Bartomeu Colom

Leukotriene B4-Neutrophil Elastase Axis Drives Neutrophil Reverse Transendothelial Cell Migration In Vivo.

Summary Breaching endothelial cells (ECs) is a decisive step in the migration of leukocytes from the vascular lumen to the extravascular tissue, but fundamental aspects of this response remain largely unknown. We have previously shown that neutrophils can exhibit abluminal-to-luminal migration through EC junctions within mouse cremasteric venules and that this response is elicited following reduced expression and/or functionality of the EC junctional adhesion molecule-C (JAM-C). Here we demonstrate that the lipid chemoattractant leukotriene B4 (LTB4) was efficacious at causing loss of venular JAM-C and promoting neutrophil reverse transendothelial cell migration (rTEM) in vivo. Local proteolytic cleavage of EC JAM-C by neutrophil elastase (NE) drove this cascade of events as supported by presentation of NE to JAM-C via the neutrophil adhesion molecule Mac-1. The results identify local LTB4-NE axis as a promoter of neutrophil rTEM and provide evidence that this pathway can propagate a local sterile inflammatory response to become systemic.

Skeletal Muscle of Female Rats Exhibit Higher Mitochondrial Mass and Oxidative- Phosphorylative Capacities Compared to Males

The effect of gender and caloric restriction on mitochondrial content and oxidative-phosphorylative capacities has been investigated in rat gastrocnemius muscle. Muscle protein, mitochondrial protein and DNA contents, enzymatic activities of mitochondrial oxidative and phosphorylative system, mitochondrial antioxidant enzymes, protein levels of complex IV (subunit I and IV) and ATPase, and the gene and protein expression of mitochondrial transcription factor A (TFAM), involved in mitochondrial replication and transcription, were measured in rats of both genders fed ad libitum and subjected to three months of 40% caloric restriction. Compared to males, gastrocnemius muscle of female rats showed higher mitochondrial DNA and protein contents, TFAM protein level, oxidative and phosphorylative machinery and activities, and glutathione peroxidase activity. In conclusion, the present data show a clear gender dimorphism in rat muscle mitochondrial features, which could explain the higher facility of females to adapt to altered metabolic energy situations.

Junctional Adhesion Molecule-C Mediates Leukocyte Infiltration in Response to Ischemia Reperfusion Injury

Objective—Junctional adhesion molecule–C (JAM-C) is an adhesion molecule that has multiple roles in inflammation and vascular biology, but many aspects of its functions under pathological conditions are unknown. Here we investigated the role of JAM-C in leukocyte migration in response to ischemia reperfusion (I/R) injury. Methods and Results—Pretreatment of mice with soluble JAM-C (sJAM-C), used as a pharmacological blocker of JAM-C–mediated reactions, significantly suppressed leukocyte migration in models of kidney and cremaster muscle I/R injury (39 and 51% inhibition, respectively). Furthermore, in the cremaster muscle model (studied by intravital microscopy), both leukocyte adhesion and transmigration were suppressed in JAM-C–deficient mice (JAM-C−/−) and enhanced in mice overexpressing JAM-C in their endothelial cells (ECs). Analysis of JAM-C subcellular expression by immunoelectron microscopy indicated that in I/R-injured tissues, EC JAM-C was redistributed from cytoplasmic vesicles and EC junctional sites to nonjunctional plasma membranes, a response that may account for the role of JAM-C in both leukocyte adhesion and transmigration under conditions of I/R injury. Conclusions—The findings demonstrate a role for EC JAM-C in mediating leukocyte adhesion and transmigration in response to I/R injury and indicate the existence of a novel regulatory mechanism for redistribution and hence function of EC JAM-C in vivo.

Mitochondrial Transcription Factor A (TFAM) is Increased in Rat Embryo During Placentation and Associated with Mitochondrial Differentiation

In the current study, the mitochondrial proliferationdifferentiation process was investigated in rat embryo during the placentation process, straight after organogenesis, when there is an important oxidative metabolism activation. For this purpose, on gestational days 11, 12 and 13 we studied the mitochondrial DNA (mtDNA) content and the relative gene expression of proteins involved in mtDNA replication (mitochondrial single strand DNA binding protein (mtSSB)), mtDNA transcription (mitochondrial transcription factor A (TFAM)), as well as in mitochondrial function (cytochrome c oxidase subunit I (COXI)). The results indicated that during placentation important changes in mitochondrial proliferation-differentiation process take place in rat embryo. There is a great decrease in cellular mtDNA content and a rise in the ratio between TFAM and mtDNA accompanied by an increase in COXI gene expression. Thus, we can conclude that on gestational day 13 mitochondrial differentiation predominates over mitochondrial proliferation in embryo cells. Besides, our work reveals that in a physiological condition such as embryonic development the TFAM levels change in order to regulate the transcriptional activity of mtDNA.

Endothelial Cell Junctional Adhesion Molecules: Role and Regulation of Expression in Inflammation.

Endothelial cells line the lumen of all blood vessels and play a critical role in maintaining the barrier function of the vasculature. Sealing of the vessel wall between adjacent endothelial cells is facilitated by interactions involving junctionally expressed transmembrane proteins, including tight junctional molecules, such as members of the junctional adhesion molecule family, components of adherence junctions, such as VE-Cadherin, and other molecules, such as platelet endothelial cell adhesion molecule. Of importance, a growing body of evidence indicates that the expression of these molecules is regulated in a spatiotemporal manner during inflammation: responses that have significant implications for the barrier function of blood vessels against blood-borne macromolecules and transmigrating leukocytes. This review summarizes key aspects of our current understanding of the dynamics and mechanisms that regulate the expression of endothelial cells junctional molecules during inflammation and discusses the associated functional implications of such events in acute and chronic scenarios.

Schwann cell-specific JAM-C-deficient mice reveal novel expression and functions for JAM-C in peripheral nerves

Junctional adhesion molecule‐C (JAM‐C) is an adhesion molecule expressed at junctions between adjacent endothelial and epithelial cells and implicated in multiple inflammatory and vascular responses. In addition, we recently reported on the expression of JAM‐C in Schwann cells (SCs) and its importance for the integrity and function of peripheral nerves. To investigate the role of JAM‐C in neuronal functions further, mice with a specific deletion of JAM‐C in SCs (JAM‐C SC KO) were generated. Compared to wild‐type (WT) controls, JAM‐C SC KO mice showed electrophysiological defects, muscular weakness, and hypersensitivity to mechanical stimuli. In addressing the underlying cause of these defects, nerves from JAM‐C SC KO mice were found to have morphological defects in the paranodal region, exhibiting increased nodal length as compared to WTs. The study also reports on previously undetected expressions of JAM‐C, namely on perineural cells, and in line with nociception defects of the JAM‐C SC KO animals, on finely myelinated sensory nerve fibers. Collectively, the generation and characterization of JAM‐C SC KO mice has provided unequivocal evidence for the involvement of SC JAM‐C in the fine organization of peripheral nerves and in modulating multiple neuronal responses.—Colom, B., Poitelon, Y., Huang, W., Woodfin, A., Averill, S., Del Carro, U., Zambroni, D., Brain, S. D., Perretti, M., Ahluwalia, A., Priestley, J. V., Chavakis, T., Imhof, B. A., Feltri, M. L., Nourshargh, S. Schwann cell‐specific JAM‐C‐deficient mice reveal novel expression and functions for JAM‐C in peripheral nerves. FASEB J. 26, 1064–1076 (2012). www.fasebj.org

Sexual Dimorphism in the Alterations of Cardiac Muscle Mitochondrial Bioenergetics Associated to the Ageing Process

The incidence of cardiac disease is age and sex dependent, but the mechanisms governing these associations remain poorly understood. Mitochondria are the organelles in charge of producing energy for the cells, and their malfunction has been linked to cardiovascular disease and heart failure. Interestingly, heart mitochondrial content and functionality are also age and sex dependent. Here we investigated the combinatory effects of age and sex in mitochondrial bioenergetics that could help to understand their role on cardiac disease. Cardiac mitochondria from 6- and 24-month-old male and female Wistar rats were isolated, and the enzymatic activities of the oxidative-phosphorylative complexes I, III, and IV and ATPase, as well as the protein levels of complex IV, β-ATPase, and mitochondrial transcription factor A (TFAM), were measured. Furthermore, heart DNA content, citrate synthase activity, mitochondrial protein content, oxygen consumption, and H2O2 generation were also determined. Results showed a reduction in heart mitochondrial mass and functionality with age that correlated with increased H2O2 generation. Moreover, sex-dependent differences were found in several of these parameters. In particular, old females exhibited a significant loss of mitochondrial function and increased relative H2O2 production compared with their male counterparts. The results demonstrate a sex dimorphism in the age-associated defects on cardiac mitochondrial function.

Endothelial cell junctional adhesion molecule C plays a key role in the development of tumors in a murine model of ovarian cancer

Junctional adhesion molecule C (JAM‐C) is a transmembrane protein with significant roles in regulation of endothelial cell (EC) functions, including immune cell recruitment and angiogenesis. As these responses are important in promoting tumor growth, the role of EC JAM‐C in tumor development was investigated using the ID8 syngeneic model of ovarian cancer. Within 10–15 wk, intraperitoneally injected ID8 cells form multiple tumor deposits and ascites that resemble human high‐grade serous ovarian cancer. Compared to wild‐type mice, survival in this model was increased in EC JAM‐C knockouts (KOs; 88 vs. 96 d, P=0.04) and reduced in EC JAM‐C transgenics (88 vs. 78.5 d, P=0.03), mice deficient in or overexpressing EC JAM‐C, respectively. While tumor growth was significantly reduced in EC JAM‐C KOs (87% inhibition at 10 wk, P<0.0005), this was not associated with alterations in tumor vessel density or immune cell infiltration. However, tumor microvessels from EC JAM‐C‐deficient mice exhibited reduced pericyte coverage and increased vascular leakage, suggesting a role for EC JAM‐C in the development of functional tumor vessels. These findings provide evidence for a role for EC JAM‐C in tumor growth and aggressiveness as well as recruitment of pericytes to newly formed blood vessels in a model of ovarian cancer.—Leinster, D. A., Colom, B., Whiteford, J. R., Ennis, D. P., Lockley, M., McNeish, I. A., Aurrand‐Lions, M., Chavakis, T., Imhof, B. A., Balkwill, F. R., Nourshargh, S., Endothelial cell junctional adhesion molecule C plays a key role in the development of tumors in a murine model of ovarian cancer. FASEB J. 27, 4244–4253 (2013). www.fasebj.org

The spatiotemporal localization of JAM-C following sciatic nerve crush in adult rats

JAM‐C is a junctional adhesion molecule, enriched at tight junctions on endothelial and epithelial cells, and also localized to Schwann cells at junctions between adjoining myelin end loops. The role of JAM‐C following peripheral nerve injury (PNI) is currently unknown. We examined the localization of JAM‐C after sciatic nerve crush injury in adult rats. JAM‐C immunoreactivity was present in paranodes and incisures in sham surgery control nerve, but distal to the crush injury significantly decreased at three and 14 days. JAM‐C was re‐expressed at 28 days and, by 56 days, was significantly increased in the distal nerve compared to controls. In a 7‐mm length of sciatic nerve sampled distal to the crush site, the densities of JAM‐C immunoreactive paranodes increased in the distal direction. Conversely, the densities of JAM‐C immunoreactive incisures were highest immediately distal to the crush site and decreased in the more distal direction. Further analysis revealed a strong correlation between JAM‐C localization and remyelination. Fifty‐six days after crush injury, greater densities of JAM‐C paranodes were seen compared to the nodal marker jacalin, suggesting that paranodal JAM‐C precedes node formation. Our data are the first to demonstrate a potential role of JAM‐C in remyelination after PNI.