Pertteli Salmenperä

Suppression of pro-inflammatory cytokine release by selective inhibition of inducible nitric oxide synthase in mucosal explants from patients with ulcerative colitis

Background: In ulcerative colitis (UC), inflammatory damage is associated with increased production of pro-inflammatory cytokines and nitric oxide through the inducible nitric oxide synthase (iNOS) pathway. In an animal model of acute experimental colitis we have previously shown amelioration of inflammation with the highly selective iNOS inhibitor 1400 W. The aim of the present study was to investigate the effects of selective iNOS inhibition on the production of pro-inflammatory cytokines by the colon mucosa in UC. Methods: Inflamed and uninflamed mucosa from patients with severe UC were incubated with a highly selective iNOS inhibitor N-[3-(aminomethyl)benzyl]acetamidine (1400 W), with a relatively selective cNOS inhibitor N(G)-nitro-L-arginine-methyl-esther (L-NAME), or with an NO-donor, S-nitroso-acetylpenicillamine (SNAP). Cytokine concentrations in the incubation medium were quantitated with ELISA. Results: Compared to uninflamed mucosa there was an increase in iNOS protein and nitrotyrosine levels in inflamed mucosal samples. Immunolocalization of iNOS and nitrotyrosine showed their expression in inflammatory cells in the lamina propria. Expression of iNOS was also found in the epithelial brush border. Selective inhibition of iNOS suppressed the release of tumour necrosis factor alpha (TNF-α, by 66%) and interleukin-6 (IL-6, by 27%). The NO-donor, SNAP, augmented the secretion of TNF-α, IL-6 and IL-1-β (by 62%, 52% and 175%, respectively) and decreased the release of IL-1 receptor antagonist (IL-1Ra, by 34%) by the inflamed mucosa. Moreover, in uninflamed samples, 1400 W suppressed the production of TNF-α (by 69%) and incubation with SNAP decreased IL-6 concentrations by 48%. The cNOS over iNOS selective inhibitor L-NAME had no significant effects on the accumulation of cytokines. Conclusion: Selective inhibition of iNOS suppresses mucosal TNF-α and IL-6 release in active UC, whereas NO seems to exacerbate the inflammatory response. These results suggest that selective iNOS inhibition may have therapeutic promise in the treatment of UC.

Acute effects of the cys-leukotriene-1 receptor antagonist, montelukast, on experimental colitis in rats

Cysteinyl leukotrienes play a part in inflammatory reactions such as inflammatory bowel diseases. The aim of the present study was to evaluate the acute effects of a cys-leukotriene-1 receptor antagonist, montelukast, on trinitrobenzene sulphonic acid (TNBS)-induced colitis in rats. Montelukast (5, 10 or 20 mg kg(-1) day(-1)), a 5-lipoxygenase inhibitor, zileuton (50 or 100 mg kg(-1) day(-1), a positive control), or the vehicle was administered intracolonically to the rats twice daily throughout the study, starting 12 h before the induction of colitis with TNBS. The severity of colitis (macroscopic and histological assessment, as well as myeloperoxidase activity), the protein expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2, and eicosanoid production in colonic tissue incubation were assessed 24 and 72 h after colitis induction. Montelukast increased prostaglandin E(2) production at 24 h and tended to reduce the cyclooxygenase-2 protein expression at 72 h, but did not influence the severity of colitis. Zileuton failed to decrease the inflammatory reaction in spite of reduced leukotriene B(4) production at 72 h. The results suggest that drugs that block cysteinyl leukotriene receptors have limited potential to ameliorate acute TNBS-induced colitis, but that they exert some beneficial effects which make them capable of modulating the course of colitis.

Nemosis, a novel way of fibroblast activation, in inflammation and cancer.

Malignant cells when grown in suspension, as a rule, proliferate and can form spheroids that have been used as a model of tumor nodules, micrometastases and avascular tumors. In contrast, normal adherent cells cannot be stimulated to grow as multicellular aggregates. Now, recent results show that normal fibroblasts if forced to cluster (spheroid formation) do not grow but undergo a new pathway of cell activation (nemosis) leading to a massive proinflammatory, proteolytic and growth factor response. The clustering and activation are initiated by fibronectin-integrin interaction. The activated fibroblasts are able to modulate the behavior of cancer cells and, furthermore malignant cells boost this activation even further. In this model, the activation of fibroblasts terminates in programmed necrosis-like cell death. Activation of the tumor stroma, especially of fibroblasts, is of critical importance for tumor progression, although mechanisms leading to their activation are still largely uncharacterized. In summary, our results suggest that this kind of fibroblast activation (nemosis) may be involved in pathological conditions such as inflammation and cancer.

Formation and activation of fibroblast spheroids depend on fibronectin-integrin interaction

Clustering of fibroblasts into spheroids induces a massive proinflammatory, proteolytic and growth-factor response, named nemosis, which promotes tumor cell invasiveness and differentiation of leukemia cells. We have now sought to investigate mechanisms leading to the formation of multicellular spheroids and subsequent activation of fibroblasts (nemosis). Cell lines either lacking fibronectin expression (FN-/-) or expressing FN with a mutated integrin-binding site (FNRGE/RGE) were unable to form compact spheroids. Furthermore, inhibition of FN synthesis by siRNA or functional inhibition of FN or its integrins impaired spheroid formation (alpha5, beta1) and quenched fibroblast activation (alphaV). The integrin ligand GRGDSP hexapeptide interfered with spheroid formation and induced activation of fibroblasts. Surprisingly, a 70 kDa FN fragment, which prevents deposition of FN matrix but does not interfere with FN-integrin interaction, prevented spheroid formation only marginally and did not block the activation. Our results present a new mechanism of fibroblast activation, which is initiated by interaction of FN with its integrin receptors.

Clustering of fibroblasts induces proinflammatory chemokine secretion promoting leukocyte migration.

Fibroblasts can acquire an immunoregulatory phenotype and they play an important role in triggering and upholding inflammation. Yet, the mechanism of this immunoactivation remains unknown. Previously we showed that spheroid formation by human fibroblasts leads to nemosis: activation through upregulation of cyclooxygenase-2, production of growth factors, and proteolysis. We now show that clustering of fibroblasts to spheroids leads to a significant induction of chemotactic cytokines able to attract various leukocyte subtypes. The mRNA contents of several chemokines (CCL2-5, CXCL1-3, and CXCL8) were 6-169-fold higher in fibroblast spheroids than in monolayer controls 36 h after spheroid formation. Similarly, CCL3, CCL5 and CXCL8 levels in spheroid medium were significantly higher than in monolayer medium. Conditioned fibroblast spheroid medium induced chemotaxis of primary human neutrophils and monocyte-like THP-1 cells, and the effects were significantly inhibited by antibodies against CXCL8 and the chemokine receptor CCR1, respectively. The decreased levels of IkappaB alpha and presence of DNA-binding nuclear factor-kappaB (NF-kappaB) after spheroid formation indicate NF-kappaB activity. In conclusion, clustering of fibroblasts provides an experimental model to study their activation and is sufficient to induce substantial proinflammatory chemokine secretion functionally promoting leukocyte migration, and the mechanism seems to involve the NF-kappaB signalling pathway.

Effects of Lactobacillus rhamnosus GG and Lactobacillus reuteri R2LC on Acetic Acid-Induced Colitis in Rats

Background: Certain lactobacilli reduce the severity of experimental colitis. The aim of this study was to compare the effects of a human strain Lactobacillus rhamnosus GG and a rat strain Lactobacillus reuteri R2LC on acetic acid-induced colitis in rats. Methods:Lactobacillus rhamnosus GG, Lactobacillus reuteri R2LC or sulphasalazine were given orally to the rats. Colitis was assessed 72 h after induction with acetic acid. Results:Lactobacillus reuteri R2LC significantly antagonized body weight loss caused by inflammation compared with Lactobacillus rhamnosus GG and sulphasalazine, and oedema formation in the colon compared with sulphasalazine. Lactobacillus reuteri R2LC reduced the median value of macroscopic ulceration and the protein content of inducible nitric oxide synthase by 50% and the median of the protein content of inducible cyclooxygenase by 30% compared with that of the colitis control group, and Lactobacillus rhamnosus GG reduced the median of inducible nitric oxide protein content by 40% and increased the median of inducible cyclooxygenase protein content by 30% compared with the median value of the colitis control group, but these differences were not statistically significant. Conclusions: The rat strain Lactobacillus reuteri R2LC, but not the human strain Lactobacillus rhamnosus GG, is of benefit in reducing the severity of acetic acid-induced colitis in rats. These results suggest that it is not the total amount of Lactobacillus but the particular species or strain of Lactobacillus that is important in attenuating experimental colitis.BACKGROUND Certain lactobacilli reduce the severity of experimental colitis. The aim of this study was to compare the effects of a human strain Lactobacillus rhamnosus GG and a rat strain Lactobacillus reuteri R2LC on acetic acid-induced colitis in rats. METHODS Lactobacillus rhamnosus GG, Lactobacillus reuteri R2LC or sulphasalazine were given orally to the rats. Colitis was assessed 72 h after induction with acetic acid. RESULTS Lactobacillus reuteri R2LC significantly antagonized body weight loss caused by inflammation compared with Lactobacillus rhamnosus GG and sulphasalazine, and oedema formation in the colon compared with sulphasalazine. Lactobacillus reuteri R2LC reduced the median value of macroscopic ulceration and the protein content of inducible nitric oxide synthase by 50% and the median of the protein content of inducible cyclooxygenase by 30% compared with that of the colitis control group, and Lactobacillus rhamnosus GG reduced the median of inducible nitric oxide protein content by 40% and increased the median of inducible cyclooxygenase protein content by 30% compared with the median value of the colitis control group, but these differences were not statistically significant. CONCLUSIONS The rat strain Lactobacillus reuteri R2LC, but not the human strain Lactobacillus rhamnosus GG, is of benefit in reducing the severity of acetic acid-induced colitis in rats. These results suggest that it is not the total amount of Lactobacillus but the particular species or strain of Lactobacillus that is important in attenuating experimental colitis.

Differences in the Nemosis Response of Normal and Cancer-Associated Fibroblasts from Patients with Oral Squamous Cell Carcinoma

Background Tumor-stroma reaction is associated with activation of fibroblasts. Nemosis is a novel type of fibroblast activation. It leads to an increased production of growth factors and proinflammatory and proteolytic proteins, while at the same time cytoskeletal proteins are degraded. Here we used paired normal skin fibroblasts and cancer-associated fibroblasts (CAF) and primary and recurrent oral squamous cell carcinoma (SCC) cells to study the nemosis response. Principal Findings Fibroblast nemosis was analyzed by protein and gene expression and the paracrine regulation with colony formation assay. One of the normal fibroblast strains, FB-43, upregulated COX-2 in nemosis, but FB-74 cells did not. In contrast, CAF-74 spheroids expressed COX-2 but CAF-43 cells did not. Alpha-SMA protein was expressed in both CAF strains and in FB-74 cells, but not in FB-43 fibroblasts. Its mRNA levels were downregulated in nemosis, but the CAFs started to regain the expression. FSP1 mRNA was downregulated in normal fibroblasts and CAF-74 cells, but not in CAF-43 fibroblasts. Serine protease FAP was upregulated in all fibroblasts, more so in nemotic CAFs. VEGF, HGF/SF and FGF7 mRNA levels were upregulated to variable degree in nemosis. CAFs increased the colony formation of primary tumor cell lines UT-SCC-43A and UT-SCC-74A, but normal fibroblasts inhibited the anchorage-independent growth of recurrent UT-SCC-43B and UT-SCC-74B cells. Conclusions Nemosis response, as observed by COX-2 and growth factor induction, and expression of CAF markers α-SMA, FSP1 and FAP, varies between fibroblast populations. The expression of CAF markers differs between normal fibroblasts and CAFs in nemosis. These results emphasize the heterogeneity of fibroblasts and the evolving tumor-promoting properties of CAFs.

Bone marrow mesenchymal stem cells undergo nemosis and induce keratinocyte wound healing utilizing the HGF/c‐Met/PI3K pathway

We previously showed cell–cell contacts of human dermal fibroblasts to induce expression of the hepatocyte growth factor/scatter factor (HGF) in a process designated as nemosis. Now we report on nemosis initiation in bone marrow mesenchymal stem cells (BMSCs). Because BMSCs are being used increasingly in cell transplantation therapy we aimed to demonstrate a functional effect and benefit of BMSC nemosis for wound healing. Nemotic and monolayer cells were used to stimulate HaCaT keratinocyte migration in a scratch‐wound healing assay. Both indicators of nemosis, HGF production and cyclooxygenase‐2 expression, were induced in BMSC spheroids. When compared with a similar amount of cells as monolayer, nemotic cells induced keratinocyte in vitro scratch‐wound healing in a concentration‐dependent manner. The HGF receptor, c‐Met, was rapidly phosphorylated in the nemosis‐stimulated keratinocytes. Nemosis‐induced in vitro scratch‐wound healing was inhibited by an HGF‐neutralizing antibody as well as the small molecule c‐Met inhibitor, SU11274. HGF‐induced in vitro scratch‐wound healing was inhibited by PI3K inhibitors, wortmannin and LY294002, while LY303511, an inactive structural analogue of LY294002, had no effect. Inhibitors of the mitogen‐activated protein kinases MEK/ERK1/2 (PD98059 and U0126), and p38 (SB203580) attenuated HGF‐induced keratinocyte in vitro scratch‐wound healing. We conclude that nemosis of BMSCs can induce keratinocyte in vitro scratch‐wound healing, and that in this effect signaling via HGF/c‐Met is involved.

Fibroblast nemosis arrests growth and induces differentiation of human leukemia cells

Interactive signaling between cancer cells and stroma plays an important role in determining tumor development. We recently found tumor cell‐derived factors to induce fibroblast clustering, and that the high amounts of hepatocyte growth factor/scatter factor (HGF/SF) produced by these cell–cell contact‐activated fibroblasts enhanced the invasiveness of c‐Met‐expressing cancer cells. We now observed that leukemia cells lacking c‐Met respond to this novel type of fibroblast activation, nemosis, with growth arrest and differentiation to a dendritic cell‐like phenotype. This effect was counteracted by introduction of c‐Met expression into these cells. Moreover, those leukemia cell lines harboring properly processed c‐Met showed no effect in response to nemosis. We propose this effect to be mediated by nemosis‐derived cytokine signals, and present the potential candidates induced in the nemotic fibroblasts: interleukins‐1, ‐6, ‐8, ‐11, leukemia inhibitory factor and granulocyte‐macrophage‐colony‐stimulating factor. Our results emphasize the role of activated stromal fibroblasts in controlling progression of certain hematologic malignancies in a c‐Met expression‐dependent manner.

Cell‐cell contact activation of fibroblasts increases the expression of matrix metalloproteinases

Background. We recently found that direct homotypic cell‐cell contacts between human dermal fibroblasts induce a novel form of cell activation leading to non‐apoptotic programmed cell death. As the major features of this process we identified massive induction of cyclo‐oxygenase‐2 and production of inflammatory prostaglandins. On the surface of the decomposing spheroids, activation of the major extracellular proteolytic cascade, plasminogen activation, associated with surface exposure of α‐enolase, took place. Aim. To further characterize pericellular proteolysis by cell‐cell contact‐activated fibroblasts we studied the role of the other major extracellular proteolytic system, matrix metalloproteinases (MMPs). Methods. MMP expression in fibroblast clusters and monolayers was compared using mRNA microarrays and immunoblot analyses. The activities of MMPs were confirmed using MMP inhibitors and caseinolysis. Results. In microarrays MMP‐1, ‐10, and ‐14 (MT1‐MMP) were induced 5.8‐, 106‐, and 5.6‐fold, respectively. These findings were confirmed by immunoblotting. Radial caseinolysis showed low level of proteolytic activity in spheroid‐conditioned media; ilomastat, a general inhibitor of MMPs, suppressed 50% of the proteolytic activity thus confirming it to be at least in part due to MMPs. A cocktail of tetracycline‐derived MMP inhibitors suppressed lactate dehydrogenase (LDH) release only 11%, and if combined with aprotinin 28%. Conclusions. Cell‐cell contact activation of fibroblasts induced MMP‐1, ‐10, and MT1‐MMP expression, suggesting similar signaling to that in inflammation and cancer.