Identification of apoptotic genes mediating TGF-beta/Smad3-induced cell death in intestinal epithelial cells using a genomic approach

Aging- and alcohol-associated spatial transcriptomic signature in mouse acute pancreatitis reveals heterogeneity of inflammation and potential pathogenic factors

The rapidly aging population is consuming more alcohol, leading to increased alcohol-associated acute pancreatitis (AAP) with high mortality. However, the mechanisms remain undefined, and currently there are no effective therapies available. This study aims to elucidate aging- and alcohol-associated spatial transcriptomic signature by establishing an aging AAP mouse model and applying Visium spatial transcriptomics for understanding of the mechanisms in the context of the pancreatic tissue. Upon alcohol diet feeding and caerulein treatment, aging mice (18 months) developed significantly more severe AAP with 5.0-fold increase of injury score and 2.4-fold increase of amylase compared to young mice (3 months). Via Visium spatial transcriptomics, eight distinct tissue clusters were revealed from aggregated transcriptomes of aging and young AAP mice: five acinar, two stromal, and one islet, which were then merged into three clusters: acinar, stromal, and islet for the comparative analysis. Compared to young AAP mice, > 1300 differentially expressed genes (DEGs) and approximately 3000 differentially regulated pathways were identified in aging AAP mice. The top five DEGs upregulated in aging AAP mice include Mmp8, Ppbp, Serpina3m, Cxcl13, and Hamp with heterogeneous distributions among the clusters. Taken together, this study demonstrates spatial heterogeneity of inflammatory processes in aging AAP mice, offering novel insights into the mechanisms and potential drivers for AAP development. KEY MESSAGES: Mechanisms regarding high mortality of AAP in aging remain undefined. An aging AAP mouse model was developed recapturing clinical exhibition in humans. Spatial transcriptomics identified contrasted DEGs in aging vs. young AAP mice. Top five DEGs were Mmp8, Ppbp, Serpina3m, Cxcl13, and Hamp in aging vs. young AAP mice. Our findings shed insights for identification of molecular drivers in aging AAP.

A negative feedback loop centered on SMAD3 expression in transforming growth factor β1-induced corneal myofibroblast differentiation

SMAD3 downregulation is documented in transforming growth factor β1 (TGF-β1)-induced corneal fibroblasts differentiation to myofibroblasts ("fibroTOmyoDiff") or corneal wound healing. However, the exact regulatory mechanism of TGF-β1/SMAD3 pathway in this context remains unclear. Here, we investigated the role and related mechanism of SMAD3 down-regulation in TGF-β1-induced human corneal fibroTOmyoDiff. By detecting expression changes of SMAD family during this process, we demonstrated that SMAD3 protein expression was dramatically decreased in the process and the decrease occurred mainly in SMAD3 gene transcription. Furthermore, SMAD3 overexpression using lentivirus infection and knockdown using sgRNA lentivirus infection or siRNAs revealed that SMAD3 overexpression enhanced TGF-β1-induced corneal fibroTOmyoDiff and vice versa. In addition, specific siRNAs and inhibitors targeting particular signaling pathway were used to figure out the intracellular signaling pathway regulating SMAD3, and the result showed that the decease of SMAD3 induced by TGF-β1 stimulation in human corneal fibroblasts (HCFs) was strikingly prevented by SMAD4 knockdown or p38 signaling inhibitor SB203580 treatment. Collectively, these results demonstrate that, in TGF-β1 induced corneal fibroTOmyoDiff, down-regulation of SMAD3 expression regulated by SMAD4 and p38 signaling pathways forms a negative feedback loop of TGFβ signaling to avoid excessive activation of the signaling, which suggest that SMAD3 may be a key target for corneal fibrosis treatment.

Association Study of Transforming Growth Factor Beta 1 + 29 T/C exon 1 Polymorphism in Breast Cancer Patients from North Indian Population

BACKGROUND

TGFB1 cytokine is involved in normal mammary epithelial development as well as in breast tumorigenesis. It has role in both breast tumor suppression and progression. TGFB1 gene has several single nucleotide polymorphisms (SNPs) many of which modulate the activity of TGFB1. Our aim in this study was to analyze TGFB1 + 29 polymorphism in breast cancer individuals from North Indian population.

METHODS

TGFB1 + 29 T/C polymorphism was analyzed using Sanger sequencing in 285 breast cancer patients and age matched 363 healthy controls from North Indian population. Next, transcript expression of 13 apoptotic genes, TRAIL, DR4, DR5, DcR1, DcR2, Bcl2, cytochrome c, Casp8L, Casp8, FlipS, FlipL, Casp3s and Casp3 were carried out in 77 breast tumor tissues obtained from 77 individuals.

RESULTS

TGFB1 + 29 CC genotype provided protection against the development of breast cancer (P = 0.012). This was mainly attributable to higher age group (> 45 years) women (P = 0.016). Individuals having CC protector genotype showed significantly higher expression of TGFB1 transcript compared to the TT and TC risk genotypes (P = 0.044). Furthermore, we observed that TGFB1 + 29 CC genotype showed increased TRAIL mediated apoptosis via the extrinsic pathway in breast tumor patients with age greater than 45 years (P = 0.027).

CONCLUSION

TGFB1 + 29 homozygous mutant CC genotype is related to protection against breast cancer in North Indian women population greater than 45 years of age.

IL-6 inhibitors effectively reverse post-infarction cardiac injury and ischemic myocardial remodeling via the TGF-β1/Smad3 signaling pathway

Approximately one in four myocardial infarctions occur in older patients. The majority of therapeutic advances are either not appropriate or not tested in elderly patients. The main reasons for deviating from the guidelines are justified concerns regarding the effectiveness of the recommended forms of therapy, fear of adverse drug reactions and ethical concerns. Targeting interleukin 6 (IL-6) for ventricular remodeling after cardiovascular damage is a feasible alternative to standard polypharmaceutics, but the underlying molecular mechanisms are not well understood. Continuous activation of the IL-6-associated cytokine receptor gp130 leads to cardiomyopathic hypertrophy. TGFβ1 is involved in forming fibrosis in various organs, and its overexpression can cause myocardial hypertrophy and fibrosis. Il-6 has been hypothesized to be indirectly involved in cardiac remodeling via the TGFβ1/Smad signaling transduction pathway. In the present study, a rat model of acute myocardial ischemia, IL-6 and IL-6 receptor blockers were injected directly into the necrotic myocardium. Changes in cardiac function, myocardial infarction area, myocardial collagen, necrotic myocardial fibrosis and levels of TGFβ1, IL-6 and MMP2/9 were quantified in myocardial tissue fibrosis by ELISA. The present study demonstrated that IL-6 stimulated myocardial fibrosis through the TGFβ1-Smad-MM2/9 signaling transduction pathway. Overall, this provided a solid foundation for understanding the relationship between IL-6 and ventricular remodeling.

Exendin-4 inhibits small intestinal glucose sensing and absorption through repression of T1R2/T1R3 sweet taste receptor signalling in streptozotocin diabetic mice

The small intestine, which is the area where sugars are absorbed, should be considered in the approaches developed for the treatment of diabetes. However, studies on small intestine damage in diabetic individuals, and the effects of current treatments on the small intestine are very limited. This is the first study to investigate the effects of exendin-4, a GLP-1 receptor agonist, on small intestine injury in diabetic mice. BALB/c male mice were divided into 4 groups for this study. The first group was given citrate buffer, the second group was given exendin-4, the third group was given streptozotocin (STZ), and the fourth group was given both exendin-4, and STZ. As the results, we determined a decrease in the edema and deterioration in the integrity of the villi, disruption in continuity of the brush border, fibrosis and enterocyte apoptosis, while the TNFα level and crypt cell proliferation were increased in the small intestinal tissue of exendin-4 treated STZ diabetic mice. Furthermore, the levels of duodenal tissue glucose, SGLT1, and GLUT2 were decreased, whereas there was an increase in GIP level in diabetic mice administered with exendin-4. Moreover, we determined that the sweet taste receptors T1R2/T1R3, downstream molecules PLCβ2, α-gustducin and associated secondary messengers IP3, cAMP, which were increased in the duodenal tissue of STZ-diabetic mice, decreased with exendin-4 administration. These findings were evaluated as that exendin-4 reduces glucose absorption by suppressing the T1R2/T1R3 sweet taste signal perception pathway in duodenum of STZ diabetic mice.

Regulation of homeostasis and regeneration in the adult intestinal epithelium by the TGF-β superfamily

The delicate balance between the homeostatic maintenance and regenerative capacity of the intestine makes this a fascinating tissue of study. The intestinal epithelium undergoes continuous homeostatic renewal but is also exposed to a diverse array of stresses that can range from physiological processes such as digestion, to exposure to infectious agents, drugs, radiation therapy, and inflammatory stimuli. The intestinal epithelium has thus evolved to efficiently maintain and reinstate proper barrier function that is essential for intestinal integrity and function. Factors governing homeostatic epithelial turnover are well described, however, the dynamic regenerative mechanisms that occur following injury are the subject of intense ongoing investigations. The TGF-β superfamily is a key regulator of both homeostatic renewal and regenerative processes of the intestine. Here we review the roles of TGF-β and BMP on the adult intestinal epithelium during self-renewal and injury to provide a framework for understanding how this major family of morphogens can tip the scale between intestinal health and disease. This article is protected by copyright. All rights reserved.

Identification of Fibrinogen as a Key Anti-Apoptotic Factor in Human Fresh Frozen Plasma for Protecting Endothelial Cells In Vitro

Resuscitation with human fresh frozen plasma (FFP) in hemorrhagic shock (HS) patients is associated with improved clinical outcomes. Our group has demonstrated that the beneficial effect of FFP is due to its blockade on endothelial hyperpermeability, thereby improving vascular barrier function. The current study aimed to investigate HS-induced endothelial cell apoptosis, a potential major contributor to the endothelial hyperpermeability, and to determine the effect and the key components/factors of FFP on protecting endothelial cells from apoptosis. We first measured and demonstrated an increase in apoptotic endothelial microparticles (CD146AnnexinV) in patients in shock compared to normal subjects, indicating the induction of endothelial cell activation and apoptosis in shock patients. We then transfused HS rats with FFP and showed that FFP blocked HS-induced endothelial cell apoptosis in gut tissue. To identify the anti-apoptotic factors in FFP, we utilized high-performance liquid chromatography, fractionated FFP, and screened the fractions in vitro for the anti-apoptotic effects. We selected the most effective fractions, performed mass spectrometry, and identified fibrinogen as a potent anti-apoptotic factor. Taken together, our findings suggest that HS-induced endothelial apoptosis may constitute a major mechanism underlying the vascular hyperpermeability. Furthermore, the identified anti-apoptotic factor fibrinogen may contribute to the beneficial effects of FFP resuscitation, and therefore, may have therapeutic potential for HS.

Distinct Murine Pancreatic Transcriptomic Signatures during Chronic Pancreatitis Recovery

We have previously demonstrated that the pancreas can recover from chronic pancreatitis (CP) lesions in the cerulein-induced mouse model. To explore how pancreatic recovery is achieved at the molecular level, we used RNA-sequencing (seq) and profiled transcriptomes during CP transition to recovery. CP was induced by intraperitoneally injecting cerulein in C57BL/6 mice. Time-matched controls (CON) were given normal saline. Pancreata were harvested from mice 4 days after the final injections (designated as CP and CON) or 4 weeks after the final injections (designated as CP recovery (CPR) and control recovery (CONR)). Pancreatic RNAs were extracted for RNA-seq and quantitative (q) PCR validation. Using RNA-seq, we identified a total of 3,600 differentially expressed genes (DEGs) in CP versus CON and 166 DEGs in CPR versus CONR. There are 132 DEGs overlapped between CP and CPR and 34 DEGs unique to CPR. A number of selected pancreatic fibrosis-relevant DEGs were validated by qPCR. The top 20 gene sets enriched from DEGs shared between CP and CPR are relevant to extracellular matrix and cancer biology, whereas the top 10 gene sets enriched from DEGs specific to CPR are pertinent to DNA methylation and specific signaling pathways. In conclusion, we identified a distinct set of DEGs in association with extracellular matrix and cancer cell activities to contrast CP and CPR. Once during ongoing CP recovery, DEGs relevant to DNA methylation and specific signaling pathways were induced to express. The DEGs shared between CP and CPR and the DEGs specific to CPR may serve as the unique transcriptomic signatures and biomarkers for determining CP recovery and monitoring potential therapeutic responses at the molecular level to reflect pancreatic histological resolution.

Impact of EGCG Supplementation on the Progression of Diabetic Nephropathy in Rats: An Insight into Fibrosis and Apoptosis

Apoptosis is an active response of cells to altered microenvironments, which is characterized by cell shrinkage, chromatin condensation, and DNA fragmentation, in a variety of cell types such as renal epithelial cells, endothelial cells, mesangial cells, and podocytes. Hyperglycemia is among the microenvironmental factors that may facilitate apoptosis, which plays a decisive role in the initiation of diabetic nephropathy. Transforming growth factor-β emerges as a powerful fibrogenic factor in the development of renal hypertrophy. Although, a number of potential treatment strategies exist for diabetic nephropathy, considering the ease of use and bioavailability, phytochemicals stands distinct as the preeminent option. EGCG, a green tea catechin is one such phytochemical which possesses hypoglycemic and antifibrotic activity. The present study aims to explore the potential of EGCG to prevent apoptosis in a high-fat diet and STZ induced diabetic nephropathy rats by assessing renal function, pro-fibrotic marker, and the expression of apoptotic and antiapoptotic proteins. Our results validate EGCG as a potential antiapoptotic agent evidently by improving renal function via down regulating TGF-β, consequently ameliorating diabetic nephropathy. In accordance with this, EGCG might be regarded as a prospective therapeutic candidate in modulating diabetic nephropathy, thus being a promising treatment.

SMAD3 expression and regulation of fibroplasia in vocal fold injury

OBJECTIVE

Recent reports highlight the efficacy of small interfering RNA (siRNA) targeting SMAD3 to regulate transforming growth factor β (TGF-β)-mediated fibroplasia in vocal fold fibroblasts. The current study sought to investigate SMAD3 expression during wound healing in vivo and quantify the downstream transcriptional events associated with SMAD3 knockdown in vitro.

STUDY DESIGN

In vivo and in vitro.

METHODS

Unilateral vocal fold injury was created in a rabbit model. SMAD3 and SMAD7 mRNA expression was quantified at 1 hour and 1, 3, 7, 14, 30, 60, and 90 days following injury. In vitro, multi-gene analysis technology was employed in our immortalized human vocal-fold fibroblast cell line following TGF-β1 stimulation ± SMAD3 knockdown across time points.

RESULTS

SMAD3 mRNA expression increased following injury; upregulation was significant at 3 and 7 days compared to control (both P < 0.001). SMAD7 mRNA was also upregulated at 3, 7, and 14 days (P = 0.02, P < 0.001, and P < 0.001, respectively). In vitro, SMAD3 knockdown reduced the expression of multiple profibrotic, TGF-β signaling, and extracellular matrix metabolism genes at 6 and 24 hours following TGF-β1 stimulation.

CONCLUSION

Cumulatively, these data support SMAD3 as a potential master regulator of TGF-β-mediated fibrosis. SMAD3 transcription peaked 7 days following injury. Multi-gene analysis indicated that the therapeutic effectiveness of SMAD3 knockdown may be related to regulation of downstream mediators of fibroplasia and altered TGF-β signaling.

LEVEL OF EVIDENCE

NA. Laryngoscope, 127:E308-E316, 2017.

Repression of Smad3 by Stat3 and c-Ski/SnoN induces gefitinib resistance in lung adenocarcinoma

Cancer-associated inflammation develops resistance to the epidermal growth-factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) in non-small cell lung cancers (NSCLCs) harboring oncogenic EGFR mutations. Stat3-mediated interleukin (IL)-6 signaling and Smad-mediated transforming growth factor-β (TGF-β) signaling pathways play crucial regulatory roles in cancer-associated inflammation. However, mechanisms how these pathways regulate sensitivity and resistance to EGFR-TKI in NSCLCs remain largely undetermined. Here we show that signal transducer and activator of transcription (Stat)3 represses Smad3 in synergy with the potent negative regulators of TGF-β signaling, c-Ski and SnoN, whereby renders gefitinib-sensitive HCC827 cells resistant. We found that IL-6 signaling via phosphorylated Stat3 induced gefitinib resistance as repressing transcription of Smad3, whereas TGF-β enhanced gefitinib sensitivity as activating transcription of Smad3 in HCC827 cells with gefitinib-sensitizing EGFR mutation. Promoter analyses showed that Stat3 synergized with c-Ski/SnoN to repress Smad2/3/4-induced transcription of the Smad3 gene. Smad3 was found to be an apoptosis inducer, which upregulated pro-apoptotic genes such as caspase-3 and downregulated anti-apoptotic genes such as Bcl-2. Our results suggest that derepression of Smad3 can be a therapeutic strategy to prevent gefitinib-resistance in NSCLCs with gefitinib-sensitizing EGFR mutation.

Molecular insights on the effect of TGF-β1/-β3 in human corneal fibroblasts

Transforming growth factor β (TGF-β) plays a critical role in wound healing and the pathogenesis of fibrosis (scarring). Three isoforms of TGF-β have been identified in mammals. Previous studies have shown that the addition of TGF-β1 (T1) or -β2 (T2) to human corneal fibroblasts (HCF) cultured in a 3-dimensional construct resulted in a fibrotic matrix, while the addition of TGF-β3 (T3) resulted in the production of enhanced non-fibrotic matrix as compared to control (Vitamin C [VitC] only). In the current investigation, we undertook the molecular comparison of fibrosis-related gene expression in T1 or T3-treated HCF to gain further insights into the regulation and roles of these two isoforms on the fibrotic response. HCF were cultured in 100 mm dishes in basic medium (Eagles minimum essential medium [EMEM] with 10% fetal bovine serum [FBS]). At 70-80% confluency, cells were exposed to basic medium with 0.5 mM 2-O-α-d-glucopyranosyl-l-ascorbic acid (VitC) ± 2 ng/ml of T1 or T3. After 4 h or 3 days, cells were harvested, and mRNA or protein was isolated. Fibrosis related mRNA levels were assayed using a commercial qRT-PCR Array. Selected proteins were examined using Western blotting (WB). Experiments were performed 6 times for the qRT-PCR and 4 times for WB for each condition. qRT-PCR results showed that most of the fibrosis-related genes were up or downregulated in HCF exposed to T1 or T3 as compared with VitC control. At 4 h, only Smad7 expression was significantly altered in T3-treated HCF, compared to T1, and at 3 days, five genes were altered. WB confirmed that T1 significantly decreased Smad7 expression compared to T3 and control, and that the expression of thrombospondin-1 in T3-stimulated HCF was enhanced compared to T1-treated cells. Finally, both T1 and T3 decreased Smad3 expression dramatically at both time points. At early time points, T1 and T3 have similar effects on expression of fibrosis related genes; however, with a longer exposure, an increasing number of genes were differentially expressed. Interestingly, most of the differentially expressed gene products are secreted by the cells and may be related to the modulation of extracellular matrix.

Gremlin is a key pro-fibrogenic factor in chronic pancreatitis

The current study aims to identify the pro-fibrogenic role of Gremlin, an endogenous antagonist of bone morphogenetic proteins (BMPs) in chronic pancreatitis (CP). CP is a highly debilitating disease characterized by progressive pancreatic inflammation and fibrosis that ultimately leads to exocrine and endocrine dysfunction. While transforming growth factor (TGF)-β is a known key pro-fibrogenic factor in CP, the TGF-β superfamily member BMPs exert an anti-fibrogenic function in CP as reported by our group recently. To investigate how BMP signaling is regulated in CP by BMP antagonists, the mouse CP model induced by cerulein was used. During CP induction, TGF-β1 messenger RNA (mRNA) increased 156-fold in 2 weeks, a BMP antagonist Gremlin 1 (Grem1) mRNA levels increased 145-fold at 3 weeks, and increases in Grem1 protein levels correlated with increases in collagen deposition. Increased Grem1 was also observed in human CP pancreata compared to normal. Grem1 knockout in Grem1 (+/-) mice revealed a 33.2 % reduction in pancreatic fibrosis in CP compared to wild-type littermates. In vitro in isolated pancreatic stellate cells, TGF-β induced Grem1 expression. Addition of the recombinant mouse Grem1 protein blocked BMP2-induced Smad1/5 phosphorylation and abolished BMP2's suppression effects on TGF-β-induced collagen expression. Evidences presented herein demonstrate that Grem1, induced by TGF-β, is pro-fibrogenic by antagonizing BMP activity in CP.

KEY MESSAGES

• Gremlin is upregulated in human chronic pancreatitis and a mouse CP model in vivo. • Deficiency of Grem1 in mice attenuates pancreatic fibrosis under CP induction in vivo. • TGF-β induces Gremlin mRNA and protein expression in pancreatic stellate cells in vitro. • Gremlin blocks BMP2 signaling and function in pancreatic stellate cells in vitro. • This study discloses a pro-fibrogenic role of Gremlin by antagonizing BMP activity in chronic pancreatitis.

Bone morphogenetic protein signaling protects against cerulein-induced pancreatic fibrosis

Bone morphogenetic proteins (BMPs) have an anti-fibrogenic function in the kidney, lung, and liver. However, their role in chronic pancreatitis (CP) is unknown. The aim of this study was to define the anti-fibrogenic role of BMP signaling in the pancreas in vivo under CP induction. Mice with a deletion of BMP type II receptor (BMPR2^+/−) were used in this study in comparison with wild-type mice. CP was induced by repetitive cerulein injection intraperitoneally for 4 weeks, and the severity of CP was evaluated. Pancreatic stellate cells (PSCs) were isolated from the mice and treated with BMP2 and TGF-β in vitro, and extracellular matrix protein (ECM) production was measured. Smad and mitogen-activated protein kinase (MAPK) signaling was also evaluated. BMPR2^+/− mice revealed a greater pancreatic fibrosis, PSC activation and leukocyte infiltration after CP induction compared to wild-type mice (P<0.05). Under CP induction, phospho (p)Smad1/5/8 was elevated in wild-type mice and this effect was abolished in BMPR2^+/− mice; pSmad2 and pp38^MAPK were further enhanced in BMPR2^+/− mice compared to wild-type mice (P<0.05). In vitro, BMP2 inhibited TGF-β-induced ECM protein fibronectin production in wild-type PSCs; this effect was abolished in BMPR2^+/− PSCs (P<0.05). In BMPR2^+/− PSCs, pSmad1/5/8 level was barely detectable upon BMP2 stimulation, while pSmad2 level was further enhanced by TGF-β stimulation, compared to wild-type PSCs (P<0.05). BMPR2/Smad1/5/8 signaling plays a protective role against cerulein-induced pancreatic fibrosis by inhibiting Smad2 and p38^MAPK signaling pathways.

BMP2 inhibits TGF-β-induced pancreatic stellate cell activation and extracellular matrix formation

Activation of pancreatic stellate cells (PSCs) by transforming growth factor (TGF)-β is the key step in the development of pancreatic fibrosis, a common pathological feature of chronic pancreatitis (CP). Bone morphogenetic proteins (BMPs), members of the TGF-β superfamily, have anti-fibrogenic functions, in contrast to TGF-β, in the kidney, lung, and liver. However, it is not known whether BMPs have an anti-fibrogenic role in the pancreas. The current study was designed to investigate the potential anti-fibrogenic role of BMPs in the pancreas using an in vivo CP model and an in vitro PSC model. CP was induced by repetitive intraperitoneal injections of cerulein in adult Swiss Webster mice. The control mice received saline injections. Compared with the control, cerulein injections induced a time-dependent increase in acinar injury and progression of fibrosis and a steady increase in inflammation. Cerulein injections also induced increases of the extracellular matrix (ECM) protein fibronectin and of α-smooth muscle actin (α-SMA)-positive stellate cells (PSCs). The mice receiving cerulein injections showed increased BMP2 protein levels and phosphorylated Smad1 levels up to 4 wk and then declined at 8 wk to similar levels as the control. In vitro, the isolated mouse and human PSCs were cultured and pretreated with BMP2 followed by TGF-β treatment. BMP2 pretreatment inhibited TGF-β-induced α-SMA, fibronectin, and collagen type Ia expression. Knocking down Smad1 with small-interfering RNA reversed the inhibitory effect of BMP2 on TGF-β-induced α-SMA and fibronectin expression. Thus, BMP2 opposes the fibrogenic function of TGF-β in PSCs through the Smad1 signaling pathway.

Dietary fiber enhances TGF-β signaling and growth inhibition in the gut

Dietary fiber intake links to decreased risk of colorectal cancers. The underlying mechanisms remain unclear. Recently, we found that butyrate, a short-chain fatty acid produced in gut by bacterial fermentation of dietary fiber, enhances TGF-β signaling in rat intestinal epithelial cells (RIE-1). Furthermore, TGF-β represses inhibitors of differentiation (Ids), leading to apoptosis. We hypothesized that dietary fiber enhances TGF-β's growth inhibitory effects on gut epithelium via inhibition of Id2. In this study, Balb/c and DBA/2N mice were fed with a regular rodent chow or supplemented with a dietary fiber (20% pectin) and Smad3 level in gut epithelium was measured. In vitro, RIE-1 cells were treated with butyrate and TGF-β(1), and cell functions were evaluated. Furthermore, the role of Ids in butyrate- and TGF-β-induced growth inhibition was investigated. We found that pectin feeding increased Smad3 protein levels in the jejunum (1.47 ± 0.26-fold, P = 0.045, in Balb/c mice; 1.49 ± 0.19-fold, P = 0.016, in DBA/2N mice), and phospho-Smad3 levels (1.92 ± 0.27-fold, P = 0.009, in Balb/c mice; 1.83 ± 0.28-fold, P = 0.022, in DBA/2N mice). Butyrate or TGF-β alone inhibited cell growth and induced cell cycle arrest. The combined treatment of butyrate and TGF-β synergistically induced cell cycle arrest and apoptosis in RIE-1 cells and repressed Id2 and Id3 levels. Furthermore, knockdown of Id2 gene expression by use of small interfering RNA caused cell cycle arrest and apoptosis. We conclude that dietary fiber pectin enhanced Smad3 expression and activation in the gut. Butyrate and TGF-β induced cell cycle arrest and apoptosis, which may be mediated by repression of Id2. Our results implicate a novel mechanism of dietary fiber in reducing the risk of colorectal cancer development.

Increased transforming growth factor β contributes to deterioration of refrigerated fresh frozen plasma's effects in vitro on endothelial cells

Resuscitation with fresh frozen plasma (FFP) is associated with improved outcomes after hemorrhagic shock. Many trauma centers are using thawed plasma that has been stored for up to 5 days at 4°C (refrigeration), yet the effect of refrigeration on FFP is relatively unknown. Previously, our group showed that refrigeration of FFP changed its coagulation factors and diminished its beneficial effects on endothelial cell (EC) function and resuscitation in an animal model of hemorrhagic shock. We hypothesize that growth factor composition of FFP is altered during refrigeration, leading to a diminished beneficial effect on EC. Transforming growth factor (TGF-β) is a potent inhibitor of EC migration and is released during refrigeration of platelets. We found increased TGF-β1 protein levels and greater activation of downstream mediators Smad2/3 during refrigeration of FFP. Both day 0 FFP (used on the same day after being thawed) and day 5 FFP (used after being thawed and refrigerated for 5 days) stimulated EC migration in vitro; however, the EC migration in day 5 FFP was significantly reduced. Inhibition of TGF-β type I receptor blocked FFP-induced Smad3 signaling in EC cells and restored the effectiveness of day 5 FFP on EC migration to a comparable level seen in day 0 FFP. These data suggest that the increased TGF-β levels during FFP refrigeration contribute to the deterioration of refrigerated FFP's effects on EC migration. This study identifies a novel molecular mechanism contributing to the reduced efficacy of refrigerated FFP.

Transforming growth factor-beta1 expression is up-regulated in maturation-stage enamel organ and may induce ameloblast apoptosis

Transforming growth factor-beta1 (TGF-beta1) regulates a variety of cellular responses that are dependent on the developmental stage and on the origins of the cell or the tissue. In mature tissues, and especially in tissues of epithelial origin, TGF-beta1 is generally considered to be a growth inhibitor that may also promote apoptosis. The ameloblast cells of the enamel organ epithelium are adjacent to and responsible for the developing enamel layer on unerupted teeth. Once the enamel layer reaches its full thickness, the tall columnar secretory-stage ameloblasts shorten, and a portion of these maturation-stage ameloblasts become apoptotic. Here we investigate whether TGF-beta1 plays a role in apoptosis of the maturation-stage ameloblasts. We demonstrate in vitro that ameloblast lineage cells are highly susceptible to TGF-beta1-mediated growth arrest and are prone to TGF-beta1-mediated cell death/apoptosis. We also demonstrate in vivo that TGF-beta1 is expressed in the maturation-stage enamel organ at significantly higher levels than in the earlier secretory-stage enamel organ. This increased expression of TGF-beta1 correlates with an increase in expression of the enamel organ immediate-early stress-response gene and with a decrease in the anti-apoptotic Bcl2 : Bax expression ratio. We conclude that TGF-beta1 may play an important role in ameloblast apoptosis during the maturation stage of enamel development.

Bombesin enhances TGF-beta growth inhibitory effect through apoptosis induction in intestinal epithelial cells

Mammalian intestinal epithelium undergoes continuous cell turn over, with cell proliferation in the crypts and apoptosis in the villus. Both transforming growth factor (TGF)-beta and gastrin-releasing peptide (GRP) are involved in the regulation of intestinal epithelial cells for division, differentiation, adhesion, migration and death. Previously, we have shown that TGF-beta and bombesin (BBS) synergistically induce cyclooxygenase-2 (COX-2) expression and subsequent prostaglandin E(2) (PGE2) production through p38(MAPK) in rat intestinal epithelial cell line stably transfected with GRP receptor (RIE/GRPR), suggesting the interaction between TGF-beta signaling pathway and GRPR. The current study examined the biological responses of RIE/GRPR cells to TGF-beta and BBS. Treatment with TGF-beta1 (40 pM) and BBS (100 nM) together synergistically inhibited RIE/GRPR growth and induced apoptosis. Pretreatment with SB203580 (10 microM), a specific inhibitor of p38(MAPK), partially blocked the synergistic effect of TGF-beta and BBS on apoptosis. In conclusion, BBS enhanced TGF-beta growth inhibitory effect through apoptosis induction, which is at least partially mediated by p38(MAPK).

TGF-beta repression of Id2 induces apoptosis in gut epithelial cells

Transforming growth factor-beta (TGF-beta) regulates epithelial tissue homeostasis by activating processes that control cell cycle arrest, differentiation and apoptosis. Disruption of the TGF-beta signaling pathway often occurs in colorectal cancers. Earlier, we have shown that TGF-beta induces apoptosis through the transcription factor Smad3. Affymetrix oligonucleotide microarrays were used to identify TGF-beta/Smad3 target genes that regulate apoptosis in rat intestinal epithelial cells (RIE-1). We found that TGF-beta repressed the expression of the inhibitor of differentiation (Id) gene family. Knockdown of Id1 and Id2 gene expression induced apoptosis in RIE-1 cells, whereas overexpression of Id2 attenuated TGF-beta-induced apoptosis. TranSignal Protein/DNA arrays were used to identify the hypoxia-inducing factor-1 (HIF-1) as a downstream target of TGF-beta. HIF-1 is a basic helix-loop-helix protein, and overexpression of Id2 blocked HIF-1 activation by TGF-beta. Furthermore, knockdown of HIF-1 blocked TGF-beta-induced apoptosis. Thus, we have identified HIF-1 as a novel mediator downstream of Id2 in the pathway of TGF-beta-induced apoptosis.

Effects of TGFbeta1 on gene expression in the HP75 human pituitary tumor cell line identified by gene expression profiling

The pathogenesis of pituitary adenomas and many of the genes influencing growth of these tumors are unknown. TGFbeta is known to inhibit proliferation of cultured anterior pituitary cells and anterior pituitary tumors, but the signal transduction pathways involved in the inhibition of growth are unclear. We treated the human HP75 pituitary cell line with 10(-9) M TGFbeta1 for 4, 24, and 96 h and performed global gene expression profiling by Affymetrix GeneChip microarray analysis. Quantitative PCR validation of specific genes involved in the TGFbeta1-induced regulation of pituitary cell growth was also done. Of the 15,000 genes queried, there were 37 genes up-regulated and 48 genes down-regulated twofold or more after 4 h of TGFbeta1 treatment. There were 121 genes up-regulated and 109 genes down-regulated twofold or more after 24 h of TGFbeta1 treatment and 112 genes up-regulated and 43 genes down-regulated twofold or more after 96 h of TGFbeta1 treatment. Galectin-3 (Gal-3) protein was decreased by TGFbeta1 treatment and several genes which interacted with Gal-3 including RUNX1 and WNT5B were up-regulated after TGFbeta1 treatment. SOX4 was also up-regulated by TGFbeta1 treatment. SMAD3, which is directly involved in the TGFbeta signal transduction pathway, was down-regulated by TGFbeta1 treatment. These findings highlight the diverse gene networks and pathways through which TGFbeta operates in its effects on pituitary tumor cells.

Pivotal role of Smad3 in a mouse model of T cell-mediated hepatitis

Transforming growth factor beta (TGFbeta) promotes hepatocellular apoptosis and suppresses hepatic lymphocyte responses in part through activation of Smad3. The purpose of the current study was to determine the importance of Smad3 signaling in an experimental model of autoimmune hepatitis induced by concanavalin A (ConA), a process involving T cell activation and hepatocellular apoptosis. C57Bl/6 wild-type (Wt) or Smad3-deficient (Smad3(-/-)) mice were injected intravenously with 15 mg/kg ConA or vehicle. Nine hours post ConA injection, Wt mice presented with severe hepatitis as assessed by increased liver transferases. This injury was associated with eosinophil accumulation and preceded at 3 hours post-injection by significant increases in hepatic T helper 1 (interferon gamma) and T helper 2 (interleukin-4) cytokine production. Absence of Smad3 significantly blunted hepatocellular injury 9 hours post ConA injection, which was associated with reduced early T helper 1 and T helper 2 cytokine production and eosinophil accumulation. Smad3(-/-) livers also showed significant reductions in hepatocellular apoptosis as assessed by terminal UTP nick-end labeling when compared to ConA-treated Wt mice in conjunction with reduced caspase 3 cleavage, which was likely mediated by a Smad3-dependent inhibition of the survival factor extracellular signal-regulated kinase 1/2. In vitro, Smad3(-/-) hepatocytes were resistant to TGFbeta-induced apoptosis, and this protection was dependent on extracellular signal-regulated kinase activation.

CONCLUSION

Together, these results show, for the first time, the significance of Smad3 signaling in autoimmune hepatitis, underlining the control of Smad3-dependent TGFbeta signaling on proinflammatory cytokine production, eosinophil recruitment, and hepatocellular apoptosis. Interruption of this pathway could be beneficial clinically to limit acute fulminant liver pathologies.

Expression profiling of genes regulated by TGF-beta: differential regulation in normal and tumour cells

Background

TGF-beta is one of the key cytokines implicated in various disease processes including cancer. TGF-beta inhibits growth and promotes apoptosis in normal epithelial cells and in contrast, acts as a pro-tumour cytokine by promoting tumour angiogenesis, immune-escape and metastasis. It is not clear if various actions of TGF-beta on normal and tumour cells are due to differential gene regulations. Hence we studied the regulation of gene expression by TGF-beta in normal and cancer cells.

Results

Using human 19 K cDNA microarrays, we show that 1757 genes are exclusively regulated by TGF-beta in A549 cells in contrast to 733 genes exclusively regulated in HPL1D cells. In addition, 267 genes are commonly regulated in both the cell-lines. Semi-quantitative and real-time qRT-PCR analysis of some genes agrees with the microarray data. In order to identify the signalling pathways that influence TGF-beta mediated gene regulation, we used specific inhibitors of p38 MAP kinase, ERK kinase, JNK kinase and integrin signalling pathways. The data suggest that regulation of majority of the selected genes is dependent on at least one of these pathways and this dependence is cell-type specific. Interestingly, an integrin pathway inhibitor, RGD peptide, significantly affected TGF-beta regulation of Thrombospondin 1 in A549 cells.

Conclusion

These data suggest major differences with respect to TGF-beta mediated gene regulation in normal and transformed cells and significant role of non-canonical TGF-beta pathways in the regulation of many genes by TGF-beta.