Roles of Thromboxane Receptor Signaling in Enhancement of Lipopolysaccharide-Induced Lymphangiogenesis and Lymphatic Drainage Function in Diaphragm.

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RAMP1 signaling in immune cells regulates inflammation-associated lymphangiogenesis.

Calcitonin gene-related peptide (CGRP) regulates inflammation via signaling through receptor activity-modifying protein (RAMP) 1. Here, we investigated the role of RAMP1 signaling in growth of lymphatic vessels during inflammation. Lymphangiogenesis in the diaphragm of RAMP1-deficient (-/-) mice or their wild-type (WT) counterparts was induced by repeated intraperitoneal injection of lipopolysaccharide (LPS). Compared with WT mice, LPS-induced lymphangiogenesis in RAMP1-/- mice was suppressed. This was accompanied by the reduced expression of vascular endothelial growth factor (VEGF)-C and VEGF-D. The number of CD4+ cells in diaphragm tissue from WT mice was greater than RAMP1-/- mice. Removing CD4+ cells attenuated lymphangiogenesis and expression of VEGF-C and VEGF-D. CD4+ cells isolated from RAMP1-/- mice exhibited reduced expression of VEGF-C and VEGF-D. The number of CD11b+ cells from RAMP1-/- mice was higher than WT mice and was associated with the upregulated expression of genes related to pro-inflammatory macrophage phenotype and downregulation of reparative macrophage phenotype-related expression. When fluorescein isothiocyanate (FITC)-dextran was injected into the peritoneal cavity, the amount of residual FITC-dextran in WT mice was lower than that in RAMP1-/- mice. The present results suggest that RAMP1 signaling in immune cells plays a critical role in inflammation-related lymphangiogenesis; therefore, it represents a novel target for controlling lymphangiogenesis.

Roles of mPGES-1, an inducible prostaglandin E synthase, in enhancement of LPS-induced lymphangiogenesis in a mouse peritonitis model.

AIMS: Lymphangiogenesis is frequently observed during inflammation, and this inflammation-induced lymphangiogenesis (IL) is a phenomenon actively involved in the pathophysiology of inflammation. We explored the roles of an inducible prostaglandin E synthase, mPGES-1, in IL elicited by lipopolysaccharide (LPS). MAIN METHODS: Peritonitis was induced in mice by intraperitoneal injection of LPS (E. coli 0111-B4; 25µg/mouse every 2days), and IL was evaluated by LYVE-1 immunostaining of whole-mount diaphragm tissues. KEY FINDINGS: Compared to vehicle-treated wild-type (WT) mice, lymphatics in the diaphragms of mice injected with LPS were widened and the number of LYVE-1-positive ladder-structured lymphatics increased temporally. This increase in lymphangiogenesis was accompanied by increased expression of vascular endothelial growth factor (VEGF)-C/D in the diaphragms. In mice treated with celecoxib, a cyclooxygenase-2 inhibitor, IL was suppressed with reduced expression of VEGF-C/D. This was also observed in mPGES-1 knockout mice (KO). Immunoreactive COX-2 and mPGES-1 were detected in both CD11b-positive and CD3ε-positivecells in the diaphragm. When FITC-dextran was injected into the peritoneal cavities, the amount of residual FITC-dextran was reduced significantly in WT mice injected with LPS, and this reduction was significantly decreased in mPGES-1 KO mice. SIGNIFICANCE: The present results suggest that mPGES-1 plays a significant role in lymphangiogenesis during inflammation, and represents a novel target for controlling IL.

Roles of receptor activity-modifying protein 1 in angiogenesis and lymphangiogenesis during skin wound healing in mice.

Receptor activity-modifying protein 1 (RAMP1) forms a complex with calcitonin receptor-like receptor (CLR) to produce the receptor for calcitonin gene-related peptide (CGRP). CGRP, a 37-aa neuropeptide, is widely distributed in neuronal tissues and exerts its biological effects via CLR/RAMP1; however, the pathophysiological roles of CLR/RAMP1 remain to be clarified. To study the functions of CLR/RAMP1, we generated RAMP1-knockout (RAMP1(-/-)) mice. Compared with those of wild-type (WT) mice, wound healing and wound-induced angiogenesis were significantly suppressed in RAMP1(-/-) mice, with reduced expression of vascular endothelial growth factor (VEGF)-A. Formation of the lymphatic vessels that drain interstitial fluids was also suppressed in RAMP1(-/-) mice, with reduced expression of VEGF-C and VEGFR-3 in wound granulation tissues. RAMP1 was expressed in endothelial cells (ECs) in the preexisting skin blood vessels, but was not observed in ECs in newly formed blood or lymphatic vessels. Macrophages in the wound granulation tissues expressed RAMP1 and produced substantial amounts of VEGF-C in response to CGRP in vitro. RAMP1(-/-) bone marrow chimeric mice showed delayed wound healing with reduced angiogenesis/lymphangiogenesis in wound granulation tissues. These findings suggest that RAMP1 plays a crucial role in wound healing and wound-induced angiogenesis and lymphangiogenesis and that it is a promising target for controlling angiogenesis and lymphangiogenesis.

Epinephrine administered with lidocaine solution does not worsen intrathecal lidocaine neurotoxicity in rats.

BACKGROUND: Epinephrine can potentially worsen the neurotoxic effects of local anesthetics when used for spinal or epidural anesthesia. The vasoconstrictive property of epinephrine reduces dural blood flow, which in turn reduces the clearance of local anesthetics from the subarachnoid space. This study examined the histological and neurofunctional effects of intrathecally administered lidocaine combined with epinephrine in rats. METHODS: Sixty-two rats were divided into 9 treatment groups: 5% or 7.5% lidocaine in 10% glucose solution with or without 0.1 or 0.5 mg/mL epinephrine, or epinephrine alone at 0.1 or 0.5 mg/mL in 10% glucose, or 10% glucose alone. Hind-limb motor function was evaluated immediately after drug injection by walking behavior. Sensory function was assessed by the response to radiant heat stimulation at just before and 1 week after the injection. Seven days after the injection, L3 spinal cord with anterior and posterior roots, the dorsal ganglion, and cauda equina were harvested and examined histologically. RESULTS: Histological lesions were limited to the posterior root just at entry into the spinal cord in rats injected with 7.5% lidocaine, with and without epinephrine. No histological abnormalities were noted in other areas or other groups. There was no significant change in sensory threshold in all groups. Significantly, prolongation of gait recovery time was noted in 5% and 7.5% lidocaine with epinephrine groups compared with 5% or 7.5% lidocaine alone. CONCLUSIONS: Intrathecal epinephrine prolonged the action of intrathecal lidocaine but did not worsen lidocaine-induced histological damage and functional impairment.