotic cells, thus uncovering a novel mechanism of the antiinflammatory activity of p21-/- macrophages.

CONCLUSIONS

Loss of p21 protects against atherosclerosis in apoE-/- mice. The data underscore the important role of p21 in macrophage function and inflammation and provide insight into the mechanism of the proatherogenic effect of p21.

The calcium channel blocker amlodipine exerts its anti¬proliferative action via p21 (Waf1/Cip1) gene activation

Proliferation of vascular smooth muscle cells (VSMC) contributes to the progression of atherosclerotic plaques. Calcium channel blockers have been shown to reduce VSMC proliferation, but the underlying molecular mechanism remains unclear. p21(Waf1/Cip1) is a potent inhibitor of cell cycle progression. Here, we demonstrate that amlodipine (10(-6) to 10(-8) M) activates de novo synthesis of p21(Waf1/Cip1) in vitro. We show that amlodipine-dependent activation of p21(Waf1/Cip1) involves the action of the glucocorticoid receptor (GR) and C/EBP-alpha. The underlying pathway apparently involves the action of mitogen-activated protein kinase or protein kinase C, but not of extracellular signal-related kinase or changes of intracellular calcium. Amlodipine-induced p21(Waf1/Cip1) promoter activity and expression were abrogated by C/EBP-alpha antisense oligonucleotide or by the GR antagonist RU486. Amlodipine-dependent inhibition of cell proliferation was partially reversed by RU486 at 10(-8) M (58%+/-29%), antisense oligonucleotides targeting C/EBP-alpha (91%+/-26%), or antisense mRNAs targeting p21(Waf1/Cip1) (96%+/-32%, n=6); scrambled antisense oligonucleotides or those directed against C/EBP-beta were ineffective. The data suggest that the anti-proliferative action of amlodipine is achieved by induction of the p21 (Waf1/Cip1) gene, which may explain beneficial covert effects of this widely used cardiovascular therapeutic drug beyond a more limited role as a vascular relaxant.

The Effect of Neonatal Hyperoxia on the Lung of p21Waf1/Cip1/Sdi1-Deficient Mice

Hyperoxia is an important factor in the development of bronchopulmonary dysplasia and is associated with growth arrest and impaired alveolar septal development in the neonatal lung. p21(Waf1/Cip1/Sdi1) (p21), a cyclin-dependent kinase inhibitor, acts as a checkpoint regulator in the cell cycle during periods of stress and is induced in neonatal lung during hyperoxia exposure. To determine if p21 protects against lung injury during neonatal lung development, we placed newborn p21 knockout (p21(-/-)) and p21 wild-type (p21(+/+)) mice in 85-90% O(2) for 4 d. We found that newborn p21(-/-) mice exposed to O(2) had decreased survival in hyperoxia compared with p21(+/+) mice (P < 0.01). At 2 and 6 wk after exposure to neonatal hyperoxia, p21(-/-) O(2) lung had significantly larger alveoli then p21(-/-) control lung, as assessed by mean alveolar size and mean linear intercept. Pulmonary function tests at 6 wk demonstrated increased lung volume in both p21(-/-) and p21(+/+) O(2) mice consistent with altered lung growth from neonatal exposure to hyperoxia. Antibodies to nitrotyrosine, a marker for oxidative stress revealed that at 2 and 6 wk of age, p21(-/-) O(2) lung had significantly more oxidative stress than p21(-/-) and p21(+/+) control and p21(+/+) O(2) lung. We therefore conclude that p21 confers some additional protection to the lung during exposure to neonatal hyperoxia. Furthermore, p21 may be important during recovery from lung injury because it is associated with lower levels of oxidative stress and increased oxidative stress may contribute to alveolar growth abnormalities in the p21(-/-) O(2) lung.

Concerted effect of transforming growth factor-β, cyclin inhibitor p21, and c-mycon smooth muscle cell proliferation

Increased aortic smooth muscle cell (SMC) proliferation is a key event in the pathogenesis of atherosclerosis. Transforming growth factor-β (TGF-β) is one of the potent inhibitors of SMC proliferation. The purpose of this study was 1) to explore the effect of TGF-β inhibition on proliferation of SMC and expression of growth regulatory molecules like p21 and c- myc and 2) to determine whether restoration of cell cycle regulatory molecules normalizes the altered proliferation. To test the role of TGF-β in SMC proliferation, using antisense plasmid DNA, we inhibited TGF-β gene from aortic SMC, which resulted in a significant increase ( P < 0.03) in proliferation (studied by quantifying new DNA synthesis with [3H]thymidine uptake assay). In TGF-β-altered SMC (TASMC), the mRNA expression (studied by RT-PCR) of c- myc was increased whereas that of the cyclin inhibitor p21 was completely inhibited. Using p21 sense plasmid DNA, we transfected p21 gene in TASMC, which restored p21 mRNA and protein expression and decreased proliferation ( P < 0.002) in TASMC. Similar treatment with c- myc antisense oligonucleotides significantly ( P < 0.001) decreased the proliferation of TASMC. TASMC also exhibited alteration in morphological changes in SMC but returned to normal with treatment of p21 and TGF-β sense plasmid DNA. Two-dimensional gel electrophoresis analysis of SMC and TASMC demonstrated differential expression of proteins relevant to cellular proliferation and atherosclerosis. This study uniquely analyzes the effect of TGF-β at the molecular level on proliferation of SMC and on cell cycle regulatory molecules, implicating their potential role in the pathogenesis of atherosclerosis.

The role of inflammation in vascular injury and repair

Inflammation plays a critical role in the vascular response to injury. In particular, mechanical injury using techniques such as balloon angioplasty and stenting results in complex inflammatory reactions which influence proliferation of vessel wall constituents such as endothelial cells, smooth muscle cells, and extracellular matrix proteins. Inflammatory cells are recruited to the injured vessel wall initially as a reparative mechanism; however, these same inflammatory processes are also pivotal in the development of restenotic lesions. Leukocytes serve as the primary inflammatory cells but we now know that platelets produce a number of important inflammatory mediators. This review describes the mechanisms that regulate endothelial cell migration, smooth muscle cell activation, and extracellular matrix protein production, all of which are key components in the inflammatory response to vascular injury.

Green tea polyphenol epigallocatechin-3 gallate induces apoptosis of proliferating vascular smooth muscle cells via activation of p53

Green tea polyphenols (GTPs), which possess antioxidant properties, have been shown to inhibit the development of atherosclerotic lesions. Epigallocatechin-3-gallate (EGCG), the most abundant GTP, displays antiproliferative effects in a variety of cell types. Here, we examined the effects of GTPs on aortic smooth muscle cell (SMC) proliferation. Treatment with a GTP mixture or EGCG at a dose of 40 to 50 microg/ml slowed SMC growth, while at a higher dose of 80 microg/ml EGCG also induced cell death as judged by TUNEL assay. Apoptosis was mainly observed in proliferating SMCs in subconfluent cultures; whereas at higher confluency, cell viability was largely unaffected. Treatment with 80 microg/ml EGCG induced the tumor suppressor p53, which was functional as judged by activation of the target cyclin-dependent kinase inhibitor p21CIP1. Inhibition of p53 activity with a dominant negative mutant reduced cell death. The increase in p53 protein was due to increased stability. EGCG also induced functional nuclear factor-kappaB (NF-kappaB) complexes, and inhibition of this activity reduced the extent of cell death. Thus, EGCG inhibits growth and induces death of SMCs in a p53- and NF-kappaB-dependent manner. These results provide evidence for a new molecular mechanism whereby green tea polyphenols inhibit SMC proliferation and function to prevent the development of atherosclerosis.

Coordinate control of proliferation and migration by the p27Kip1/cyclin-dependent kinase/retinoblastoma pathway in vascular smooth muscle cells and fibroblasts

Previous studies have demonstrated a protective effect of the cyclin-dependent kinase (CDK) inhibitor p27Kip1 against atherosclerosis and restenosis, two disorders characterized by abundant proliferation and migration of vascular smooth muscle cells and adventitial fibroblasts. These therapeutic effects might result from p27Kip1-dependent suppression of both cell proliferation and migration. However, the interplay between cell growth and locomotion remains obscure. We show here that p27Kip1 inhibits cellular changes that normally occur during cell locomotion (eg, lamellipodia formation and reorganization of actin filaments and focal adhesions). Importantly, a p27Kip1 mutant lacking CDK inhibitory activity failed to inhibit vascular smooth muscle cell and fibroblast proliferation and migration. Moreover, a constitutively active mutant of the retinoblastoma protein (pRb) insensitive to CDK-dependent hyperphosphorylation inhibited both cell proliferation and migration. In contrast, inactivation of pRb by forced expression of the adenoviral oncogene E1A correlated with high proliferative and migratory activity. Collectively, these results suggest that cellular proliferation and migration are regulated in a coordinated manner by the p27Kip1/CDK/pRb pathway. These findings might have important implications for the development of novel therapeutic strategies targeting the fibroproliferative/migratory component of vascular occlusive disorders.

Deletion of the p66Shc longevity gene reduces systemic and tissue oxidative stress, vascular cell apoptosis, and early atherogenesis in mice fed a high-fat diet

Several experimental and clinical studies have shown that oxidized low-density lipoprotein and oxidation-sensitive mechanisms are central in the pathogenesis of vascular dysfunction and atherogenesis. Here, we have used p66(Shc-/-) and WT mice to investigate the effects of high-fat diet on both systemic and tissue oxidative stress and the development of early vascular lesions. To date, the p66(Shc-/-) mouse is the unique genetic model of increased resistance to oxidative stress and prolonged life span in mammals. Computer-assisted image analysis revealed that chronic 21% high-fat treatment increased the aortic cumulative early lesion area by approximately 21% in WT mice and only by 3% in p66(Shc-/-) mice. Early lesions from p66(Shc-/-) mice had less content of macrophage-derived foam cells and apoptotic vascular cells, in comparison to the WT. Furthermore, in p66(Shc-/-) mice, but not WT mice, we found a significant reduction of systemic and tissue oxidative stress (assessed by isoprostanes, plasma low-density lipoprotein oxidizability, and the formation of arterial oxidation-specific epitopes). These results support the concept that p66(Shc-/-) may play a pivotal role in controlling systemic oxidative stress and vascular diseases. Therefore, p66(Shc) might represent a molecular target for therapies against vascular diseases.

New insights in the transcriptional activity and coregulator molecules in the arterial wall

A number of vascular diseases are associated with abnormal expression of genes that contribute to their pathophysiological and clinical manifestations, but at the same time offer potential therapeutic targets. One of the promising therapeutic approaches targets the pathophysiological pathways leading to aberrant gene activation, namely transcriptional activity and its molecular modulators (agonists, antagonists, coregulators, and nuclear receptors). The transcription factors can be divided into four classes (I-IV) classified by structural elements, like basic leucine zipper (bZIP) or basic helix-loop-helix (bHLH), which mediate their DNA binding activity but also determine the classes of drugs that can affect their activity. For example, statins modulate activation of the class-I transcription factor sterol responsive element-binding protein (SREBP), whose target genes including hydroxyl-methyl-glutaryl acetyl Coenzyme-A (HMG-CoA) reductase, HMG-CoA synthase, and the low-density lipoprotein receptor, all of which are involved in cholesterol and fatty acid metabolism. Similarly, insulin-like drugs target the nuclear receptor peroxisome-proliferator-activator-receptor (PPAR)-gamma (class-II), several anti-inflammatory drugs inhibit activation of nuclear factor kappa B (NFkappaB) (class-IV), while others (e.g. flavopiridol, rapamycin, and paclitaxel) target regulation of cell-cycle proteins. Increased understanding of the genetic and molecular basis of disease (e.g. transcriptional activity and its coregulation) will potentially enhance future diagnosis, treatment, and prevention of vascular diseases.

Post-intervention vessel remodeling

By-pass surgery and percutaneous transluminal (coronary) angioplasty, PT(C)A, are standard techniques for the treatment of vascular occlusions. Their usefulness is limited by by-pass graft failure and restenosis occurring after the procedures. Twenty percent of patients treated with PTCA/PTA need a new revascularization procedure within 6 months, despite a successful procedure. Stents are used to prevent restenosis in selected lesions, but in-stent restenosis also remains an important clinical problem. In this review we discuss progress of gene therapy for the treatment of post-PT(C)A restenosis, in-stent restenosis and by-pass graft stenosis over the last 2 years (2000-2002).

Genes potentially involved in plaque rupture

PURPOSE OF REVIEW

Rupture of an atherosclerotic plaque is the predominant underlying event in the pathogenesis of acute coronary syndromes and stroke. While ruptured plaques are morphologically well described, the precise molecular mechanisms involved in plaque rupture are still incompletely understood. Over the last few years, techniques like microarray, suppression subtractive hybridization and differential display enabled us to study complex gene expression profiles that occur during the process of atherogenesis. In this review we focus on recent large-scale gene expression profiles performed on whole mount vascular specimens.

RECENT FINDINGS

The gene expression profiles on whole mount vascular tissue confirmed that at least three mechanisms are involved in plaque rupture: (1) a disturbed balance in extracellular matrix turnover, (2) disturbed regulation of cell turnover and (3) processes involved in lipid metabolism. Animal models exhibiting features of plaque rupture reflect the involvement of these three mechanisms. The most dramatic mouse phenotypes were observed after interventions in at least two of these mechanisms.

SUMMARY

The observation of plaque rupture in recent mice models is indicative of the multifactorial process of plaque rupture. This multifactorial character of plaque rupture suggests that interventions may be most effective when they influence more than one mechanisms at a time.

Efficacy and age-related effects of nitric oxide-releasing aspirin on experimental restenosis

Restenosis after percutaneous transluminal coronary angioplasty is caused by neointimal hyperplasia, which involves impairment of nitric oxide (NO)-dependent pathways, and may be further exacerbated by a concomitant aging process. We compared the effects of NO-releasing-aspirin (NCX-4016) and aspirin (ASA) on experimental restenosis in both adult and elderly rats. Moreover, to ascertain the efficacy of NCX-4016 during vascular aging, we fully characterized the release of bioactive NO by the drug. Sprague-Dawley rats aged 6 and 24 months were treated with NO releasing-aspirin (55 mg/kg) or ASA (30 mg/kg) for 7 days before and 21 days after standard carotid balloon injury. Histological examination and immunohistochemical double-staining were used to evaluate restenosis. Plasma nitrite and nitrate and S-nitrosothiols were determined by a chemiluminescence-based assay. Electron spin resonance was used for determining nitrosylhemoglobin. Treatment of aged rats with NCX-4016 was associated with increased bioactive NO, compared with ASA. NO aspirin, but not ASA, reduced experimental restenosis in old rats, an effect associated with reduced vascular smooth muscle cell proliferation. NCX-4016, but not ASA, was well tolerated and virtually devoid of gastric damage in either adult or old rats. Thus, impairment of NO-dependent mechanisms may be involved in the development of restenosis in old rats. We suggest that an NCX-4016 derivative could be an effective drug in reducing restenosis, especially in the presence of aging and/or gastrointestinal damage.