Kristofer Rubin - Academia.edu (original) (raw)

Papers by Kristofer Rubin

Circulation Research, 1992

The increased capillary fluid filtration required to rapidly create edema in acute inflammation c... more The increased capillary fluid filtration required to rapidly create edema in acute inflammation can be generated by increased negativity of the interstitial fluid pressure (Pif). This observation suggests that connective tissues can "actively" enhance capillary fluid filtration. We now show that in vivo blockade of beta 1-integrin adhesion receptors in rat skin causes local edema concomitant with increased negativity of Pif. Experiments were performed on the dorsal side of the hind paw, and Pif was measured with sharpened glass capillaries (tip diameter, 3-7 microns) connected to a servo-controlled counterpressure system. Measurements were made after circulatory arrest had been induced with intracardiac potassium chloride in pentobarbital anesthesia. This procedure prevents the vascular phenomena of increased fluid and protein flux leading to edema formation, which in turn can increase Pif and therefore potentially mask an increased negativity of Pif. Control Pif averaged ...

Information about reprints can be found online at: Reprints: document. Permissions and Rights Que... more Information about reprints can be found online at: Reprints: document. Permissions and Rights Question and Answer about this process is available in the located, click Request Permissions in the middle column of the Web page under Services. Further information Editorial Office. Once the online version of the published article for which permission is being requested is can be obtained via RightsLink, a service of the Copyright Clearance Center, not theCirculation Researchin Requests for permissions to reproduce figures, tables, or portions of articles originally publishedPermissions: by guest on March 4,

Journal of Cell Science, 1992

We have examined the effects of three macrophage-derived cytokines, platelet-derived growth facto... more We have examined the effects of three macrophage-derived cytokines, platelet-derived growth factor (PDGF), transforming growth factor-β1 (TGF-β1) and interleukin-la (IL-1 a) on the contraction of collagen type I gels populated by human foreskin fibroblasts. Contraction was quantified as loss in gel weight. Both PDGF-A A and PDGF-BB were found to induce a rapid collagen-gel contraction. TGF-β1 also stimulated gel contraction but with a delayed onset and at a slower rate than the PDGF-stimulated contraction. Rabbit polyclonal IgGs recognizing PDGF-A A and PDGF-BB, respectively, specifically inhibited the effects of the corresponding PDGF isoforms. However, the stimulatory effect of TGF-JÎ1 was not affected by any of the anti-PDGF antibodies. The ability of PDGF to stimulate contraction became less pronounced in collagen gel cultures grown in the absence of growth factors over periods of several days. Under the same conditions, the stimulatory effect of TGF-β1 was not reduced. The redu...

Experimental Physiology, 2018

New Findings What is the central question of this study? Collagen‐binding β1‐integrins function p... more New Findings What is the central question of this study? Collagen‐binding β1‐integrins function physiologically in cellular control of dermal interstitial fluid pressure (PIF) in vivo and thereby participate in control of extravascular fluid volume. During anaphylaxis, simulated by injection of compound 48/80, integrin αVβ3 takes over this physiological function. Here we addressed the question whether integrin αVβ3 can replace collagen‐binding β1‐integrin to maintain a long‐term homeostatic PIF. What is the main finding and its importance? Mice lacking the collagen‐binding integrin α11β1 show a complex dermal phenotype with regard to the interstitial physiology apparent in the control of PIF. Notably dermal PIF is not lowered with compound 48/80 in these animals. Our present data imply that integrin αVβ3 is the likely candidate that has taken over the role of collagen‐binding β1‐integrins for maintaining a steady‐state homeostatic PIF. A better understanding of molecular processes i...

Cell Communication and Signaling, 2018

Background: Chemotherapeutic efficacy can be improved by targeting the structure and function of ... more Background: Chemotherapeutic efficacy can be improved by targeting the structure and function of the extracellular matrix (ECM) in the carcinomal stroma. This can be accomplished by e.g. inhibiting TGF-β1 and-β3 or treating with Imatinib, which results in scarcer collagen fibril structure in xenografted human KAT-4/HT29 (KAT-4) colon adenocarcinoma. Methods: The potential role of α V β 6 integrin-mediated activation of latent TGF-β was studied in cultured KAT-4 and Capan-2 human ductal pancreatic carcinoma cells as well as in xenograft carcinoma generated by these cells. The monoclonal α V β 6 integrin-specific monoclonal antibody 3G9 was used to inhibit the α V β 6 integrin activity. Results: Both KAT-4 and Capan-2 cells expressed the α V β 6 integrin but only KAT-4 cells could utilize this integrin to activate latent TGF-β in vitro. Only when Capan-2 cells were co-cultured with human F99 fibroblasts was the integrin activation mechanism triggered, suggesting a more complex, fibroblast-dependent, activation pathway. In nude mice, a 10-day treatment with 3G9 reduced collagen fibril thickness and interstitial fluid pressure in KAT-4 but not in the more desmoplastic Capan-2 tumors that, to achieve a similar effect, required a prolonged 3G9 treatment. In contrast, a 10-day direct inhibition of TGF-β1 and-β3 reduced collagen fibril thickness in both tumor models. Conclusion: Our data demonstrate that the α V β 6-directed activation of latent TGF-β plays a pivotal role in modulating the stromal collagen network in carcinoma, but that the sensitivity to α V β 6 inhibition depends on the simultaneous presence of alternative paths for latent TGF-β activation and the extent of desmoplasia.

American Journal of Physiology-Heart and Circulatory Physiology, 2001

The increased capillary fluid filtration required to create a rapid edema formation in acute infl... more The increased capillary fluid filtration required to create a rapid edema formation in acute inflammation can be generated by lowering the interstitial fluid pressure (PIF). The lowering of PIFappears to involve dynamic β1-integrin-mediated interactions between dermal cells and extracellular matrix fibers. The present study specifically investigates the role of the cell cytoskeleton, i.e., the contractile apparatus of cells, in controlling PIFin rat skin as the integrins are linked to both the cytoskeleton and the extracellular matrix. PIFwas measured using a micropuncture technique in the dorsal skin of the hind paw at a depth of 0.2–0.5 mm and following the induction of circulatory arrest with the intravenous injection of KCl in pentobarbital anesthesia. This procedure prevented the transcapillary flux of fluid and protein leading to edema formation in acute inflammation, which in turn can increase the PIFand therefore potentially mask a decrease of PIF. Control PIF( n = 42) avera...

Scientific Reports, 2017

Cell-mediated contraction of collagenous matrices is modulated by various growth factors and cyto... more Cell-mediated contraction of collagenous matrices is modulated by various growth factors and cytokines, such as platelet-derived growth factor-BB (PDGF-BB). Here we used a genetic cell model to delineate defined signaling pathways that enhance collagen gel contraction downstream of ligand-stimulated platelet-derived growth factor receptor-β (PDGF-Rβ). Our data show that PDGF BB-enhanced activations of phosphatidylinositol 3′-kinase (PI3K) and phospholipase Cγ (PLCγ) were necessary for PDGF-enhanced collagen gel contraction. Importantly, other defined signaling pathways down-stream of PDGF-Rβ were, however, dispensable. The decisive roles for PI3K and PLCγ were corroborated by experiments using selective inhibitors. Furthermore, we show that de-phosphorylation and thereby activation of cofilin that is important for the turnover of actin filaments, is depended on PI3K and PLCγ down-stream of PDGF-Rβ. Moreover, inhibition of protein kinase C (PKC) by GÖ6976 and bisindolylmaleimide-II a...

PLOS ONE, 2017

Tumor barrier function in carcinoma represents a major challenge to treatment and is therefore an... more Tumor barrier function in carcinoma represents a major challenge to treatment and is therefore an attractive target for increasing drug delivery. Variables related to tumor barrier include aberrant blood vessels, high interstitial fluid pressure, and the composition and structure of the extracellular matrix. One of the proteins associated with dense extracellular matrices is fibromodulin, a collagen fibrillogenesis modulator expressed in tumor stroma but scarce in normal loose connective tissues. Here, we investigated the effects of fibromodulin on stroma ECM in a syngeneic murine colon carcinoma model. We show that fibromodulin deficiency decreased collagen fibril thickness but glycosaminoglycan content and composition were unchanged. Furthermore, vascular density, pericyte coverage and macrophage amount were unaffected. Fibromodulin can therefore be a unique effector of dense collagen matrix assembly in tumor stroma and, without affecting other major matrix components or the cellular composition, can function as a main agent in tumor barrier function.

Journal of translational medicine, Jan 23, 2017

Imatinib causes increased turnover of stromal collagen, reduces collagen fibril diameter, enhance... more Imatinib causes increased turnover of stromal collagen, reduces collagen fibril diameter, enhances extracellular fluid turnover and lowers interstitial fluid pressure (IFP) in the human colonic carcinoma KAT-4/HT-29 (KAT-4) xenograft model. We compared the effects of imatinib on oxygen levels, vascular morphology and IFP in three experimental tumor models differing in their content of a collagenous extracellular matrix. Neither the KAT4 and CT-26 colonic carcinoma models, nor B16BB melanoma expressed PDGF β-receptors in the malignant cells. KAT-4 tumors exhibited a well-developed ECM in contrast to the other two model systems. The collagen content was substantially higher in KAT-4 than in CT-26, while collagen was not detectable in B16BB tumors. The pO2 was on average 5.4, 13.9 and 19.3 mmHg in KAT-4, CT-26 and B16BB tumors, respectively. Treatment with imatinib resulted in similar pO2-levels in all three tumor models but only in KAT-4 tumors did the increase reach statistical signi...

Molecular Cancer Therapeutics, 2016

A typical obstacle to cancer therapy is the limited distribution of low molecular weight anticanc... more A typical obstacle to cancer therapy is the limited distribution of low molecular weight anticancer drugs within the carcinoma tissue. In experimental carcinoma, imatinib (STI571) increases efficacy of synchronized chemotherapy, reduces tumor interstitial fluid pressure, and increases interstitial fluid volume. STI571 also increases the water-perfusable fraction in metastases from human colorectal adenocarcinomas. Because the mechanism(s) behind these effects have not been fully elucidated, we investigated the hypothesis that STI571 alters specific properties of the stromal extracellular matrix. We analyzed STI571-treated human colorectal KAT-4/HT-29 experimental carcinomas, known to have a well-developed stromal compartment, for solute exchange and glycosaminoglycan content, as well as collagen content, structure, and synthesis. MRI of STI571-treated KAT-4/HT-29 experimental carcinomas showed a significantly increased efficacy in dynamic exchanges of solutes between tumor interstit...

Journal of Biological Chemistry, 2016

The hallmark of fibrotic disorders is a highly cross-linked and dense collagen matrix, a property... more The hallmark of fibrotic disorders is a highly cross-linked and dense collagen matrix, a property driven by the oxidative action of lysyl oxidase. Other fibrosis-associated proteins also contribute to the final collagen matrix properties, one of which is fibromodulin. Its interactions with collagen affect collagen crosslinking, packing, and fibril diameter. We investigated the possibility that a specific relationship exists between fibromodulin and lysyl oxidase, potentially imparting a specific collagen matrix phenotype. We mapped the fibromodulin-collagen interaction sites using the collagen II and III Toolkit peptide libraries. Fibromodulin interacted with the peptides containing the known collagen cross-linking sites and the MMP-1 cleavage site in collagens I and II. Interestingly, the interaction sites are closely aligned within the quarter-staggered collagen fibril, suggesting a multivalent interaction between fibromodulin and several collagen helices. Furthermore, we detected an interaction between fibromodulin and lysyl oxidase (a major collagen cross-linking enzyme) and mapped the interaction site to 12 N-terminal amino acids on fibromodulin. This interaction also increases the activity of lysyl oxidase. Together, the data suggest a fibromodulin-modulated collagen cross-linking mechanism where fibromodulin binds to a specific part of the collagen domain and also forms a complex with lysyl oxidase, targeting the enzyme toward specific cross-linking sites.

Proceedings of the National Academy of Sciences, 2007

Research on the biology of the tumor stroma has the potential to lead to development of more effe... more Research on the biology of the tumor stroma has the potential to lead to development of more effective treatment regimes enhancing the efficacy of drug-based treatment of solid malignancies. Tumor stroma is characterized by distorted blood vessels and activated connective tissue cells producing a collagen-rich matrix, which is accompanied by elevated interstitial fluid pressure (IFP), indicating a transport barrier between tumor tissue and blood. Here, we show that the collagen-binding proteoglycan fibromodulin controls stroma structure and fluid balance in experimental carcinoma. Gene ablation or inhibition of expression by anti-inflammatory agents showed that fibromodulin promoted the formation of a dense stroma and an elevated IFP. Fibromodulin-deficiency did not affect vasculature but increased the extracellular fluid volume and lowered IFP. Our data suggest that fibromodulin controls stroma matrix structure that in turn modulates fluid convection inside and out of the stroma. T...

PLoS ONE, 2009

Elevation of the interstitial fluid pressure (IFP) of carcinoma is an obstacle in treatment of tu... more Elevation of the interstitial fluid pressure (IFP) of carcinoma is an obstacle in treatment of tumors by chemotherapy and correlates with poor drug uptake. Previous studies have shown that treatment with inhibitors of platelet-derived growth factor (PDGF) or vascular endothelial growth factor (VEGF) signaling lowers the IFP of tumors and improve chemotherapy. In this study, we investigated whether the combination of PDGFR and VEGFR inhibitors could further reduce the IFP of KAT-4 human carcinoma tumors. The tumor IFP was measured using the wick-in-needle technique. The combination of STI571 and PTK/ZK gave an additive effect on the lowering of the IFP of KAT-4 tumors, but the timing of the treatment was crucial. The lowering of IFP following combination therapy was accompanied by vascular remodeling and decreased vascular leakiness. The effects of the inhibitors on the therapeutic efficiency of Taxol were investigated. Whereas the anti-PDGF and anti-VEGF treatment did not significantly inhibit tumor growth, the inhibitors enhanced the effect of chemotherapy. Despite having an additive effect in decreasing tumor IFP, the combination therapy did not further enhance the effect of chemotherapy. Simultaneous targeting of VEGFR and PDGFR kinase activity may be a useful strategy to decrease tumor IFP, but the timing of the inhibitors should be carefully determined.

Laboratory Investigation, 2005

A pathologically elevated interstitial fluid pressure (IFP) is a characteristic of both clinical ... more A pathologically elevated interstitial fluid pressure (IFP) is a characteristic of both clinical and experimental carcinoma. The soluble TGF-b receptor type II-murine Fc:IgG 2A chimeric protein (Fc:TbRII) lowers IFP in the KAT-4 experimental model for anaplastic thyroid carcinoma. Analyses of messenger RNA (mRNA) expressions by Affymetrix microarrays and RNase protection assays, as well as of protein expressions identified tumor macrophages as targets for Fc:TbRII. Treatment with Fc:TbRII reduced albumin extravasation, increased coverage of a-smooth muscle actin-positive cells and reduced expression of NG2, a marker of activated pericytes, in KAT-4 carcinoma blood vessels. Specific inhibition of interleukin-1 (IL-1), a major cytokine produced by activated macrophages, lowered carcinoma IFP to a similar degree as Fc:TbRII but had no significant effect on the parameters of blood vessel maturation. Neither Fc:TbRII nor inhibition of IL-1 changed blood vessel density. Finally, pretreatment of KAT-4 carcinomas with Fc:TbRII increased the antitumor efficacy of doxorubicin. Our data emphasize a potential role of tumor macrophages in carcinoma physiology and identify these cells as potential stromal targets for treatment aimed to improve efficacy of chemotherapy.

Journal of Clinical Investigation, 1993

The expression and localization of PDGF f8 receptors and PDGF-AB/BB in human healing wounds was e... more The expression and localization of PDGF f8 receptors and PDGF-AB/BB in human healing wounds was evaluated by immunohistochemical techniques and in situ hybridization. Expression of PDGF ft receptor protein and PDGF-AB/BB were analyzed in wound margin biopsies using the PDGFR-B2 and PDGF 007 antibodies. PDGF ft receptor expression was minor in normal skin. An increased expression of PDGF f receptor protein was prominent in vessels in the proliferating tissue zone in wounds as early as 1 d after surgery and was apparent c 4 wk after surgery. There was also a concordant increase in PDGF , receptor mRNA detected by in situ hybridization. PDGF-AB/ BB was present in healing wounds as well as in normal skin. In normal skin, expression of PDGF-AB /BB was confined to peripheral nerve fibers and to solitary cells of the epidermis and of the superficial dermis. In wounds, infiltrating mononuclear cells also stained for PDGF-AB/BB. To identify cell types expressing PDGF AB/BB and PDGF f receptors, respectively, we performed double immunofluorescence stainings. PDGF ft receptors were expressed by vascular smooth muscle cells and cells in capillary walls; the receptor protein could not be detected in neurofilament containing structures, T lymphocytes, or CD68 expressing macrophages. PDGF-AB/BB colcalized with neurofilaments, it was present in Langerhans cells of the epidermis and in HLA-DR positive cells located in the epidermal/dermal junction area. Of the macrophages infiltrating the wound, 43±18% stained positively for PDGF AB/BB. Since PDGF-AB/BB and PDGF 13 receptors are expressed in the healing wound, two essential prerequisites for a role of PDGF in wound healing are fulfilled.

Journal of Cellular and Molecular Medicine, 2008

Stroma formation in solid tumours, chronic inflammatory lesions and tissue repair share several f... more Stroma formation in solid tumours, chronic inflammatory lesions and tissue repair share several features including infiltration of inflammatory cells, activation of blood vessels and angiogenesis. Of further and central pathophysiological importance, persistent activation of connective tissue cells leads to excessive extracellular matrix (ECM) deposition, dominated by collagen type I, which, in turn, leads to fibrosis and ultimately organ dysfunction [1-5]. The amount of fibrosis is not necessarily linked to the severity of inflammation, indicating mechanisms, in part, distinct from those that regulate inflammation [6]. Thus, tissue damage due to severe inflammation can, in some instances, be reversible with the reinstatement of organ architecture and function [7]. The underlying processes that result, on the one hand, in reinstatement of organ function and, on the other hand, in a chronic state resulting in fibrosis and organ dysfunction despite similar initial pathophysiology are largely unknown. Myofibroblasts, as defined by their expression of ␣-smooth muscle actin (␣-SMA), play a central role in the deposition and organization of ECM and thus also in the formation of fibrotic tissue [5, 8, 9]. They are related to fibroblasts and exhibit a hybrid phenotype between fibroblasts and smooth muscle cells/pericytes [5]. It has been suggested that the latter two cell types are derived from a common cell lineage [5, 10-14]. The origin of the myofibroblast is yet unclear. Resident tissue fibroblasts [5, 14], vascular cells such as smooth muscle cells and/or pericytes [10-13] and bone marrow-derived precursor cells [14] have been suggested as potential sources. The transition to the myofibroblast phenotype in culture depends on the concerted action of cytokines such as transforming growth factor (TGF)-␤ and specific ECM proteins such as the Integrin ␣ 1 ␤ 1 is involved in the differentiation into myofibroblasts in adult reactive tissues in vivo

Journal of Biological Chemistry, 2010

Collagen fibers expose distinct domains allowing for specific interactions with other extracellul... more Collagen fibers expose distinct domains allowing for specific interactions with other extracellular matrix proteins and cells. To investigate putative collagen domains that govern integrin ␣ V ␤ 3-mediated cellular interactions with native collagen fibers we took advantage of the streptococcal protein CNE that bound native fibrillar collagens. CNE specifically inhibited ␣ V ␤ 3-dependent cell-mediated collagen gel contraction, PDGF BB-induced and ␣ V ␤ 3-mediated adhesion of cells, and binding of fibronectin to native collagen. Using a Toolkit composed of overlapping, 27-residue triple helical segments of collagen type II, two CNE-binding sites present in peptides II-1 and II-44 were identified. These peptides lack the major binding site for collagen-binding ␤ 1 integrins, defined by the peptide GFOGER. Peptide II-44 corresponds to a region of collagen known to bind collagenases, discoidin domain receptor 2, SPARC (osteonectin), and fibronectin. In addition to binding fibronectin, peptide II-44 but not II-1 inhibited ␣ V ␤ 3-mediated collagen gel contraction and, when immobilized on plastic, supported adhesion of cells. Reduction of fibronectin expression by siRNA reduced PDGF BB-induced ␣ V ␤ 3-mediated contraction. Reconstitution of collagen types I and II gels in the presence of CNE reduced collagen fibril diameters and fibril melting temperatures. Our data indicate that contraction proceeded through an indirect mechanism involving binding of cell-produced fibronectin to the collagen fibers. Furthermore, our data show that cell-mediated collagen gel contraction does not directly depend on the process of fibril formation.

Cardiovascular Research, 2010

This review will summarize current knowledge on the role of the extracellular matrix (ECM) in gen... more This review will summarize current knowledge on the role of the extracellular matrix (ECM) in general and on the interstitial fluid pressure (P if) in particular with regard to their importance in transcapillary exchange. The fluid volume in the interstitial space is normally regulated within narrow limits by automatic readjustment of the interstitial hydrostatic and colloid osmotic pressures in response to perturbations in capillary filtration and by the lymphatics. Contrary to this commonly accepted view, P if can become an active force and create a fluid flux across the capillaries in several inflammatory reactions and trauma situations rather than limit the changes occurring. The molecular mechanisms involved in the lowering of P if include the release of cellular tension exerted on the collagen and microfibril networks in the connective tissue via the collagen-binding b 1-integrins, thereby allowing the glycosaminoglycan ground substance, which is normally underhydrated, to expand and take up fluid. Several growth factors and cytokines, including the platelet-derived growth factor BB, are able to reverse a lowering of P if and restore the normal compaction of the ECM. The magnitude of the lowering of P if varies with the inflammatory response. In several inflammatory reactions, a lowering of P if to 25 to 210 mmHg is seen, which will increase capillary filtration by 10-20 times since the normal capillary filtration pressure is usually 0.5-1 mmHg (skin and skeletal muscle). Unless this lowering of P if is taken into account, the enhanced solute flux resulting from an inflammatory response will be ascribed to an increased capillary permeability.