Sensitive and non-invasive method for the in vivo analysis of membrane permeability in small animals.

Tissue membranes are boundaries that isolate organs or cavities in the body. These semi-permeable membranes are responsible for passive protection that acts through the regulation of nutrient absorption, secretion and filtration of small molecules. These functions could be altered as a consequence of inflammation or trauma, which in turn could lead to changes in permeability, allowing the entrance of toxins, antigens, proteins or facilitating the spread of tumors. Membrane permeability therefore plays an important role in numerous diseases. However, current experimental techniques that are available to quantify membrane permeability in small animals have limited precision and temporal specificity. Improvements in such measurements would lead to a deeper understanding of disease pathogenesis and this may accelerate the development of specific therapies. The study reported here concerns the efficacy of a novel, non-invasive imaging analysis-based measurement method that significantly improves the quantification of tissue membrane permeability in small animals, while at the same time mitigating the adverse effects experienced by the animals under study.

TGF-Beta Blockade Increases Renal Inflammation Caused by the C-Terminal Module of the CCN2.

The CCN family member 2 (CCN2, also known as connective tissue growth factor) may behave as a risk biomarker and a potential therapeutic target for renal disease. CCN2 participates in the regulation of inflammation and fibrosis. TGF-ß is considered the main fibrogenic cytokine; however, in some pathological settings TGF-ß also has anti-inflammatory properties. CCN2 has been proposed as a downstream profibrotic mediator of TGF-ß, but data on TGF-ß role in CCN2 actions are scarce. Our aim was to evaluate the effect of TGF-ß blockade in CCN2-mediated experimental renal damage. Systemic administration of the C-terminal module of CCN2 to mice caused sustained renal inflammation. In these mice, TGF-ß blockade, using an anti-TGF-ß neutralizing antibody, significantly increased renal expression of the NGAL (a kidney injury biomarker), kidney infiltration by monocytes/macrophages, and upregulation of MCP-1 expression. The anti-inflammatory effect of TGF-ß seems to be mediated by a dysregulation of the systemic Treg immune response, shown by decreased levels of circulating CD4(+)/Foxp3(+)Treg cells. Our experimental data support the idea that TGF-ß exerts anti-inflammatory actions in the kidney and suggest that it is not an optimal therapeutic target.

Paricalcitol reduces peritoneal fibrosis in mice through the activation of regulatory T cells and reduction in IL-17 production.

Fibrosis is a significant health problem associated with a chronic inflammatory reaction. The precise mechanisms involved in the fibrotic process are still poorly understood. However, given that inflammation is a major causative factor, immunomodulation is a possible therapeutic approach to reduce fibrosis. The vitamin D receptor (VDR) that is present in all hematopoietic cells has been associated with immunomodulation. We investigated whether the intraperitoneal administration of paricalcitol, a specific activator of the VDR, modulates peritoneal dialysis fluid (PDF)-induced peritoneal fibrosis. We characterized the inflammatory process in the peritoneal cavity of mice treated or not treated with paricalcitol and analyzed the ensuing fibrosis. The treatment reduced peritoneal IL-17 levels, which strongly correlated with a significantly lower peritoneal fibrotic response. In vitro studies demonstrate that both CD4+ and CD8+ regulatory T cells appear to impact the regulation of IL-17. Paricalcitol treatment resulted in a significantly increased frequency of CD8+ T cells showing a regulatory phenotype. The frequency of CD4+ Tregs tends to be increased, but it did not achieve statistical significance. However, paricalcitol treatment increased the number of CD4+ and CD8+ Treg cells in vivo. In conclusion, the activation of immunological regulatory mechanisms by VDR signaling could prevent or reduce fibrosis, as shown in peritoneal fibrosis induced by PDF exposure in mice.

TWEAK promotes peritoneal inflammation.

Peritoneal dialysis (PD) is complicated by peritonitis episodes that cause loss of mesothelium and eventually sclerosing peritonitis. An improved understanding of the molecular contributors to peritoneal injury and defense may increase the therapeutic armamentarium to optimize peritoneal defenses while minimizing peritoneal injury. There is no information on the expression and function of the cytokine TWEAK and its receptor Fn14 during peritoneal injury. Fn14 expression and soluble TWEAK levels were measured in human PD peritoneal effluent cells or fluids with or without peritonitis. Fn14 expression was also analyzed in peritoneal biopsies from PD patients. Actions of intraperitoneal TWEAK were studied in mice in vivo. sTWEAK levels were increased in peritoneal effluent in PD peritonitis. Effluent sTWEAK levels correlated with the number of peritoneal macrophages (r=0.491, p=0.002). Potential TWEAK targets that express the receptor Fn14 include mesothelial cells and macrophages, as demonstrated by flow cytometry of peritoneal effluents and by analysis of peritoneal biopsies. Peritoneal biopsy Fn14 correlated with mesothelial injury, fibrosis and inflammation, suggesting a potential deleterious effect of TWEAK/Fn14. In this regard, intraperitoneal TWEAK administration to mice promoted peritoneal inflammation characterized by increased peritoneal effluent MCP-1, Fn14 and Gr1+ macrophages, increased mesothelial Fn14, MCP-1 and CCL21 expression and submesothelial tissue macrophage recruitment. Taken together these data suggest that the TWEAK/Fn14 system may promote inflammation and tissue injury during peritonitis and PD.

IL-17A is a novel player in dialysis-induced peritoneal damage.

The classical view of the immune system has changed by the discovery of novel T-helper (Th) subsets, including Th17 (IL-17A-producing cells). IL-17A participates in immune-mediated glomerulonephritis and more recently in inflammatory pathologies, including experimental renal injury. Peritoneal dialysis patients present chronic inflammation and Th1/Th2 imbalance, but the role of the Th17 response in peritoneal membrane damage has not been investigated. In peritoneal biopsies from dialyzed patients, IL-17A immunostaining was found mainly in inflammatory areas and was absent in the healthy peritoneum. IL-17A-expressing cells included lymphocytes (CD4+ and γδ), neutrophils, and mast cells. Elevated IL-17A effluent concentrations were found in long-term peritoneal dialysis patients. Studies in mice showed that repeated exposure to recombinant IL-17A caused peritoneal inflammation and fibrosis. Moreover, chronic exposure to dialysis fluids resulted in a peritoneal Th17 response, including elevated IL-17A gene and protein production, submesothelial cell infiltration of IL-17A-expressing cells, and upregulation of Th17 differentiation factors and cytokines. IL-17A neutralization diminished experimental peritoneal inflammation and fibrosis caused by chronic exposure to dialysis fluids in mice. Thus, IL-17A is a key player of peritoneum damage and it may be a good candidate for therapeutic intervention in peritoneal dialysis patients.

The C-terminal module IV of connective tissue growth factor is a novel immune modulator of the Th17 response.

Connective tissue growth factor (CTGF/CCN2) is a matricellular protein susceptible to proteolytic degradation. CCN2 levels have been suggested as a potential risk biomarker in several chronic diseases. In body fluids, CCN2 full-length and its degradation fragments can be found; however, their in vivo effects are far from being elucidated. CCN2 was described as a profibrotic mediator, but this concept is changing to a proinflammatory cytokine. In vitro, CCN2 full-length and its C-terminal module IV (CCN2(IV)) exert proinflammatory properties. Emerging evidence suggest that Th17 cells, and its effector cytokine IL-17A, participate in chronic inflammatory diseases. Our aim was to explore whether CCN2(IV) could regulate the Th17 response. In vitro, stimulation of human naive CD4+ T lymphocytes with CCN2(IV) resulted in differentiation to Th17 phenotype. The in vivo effects of CCN2(IV) were studied in C57BL/6 mice. Intraperitoneal administration of recombinant CCN2(IV) did not change serum IL-17A levels, but caused an activation of the Th17 response in the kidney, characterized by interstitial infiltration of Th17 (IL17A+/CD4+) cells and upregulation of proinflammatory mediators. In CCN2(IV)-injected mice, elevated renal levels of Th17-related factors (IL-17A, IL-6, STAT3 and RORγt) were found, whereas Th1/Th2 cytokines or Treg-related factors (TGF-ß and Foxp-3) were not modified. Treatment with an anti-IL-17A neutralizing antibody diminished CCN2(IV)-induced renal inflammation. Our findings unveil that the C-terminal module of CCN2 induces the Th17 differentiation of human Th17 cells and causes a renal Th17 inflammatory response. Furthermore, these data bear out that IL-17A targeting is a promising tool for chronic inflammatory diseases, including renal pathologies.

TH1/TH2 Cytokine profile in relapsing-remitting multiple sclerosis patients treated with Glatiramer acetate or Natalizumab.

BACKGROUND: The balance between T helper cells Th2- and Th1-related cytokines plays a key role in multiple sclerosis (MS). A shift from a Th1 towards a Th2 cytokine profile could have a beneficial effect on the clinical course of the disease. The objective of this study was to assess Th2/Th1 cytokine profile in relapsing-remitting MS (RRMS) patients receiving an immunosuppressive treatment with natalizumab (NAT), or an immunomodulatory treatment with glatiramer acetate (GA) after one year of treatment. METHODS: This was an observational cross-sectional study. All consecutive patients diagnosed with RRMS who had received GA or NAT for 12 months were included in the study. We determined serum levels of Th1 and Th2 cytokines (interleukin [IL]-1a, IL-1b, IL-2, IL-4, IL-5, IL-6, IL-8, IL-10, IL-12p70, IL-13, monocyte chemotactic protein [MCP]-1, tumor-necrosis factor [TNF]-α, interferon [IFN]-γ and granulocyte macrophage colony stimulating factor [GM-CSF]) by flow cytometry. Th2/Th1 bias was defined based on the ratio of IL-4, IL-5, IL-6 or IL-10 Th2 cytokines and proinflammatory INF-γ or TNF-α Th1 cytokines. RESULTS: Eleven patients under treatment with NAT and 12 patients treated with GA were evaluated. RRMS patients treated with NAT showed significantly higher levels of IL-6 (p < 0.05), MCP-1 (p < 0.01), and GM-CSF (p < 0.05) compared to GA patients after one year of treatment. A trend for increasing of IL-12p70, IL-1b, TNF- α and IFN- γ levels was also found in patients receiving NAT compared to GA patients. IL-4/IFN-γ, IFN-γ/TNF-α and IL-10/IFN-γ ratios as markers of Th2/Th1 ratio were significantly elevated in GA patients compared to those receiving NAT (p < 0.05). CONCLUSION: In conclusion, our findings suggest that GA promotes a superior Th2-biased anti-inflammatory response as compared with NAT in the systemic circulation of RRMS patients. Future studies with larger cohorts will determine whether this immune Th2 shift in GA patients is associated with a beneficial effect on disease outcome.

Influence of bicarbonate/low-GDP peritoneal dialysis fluid (BicaVera) on in vitro and ex vivo epithelial-to-mesenchymal transition of mesothelial cells.

BACKGROUND: Peritoneal membrane damage induced by peritoneal dialysis (PD) is largely associated with epithelial-to-mesenchymal transition (EMT) of mesothelial cells (MCs), which is believed to be a result mainly of the glucose degradation products (GDPs) present in PD solutions. OBJECTIVES: This study investigated the impact of bicarbonate-buffered, low-GDP PD solution (BicaVera: Fresenius Medical Care, Bad Homburg, Germany) on EMT of MCs in vitro and ex vivo. IN VITRO STUDIES: Omentum-derived MCs were incubated with lactate-buffered standard PD fluid or BicaVera fluid diluted 1:1 with culture medium. Ex vivo studies: From 31 patients randomly distributed to either standard or BicaVera solution and followed for 24 months, effluents were collected every 6 months for determination of EMT markers in effluent MCs. RESULTS: Culturing of MCs with standard fluid in vitro resulted in morphology change to a non-epithelioid shape, with downregulation of E-cadherin (indicative of EMT) and strong induction of vascular endothelial growth factor (VEGF) expression. By contrast, in vitro exposure of MCs to bicarbonate/low-GDP solution had less impact on both EMT parameters. Ex vivo studies partially confirmed the foregoing results. The BicaVera group, with a higher prevalence of the non-epithelioid MC phenotype at baseline (for unknown reasons), showed a clear and significant trend to gain and maintain an epithelioid phenotype at medium- and longer-term and to show fewer fibrogenic characteristics. By contrast, the standard solution group demonstrated a progressive and significantly higher presence of the non-epithelioid phenotype. Compared with effluent MCs having an epithelioid phenotype, MCs with non-epithelioid morphology showed significantly lower levels of E-cadherin and greater levels of fibronectin and VEGF. In comparing the BicaVera and standard solution groups, MCs from the standard solution group showed significantly higher secretion of interleukin 8 and lower secretion of collagen I, but no differences in the levels of other EMT-associated molecules, including fibronectin, VEGF, E-cadherin, and transforming growth factor ß1. Peritonitis incidence was similar in both groups. Functionally, the use of BicaVera fluid was associated with higher transport of small molecules and lower ultrafiltration capacity. CONCLUSIONS: Effluent MCs grown ex vivo from patients treated with bicarbonate/low-GDP BicaVera fluid showed a trend to acquire an epithelial phenotype, with lower production of proinflammatory cytokines and chemokines (such as interleukin 8) than was seen with MCs from patients treated with a lactate-buffered standard PD solution.

Treatment with natalizumab in relapsing-remitting multiple sclerosis patients induces changes in inflammatory mechanism.

Natalizumab is a widely accepted drug for the relapsing-remitting subtype of multiple sclerosis (RRMS). The present longitudinal exploratory study in RRMS patients analyzes the effects of natalizumab treatment on the levels of pro-inflammatory and anti-inflammatory cytokine protein levels and also the frequency and suppressor function of regulatory T cells. Flow cytometry was used to determine cytokines and regulatory T cell frequency while regulatory T cell suppressor function was assayed in vitro at different time-points after starting with natalizumab. Results showed serum levels of pro-inflammatory interferon gamma and interleukin (IL)-12p70, as well as anti-inflammatory IL-4 and IL-10, were elevated just a few hours or days after first IV infusion of natalizumab. Interestingly, other cytokines like IL-5 or IL-13 were also elevated while pro-inflammatory IL-17, IL-2, and IL-1ß increased only after a long-term treatment, suggesting different immune mechanisms. In contrast, we did not observe any effect of natalizumab treatment on regulatory T cell frequency or activity. In conclusion, these results suggest natalizumab has other immunological effects beyond VLA-4 interaction and inhibition of CNS extravasation, the relevance of which is as yet unknown and warrants further investigation.

A natural anti-T-cell receptor monoclonal antibody protects against experimental autoimmune encephalomyelitis.

The therapeutic potential of natural anti-T-cell receptor (TCR) antibodies is largely unknown. We investigated whether passive administration of C1-19, a novel natural anti-TCRVß8 monoclonal antibody, could interfere with the development of EAE. Treatment with C1-19 prevented myelin basic protein (MBP)-induced EAE in Vß8-sufficient B10.PL but not in Vß8-deficient SJL mice. Furthermore, C1-19 reduced disease severity when administrated shortly after disease onset. These protective effects of C1-19 correlated with a Th2 bias of the cytokine response, in the absence of T-cell deletion or anergy. Together, these findings indicate that natural anti-TCR antibodies could function as therapeutic tools in autoimmune inflammatory diseases.

H-ras and N-ras are dispensable for T-cell development and activation but critical for protective Th1 immunity.

The small guanine nucleotide binding proteins of the Ras family, including in mammals the highly homologous H-ras, N-ras, and K-ras isoforms, are rapidly activated on ligation of the T-cell antigen receptor (TCR), but whether each isoform plays specific roles in T cells is largely unknown. Here, we show, with the use of mice specifically lacking H-ras or N-ras, that these isoforms are dispensable for thymocyte development and mature T-cell activation. By contrast, CD4⁺ T cells from Ras-deficient mice exhibited markedly decreased production of the Th1 signature cytokine IFN-γ early after TCR stimulation, concomitantly with impaired induction of the Th1-specific transcription factor T-bet. Accordingly, Ras-deficient mice failed to mount a protective Th1 response in vivo against the intracellular parasite Leishmania major, although they could be rendered resistant to infection if a Th1-biased milieu was provided during parasite challenge. Collectively, our data indicate that the TCR recruits distinct Ras isoforms for signal transduction in developing and mature T cells, thus providing a mechanism for differential signaling from the same surface receptor. Furthermore, we demonstrate for the first time that H-ras and N-ras act as critical controllers of Th1 responses, mostly by transmitting TCR signals for Th1 priming of CD4⁺ T cells.

Alternative activation of macrophages in human peritoneum: implications for peritoneal fibrosis.

BACKGROUND: Depending on the cytokine microenvironment, macrophages (Mϕ) can adopt a proinflammatory (M1) or a profibrotic (M2) phenotype characterized by the expression of cell surface proteins such as CD206 and CD163 and soluble factors such as CC chemokine ligand 18 (CCL18). A key role for Mϕ in fibrosis has been observed in diverse organ settings. We studied the Mϕ population in a human model of peritoneal dialysis in which continuous stress due to dialysis fluids and recurrent peritonitis represent a risk for peritoneal membrane dysfunction reflected as ultrafiltration failure (UFF) and peritoneal fibrosis. METHODS: We used flow cytometry and quantitative reverse transcription-polymerase chain reaction to analyse the phenotype of peritoneal effluent Mϕ and tested their ability to stimulate the proliferation of human fibroblasts. Mϕ from non-infected patients were compared with those from patients with active peritonitis. Cytokine production was evaluated by enzyme-linked immunosorbent assay (ELISA) in spent dialysates and cell culture supernatants. RESULTS: CD206(+) and CD163(+) M2 were found within peritoneal effluents by flow cytometry analysis, with increased frequencies of CD163(+) cells during peritonitis (P = 0.003). TGFB1, MMP9 and CCL18 messenger RNA (mRNA) levels in peritoneal macrophages (pMϕ) were similar to those found in M2 cells differentiated in vitro. The ability of pMϕ to stimulate fibroblast proliferation correlated with CCL18 mRNA levels (r = 0.924, P = 0.016). CCL18 production by pMϕ was confirmed by immunostaining of cytospin samples and ELISA. Moreover, CCL18 effluent concentrations correlated with decreased peritoneal function, which was evaluated as dialysate to plasma ratio of creatinine (r = 0.724, P < 0.0001), and were significantly higher in patients with UFF (P = 0.0025) and in those who later developed sclerosing peritonitis (P = 0.024). CONCLUSIONS: M2 may participate in human peritoneal fibrosis through the stimulation of fibroblast cell growth and CCL18 production as high concentrations of CCL18 are associated with functional deficiency and fibrosis of the peritoneal membrane.

BMP-7 blocks mesenchymal conversion of mesothelial cells and prevents peritoneal damage induced by dialysis fluid exposure.

BACKGROUND: During peritoneal dialysis (PD), mesothelial cells (MC) undergo an epithelial-to-mesenchymal transition (EMT), and this process is associated with peritoneal membrane (PM) damage. Bone morphogenic protein-7 (BMP-7) antagonizes transforming growth factor (TGF)-beta1, modulates EMT and protects against fibrosis. Herein, we analysed the modulating role of BMP-7 on EMT of MC in vitro and its protective effects in a rat PD model. METHODS: Epitheliod or non-epitheliod MC were analysed for the expression of BMP-7, TGF-beta1, activated Smads, epithelial cadherin (E-cadherin), collagen I, alpha smooth muscle cell actin (alpha-SMA) and vascular endothelial growth factor (VEGF) using standard procedures. Rats were daily instilled with PD fluid with or without BMP-7 during 5 weeks. Histological analyses were carried out in parietal peritoneum. Fibrosis was quantified with van Gieson or Masson's trichrome staining. Vasculature, activated macrophages and invading MC were quantified by immunofluorescence analysis. Quantification of infiltrating leukocytes and MC density in liver imprints was performed by May-Grünwald-Giemsa staining. Hyaluronic acid levels were determined by ELISA. RESULTS: MC constitutively expressed BMP-7, and its expression was downregulated during EMT. Treatment with recombinant BMP-7 resulted in blockade of TGF-beta1-induced EMT of MC. We provide evidence of a Smad-dependent mechanism for the blockade of EMT. Exposure of rat peritoneum to PD fluid resulted in inflammatory and regenerative responses, invasion of the compact zone by MC, fibrosis and angiogenesis. Administration of BMP-7 decreased the number of invading MC and reduced fibrosis and angiogenesis. In contrast, BMP-7 had no effect on inflammatory and regenerative responses, suggesting that these are EMT-independent, and probably upstream, processes. CONCLUSIONS: Data point to a balance between BMP-7 and TGF-beta1 in the control of EMT and indicate that blockade of EMT may be a therapeutic approach to ameliorate peritoneal membrane damage during PD.

A nanoconjugate Apaf-1 inhibitor protects mesothelial cells from cytokine-induced injury.

BACKGROUND: Inflammation may lead to tissue injury. We have studied the modulation of inflammatory milieu-induced tissue injury, as exemplified by the mesothelium. Peritoneal dialysis is complicated by peritonitis episodes that cause loss of mesothelium. Proinflammatory cytokines are increased in the peritoneal cavity during peritonitis episodes. However there is scarce information on the modulation of cell death by combinations of cytokines and on the therapeutic targets to prevent desmesothelization. METHODOLOGY: Human mesothelial cells were cultured from effluents of stable peritoneal dialysis patients and from omentum of non-dialysis patients. Mesothelial cell death was studied in mice with S. aureus peritonitis and in mice injected with tumor necrosis factor alpha and interferon gamma. Tumor necrosis factor alpha and interferon gamma alone do not induce apoptosis in cultured mesothelial cells. By contrast, the cytokine combination increased the rate of apoptosis 2 to 3-fold over control. Cell death was associated with the activation of caspases and a pancaspase inhibitor prevented apoptosis. Specific caspase-8 and caspase-3 inhibitors were similarly effective. Co-incubation with both cytokines also impaired mesothelial wound healing in an in vitro model. However, inhibition of caspases did not improve wound healing and even impaired the long-term recovery from injury. By contrast, a polymeric nanoconjugate Apaf-1 inhibitor protected from apoptosis and allowed wound healing and long-term recovery. The Apaf-1 inhibitor also protected mesothelial cells from inflammation-induced injury in vivo in mice. CONCLUSION: Cooperation between tumor necrosis factor alpha and interferon gamma contributes to mesothelial injury and impairs the regenerative capacity of the monolayer. Caspase inhibition attenuates mesothelial cell apoptosis but does not facilitate regeneration. A drug targeting Apaf-1 allows protection from apoptosis as well as regeneration in the course of inflammation-induced tissue injury.

CTGF promotes inflammatory cell infiltration of the renal interstitium by activating NF-kappaB.

Connective tissue growth factor (CTGF) is an important profibrotic factor in kidney diseases. Blockade of endogenous CTGF ameliorates experimental renal damage and inhibits synthesis of extracellular matrix in cultured renal cells. CTGF regulates several cellular responses, including adhesion, migration, proliferation, and synthesis of proinflammatory factors. Here, we investigated whether CTGF participates in the inflammatory process in the kidney by evaluating the nuclear factor-kappa B (NF-kappaB) pathway, a key signaling system that controls inflammation and immune responses. Systemic administration of CTGF to mice for 24 h induced marked infiltration of inflammatory cells in the renal interstitium (T lymphocytes and monocytes/macrophages) and led to elevated renal NF-kappaB activity. Administration of CTGF increased renal expression of chemokines (MCP-1 and RANTES) and cytokines (INF-gamma, IL-6, and IL-4) that recruit immune cells and promote inflammation. Treatment with a NF-kappaB inhibitor, parthenolide, inhibited CTGF-induced renal inflammatory responses, including the up-regulation of chemokines and cytokines. In cultured murine tubuloepithelial cells, CTGF rapidly activated the NF-kappaB pathway and the cascade of mitogen-activated protein kinases, demonstrating crosstalk between these signaling pathways. CTGF, via mitogen-activated protein kinase and NF-kappaB activation, increased proinflammatory gene expression. These data show that in addition to its profibrotic properties, CTGF contributes to the recruitment of inflammatory cells in the kidney by activating the NF-kappaB pathway.

Análise de desempenho econômico da produção orgânica de leite: estudo de caso no Distrito Federal / Assessment of economic performance of organic milk production: case study in the Brazilian federal district

Neste trabalho, objetivou-se analisar economicamente a produção orgânica de leite. Para esta avaliação foram utilizados os dados obtidos em uma propriedade certificada como orgânica, localizada no Distrito Federal, durante os períodos de 2002 e 2003. A Renda Líquida (RL) por litro de leite foi positiva no ano de 2002 e negativa no de 2003, considerando-se o preço do leite a R$ 0,40/ L, (preço histórico pago ao produtor de leite convencional na região), apresentando resultados positivos com o preço simulado de R$ 0,80/L (preço pago aos produtores orgânicos nas Regiões Sul e Sudeste do país). Os índices de produtividade foram semelhantes aos observados nas propriedades convencionais. A produção orgânica de leite pode ser uma alternativa economicamente viável para a pecuária, desde que haja uma remuneração superior à praticada para o leite convencional.

The objective of the present work is the economical analysis of the organic milk production. For this evaluation, statistics from a farm with organic certificate located in the Brazilian Federal District were appraised, during the period of 2002 and 2003. The Net Operating Revenue (NOR) displayed a positive general average per liter of milk for 2002 and a negative average for 2003, considering the milk price at R$ 0.40/l (this being the historical price of the conventional milk in that region), presenting positive results at the simulated price of R$ 0.80/l (this being the common price of organic milk marketed at Southeast and South regions). The productivity indicators were similar to those observed for traditional properties. The organic milk production may become an economically practicable alternative for the national cattle farming, as long as the remuneration stays higher than that practiced for the conventional milk.

Cyclooxygenase-2 mediates dialysate-induced alterations of the peritoneal membrane.

During peritoneal dialysis (PD), exposure of the peritoneal membrane to nonphysiologic solutions causes inflammation, ultimately leading to altered structure and function. Myofibroblasts, one of the cell types that contribute to dysfunction of the peritoneal membrane, can originate from mesothelial cells (MCs) by epithelial-to-mesenchymal transition (EMT), a process that has been associated with an increased rate of peritoneal transport. Because cyclooxygenase-2 (COX-2) is induced by inflammation, we studied the role of COX-2 in the deterioration of the peritoneal membrane. We observed that nonepithelioid MCs found in peritoneal effluent expressed higher levels of COX-2 than epithelioid MCs. The mass transfer coefficient for creatinine correlated with MC phenotype and with COX-2 levels. Although COX-2 was upregulated during EMT of MCs in vitro, COX-2 inhibition did not prevent EMT. In a mouse model of PD, however, COX-2 inhibition with Celecoxib resulted in reduced fibrosis and in partial recovery of ultrafiltration, outcomes that were associated with a reduction of inflammatory cells. Furthermore, PD fluid with a low content of glucose degradation products did not induce EMT or COX-2; the peritoneal membranes of mice treated with this fluid showed less worsening than mice exposed to standard fluid. In conclusion, upregulation of COX-2 during EMT may mediate peritoneal inflammation, suggesting COX-2 inhibition as a potential strategy to ameliorate peritoneal deterioration in PD patients.