Transforming growth factor-beta 1 as a signal for induction of cell death by apoptosis

Bone Metabolism and Peritoneal Membrane Transport in Children on Chronic Peritoneal Dialysis

Objective

The aim of the study was to assess the influence of peritoneal membrane permeability on bone metabolism in dialyzed children.

Patients and Methods

24 children with end-stage renal failure and being treated with peritoneal dialysis (PD) were studied. The children were divided into two groups based on the results of a standard peritoneal equilibration test: group I, high peritoneal transport [ratio of dialysate glucose concentration at 4 hours to dialysate glucose concentration at 0 hours (D/D0) < 0.26, dialysate-to-serum ratio of creatinine concentration at 4 hours (D/P) > 0.81], 10 children aged 9.9 ± 2.9 years; group II, other peritoneal transport types (D/D0 > 0.26, D/P < 0.81), 14 children aged 11.4± 2.7 years. Serum levels of calcium (sCa), phosphorus (sP), protein, albumin, alkaline phosphatase (AP), and parathormone (PTH) were measured, and bone biopsies were performed in all children. Alfacalcidol and calcium carbonate doses were adjusted to sCa, sP, and PTH levels in all patients.

Results

No statistically significant differences (NS) between the two groups were found in age, duration of PD, sCa, sP, AP, PTH, protein, or albumin levels. The mean alfacalcidol dose was 0.055 ± 0.057 μg/kg body weight/week in group I and 0.099 ± 0.065 μg/kg/week in group II ( p = NS). In group I, the high peritoneal transport group, significantly lower osteoclast surface (OcS/BS) and bone formation rate (BFR/TV) were found compared with group II (3.1% ± 1.7% vs 4.6% ± 2.0%, and 483.5 ± 329.2 μm3/mm2/day vs 913.9 ± 558.3 μm3/mm2/day, respectively, p < 0.05). We also found significant positive correlation between D/D0 and BFR/TV and OcS/BS ( r = 0.45, p < 0.05).

Conclusion

Bone turnover in children treated with PD may depend on peritoneal permeability.

Adaptive immune cells in calcific aortic valve disease

Calcific aortic valve disease (CAVD) is highly prevalent and has no pharmaceutical treatment. Surgical replacement of the aortic valve has proved effective in advanced disease but is costly, time limited, and in many cases not optimal for elderly patients. This has driven an increasing interest in noninvasive therapies for patients with CAVD. Adaptive immune cell signaling in the aortic valve has shown potential as a target for such a therapy. Up to 15% of cells in the healthy aortic valve are hematopoietic in origin, and these cells, which include macrophages, T lymphocytes, and B lymphocytes, are increased further in calcified specimens. Additionally, cytokine signaling has been shown to play a causative role in aortic valve calcification both in vitro and in vivo. This review summarizes the physiological presence of hematopoietic cells in the valve, innate and adaptive immune cell infiltration in disease states, and the cytokine signaling pathways that play a significant role in CAVD pathophysiology and may prove to be pharmaceutical targets for this disease in the near future.

The concomitant apoptosis and EMT underlie the fundamental functions of TGF-β

TGF-β's multipotent cellular effects and their relations are critical for TGF-β's pathophysiological functions. However, these effects may appear to be paradoxical in understanding TGF-β's functions. Apoptosis and epithelial-mesenchymal transition (EMT) are two fundamental events that are deeply linked to various physiological and disease-related processes. These two major cellular fates are subtly regulated and can be potently stimulated by TGF-β, which profoundly contribute to the biological roles of TGF-β. Moreover, these two events are also indirectly and directly correlated with TGF-β-mediated growth inhibition and are relevant to the current understanding of the roles of TGF-β in tumorigenesis and cancer progression. Although TGF-β-induced apoptosis and EMT can be singly independent cellular events, they can also be mutually exclusive but interrelated concomitant events in various cases. Thus, the modulation of apoptosis and EMT is essential for the seemingly paradoxical functions of TGF-β. However, the concomitant effect of TGF-β on apoptosis and EMT, the balance and regulated alterations of them are still been ignored or underestimated. This review focuses on the TGF-β-induced concomitant apoptosis and EMT. We aim to provide an insight in understanding their significance, balance, and modulation in TGF-β-mediated biological functions.

Oxidative Modification of Biomolecules in the Nonstimulated and Stimulated Saliva of Patients with Morbid Obesity Treated with Bariatric Surgery

Morbid obesity leads to progressive failure of many human organs and systems; however, the role of oxidative damage to salivary composition is still unknown in the obese patients. In this study, we assessed the effect of bariatric surgery on oxidative damage in nonstimulated (NS) and stimulated (S) whole saliva. The study included 47 subjects with morbid obesity as well as 47 age- and gender-matched healthy volunteers. Oxidative modifications to lipids (4-hydroxynonenal (4-HNE) and 8-isoprostanes (8-isoP)), proteins (advanced oxidation protein products (AOPP) and protein carbonyl groups (PC)), and DNA (8-hydroxy-D-guanosine (8-OHdG)) were analyzed in morbidly obese patients before and after bariatric surgery as well as in the healthy controls. The concentrations of 8-isoP, AOPP, PC, and 8-OHdG were significantly higher in both NS and S of patients with morbid obesity than in the control patients and compared to the results obtained 6 months after bariatric surgery. The levels of oxidative damage markers were also higher in S versus NS of morbidly obese patients. In summary, morbid obesity is associated with oxidative damage to salivary proteins, lipids, and DNA, while bariatric treatment generally lowers the levels of salivary oxidative damage.

Binding and biologic characterization of recombinant human serum albumin-eTGFBR2 fusion protein expressed in CHO cells

Transforming growth factor-β1 (TGF-β1) signaling is involved in cell metabolism, growth, differentiation, carcinoma invasion and fibrosis development, which suggests TGF-β1 can be treated as a therapeutic target extensively. Because TGF-β1 receptor type α(TGFBR2) is the directed and essential mediator for TGF-β1 signals, the extracellular domain of TGFBR2 (eTGFBR2), binding partner for TGF-β1, has been produced in a series of expression systems to inhibit TGF-β1 signaling. However, eTGFBR2 is unstable with a short half-life predominantly because of enzymatic degradation and kidney clearance. In this study, a fusion protein consisting of human eTGFBR2 fused at the C-terminal of human serum albumin (HSA) was stably and highly expressed in Chinese Hamster Ovary (CHO) cells. The high and stable expression sub-clones with Ig kappa signal peptide were selected by Western blot analysis and used for suspension culture. After fed-batch culture over 8 d, the expression level of HSA-eTGFBR2 reached 180 mg/L. The fusion protein was then purified from culture medium using a 2-step chromatographic procedure that resulted in 39% recovery rate. The TGF-β1 binding assay revealed that HSA-eTGFBR2 could bind to TGF-β1 with the affinity constant (K_D of 1.42 × 10^-8 M) as determined by the ForteBio Octet System. In addition, our data suggested that HSA-eTGFBR2 exhibited a TGF-β1 neutralizing activity and maintained a long-term activity more than eTGFBR2. It concluded that the overexpressing CHO cell line supplied sufficient recombinant human HSA-eTGFBR2 for further research and other applications.

A focus on the role of platelets in liver regeneration: Do platelet-endothelial cell interactions initiate the regenerative process?

Platelets are involved in the early phases of liver regeneration. Moreover, platelet transfusion and thrombocytosis were recently shown to enhance hepatocyte proliferation. However, the precise mechanisms remain elusive. This review discusses the latest updates regarding the mechanisms by which platelets stimulate liver regeneration, focusing on their interactions with liver sinusoidal endothelial cells and on their fate within the liver. Following liver injury, platelets are recruited to and trapped within the liver, where they adhere to the endothelium. Subsequent platelet activation results in the release of platelet granules, which stimulate hepatocyte proliferation through activation of the Akt and ERK1/2 signalling pathways. Platelets activate liver sinusoidal endothelial cells, leading to the secretion of growth factors, such as interleukin-6. Finally, liver sinusoidal cells and hepatocytes can also internalize platelets, but the effects of this alternate process on liver regeneration remain to be explored. A better understanding of the mechanisms by which platelets stimulate liver regeneration could lead to improvement in post-operative organ function and allow hepatectomies of a greater extent to be performed.

Evaluation of the inflammatory response in macrophages stimulated with exosomes secreted by Mycobacterium avium-infected macrophages

Exosomes secreted from Mycobacterium avium-infected macrophages contain numerous antigens of both M. avium and the host cell and are involved in the induction and expression of the inflammatory responses in macrophages. The interaction between exosomes secreted from M. avium-infected macrophages and macrophage phagocytosis, cytokine secretion, immunostimulation, and apoptosis was analyzed. Upon stimulation with exosomes secreted from M. avium-infected macrophages, the phagocytosis of dextran by treated macrophages was increased. Furthermore, the expression of CD40, CD80, CD81, CD86, HLA-DR, and most notably CD195 was enhanced. Additionally, the secretion of IL-6, IL-8, IL-10, IFN-γ, and TNF-α was increased by stimulated macrophages. Exosome stimulation did not induce macrophage apoptosis when compared with macrophages infected with M. avium. Caspase expression, including that of caspases 3, 6, and 8, was also not altered in exosome stimulated macrophages. Thus exosomes trigger the inflammatory response in macrophages owing to the presence of bacterial antigens but have no effect on macrophage viability.

Hashimoto's Thyroiditis: From Genes to the Disease

Hashimoto's thyroiditis (HT) is the most prevalent autoimmune thyroid disorder. Intrathyroidal lymphocytic infiltration is followed by a gradual destruction of the thyroid gland which may lead to subclinical or overt hypothyroidism. Biochemical markers of the disease are thyroid peroxidase and/or thyroglobulin autoantibodies in the serum which are present with a higher prevalence in females than in males and increase with age. Although exact mechanisms of aetiology and pathogenesis of the disorder are not completely understood, a strong genetic susceptibility to the disease has been confirmed predominantly by family and twin studies. Several genes were shown to be associated with the disease occurrence, progression, and severity. Genes for human leukocyte antigen, cytotoxic T lymphocyte antigen-4, protein tyrosine phosphatase nonreceptor-type 22, thyroglobulin, vitamin D receptor, and cytokines are considered to be of utmost importance. Amongst endogenous factors for the disease development, the attention is focused predominantly on female sex, pregnancy with postpartum period and fetal microchimerism. Environmental factors influencing HT development are iodine intake, drugs, infections and different chemicals. Disturbed self-tolerance accompanied by the increased antigen presentation is a prerequisite for the HT occurrence, whereas proper interaction of thyroid cells, antigen presenting cells, and T cells are necessary for the initiation of thyroid autoimmunity. Secreted cytokines lead predominantly to T-helper type 1 (Th1) response as well as to Th 17 response which has only recently been implicated. Final outcome of HT is thyroid destruction which is mostly a consequence of the apoptotic processes combined with T-cell mediated cytotoxicity.

Nitric oxide and redox regulation in the liver: Part I. General considerations and redox biology in hepatitis

Reactive oxygen species (ROS) and reactive nitrogen species (RNS) are created in normal hepatocytes and are critical for normal physiologic processes, including oxidative respiration, growth, regeneration, apoptosis, and microsomal defense. When the levels of oxidation products exceed the capacity of normal antioxidant systems, oxidative stress occurs. This type of stress, in the form of ROS and RNS, can be damaging to all liver cells, including hepatocytes, Kupffer cells, stellate cells, and endothelial cells, through induction of inflammation, ischemia, fibrosis, necrosis, apoptosis, or through malignant transformation by damaging lipids, proteins, and/or DNA. In Part I of this review, we will discuss basic redox biology in the liver, including a review of ROS, RNS, and antioxidants, with a focus on nitric oxide as a common source of RNS. We will then review the evidence for oxidative stress as a mechanism of liver injury in hepatitis (alcoholic, viral, nonalcoholic). In Part II of this review, we will review oxidative stress in common pathophysiologic conditions, including ischemia/reperfusion injury, fibrosis, hepatocellular carcinoma, iron overload, Wilson's disease, sepsis, and acetaminophen overdose. Finally, biomarkers, proteomic, and antioxidant therapies will be discussed as areas for future therapeutic interventions.

Apoptosis in bone for tissue engineering

Bone loss due to congenital defects, trauma, improper fracture fixation, metabolic disturbances, infections, or after tumor resection represents a major clinical problem in head and neck surgery. To address these issues, different types of scaffolds, growth factors and cell sources -- alone or in various combinations -- have been applied for development of bioartificial bone tissues. Although these applications have received increasing interest, use of autologous bone grafts is still considered as the gold standard for tissue repair. Despite progress in some areas of tissue regeneration, significant translation into clinical practice has not been achieved. Reasons for this impass include rejection of engineered tissue implants by the immune system, limited blood supply, or morbidity of the donor site. During the process of bone regeneration, approximately 50-70% of osteoblasts undergo apoptosis. Apoptosis is a naturally occurring cell death pathway induced in a variety of cell types and is associated with caspase activation or caspase mediation. It is recognized as an important component of embryogenesis and tissue morphogenesis and, in adult skeletons, it contributes substantially to physiological bone turnover, repair, and regeneration. Intracellular mechanisms are orchestrated by a variety of proteins, the interplay of which seems to vary, depending on the differentiation state of the cell or the current status of the tissue. Closing gaps in current knowledge of the apoptosis of bone and understanding the mechanisms of cell death in tissue engineered bone will improve results in the translation from bench to bedsite. This review aims to provide a broad overview of the current general concepts in apoptosis with a special focus on its regulation in osteoblasts and its significance for bone tissue engineering.

Nickel Compounds Render Anti-apoptotic Effect to Human Bronchial Epithelial Beas-2B Cells by Induction of Cyclooxygenase-2 through an IKKβ/p65-dependent and IKKα- and p50-independent Pathway

The carcinogenicity of nickel compounds has been well documented both in vitro and in vivo; however, the molecular mechanisms by which nickel compounds cause cancers are far from understood. Because suppression of apoptosis is thought to contribute to carcinogenesis, we investigated the mechanisms implicated in nickel-induced anti-apoptotic effect in human bronchial epithelial (Beas-2B) cells. We found that exposure of Beas-2B cells to nickel compounds resulted in increased cyclooxygenase-2 (COX-2) expression and that small interfering RNA (siCOX-2) knockdown of COX-2 expression resulted in increased cell sensitivity to nickel-triggered cell apoptosis, demonstrating that COX-2 induction has an anti-apoptotic effect on Beas-2B cells. Overexpression of IKKbeta-KM, a kinase inactive mutant of IKKbeta, blocked NF-kappaB activation and COX-2 induction by nickel compounds, indicating that activated NF-kappaB may be a mediator for COX-2 induction. To further explore the contribution of the NF-kappaB pathway in COX-2 induction and in protection from nickel exposure, mouse embryonic fibroblasts deficient in IKKbeta, IKKalpha, p65, and p50 were analyzed. Loss of IKKbeta impaired COX-2 induction by nickel exposure, whereas knockout of IKKalpha had a marginal effect. Moreover, the NF-kappaB p65, and not the p50 subunit, was critical for nickel-induced COX-2 expression. In addition, a deficiency of IKKbeta or p65 rendered cells more sensitive to nickel-induced apoptosis as compared with those in wild type cells. Finally, it was shown that reactive oxygen species H(2)O(2) were involved in both NF-kappaB activation and COX-2 expression. Collectively, our results demonstrate that COX-2 induction by nickel compounds occurs via an IKKbeta/p65 NF-kappaB-dependent but IKKalpha- and p50-independent pathway and plays a crucial role in antagonizing nickel-induced cell apoptosis in Beas-2B cells.

Augmenter of liver regeneration promotes hepatocyte proliferation induced by Kupffer cells

AIM

To observe the effects of augmenter of liver regeneration (ALR) on Kupffer cells and to determine whether ALR promotes hepatocyte proliferation induced by Kupffer cells.

METHODS

Kupffer cells and hepatocytes were cultured in vitro and various concentrations of recombinant rat ALR (rrALR) were added. 3H-thymidine, BrdU and 3H-leucine incorporation was determined in cultured Kupffer cells and hepatocytes, in hepatocytes conditioned by Kupffer cells, and in associated medium. rrALR was labeled by iodination and used to determine its binding activity by Scatchard analysis in Kupffer cells and primarily cultured rat hepatocytes.

RESULTS

rrALR stimulated DNA replication in Kupffer cells and protein synthesis both in cells and in medium in a non-concentration-dependent manner. The effect was significant at the concentration of 1 microg/L ALR. However, rrALR had no effect on primarily cultured hepatocytes, when hepatocytes were cultured with the Kupffer cell medium conditioned by ALR, DNA replication and protein synthesis in hepatocytes increased significantly at the concentration of 1 microg/L ALR. When the ALR concentration was increased, its effect on hepatocyte proliferation decreased to the basal level. Scatchard analysis indicated the presence of a single class of high affinity receptors with a dissociation constant (Kd) of 0.883 nmol/L and a maximum binding capacity (Bmax) of 126.1 pmol/g protein in the rat Kupffer cells.

CONCLUSION

ALR can promote hepatocyte proliferation induced by Kupffer cells, which is associated with the concentration of ALR, suggesting that Kupffer cells play a dual role in liver regeneration.

Molecular control of liver development

Recent studies using animal models have elucidated a growing number of evolutionarily conserved genes and pathways that control liver development from the embryonic endoderm. It is increasingly clear that the genetic programs active in embryogenesis are often deregulated or reactivated in disease, cancer, and tissue repair. Understanding the molecular control of liver development should impact diagnosis and treatment of pediatric and adult liver diseases and aid in efforts to differentiate liver tissue in vitro for stem cell-based therapies.

Histopathological and ultrastructural effects of Losartan on embryonic rat kidney

The aim of our study was to investigate the histopathological, immunohistochemical and ultrastructural effects of Losartan (a selective angiotensin II type-1 receptor blocker) on renal development in rats. Twelve pregnant rats were divided into control and experimental groups. In the experimental group, Losartan (10 mg/kg/day) was given via nasogastric tube, between the sixth day of implantation and time of sacrifice on embryonic days 18 and 20. All formalin-fixed, paraffin wax-embedded renal tissue sections were stained with hematoxylin and eosin or labelled for binding of primary antibodies against transforming growth factor-beta (TGF-beta 1,-2,-3) using an avidin-biotin-peroxidase method. For electron microscopic examination, samples were fixed with glutaraldehyde and osmium tetroxide and embedded in araldite. Glomerular basement membrane (GBM) thickness was measured and compared using an unpaired t-test. Angiotensin II type-1 receptor antagonism by Losartan inhibited renal growth and delayed nephron maturation. Increased immunoreactivity of TGF-beta's was observed in developing nephron precursors and interstitial cells in the experimental group. Electron microscopical examination showed that thickening of the GBM was normal in the control group but an irregular thickening was seen in the experimental group (p < 0.001). It was also seen that epithelial cells of developing tubules underwent apoptosis in the experimental group. Thus, renal development in rats seems to depend on an intact renin-angiotensin system.

Differential Rates of Apoptosis in Bronchoalveolar Lavage and Blood of Lung Transplant Patients

BACKGROUND

Lung transplant tolerance depends on effective control of T-cell proliferation and activation. Commonly used immunosuppressive agents promote peripheral blood-derived lymphocyte apoptosis and inhibit production of cytokines involved in lymphocyte proliferation and survival. However, there have been no studies of the effectiveness of immunosuppressive treatments on apoptosis of T cells derived from the airways of lung transplant recipients. Our main aim was to compare apoptosis of T cells derived from peripheral blood and bronchoalveolar lavage (BAL) from lung transplant recipients, with no evidence of chronic or acute cellular rejection, and healthy volunteers. Lung transplantation may also be associated with increased apoptosis of airway epithelial cells. To investigate this possibility, we also examined apoptosis of epithelial cells derived from bronchial brushing.

METHODS

BAL, blood, and bronchial brushings were obtained from lung transplant recipients (n = 9) and age-matched controls (n = 15). T cell and epithelial cell apoptosis, Fas, Bax, Bcl-2, and p53 were evaluated by flow cytometry.

RESULTS

Increased apoptosis of peripheral blood T cells and decreased Bcl-2 were observed in the transplant patients. In contrast, there was no significant change in apoptosis of airway T cells or apoptosis-related proteins. Increased apoptosis and increased p53 were observed in the airway epithelial cells from the transplant recipients, possibly as a result of ineffective control of infiltrating cytotoxic T cells.

CONCLUSIONS

Immunosuppressive agents may not be as effective in inducing apoptosis of airway-derived T cells as peripheral blood-derived T cells after lung transplantation. These findings may have implications on the outcome of the immune response in the airways after immunosuppressive therapy and may be particularly relevant to lung allograft rejection.

Characterization of an Acute Molecular Marker of Nongenotoxic Rodent Hepatocarcinogenesis by Gene Expression Profiling in a Long Term Clofibric Acid Study

Evaluation of the nongenotoxic potential early during the development of a drug presents a major challenge. Recently, two genes were identified as potential molecular markers of rodent hepatic carcinogenesis: transforming growth factor-beta stimulated clone 22 (TSC-22) and NAD(P)H cytochrome P450 oxidoreductase (CYP-R) (1). They were identified after comparing the gene expression profiles obtained from the livers of Sprague-Dawley rats treated with different genotoxic and nongenotoxic compounds in a 5 day repeat dose in vivo study. To assess the potential of these two genes as acute markers of carcinogenesis, we investigated their modulation during a long-term nongenotoxic study in the rat using a classic initiation-promotion regime. Clofibric acid (CLO), which belongs to the broad class of chemicals known as peroxisome proliferators, was used as a nongenotoxic hepatocarcinogen. Male F344 rats were given a single nonnecrogenic injection of diethylnitrosamine (0 or 30 mg/kg) and fed a diet containing none or 5000 ppm CLO for up to 20 months. Necropsies of five rats per groups were performed at 18, 46, 102, 264, 377, 447 (control, DEN, and DEN + CLO rats), 524, and 608 days (for the CLO and control rats). Gross macroscopic and microscopic evaluation and gene expression profiling (on Affymetrix microarrays) were performed in peritumoral and tumoral liver tissues. Bioanalysis of the liver gene expression data revealed that TSC-22 was strongly down-regulated early in the study. Its underexpression was maintained throughout the study but disappeared upon CLO withdrawal. These modulations were confirmed by real-time polymerase chain reaction. However, CYP-R gene expression was not significantly altered in our study. Taken together, our results showed that TSC-22, but not CYP-R, has the potential to be an acute early molecular marker for nongenotoxic hepatocarcinogenesis in rodents.

Immunohistochemical detection of activated caspases in apoptotic hepatocytes in rat liver

In our study we tested the utility of antibodies that specifically recognize the cleaved large (active) subunits of caspase-3 and caspase-9 for immunohistochemical detection of apoptotic hepatocytes in rat liver sections using archival material from cyproterone acetate (CPA)-treated and control rats. CPA blocks apoptosis of hepatocytes and discontinuation of CPA treatment results in a syncronized wave of hepatocyte apoptosis. By comparing liver sections from CPA-treated and control rats with high and low rates of apoptosis we observed a close correlation between the occurrence of cleaved caspase-positive apoptotic figures and H&E-stained apoptotic bodies when evaluated in parallel sections. Caspase-stained figures were either immuno-positive apoptotic bodies or pre-apoptotic hepatocytes showing cytoplasmic and/or nuclear caspase-staining with otherwise normal cellular appearance. In extension of these observations we developed a double-immunohistochemical staining procedure which enables the detection of caspase-3-positive apoptotic hepatocytes within glutathione-S-transferase-P (GST-P)-positive preneoplastic liver foci. By use of this technique, inhibition of apoptosis by 2,3,7,8-tetrachlorodibenzo-p-dioxin as detected by counting of H&E-stained apoptotic bodies was found to correlate with a strong reduction of cleaved caspase-positive hepatocytes in GST-P-positive preneoplastic foci. In summary, this study demonstrates that cleaved caspase-positive apoptotic hepatocytes could be reliably identified and quantified both in normal and neoplastically transformed liver tissue.

Hepatitis C virus core protein upregulates transforming growth factor-beta 1 transcription

The majority of persons with chronic hepatitis C virus (HCV) infection develop liver fibrosis. Transforming growth factor (TGF)-beta 1 plays a pivotal role in the pathogenesis of post-inflammatory liver scarring. To clarify the influence of HCV infection on liver fibrosis, a reporter assay was used to investigate the effect of viral proteins on TGF-beta 1 expression in human hepatoma cells. Of all HCV proteins investigated (core, E1/E2/p7, NS2, NS3, NS4A, NS4B, NS5A, and NS5B), only the core protein activated the TGF-beta 1 promoter and upregulated TGF-beta 1 expression measured by an RNase protection assay. Bases -376 to -331 bp in the promoter region of TGF-beta 1 are responsible for upregulation by HCV core protein, and the nuclear protein that binds to this region increased with the stimulation of HCV core protein. Blocking the mitogen-activated protein kinase pathway prevented upregulation of TGF-beta 1 by HCV core protein. The immunological response is supposed to be a major factor to cause the secretion of TGF-beta 1 from non-parenchymal cells, but the results suggest that the HCV core protein expression may upregulate directly TGF-beta 1 transcription in parenchymal cells and suggest a new paradigm for exacerbation of liver fibrosis by HCV infection.

Induction of apoptosis in mouse liver adenoma and carcinoma in vivo by transforming growth factor-beta1

PURPOSE

In the liver, transforming growth factor beta-1 (TGF-beta1) constitutes a major negative growth regulating factor involved in the control of cell numbers; failure of this control mechanism has been associated with the development of liver cancer. Since no reports on the in vivo effects of exogenously administered TGF-beta1 on apoptosis in liver tumors have been published yet, we studied hepatocyte sensitivity to the proapoptotic action of TGF-beta1 in stages of chemically induced mouse liver carcinogenesis.

METHODS

Mouse liver carcinogenesis was initiated by a single dose of N-nitrosodiethylamine (NDEA, 90 mg/kg b.w., i.p.) to 5-week-old B6C3F1 mice. After 2 weeks, mice received either standard diet or a diet containing phenobarbital (PB, 90 mg/kg b.w) for 85 weeks. Four hours before being killed mice received a single dose of TGF-beta1 (56 microg or 200 microg TGF-beta1/kg of b.w., injected into the tail vein). Quantitative histological analysis of mitosis and apoptosis in normal liver tissue (NL), putative preneoplastic foci (PPF), hepatocellular adenoma (HCA), and hepatocellular carcinoma (HCC) was performed on H&E-stained liver sections.

RESULTS

In NDEA and NDEA + PB-treated mice, NL exhibited a very low incidence of apoptosis and mitosis, which increased in HCA and HCC. In the lesions apoptoses ranged between 0.03 and 0.6%. Two hundred micrograms of TGF-beta1/kg stimulated apoptoses in NL as well as in neoplastic lesions (significant increase in NL, HCA, and HCC); the most pronounced proapoptotic action of TGF-ss1 was observed in lesions of NDEA+PB pretreated mice (about 1.7%). Fifty-six microg TGF-beta1/kg had no detectable effect on apoptosis.

CONCLUSION

These observations indicate that during chemically induced liver carcinogenesis in B6C3F1 mice basal rates of apoptoses in adenoma and carcinoma are higher than in normal liver and can be further increased by a proapoptotic cytokine.

Activation of a caspase-dependent oxidative damage response mediates TGFbeta1 apoptosis in rat hepatocytes

Activation of transforming growth factor-beta type 1- (TGFbeta1) mediated signaling occurs in response to cell injury affecting stem-type cells and hepatocytes in liver. In this work we used WB stemlike liver epithelial cells and p53-defective CWSV-1 nontumorigenic rat hepatocytes to investigate the possible roles of caspases and oxidative stress in TGFbeta1 signaling. TGFbeta1 significantly increased the level of 4-hydroxy-2-nonenal (4-HNE), a stable product of lipid peroxidation. In addition, TGFbeta1-treated cells exhibited activation of caspases that accompanied by enhanced cleavage of the caspase substrate poly(ADP)-ribose polymerase (PARP) and induction of apoptosis. WB cells were twice as sensitive as sensitive as CWSV-1 cells to induction of TGFbeta1 apoptosis. TGFbeta1-apoptosis was significantly reduced when cells were treated with TGFbeta1 in the presence of inhibitors of caspase-1, -3, -8, and -9. Importantly, in addition to suppression of apoptosis, treatment of cells with the caspase-3 inhibitor Z-DEVD-FMK in the presence of TGFbeta1 suppressed the formation 4-HNE and restored mitotic activity. Together, these data suggest TGFbeta1 induces activation of a caspase signaling cascade that includes an oxidative damage response, PARP cleavage, and apoptosis that do not require intact p53 in rat hepatocytes.

Diminished production of anti-inflammatory mediators during neutrophil apoptosis and macrophage phagocytosis in chronic granulomatous disease (CGD)

Genetic defects in the phagocyte nicotinamide adenine dinucleotide phosphate (NADPH)-oxidase enzyme system result in chronic granulomatous disease (CGD). In addition to recurrent, life-threatening infections, patients with CGD frequently present with sterile inflammatory complications, suggesting that NADPH-oxidase deficiency predisposes to these responses in the absence of persistent microbial infection. The mechanisms involved in the aberrant, inflammatory process are unknown. In this study, we have shown that neutrophils isolated from CGD patients, which are more resistant to spontaneous apoptosis in vitro, also produce significantly less of the anti-inflammatory mediator cyclopentenone prostaglandin D(2) (PGD(2)). In addition, during phagocytosis of opsonized and nonopsonized apoptotic targets, CGD macrophages are severely compromised in their ability to produce PGD(2) and transforming growth factor-beta (TGF-beta). We suggest that delayed apoptosis of inflammatory cells, such as neutrophils and deficient production of the anti-inflammatory mediators PGD(2) and TGF-beta during macrophage clearance of apoptotic debris and invading pathogens, contributes to persistence of inflammation in CGD.

Portacaval shunt causes apoptosis and liver atrophy in rats despite increases in endogenous levels of major hepatic growth factors

BACKGROUND/AIMS

The response to the liver damage caused by portacaval shunt (PCS) is characterized by low-grade hyperplasia and atrophy. To clarify mechanisms of this dissociation, we correlated the expression of 'hepatotrophic factors' and the antihepatotrophic and proapoptotic peptide, transforming growth factor (TGF)-beta, with the pathologic changes caused by PCS in rats.

METHODS

PCS was created by side-to-side anastomosis between the portal vein and inferior vena cava, with ligation of the hilar portal vein. Hepatic growth mediators were measured to 2 months.

RESULTS

The decrease in the liver/body weight ratio during the first 7 days which stabilized by day 15, corresponded to parenchymal cell apoptosis and increases in hepatic TGF-beta concentration that peaked at 1.4 x baseline at 15 days before returning to control levels by day 30. Variable increases in the concentrations of growth promoters (hepatocyte growth factor, TGF-alpha and augmenter of liver regeneration) also occurred during the period of hepatocellular apoptosis.

CONCLUSIONS

The development of hepatic atrophy was associated with changes in TGF-beta concentration, and occurred despite increased expression of multiple putative growth promoters. The findings suggest that apoptosis set in motion by TGF-beta constrains the amount of hepatocyte proliferation independently from control of liver volume.

Dose-related effects of the peroxisome proliferator methylclofenapate in rat liver

Male Sprague-Dawley rats were fed diets containing 0 (control) and 2.5-750 ppm of the peroxisome proliferator methylclofenapate (MCP) for 1, 4 and 13 weeks. In other studies MCP has been shown to produce liver tumors at dietary levels of 50 and 250, but not 10 ppm. MCP treatment produced increases in relative liver weight and activities of peroxisomal and microsomal fatty acid oxidising enzymes at all time points at doses as low as 10 and 2.5 ppm, respectively. Replicative DNA synthesis was studied by implanting osmotic pumps containing 5-bromo-2'-deoxyuridine during study weeks 0-1, 3-4 and 12-13. Hepatocyte labelling index values were significantly increased by treatment with 10-750 ppm MCP for 1 week and 150-750 ppm MCP for 13 weeks. Treatment with 50-750 ppm MCP for 13 weeks increased hepatic peroxisome proliferator-activated receptor alpha and transforming growth factor-β1 gene expression to 150-165 and 150-170% of control, respectively. These results demonstrate that while low doses of MCP produce sustained hepatomegaly and peroxisome proliferation in rat liver, higher doses are required to produce a sustained stimulation of replicative DNA synthesis.

Altered DNA methylation: a secondary mechanism involved in carcinogenesis

This review focuses on the role that DNA methylation plays in the regulation of normal and aberrant gene expression and on how, in a hypothesis-driven fashion, altered DNA methylation may be viewed as a secondary mechanism involved in carcinogenesis. Research aimed at discerning the mechanisms by which chemicals can transform normal cells into frank carcinomas has both theoretical and practical implications. Through an increased understanding of the mechanisms by which chemicals affect the carcinogenic process, we learn more about basic biology while, at the same time, providing the type of information required to make more rational safety assessment decisions concerning their actual potential to cause cancer under particular conditions of exposure. One key question is: does the mechanism of action of the chemical in question involve a secondary mechanism and, if so, what dose may be below its threshold?

Caspase-3 and apoptosis in experimental chronic renal scarring

BACKGROUND

Caspase-3 is a member of the caspase enzyme family, having a central role in the execution of apoptosis. However, the significance of Caspase-3 in the inappropriate and excessive apoptosis that contributes to the progression of non-immune-mediated renal scarring has not been established.

METHODS

Kidneys from sham-operated and subtotal nephrectomized (SNx) rats were harvested on days 7, 15, 30, 60, 90 and 120 post-surgery. These were analyzed for apoptosis (in situ end labeling of DNA, light and electron microscopy), Caspase-3 activity (fluorometric substrate cleavage assay), protein and mRNA (Western and Northern blotting), as well as distribution (immunohistochemistry), inflammation (ED-1 immunohistochemistry) and fibrosis (Masson's Trichrome staining).

RESULTS

Apoptosis, inflammation and fibrosis gradually increased in glomeruli, tubules and interstitium of SNx rats. Caspase-3 was mainly located in damaged tubules, but also was found in some glomerular and interstitial cells. Little or no staining was noted in sham-operated kidneys. In SNx kidneys, Caspase-3 activity was significantly increased from day 30 and peaked on day 120 (2.5-fold). This resulted from increases in the 17 and 24 kD active protein subunits. The 32 kD precursor was increased at all time points (1861% on day 120, P < 0.01). Caspase-3 changes were transcription-dependent with the 2.7 kb caspase-3 mRNA significantly increased at all time points (287% on day 120). Caspase-3 activity was a better predictor of apoptosis (Std beta coefficient = 0.347, P < 0.05) than Caspase-3 proteins or mRNA; however, Caspase-3 at all levels correlated with apoptosis, inflammation and fibrosis (all P < 0.01).

CONCLUSIONS

Up-regulation of apoptosis in remnant kidneys is likely to be Caspase-3-dependent as it is associated with increases in Caspase-3 at the activity, protein and mRNA levels. Therefore, Caspase-3 is a potential therapeutic target for the modification of renal cell apoptosis and subsequently renal fibrosis.

Detection of apoptosis in keloids and a comparative study on apoptosis between keloids, hypertrophic scars, normal healed flat scars, and dermatofibroma

Recent studies have suggested that the regulation of apoptosis during wound healing is important in scar establishment and the development of pathological scarring. In this study, we demonstrate that keloid fibroblasts can be identified as apoptotic cells because of their highly condensed chromatin and discrete nuclear fragments. To further reveal the phenomenon of apoptosis, we quantified the number of terminal deoxynucleotide transferase-mediated dUTP nick-end labeling (TUNEL)-positive cells in surgically resected tissues of keloids (N = 10), hypertrophic scars (N = 10), normal healed flat scars (N = 10), and dermatofibroma (N = 10). The number of TUNEL-positive cells was relatively low, but was significantly higher for the keloid group compared with the normally healed flat scar group (p = 0.004), suggesting reduced cell survival and increased apoptotic cell death in a subpopulation of keloid fibroblasts. Furthermore, the number of TUNEL-positive cells was significantly higher for the keloid group compared with the dermatofibroma group (p = 0.044), suggesting that a subpopulation of keloid fibroblasts may suppress tumorgenicity at a greater rate than dermatofibroma by undergoing cell death. Hypertrophic scars had significantly higher levels of apoptosis than normally healed flat scars (p = 0.033). Therefore, these results suggest that selected fibroblasts in keloids and hypertrophic scars undergo apoptosis, which may play a role in the process of pathological scarring.

Effects of phospholipid surfactant on apoptosis induction by respirable quartz and kaolin in NR8383 rat pulmonary macrophages

Apoptosis was measured in rat alveolar macrophage NR8383 cells challenged in vitro with respirable quartz or kaolin dust and with the dusts pretreated with dipalmitoyl phosphatidylcholine (DPPC) to model conditioning of respired dusts by interaction with a primary phospholipid component of pulmonary surfactant. Quartz dust is known to induce apoptosis in vitro and in vivo. For this study, quartz and kaolin were compared as dusts of similar cytotoxicity in some in vitro assays but of differing pathogenic potential: quartz can cause significant pulmonary fibrosis while kaolin generally does not. NR8383 cells exposed to native quartz at concentrations from 50 to 400 microg/ml for 6 h showed a dose-dependent increase in apoptosis measured by the TdT-mediated dUTP-fluorescein nick end labeling (TUNEL), cell death ELISA, and DNA ladder formation assays, while native kaolin induced significant response only at the higher concentrations and only in the TUNEL and ELISA assays. For cell challenge from 6 h to 5 days at 100 microg/ml of dust, quartz was active at all times while kaolin was active only at 5 days. DPPC pre-treatment suppressed quartz activity until 3 days and kaolin activity through 5 days. Cellular release of lactate dehydrogenase, measured in parallel experiments to compare dust apoptotic and necrotic activities, indicated that components of serum as well as surfactant may affect kaolin in vitro expression of those activities.

Extraction and purification of TGFβ and its effect on the induction of apoptosis of hepatocytes

AIM: To extract and purify the transforming growth factor β (TGFβ), and to demonstrate its biological activity in vivo and induction of apoptosis of hepatocytes in vitro.

METHODS: TGFβ was isolated from fresh bovine platelets by acid/ethanol extraction method and purified with ion exchange and gel chromatography. The extracted TGFβ as injected subcutaneously to mice, and its biological activity in vivo was observed 72 hrs post-injection by HE staining. The morphological changes were observed by HE staining and the occurrence of apoptosis was detected by TUNEL method after the human normal hepatic cell line QZG was treated with 8 μg·L^-1TGFβ for 12 hrs in vitro.

RESULTS: The molecular mass 25 ku TGFβ protein was successfully extracted. It was able to induce localized granulation tissue formation in vivo. TGFβ-treated hepatocytes showed obvious apoptotic morphological changes, including the pyknosis and dense-stained nuclei and cytoplasm, the fragmentary, annular or crescent nuclei, and the “bubbling” cytoplasm. Moreover, its apoptotic rate was significantly higher than that of the control group (P < 0.05).

CONCLUSION: Biological active TGFβ protein is extracted and purified successfully from bovine platelets, and it is able to induce the apoptosis of hepatocytes.

Deregulation of renal transforming growth factor-beta1 after experimental short-term ureteric obstruction in fetal sheep

Renal malformations are the commonest cause of chronic renal failure in children and they are often associated with urinary tract abnormalities that impair fetal urine flow. Up-regulation of transforming growth factor-beta1 (TGF-beta1) occurs after experimental postnatal urinary tract obstruction and we recently reported increased levels of TGF-beta1 in human renal malformations (Yang SP et al, Am J Pathol 2000, 157:1633-1647). These findings led us to propose that obstruction-induced stretch of developing renal epithelia causes up-regulation of TGF-beta1, which then perturbs renal development. In this study, therefore, we examined expression of components of the TGF-beta1 signaling axis in a previously characterized ovine model of fetal short-term urine flow impairment in which complete unilateral ureteric obstruction was induced at 90 days when a few layers of glomeruli had formed. Up-regulation of TGF-beta1 mRNA and protein was observed in obstructed kidneys, compared to sham-operated control organs, after only 10 days. Increased levels of TGF-beta1 receptors I (TGF-betaR1) and II (TGF-betaR2) were also detected on Western blot, and the cytokine and TGF-betaR1 co-localized in disrupted epithelia on immunohistochemistry. De novo expression of alpha-smooth muscle actin, a structural protein up-regulated during TGF-beta1-induced phenotypic switching between human renal dysplastic epithelial and mesenchymal lineages in vitro, was also observed in these aberrant epithelia. These findings implicate increased TGF-beta1 signaling in the early biological changes generated by fetal urinary tract obstruction.

Biology of transforming growth factor beta in hepatocarcinogenesis

TGF-beta is an important factor in the regulation of liver growth. It is an inhibitor of hepatocyte DNA synthesis and may induce active cell death, e.g., to remove excessive tissue mass. Studies using transgenic mice suggest that expression in the resting liver has to be well balanced; either under- or overexpression appear to cause an increased turnover of hepatocytes and to predispose to hepatocarcinogenesis. TGF-beta overexpression is frequently observed in human hepatocellular carcinomas, probably as a late event in tumor development. In men and mice, TGF-beta overexpression appears to be associated with loss of TGF-beta responsiveness often by disruption of TGF-beta signaling. However, mechanisms as mutations in TGF-beta receptor II or Smad2 and 4 genes, frequently observed in other human cancers, have only rarely been observed in hepatocellular carcinomas. Further studies may clarify the mechanisms by which hepatocellular tumors escape TGF-beta growth control, as well as analyze possible roles of TGF-beta overexpression in immunosuppression and angiogenesis.

Transforming growth factor beta-1 stimulates articular chondrocyte elaboration of matrix vesicles capable of greater calcium pyrophosphate precipitation

Objective To determine the role of transforming growth factor beta1 (TGFbeta) in early calcium pyrophosphate formation by measuring its effects on articular chondrocyte matrix vesicle (MV) formation, specific activity of the inorganic pyrophosphate(PPi)-generating enzyme nucleoside triphosphate pyrophospho-hydrolase (NTPPPH) and biomineralization capacity. Methods MV elaborated from mature porcine chondrocyte monolayers+/-TGFbeta were compared for protein content, NTPPPH activity, and ATP-dependent biomineralization. Precipitation of calcium pyrophosphate mineral phases by MV was determined by a radiometric assay and by Fourier transform infrared spectroscopy (FTIR). Results MV from monolayers exposed to TGFbeta were enriched in NTPPPH activity compared to MV from control monolayers (P< 0.01) and precipitated more calcium/mg MV protein than controls (P</= 0.01). FTIR spectra of mineral generated by monolayer-elaborated MV were consistent with poorly crystalline CPPD. Conclusions TGFbeta is capable of increasing the capacity of articular chondrocyte-derived MV to generate PPi via NTPPPH and precipitate calcium in the form of CPPD mineral. These data support the concept that this growth factor plays a key role in cartilage matrix CPPD deposition.

Pathomorphological Characteristics and Pathogenesis of Viral Hepatitis

Viral hepatitis (VH) is an inflammatory reaction of the liver to hepatotropic viruses. Acute VH can be classified according to the virus and type of necrosis. Chronic hepatitis (CH) might be active, persistent or lobular based on previous classification. More recently the grade (necroinflammatory activity) and stage (fibrosis and architectural distorsion) of CH have been distinguished and scored. Apoptosis and necrosis probably coexist in VH and contribute to hepatocyte death. Several "death factors", such as transforming growth factor b, Apo1/Fas and tumor necrosis factor play a role in the execution of cell death. Injury of hepatocytes during viral infection can occur as a direct effect of the virus or as a result of the host immune response. Expression of different viral antigens can be detected during VH and might be visualized. Phenotyping of the portal inflammatory cell infiltrate in CH has shown a T-cell zone comprised of CD4+ helper T cells and CD8+ supressor/cytotoxic T cells at the periphery of the lobules. The pathogenetic mechanisms responsible for the final outcome of viral infection depend on viral factors (such as genotype, mutation etc.), virus-host interaction, expression of viral protein, several cytokines etc. which finally lead to the well known histological alterations of viral hepatitis.

Biology of transforming growth factor beta in hepatocarcinogenesis

TGF-beta is an important factor in the regulation of liver growth. It is an inhibitor of hepatocyte DNA synthesis and may induce active cell death, e.g., to remove excessive tissue mass. Studies using transgenic mice suggest that expression in the resting liver has to be well balanced; either under- or overexpression appear to cause an increased turnover of hepatocytes and to predispose to hepatocarcinogenesis. TGF-beta overexpression is frequently observed in human hepatocellular carcinomas, probably as a late event in tumor development. In men and mice, TGF-beta overexpression appears to be associated with loss of TGF-beta responsiveness often by disruption of TGF-beta signaling. However, mechanisms as mutations in TGF-beta receptor II or Smad2 and 4 genes, frequently observed in other human cancers, have only rarely been observed in hepatocellular carcinomas. Further studies may clarify the mechanisms by which hepatocellular tumors escape TGF-beta growth control, as well as analyze possible roles of TGF-beta overexpression in immunosuppression and angiogenesis.

Expression of apoptosis-related genes and proteins in experimental chronic renal scarring

Apoptosis has been proposed to play an important role in the progression of renal scarring. The mechanisms that determine whether a cell enters the apoptotic program are complex. Bax and Bcl-2 are recognized modulators of this event; their relative levels determine the fate of cells. A role for apoptosis in the progression of renal scarring in the remnant kidneys of rats submitted to subtotal nephrectomy (SNx) has been described. This study investigated the expression (protein and mRNA) of Bax and Bcl-2 in remnant kidneys between day 7 and day 120 post-SNx. Northern blot analysis showed that bax mRNA was increased in remnant kidneys from day 7 (150% of control; P: < 0.05), whereas bcl-2 mRNA was decreased from day 15 (23% of control; P: < 0.05) resulting in a 14-fold increase in the ratio of bax to bcl-2 mRNA by day 120. Western blot analysis showed similar changes in Bax and Bcl-2 protein in remnant kidneys, resulting in a 147-fold increase in the ratio of Bax to Bcl-2 on day 120. Immunohistochemistry showed increases in Bax to be located predominantly in tubules in SNx kidneys. Interestingly, Bcl-2 immunostaining increased in some epithelial cells within atrophic tubules despite the overall decrease in Bcl-2 protein and mRNA. The overall renal apoptotic cells correlated closely with the ratio of bax to bcl-2 at both the mRNA and protein levels (r = 0.594 and 0.308, respectively; P: < 0.05). Furthermore, tubular apoptosis correlated positively with the mRNA level of bax (r = 0.471; P: < 0.01) and negatively with the mRNA and protein levels of bcl-2 (r = -0.443 and -0.607, respectively; P: < 0.01). The increase in the ratio of the death inducer (Bax) to the death repressor (Bcl-2) at the mRNA and protein levels may control the apoptosis associated with the progression of tubular atrophy and chronic renal fibrosis within remnant rat kidneys. These observations may have prognostic and therapeutic implications in chronic renal failure.

Autocrine expression of activated transforming growth factor-beta(1) induces apoptosis in normal rat liver

The aim of this study was to determine the differential effects of latent and activated transforming growth factor (TGF)-beta(1) in growth control of normal and proliferating hepatocytes in vivo. Rats were injected with adenoviruses expressing control transgenes (Ctrl), latent TGF-beta(1) [TGF-beta(L)], or activated TGF-beta(1) [TGF-beta(A)]. Additional animals underwent two-thirds partial hepatectomy (PH) 24 h after injection. Increased hepatocyte apoptosis was observed in TGF-beta(A)-injected but not TGF-beta(L)-injected animals 24 h postinjection (10.5%) compared with Ctrl animals (0.37%). The percent of apoptotic cells increased to 32.1% in TGF-beta(A)-injected animals 48 h after injection. Furthermore, TGF-beta(A)-injected rats did not survive 24 h after PH. Four hours after PH, 0.25 and 14.1% apoptotic hepatocytes were seen in Ctrl- and TGF-beta(A)-injected rats, respectively. TGF-beta(A)-induced apoptosis in primary rat hepatocytes was blocked with a pancaspase inhibitor. Thus autocrine expression of TGF-beta(A) but not TGF-beta(L) induces hepatocyte apoptosis in the normal rat liver. Rats overexpressing TGF-beta(A) do not survive two-thirds PH due to hepatic apoptosis. Thus activation of TGF-beta(1) may be a critical step in the growth control of normal and proliferating rat hepatocytes.

Modulation of transforming growth factor beta response and signaling during transdifferentiation of rat hepatic stellate cells to myofibroblasts

Activation of hepatic stellate cells (HSCs) is the key step in liver fibrogenesis. Increased transforming growth factor beta (TGF-beta) expression and extracellular matrix production in patients with hepatic fibrosis and experimental models of liver fibrogenesis support implication of TGF-beta in the pathogenesis of this disease. However, a causative role for TGF-beta during transdifferentiation of HSCs has not been delineated in molecular detail. Using a rat cell culture model of HSC transdifferentiation, we analyzed TGF-beta signal transduction and identified changes between stellate cells and their transdifferentiated phenotype. Fully transdifferentiated myofibroblasts, opposed to HSCs, were not inhibited in proliferation activity on treatment with TGF-beta1. Furthermore, stimulation of alpha2 (I) collagen and Smad7 messenger RNA (mRNA) expression by TGF-beta1 was achieved in stellate cells but not in myofibroblasts. Northern and Western blot analyses indicated significant expression of TGF-beta receptors I and II in both cell types. In contrast, [(125)I]-TGF-beta1 receptor affinity labeling displayed strongly reduced types I, II, and III receptor presentation at the cell surface of myofibroblasts. Moreover, myofibroblasts did not display DNA-binding SMAD proteins in electrophoretic mobility shift assays with a CAGA box. These data indicate that stellate cells are responsive to TGF-beta1 treatment and transduce a signal that may play an important role in liver fibrogenesis. Myofibroblasts display decreased availability of surface receptors for TGF-beta, which could be based on autocrine stimulation. However, lack of activated SMAD complexes with DNA-binding activity and absence of alpha2 (I) collagen transcription inhibition by latency-associated peptide (LAP)/anti-TGF-beta antibody raise the possibility of TGF-beta signaling independent receptor down-regulation in myofibroblasts.

Apoptosis and predisposition to oral cancer

The term apoptosis, also known as programmed cell death (PCD), was coined by developmental biologists a number of years ago to describe a form of cell death characterized by several unique morphological and biochemical features. Genetic studies of the round worm Caeneorhabditis elegans, a simple multicellular organism, first revealed apoptosis to be an integral part of the developmental program. Subsequently, the importance of apoptosis in higher organisms was demonstrated in several eukaryotic systems. [n mammals, apoptosis is widespread during embryogenesis and in adult tissues. It is required for normal tissue homeostasis and for clonal selection in the immune system. In both developing and adult organisms, apoptosis plays a central role in reinforcing appropriate cellular patterns and in regulating cell number by eliminating cells that are harmful or no longer needed. It is becoming increasingly clear that disruption in the apoptosis pathway can contribute to the development of a number of developmental, inflammatory, degenerative, and neoplastic diseases. The effector arm of the apoptotic program includes members of the Bcl-2 gene family that function as either death agonists or death antagonists. These proteins participate in an elaborate genetically controlled biochemical pathway that functions to maintain tissue and organ homeostasis and serve as a critical defense mechanism to guard against malignant transformation. Cancer is the result of a series of genetic lesions that include activation of oncogenes and inactivation or loss of tumor suppressor genes. Several groups of investigators have observed that deregulated expression of oncogenes can subvert apoptotic pathways, resulting in prolonged cell survival. In pathological settings such as cancer, members of the Bcl-2 gene family are able to synergize with oncogenes and tumor suppressor genes to transform cells. In this review, we describe the process of apoptosis in mammalian cells and define the role and biochemical pathways through which the Bcl-2 gene family induce and/or protect cells from apoptosis. Last, we will discuss the evidence which suggests that alterations in this pathway may play a central role in tumorigenesis by allowing genetically damaged cells normally destined for elimination to persist, predisposing them to additional mutations and driving them to malignancy.

Species differences in hepatic peroxisome proliferation, cell replication and transforming growth factor-beta1 gene expression in the rat, Syrian hamster and guinea pig

The objective of this study was to evaluate species differences in the hepatic effects of three potent rodent peroxisome proliferators, namely methylclofenapate (MCP), ciprofibrate (CIP) and Wy-14,643 (WY), particularly with respect to effects on replicative DNA synthesis and transforming growth factor-beta1 (TGF-beta1) gene expression. Male Sprague-Dawley rats, Syrian hamsters and Dunkin-Hartley guinea pigs were given daily oral doses of 0 (corn oil) and 75 mg/kg MCP for periods of 6 and 21 days. Syrian hamsters and guinea pigs were also treated with 25 mg/kg CIP and 25 mg/kg WY. Relative liver weights were significantly increased in peroxisome proliferator-treated rats and Syrian hamsters, but not in guinea pigs. Hepatic peroxisomal (palmitoyl-CoA oxidation) and microsomal (lauric acid 12-hydroxylase) fatty acid oxidising enzyme activities and CYP4A isoform mRNA levels were significantly increased in rats and Syrian hamsters, whereas only minor effects were observed in the guinea pig. Replicative DNA synthesis was studied by implanting 7-day osmotic pumps containing 5-bromo-2'-deoxyuridine during study days -1 to 6 and 14 to 21. Hepatocyte labelling index values were increased by MCP in the rat, but neither MCP, CIP nor WY produced any significant effect on replicative DNA synthesis in the Syrian hamster and guinea pig. MCP treatment increased TGF-beta1 and insulin-like growth factor II/mannose-6-phosphate (IGFII/Man6P) receptor gene expression in the rat. In the Syrian hamster, effects on TGF-beta1 and IGFII/Man6P receptor gene expression were also observed in some instances, whereas TGF-beta1 mRNA levels were essentially unchanged in the guinea pig. These results provide further evidence for marked species differences in response to rodent peroxisome proliferators. While peroxisome proliferators produce a wide spectrum of effects in rat liver, other species such as the Syrian hamster and guinea pig are less responsive and in the case of some endpoints (e.g., cell replication) may be refractory.

Angiotensin stimulates TGF-beta1 and clusterin in the hydronephrotic neonatal rat kidney

Unilateral ureteral obstruction (UUO) induces activation of the renin-angiotensin system and upregulation of transforming growth factor-beta1 (TGF-beta1; a cytokine modulating cellular adhesion and fibrogenesis) and clusterin (a glycoprotein produced in response to cellular injury). This study was designed to examine the regulation of renal TGF-beta1 and clusterin by ANG II in the neonatal rat. Animals were subjected to UUO in the first 2 days of life, and renal TGF-beta1 and clusterin mRNA were measured 3 days later. Rats were divided into treatment groups receiving saline vehicle, ANG, losartan (AT(1) receptor inhibitor), or PD-123319 (AT(2) receptor inhibitor). ANG stimulated renal TGF-beta1 expression via AT(1) receptors, a response similar to that in the adult. In contrast, clusterin expression was stimulated via AT(2) receptors, a response differing from that in the adult, in which ANG inhibits clusterin expression via AT(1) receptors. We speculate that the unique response of the neonatal hydronephrotic kidney to ANG II is due to the preponderance of AT(2) receptors in the developing kidney.

Sex-specific induction of apoptosis by cyproterone acetate in primary rat hepatocytes

The synthetic steroid cyproterone acetate (CPA) has been reported to be hepatogenotoxic in female rats depending on sex-specific expression of a hydroxysteroid sulfotransferase (HST) which is involved in the bioactivation of CPA to reactive metabolites. In the present study the ability of CPA to initiate apoptosis in rat hepatocytes in vitro was investigated with respect to sex-specific effects and dependency on HST activity. Incubation of primary hepatocytes of female rats with CPA (0.1-30 microM) caused a strong increase in percent of cells undergoing apoptosis. The lowest concentration leading to apoptosis was 0.3 microM. In contrast, hepatocytes isolated from male rats showed a very weak response at high exposure to CPA (30 microM) only. Treatment with transforming growth factor-beta1 induced high levels of apoptotis in hepatocytes of both genders. Megestrol acetate and chlormadinone acetate, two structural analogues of CPA with a much lower genotoxic potency, did not induce apoptosis. Pre-addition of 10 or 50 microM dehydroepiandrosterone (DHEA), a known inhibitor of hepatic HST, almost completely inhibited CPA-induced apoptosis in hepatocytes of female rats. Using similar test concentrations, DHEA also reduced CPA-induced DNA excision repair as measured in the unscheduled DNA synthesis test. The results suggest that apoptosis induction is directly related to DNA damage induced by HST-dependent CPA metabolites.

Cell biology of the osteoclast

The osteoclast is a hematopoietic cell derived from CFU-GM and branches from the monocyte-macrophage lineage early during the differentiation process. The marrow microenvironment appears critical for osteoclast formation due to production of RANK ligand, a recently described osteoclast differentiation factor, by marrow stromal cells in response to a variety of osteotropic factors. In addition, factors such as osteoprotegerin, a newly described inhibitor of osteoclast formation, as well as secretory products produced by the osteoclast itself and other cells in the marrow enhance or inhibit osteoclast formation. The identification of the role of oncogenes such as c-fos and pp60 c-src in osteoclast differentiation and bone resorption have provided important insights in the regulation of normal osteoclast activity. Current research is beginning to delineate the signaling pathways involved in osteoclastic bone resorption and osteoclast formation in response to cytokines and hormones. The recent development of osteoclast cell lines may make it possible for major advances to our understanding of the biology of the osteoclast to be realized in the near future.

Transforming growth factor-beta and multidrug resistance in chronic lymphocytic leukemia

Patients with chronic lymphocytic leukemia (CLL) frequently respond to initial treatment, but then become resistant to chemotherapy. Studies have shown one important cause of chemotherapeutic resistance to be multidrug resistance (MDR). To investigate the potential role of MDR and transforming growth factor-beta (TFG-beta), a potent growth inhibitor of B lymphocytes, in the development of chemotherapeutic resistance in CLL, we evaluated 22 CLL patients for loss or mutation of TGF-beta receptors (TbetaR), plasma TGF-beta1 levels, and expression of MDR1 mRNA. Receptor crosslinking and immunoprecipitation experiments did not demonstrate loss of TbetaRs in any patients studied. No relationship between plasma TGF-beta1 levels and expression of MDR1 mRNA was seen. Correlation of plasma TGF-beta1 levels to disease stage revealed a consistent decline in plasma TGF-beta1 levels with advancing disease stage (P = 0.031).

Monoterpenes in essential oils. Biosynthesis and properties

Monoterpenes are compounds found in the essential oils extracted from many plants, including fruits, vegetables, spices and herbs. These compounds contribute to the flavor and aroma of plant from which they are extracted. Monoterpenes are acyclic, monocyclic, or bicyclic C30 compounds synthesized by monoterpene synthases using geranyl pyrophosphate (GPP) as substrate. GPP is also the precursor in the synthesis of farnesyl pyrophosphate (FPP) and geranyl-geranyl pyrophosphate (GGPP), two important compounds in cell metabolism of animals, plants and yeast. Monoterpene cyclases produce cyclic monoterpenes through a multistep mechanism involving a universal intermediate, a terpinyl cation which can be transformed to several compounds. Experimental studies, using animal cancer models, have demonstrated that some monoterpenes possess anticarcinogenic properties, acting at different cellular and molecular levels. From these discoveries it seems clear that monoterpenes could be considered as effective, nontoxic dietary antitumorigenic agents that hold promise as a novel class of anticancer drugs.

Induction of apoptosis in porcine thyroid follicles by transforming growth factor beta1 and epidermal growth factor

For thyroid cells in culture DNA fragmentation and morphological changes related to apoptosis were first described in dog thyroid cells after deprivation of serum, epidermal growth factor or thyrotropin. With intact porcine thyroid follicles in three-dimensional culture, the effect of deprivation of growth factors and of incubation with transforming growth factor beta1 (TGF-beta1), epidermal growth factor (EGF), thyrotropin (TSH) or insulin-like growth factor I (IGF-I) on the incidence of apoptosis was studied. Thyroid follicles were embedded in growth factor-depleted Matrigel and cultured in serum-free medium with or without growth factors for 7 days followed by incubation for 4, 24 and 72 h with TGF-beta1 (2 or 5 ng/mL). The percentage of apoptotic cells was determined by direct counting in electron-microscopy. Approximately 1% of apoptotic bodies could be detected in unstimulated follicles. This was unchanged in the presence of TSH (1 mU/mL) or IGF (10 ng/mL) but significantly increased up to 3.99 +/- 1.24% with 2 ng/mL of EGF. After incubation with TGF-beta apoptosis increased dose-dependently to 4.05 +/- 0.67% with 2 ng/mL TGF-beta1 and 5.16 +/- 1.75% with 5 ng/mL TGF-beta1. The incidence of necrotic cells remained constant at about 1 to 2%. Preincubation of follicles with 2 ng/mL of EGF followed by incubation with 5 ng/mL TGF-beta1 increased the rate of apoptic bodies up to 13.19 +/- 1.9%. We conclude that growth factor depletion in thyroid follicles in three-dimensional culture does not lead to apoptosis. TGF-beta1, however, induces apoptosis even in quiescent thyroid follicular cells and is significantly more pronounced in growing thyroid cells. EGF, which is a dedifferentiating growth factor for thyroid cells, also induces apoptosis. As EGF enhances TGF-beta1 mRNA and protein in thyroid follicular cells, the induction of apoptosis by EGF might also be due to TGF-beta1.