Toshiaki Mishima

COX-2 and prostaglandin EP3/EP4 signaling regulate the tumor stromal proangiogenic microenvironment via CXCL12-CXCR4 chemokine systems

Bone marrow (BM)-derived hematopoietic cells, which are major components of tumor stroma, determine the tumor microenvironment and regulate tumor phenotypes. Cyclooxygenase (COX)-2 and endogenous prostaglandins are important determinants for tumor growth and tumor-associated angiogenesis; however, their contributions to stromal formation and angiogenesis remain unclear. In this study, we observed that Lewis lung carcinoma cells implanted in wild-type mice formed a tumor mass with extensive stromal formation that was markedly suppressed by COX-2 inhibition, which reduced the recruitment of BM cells. Notably, COX-2 inhibition attenuated CXCL12/CXCR4 expression as well as expression of several other chemokines. Indeed, in a Matrigel model, prostaglandin (PG) E2 enhanced stromal formation and CXCL12/CXCR4 expression. In addition, a COX-2 inhibitor suppressed stromal formation and reduced expression of CXCL12/CXCR4 and a fibroblast marker (S100A4) in a micropore chamber model. Moreover, stromal formation after tumor implantation was suppressed in EP3-/- mice and EP4-/- mice, in which stromal expression of CXCL12/CXCR4 and S100A4 was reduced. The EP3 or EP4 knockout suppressed S100A4+ fibroblasts, CXCL12+, and/or CXCR4+ stromal cells as well. Immunofluorescent analyses revealed that CXCL12+CXCR4+S100A4+ fibroblasts mainly comprised stromal cells and most of these were recruited from the BM. Additionally, either EP3- or EP4-specific agonists stimulated CXCL12 expression by fibroblasts in vitro. The present results address the novel activities of COX-2/PGE2-EP3/EP4 signaling that modulate tumor biology and show that CXCL12/CXCR4 axis may play a crucial role in tumor stromal formation and angiogenesis under the control of prostaglandins.

Calcitonin gene-related peptide facilitates revascularization during hindlimb ischemia in mice

It is known that the neural system plays a fundamental role in neovascularization. A neuropeptide, calcitonin gene-related peptide (CGRP), is widely distributed in the central and peripheral neuronal systems. However, it remains to be elucidated the role of CGRP in angiogenesis during ischemia. The present study examined whether endogenous CGRP released from neuronal systems facilitates revascularization in response to ischemia using CGRP knockout mice (CGRP-/-). CGRP-/- or their wild-type littermates (CGRP+/+) were subjected to unilateral hindlimb ischemia. CGRP-/- exhibited impaired blood flow recovery from ischemia and decreased capillary density expressed in terms of the number of CD-31-positive cells in the ischemic tissues compared with CGRP+/+. In vivo microscopic studies showed that the functional capillary density in CGRP-/- was reduced. Hindlimb ischemia increased the expression of pro-CGRP mRNA and of CGRP protein in the lumbar dorsal root ganglia. Lack of CGRP decreased mRNA expression of growth factors, including CD31, vascular endothelial growth factor-A, basic fibroblast growth factor, and transforming growth factor-β, in the ischemic limb tissue. The application of CGRP enhanced the mRNA expression of CD31 and VEGF-A in human umbilical vein endothelial cells (HUVECs) and fibroblasts. Subcutaneous infusion of CGRP8-37, a CGRP antagonist, using miniosmotic pumps delayed angiogenesis and reduced the expression of proangiogenic growth factors during hindlimb ischemia. These results indicate that endogenous CGRP facilitates angiogenesis in response to ischemia. Targeting CGRP may provide a promising approach for controlling angiogenesis related to pathophysiological conditions.

Leukotriene B4 type-1 receptor signaling promotes liver repair after hepatic ischemia/reperfusion injury through the enhancement of macrophage recruitment

Recruited macrophages play a critical role in liver repair after acute liver injury. Leukotriene B4 (LTB4) is a potent chemoattractant for macrophages. In this study, we investigated the role of LTB4 receptor type 1 (BLT1) in liver repair during hepatic ischemia/reperfusion (I/R) injury. BLT1‐knockout mice (BLT1‐/‐) or their wild‐type counterparts (WT) were subjected to partial hepatic I/R. Compared with WT, BLT1‐/‐ exhibited delayed liver repair and hepatocyte proliferation accompanied by a 70% reduction in the recruitment of macrophages and a 70–80% attenuation in hepatic expression of epidermal growth factor (EGF), vascular endothelial growth factor (VEGF), and VEGF receptor 1 (VEGFR1). Disruption of BLT1 signaling also reduced the expression of EGF by 67% on recruited macrophages expressing VEGFR1 in the injured liver. Treatment of WT mice with an EGF‐neutralizing antibody delayed liver repair and reduced macrophage recruitment, compared with control immunoglobulin G (IgG). BLT1 signaling enhanced the expression of VEGF, VEGFR1, and EGF in isolated peritoneal macrophages in vitro. These results indicate that BLT1 signaling plays a role in liver repair after hepatic I/R through enhanced expression of EGF in recruited macrophages and that the development of a specific agonist for BLT1 could be useful for liver recovery from acute liver injury.—Ohkubo, H., Ito, Y., Minamino, T., Mishima, T., Hirata, M., Hosono, K., Shibuya, M., Yokomizo, T., Shimizu, T., Watanabe, M., Majima, M., Leukotriene B4 type‐1 receptor signaling promotes liver repair after hepatic ischemia/reperfusion injury through the enhancement of macrophage recruitment. FASEB J. 27, 3132–3143 (2013). www.fasebj.org

Cerebral oximetry for cardiac surgery: a preoperative comparison of device characteristics and pitfalls in interpretation

Regional cerebral oximetry using near-infrared spectroscopy devices is commonly used for detecting cerebral ischemia during cardiopulmonary bypass, and aim to avoid poor cerebral perfusion which may result in perioperative neurological impairment. Today, several devices that can detect cerebral ischemia are commercially available. Although these devices operate on the same measurement principles, their algorithms for detecting and calculating cerebral ischemia are different and no criteria for directly comparing values measured by such different devices exist. From January 2017 to August 2017, 80 adult cardiovascular surgery patients were enrolled in the prospective study. In each patient, preoperative regional cerebral oxygen saturation values were measured by two different devices and their correlations with various preoperative factors were evaluated. Regional cerebral oxygen saturation levels were significantly higher for values of FORE-SIGHT ELITE (CAS Medical Systems, Branford, CT, USA) (F value) than those of the INVOS 5100C (Medtronic, Minneapolis, MN, USA) (I value). Scalp–cortex distance, hemoglobin concentration, and the presence or absence of hemodialysis showed significant correlations with ratios of measured values specific to each device (F/I). An appropriate device should be selected according to preoperative patient characteristics, and factors influencing regional cerebral oxygen saturation values should be considered to ensure the correct interpretation of measured values. This research was conducted with the approval of the ethics committee of our university (approval number: B16–96).

Daily transient discontinuation of extracorporeal LVAD to prevent thromboembolism of mechanical aortic valve prosthesis

Patients with mechanical aortic valves are generally contraindicated for left ventricular assist device (LVAD) insertion because the prosthetic valve often becomes fixed in closed position. A 41-year-old woman with mechanical aortic valve prosthesis experienced sudden chest pain and developed cardiogenic shock. A paracorporeal pulsatile LVAD and a monopivot centrifugal pump as a right VAD (RVAD) were implanted. The mechanical aortic valve was intentionally left in place. Soon after the operation, LVAD support was discontinued daily for few seconds to allow the mechanical aortic valve to open and to avoid thrombus formation. The patient was successfully weaned off RVAD and received anticoagulation therapy with warfarin. On postoperative day 141, she was transferred to a university hospital where a HeartMate II LVAD was implanted, and the aortic valve was successfully replaced with a bioprosthetic valve. The patient is currently awaiting heart transplantation.