Analysis of ET-A and ET-B receptors using an isolated perfused rat lung preparation

AIMS AND METHODS: The pulmonary and vascular effects of endothelin-1 receptor activation were studied in isolated perfused and ventilated lung preparations from rat. The responses to endothelin-1 (ET-1) and the endothelin B (ET(B)) receptor agonist sarafotoxin 6c (S6c) were characterized using the endothelin A (ET(A))-receptor antagonist FR 139317, the ET(B)-receptor antagonist BQ 788 and the combined ET(A)/ET(B)-receptor antagonist Bosentan. The respiratory parameter airway conductance (G(aw)) and the vascular parameter perfusion flow were analysed simultaneously. RESULTS: Concentration-response curves for ET-1 administered intra-arterially revealed that its most potent effect was on the vascular side while S6c had a more potent effect on airway conductance. ET-1, given as a bolus dose intra-arterially (100 microL of 0.2 nM), induced a strong- and long-lasting contraction of the vasculature while only a less pronounced contraction was seen in the airways. Neither of the antagonists had a significant effect per se on G(aw) or perfusion flow. FR 139317 reduced the effect of ET-1 on perfusion flow by about 50%, while airway conductance was augmented. BQ 788 enhanced the decrease in perfusion flow by ET-1 while G(aw) was not influenced. The combined ET(A)/ET(B) antagonist Bosentan powerfully prevented the ET-1-induced decrease in G(aw) but did not alter its reduction in perfusion flow. CONCLUSIONS: The potent effect of ET-1 on the vascular side of the lung is mediated mainly through ET(A) receptors, whereas both ET(A) and ET(B) receptors are involved in G(aw) in the rat lung.     

Endothelin‐1‐induced proliferation of human endothelial cells depends on activation of K+ channels and Ca2+ influx

Aims: Endothelin‐1 (ET‐1) promotes endothelial cell growth. Endothelial cell proliferation involves the activation of Ca²⁺‐activated K⁺ channels. In this study, we investigated whether Ca²⁺‐activated K⁺ channels with big conductance (BK_Ca) contribute to endothelial cell proliferation induced by ET‐1. Methods: The patch‐clamp technique was used to analyse BK_Ca activity in endothelial cells derived from human umbilical cord veins (HUVEC). Endothelial proliferation was examined using cell counts and measuring [³H]‐thymidine incorporation. Changes of intracellular Ca²⁺ levels were examined using fura‐2 fluorescence imaging. Results: Characteristic BK_Ca were identified in cultured HUVEC. Continuous perfusion of HUVEC with 10 nmol L^?1 ET‐1 caused a significant increase of BK_Ca open‐state probability (n = 14; P < 0.05; cell‐attached patches). The ET_B‐receptor antagonist (BQ‐788, 1 μmol L^?1) blocked this effect. Stimulation with Et‐1 (10 nmol L^?1) significantly increased cell growth by 69% (n = 12; P < 0.05). In contrast, the combination of ET‐1 (10 nmol L^?1) and the highly specific BK_Ca blocker iberiotoxin (IBX; 100 nmol L^?1) did not cause a significant increase in endothelial cell growth. Ca²⁺ dependency of ET‐1‐induced proliferation was tested using the intracellular Ca²⁺‐chelator BAPTA (10 μmol L^?1). BAPTA abolished ET‐1 induced proliferation (n = 12; P < 0.01). In addition, ET‐1‐induced HUVEC growth was significantly reduced, if cells were kept in a Ca²⁺‐reduced solution (0.3 mmol L^?1), or by the application of 2 aminoethoxdiphenyl borate (100 μmol L^?1) which blocks hyperpolarization‐induced Ca²⁺ entry (n = 12; P < 0.05). Conclusion: Activation of BK_Ca by ET‐1 requires ET_B‐receptor activation and induces a capacitative Ca²⁺ influx which plays an important role in ET‐1‐mediated endothelial cell proliferation.     

Glycine‐extended gastrin‐17 stimulates acid secretion only via CCK‐2 receptor‐induced histamine release in the totally isolated vascularly perfused rat stomach

The effects of gastrin precursors have been discussed during recent years. However, the mechanism for their action, whether through a novel receptor on the parietal cell or a cholecystokinin‐2 (CCK‐2) receptor on the enterochromaffin like (ECL) cells, is still not settled. This study examines the effect of glycine‐extended gastrin‐17 (Gly‐G‐17), the main non‐amidated gastrin precursor, on gastric acid secretion and histamine release in the totally isolated vascularly perfused rat stomach. Glycine‐extended gastrin‐17 at the concentrations from 0.52 to 520 nmol L^–1 was administered to the totally isolated vascularly perfused rat stomach. Glycine‐extended gastrin‐17 at 52 or 520 nmol L^–1, and gastrin‐17 at 0.52 nmol L^–1 were co‐administered to examine whether glycine‐extended gastrin augmented maximal gastrin stimulated acid secretion and histamine release. Both Gly‐G‐17 at 52 nmol L^–1 and gastrin‐17 (G‐17) at 0.52 nmol L^–1 were administered together with the histamine‐2 receptor antagonist ranitidine at 10 μmol L^–1. Gastric acid and venous histamine output were measured. Glycine‐extended gastrin‐17 at lower concentrations from 0.52 to 5.2 nmol L^–1 did not stimulate gastric acid output or histamine release, whereas higher concentrations from 52 to 520 nmol L^–1 elicited a concentration‐dependent increase in acid secretion and histamine release. The outputs of acid and histamine at 520 nmol L^–1 Gly‐G‐17 were at the same level as those found for G‐17 at its maximally effective concentration of 0.52 nmol L^–1. Glycine‐extended gastrin‐17 at maximally effective concentration of 520 nmol L^–1 did not augment maximal gastrin stimulated acid secretion or histamine release. Ranitidine inhibited G‐17 and Gly‐G‐17 stimulated acid secretion to a similar degree. This study confirms that the stimulatory effect of Gly‐G‐17 on gastric acid secretion is via a CCK‐2 receptor on the ECL cell.     

New assay to detect low‐affinity interactions and characterization of leukocyte receptors for collagen including leukocyte‐associated Ig‐like receptor‐1 (LAIR‐1)

Leukocyte activity is controlled by numerous interactions between membrane receptors and ligands on the cell surface. These interactions are of low affinity making detection difficult. We developed a sensitive assay that could readily detect extremely weak interactions such as that between CD200 and the activating receptor CD200RLa (K_d>500 μM) at the protein level. We used the new technology to screen for interactions of inhibitory receptors for collagens. We confirmed that both human and mouse leukocyte‐associated Ig‐like receptor‐1, and in addition the related inhibitory leukocyte Ig‐like receptor subfamily B member 4 (CD85K, Gp49B), bound collagen specifically, whereas other cell surface proteins gave no binding. The monomeric affinities of the interactions were then determined to allow comparison with other leukocyte interactions and indicate conditions when these interactions might lead to inhibitory signals.     

Calorie restriction increases insulin‐stimulated tyrosine phosphorylation of insulin receptor and insulin receptor substrate‐1 in rat skeletal muscle

A moderate reduction in calorie intake (calorie restriction, CR) improves insulin‐stimulated glucose transport in skeletal muscle. Therefore, we studied muscle insulin signalling in ad libitum (AL) and CR (~60% AL intake for 20 days) fed rats, which received a control injection (sterile water) or an insulin injection (30 U kg^–1 body weight). In control (not insulin‐treated) rats, there was no detectable tyrosine phosphorylation of insulin receptor (IR), regardless of diet; no diet effect on tyrosine phosphorylation of insulin receptor substrate‐1 (IRS1) or IRS1‐associated phosphatidylinositol 3‐kinase (PI3K) protein and 21% higher IRS1‐associated PI3K activity in AL vs. CR. In insulin‐treated rats, tyrosine‐phosphorylated IR was 79% higher for CR vs. AL; tyrosine‐phosphorylated IRS1 was 109% higher for CR vs. AL; IRS1‐associated PI3K protein and IRS1‐associated PI3K activity were unaffected by diet. Calorie restriction amplifies early insulin signalling steps without changing IRS1‐associated PI3K, suggesting enhanced glucose transport is mediated by altering: IRS1‐PI3K localization, PI3K associated with proteins other than IRS1 or post‐PI3K events.     

Abdominal peritoneum as a defense organ: Analysis of ICAM‐1 expression in the LPS‐stimulated rat

To investigate the immune environment of the peritoneal cavity, ICAM‐1 (intercellular adhesion molecule) expression on the apical surface of the hepatic peritoneum of LPS (lipopolysaccharide) stimulated rats was anlayzed ultrastructurally and chronologically with immnunoTEM&SEM. ICAM‐1 expression was restricted to the side of microvilli of the mesothelial cells. Microvilli demonstrated bulbous tips and included fuzzy coats and strands. Bulbous tips sometimes expressed the antigen, but fuzzy coats and strands did not. Intervillar cell surfaces lacked its expression. Although ICAM‐1 expression increased eightfold 24 hr after stimulation, the selective expression remained unchanged. These results suggest that microvilli are closely associated with cell migration in the peritoneal cavity through adhesion molecules that establish a road for migration. Clin. Anat. 12:20–26, 1999. © 1999 Wiley‐Liss, Inc.     

Exploiting scavenger receptors in cancer immunotherapy: Lessons from CD5 and SR‐B1

Scavenger receptors (SRs) are structurally heterogeneous cell surface receptors characterized by their capacity to remove extraneous or modified self‐macromolecules from circulation, thus avoiding the accumulation of noxious agents in the extracellular space. This scavenging activity makes SRs important molecules for host defense and homeostasis. In turn, SRs keep the activation of the steady‐state immune response in check, and participate as co‐receptors in the priming of the effector immune responses when the macromolecules are associated with a threat that might compromise host homeostasis. Therefore, SRs built up sophisticated sensor mechanisms controlling the immune system, which may be exploited to develop novel drugs for cancer immunotherapy. In this review, we focus on the regulation of the anti‐tumor immune response by two paradigmatic SRs: the lymphocyte receptor CD5 and the more broadly distributed scavenger receptor class B type 1 (SR‐B1). Cancer immunity can be boosted by blockade of SRs working as immune checkpoint inhibitors (CD5) and/or by proper engagement of SRs working as innate danger receptor (SR‐B1). Thus, these receptors illustrate both the complexity of targeting SRs in cancer immunotherapy and also the opportunities offered by such an approach.     

Localization of nucleic acid‐sensing toll‐like receptors in human and mouse pancreas

Nucleic acid‐sensing toll‐like receptors (TLRs) (3, 7, 8, 9) have a role both in antiviral innate immunity and in autoimmune disorders. We assessed the expression of TLR3, 7, 8 and 9 in human and mouse pancreas focusing on the subpopulations of cells in the Langerhans islets. We studied eight human samples with normal pancreatic islets and two samples from patients with type 1 diabetes. Additionally, 10 CD‐1 mouse pancreases were analysed. Immunohistochemical double‐stainings for the TLRs and insulin, glucagon or somatostatin, respectively, were performed along with appropriate controls. In human pancreas, strong immunoreaction of TLR7 and TLR8 was observed in the insulin‐positive beta cells, whereas glucagon‐ or somatostatin‐expressing cells of the islets were weakly stained or negative. In type 1 diabetes, the expression in islets was weak or lost (TLR7: p = 0.014, TLR8: p = 0.053), correlating with loss of beta cells. TLR3 and 9 were expressed only weakly with no correlation with specific cell types. In mouse pancreas, only TLR9 was detected. Intra‐pancreatic nerve ganglia strongly expressed TLR7. The strong expression of TLR7 and TLR8 in the beta cells of normal human islets could be an important piece in the puzzle of type 1 diabetes pathogenesis, and be linked with destruction of this particular subpopulation of the islet cells. In normal mice, only TLR9 can be constantly detected in the islets, highlighting differences between the species.     

KIR‐HLA‐A and B alleles of the Bw4 epitope against HIV infection in discordant heterosexual couples in Chaco Argentina

Activating and inhibitory killer immunoglobulin‐like receptors (KIR) and their ligands HLA‐Bw4 (loci A and B) were studied by way of establishing whether they can contribute to protection against HIV‐1 infection in highly exposed and persistently seronegative (HESN) patients. Twenty‐three HIV‐1 serodiscordant heterosexual couples, 100 HIV‐1⁺ patients and 200 healthy individuals were included in this retrospective case–control study. HLA typing was performed by means of PCR followed by sequence‐specific oligonucleotide probe reverse hybridization. KIR3DL1 and KIR3DS1 were studied by PCR sequence‐specific primers. The frequency of KIR3DS1(3DS1/3DL1)‐Bw4 combination was significantly higher in HESN patients versus the discordant couples (P = 0·0003) and HIV‐1⁺ patients (P = 0·0001). Conversely, the KIR3DL1/KIR3DL1 homozygosity was significantly decreased in HESN patients versus the discordant couples (P = 0·00003), and HIV‐1⁺ patients (P = 0·00066). The frequency of HLA‐A*32 and HLA‐B*44 was higher in HESN versus their discordant couples (P = 0·009; P = 0·049), and HIV‐1⁺ patients (P = 0·00002; P = 0·0001). This had greater significance in combination with KIR3DS1 (3DS1/3DL1). KIR3DS1(3DS1/3DL1) could have a greater effect on protection against HIV‐1 infection in HESN patients when bound to a specific HLA allele, in this case HLA‐A*32 and HLA‐B*44, both Bw4 alleles. The differences probably arise both in the HLA alleles and in the subtypes of KIR receptors depending on the ethnic group studied.     

Inhibition of the sodium–calcium exchanger via SEA0400 altered manganese‐induced T1 changes in isolated perfused rat hearts

Manganese (Mn²⁺)‐enhanced MRI (MEMRI) provides the potential for the in vivo evaluation of calcium (Ca²⁺) uptake in the heart. Recent studies have also suggested the role of the sodium–calcium (Na⁺–Ca²⁺) exchanger (NCX) in Mn²⁺ retention, which may have an impact on MEMRI signals. In this study, we investigated whether MEMRI with fast T₁ mapping allowed the sensitive detection of changes in NCX activity. We quantified the dynamics of the Mn²⁺‐induced T₁ changes in isolated perfused rat hearts in response to SEA0400, an NCX inhibitor. The experimental protocol comprised 30 min of Mn²⁺ perfusion (wash‐in), followed by a 30‐min wash‐out period. There were three experimental groups: 1, NCX inhibition by 1 µ m SEA0400 during Mn²⁺ wash‐in only (SEAin, n = 6); 2, NCX inhibition by 1 µ m SEA0400 during Mn²⁺ wash‐out only (SEAout, n = 6); 3, no NCX inhibition during both wash‐in and wash‐out to serve as the control group (CNTL, n = 5). Rapid T₁ mapping at a temporal resolution of 3 min was performed throughout the perfusion protocol using a triggered saturation–recovery Look–Locker sequence. Our results showed that NCX inhibition during Mn²⁺ wash‐in caused a significant increase in relaxation rate (R₁) at the end of Mn²⁺ perfusion. During the wash‐out period, NCX inhibition led to less reduction in R₁. Further analysis of Mn²⁺ content in myocardium with flame atomic absorption spectroscopy was consistent with the MRI findings. These results suggest that Mn²⁺ accumulation and retention in rat hearts are, in part, dependent on NCX activity. Hence, MEMRI may provide an imaging method that is also sensitive to changes in NCX activity. Copyright © 2012 John Wiley & Sons, Ltd.     

Regulation of embryonic lung vascular development by vascular endothelial growth factor receptors,Flk‐1 and Flt‐1

The biological effects of vascular endothelial growth factor A (VEGF‐A) are mediated by fetal liver kinase‐1 (Flk‐1) and fms‐like tyrosine kinase‐1 (Flt‐1). In lung tissue, VEGF‐A is diffusely expressed throughout the embryonic stages, whereas the development of vascular endothelial cells is not uniform. Noting the signaling properties of the two receptors, we hypothesized that Flk‐1 and Flt‐1 regulate the embryonic development of lung vasculature. We herein show the spatiotemporal expression and experimental inhibition of Flk‐1 and Flt‐1 of embryonic mouse lung tissue. When Flk‐1 was predominantly expressed (embryonic day [E] 9.5–E13.5), then vascular endothelial cells actively proliferated. When Flt‐1 was enhanced (E14.5–E16.5), these cells less actively proliferated, thereby constituting organized networks. The treatment of cultured lung buds (E11.5) with antisense oligonucleotides complementary to Flk‐1 inhibited branching of capillaries and proliferation of endothelial cells. In contrast, the inhibition of Flt‐1 promoted the branching of capillaries and enhanced proliferation of endothelial cells. Of interest, inhibition of Flt‐1 promoted Flk‐1 expression. These results suggest that the two VEGF‐A receptors regulate pulmonary vascular development by modulating the VEGF‐A signaling. Anat Rec, 290:958–973, 2007. © 2007 Wiley‐Liss, Inc.     

Efficacy and immunomodulatory actions of ONO‐4641, a novel selective agonist for sphingosine 1‐phosphate receptors 1 and 5, in preclinical models of multiple sclerosis

ONO‐4641 is a next‐generation sphingosine 1‐phosphate (S1P) receptor agonist selective for S1P receptors 1 and 5. The objective of the study was to characterize the immunomodulatory effects of ONO‐4641 using preclinical data. ONO‐4641 was tested in both in‐vitro pharmacological studies as well as in‐vivo models of transient or relapsing–remitting experimental autoimmune encephalomyelitis (EAE). In vitro, ONO‐4641 showed highly potent agonistic activities versus S1P receptors 1 and 5 [half maximal effective concentration (EC₅₀) values of 0·0273 and 0·334 nM, respectively], and had profound S1P receptor 1 down‐regulating effects on the cell membrane. ONO‐4641 decreased peripheral blood lymphocyte counts in rats by inhibiting lymphocyte egress from secondary lymphoid tissues. In a rat experimental autoimmune encephalomyelitis (EAE) model, ONO‐4641 suppressed the onset of disease and inhibited lymphocyte infiltration into the spinal cord in a dose‐dependent manner at doses of 0·03 and 0·1 mg/kg. Furthermore, ONO‐4641 prevented relapse of disease in a non‐obese diabetic mouse model of relapsing‐remitting EAE. These observations suggest that ONO‐4641 may provide therapeutic benefits in the treatment of multiple sclerosis.     

Dopamine's role in social modulation of infant isolation‐induced vocalization: II. Maternally modulated infant separation responses are regulated by D1‐ and D2‐family dopamine receptors

Mammalian infant behavior directed toward caregivers is critical to survival and may play a role in establishing social bonds. Most mammalian infants vocalize when isolated. Rat pups vocalize at a higher rate when isolated following an interaction with an adult female than after an interaction with littermates, a phenomenon termed maternal potentiation. We previously reported that the D2 receptor family agonist quinpirole disrupts maternal potentiation at a dose that does not alter vocalization rate following contact with littermates. Here we further examine the role of dopamine in maternal potentiation by testing effects of both D1 and D2 receptor family ligands, alone and in combination, on maternal potentiation. We tested the drugs' effects on isolation vocalization subsequent to littermate contact and then another isolation preceded by a brief “reunion” period of exposure either to the anesthetized dam or a handling‐only “pickup” condition. D2 receptor stimulation blocked the increase in vocalizations following reunion with the dam. The D2 agonist effect in the dam‐reunion condition was much larger than its small effect in the pickup condition, providing further evidence that D2 receptors exert a selective modulation of maternal potentiation. On the other hand, systemic administration of the D1 agonist SKF81297 reduced isolation vocalizations nonspecifically, across all the experimental conditions. Finally, the D1 and D2 receptor dual antagonist, alpha‐flupenthixol, increased isolation vocalizations and disrupted potentiation, but at doses that also inhibited locomotion. We conclude that D2 receptor family activation has a more selective effect of disrupting maternal potentiation than D1 receptor family activation. © 2008 Wiley Periodicals, Inc. Dev Psychobiol 51: 158–172, 2009     

Expression and distribution of GABA and GABAB‐receptor in the rat adrenal gland

The inhibitory effects of gamma‐aminobutyric acid (GABA) in the central and peripheral nervous systems and the endocrine system are mediated by two different GABA receptors: GABA_A‐receptor (GABA_A‐R) and GABA_B‐receptor (GABA_B‐R). GABA_A‐R, but not GABA_B‐R, has been observed in the rat adrenal gland, where GABA is known to be released. This study sought to determine whether both GABA and GABA_B‐R are present in the endocrine and neuronal elements of the rat adrenal gland, and to investigate whether GABA_B‐R may play a role in mediating the effects of GABA in secretory activity of these cells. GABA‐immunoreactive nerve fibers were observed in the superficial cortex. Some GABA‐immunoreactive nerve fibers were found to be associated with blood vessels. Double‐immunostaining revealed GABA‐immunoreactive nerve fibers in the cortex were choline acetyltransferase (ChAT)‐immunonegative. Some GABA‐immunoreactive nerve fibers ran through the cortex toward the medulla. In the medulla, GABA‐immunoreactivity was seen in some large ganglion cells, but not in the chromaffin cells. Double‐immunostaining also showed GABA‐immunoreactive ganglion cells were nitric oxide synthase (NOS)‐immunopositive. However, neither immunohistochemistry combined with fluorescent microscopy nor double‐immunostaining revealed GABA‐immunoreactivity in the noradrenaline cells with blue‐white fluorescence or in the adrenaline cells with phenylethanolamine N‐methyltransferase (PNMT)‐immunoreactivity. Furthermore, GABA‐immunoreactive nerve fibers were observed in close contact with ganglion cells, but not chromaffin cells. Double‐immunostaining also showed that the GABA‐immunoreactive nerve fibers were in close contact with NOS‐ or neuropeptide tyrosine (NPY)‐immunoreactive ganglion cells. A few of the GABA‐immunoreactive nerve fibers were ChAT‐immunopositive, while most of the GABA‐immunoreactive nerve fibers were ChAT‐immunonegative. Numerous ChAT‐immunoreactive nerve fibers were observed in close contact with the ganglion cells and chromaffin cells in the medulla. The GABA_B‐R‐immunoreactivity was found only in ganglion cells in the medulla and not at all in the cortex. Immunohistochemistry combined with fluorescent microscopy and double‐immunostaining showed no GABA_B‐R‐immunoreactivity in noradrenaline cells with blue‐white fluorescence or in adrenaline cells with PNMT‐immunoreactivity. These immunoreactive ganglion cells were NOS‐ or NPY‐immunopositive on double‐immunostaining. These findings suggest that GABA from the intra‐adrenal nerve fibers may have an inhibitory effect on the secretory activity of ganglion cells and cortical cells, and on the motility of blood vessels in the rat adrenal gland, mediated by GABA‐Rs.     

Metabolic imaging of acute and chronic infarction in the perfused rat heart using hyperpolarised [1‐13C]pyruvate

Hyperpolarised ¹³C MRI can be used to generate metabolic images of the heart in vivo. However, there have been no similar studies performed in the isolated perfused heart. Therefore, the aim of this study was to develop a method for the creation of ¹³C metabolite maps of the perfused rat heart and to demonstrate the technique in a study of acute and chronic myocardial infarction. Male Wistar rat hearts were isolated, perfused and imaged before and after occlusion of the left anterior descending (LAD) coronary artery, creating an acute infarct group. In addition, a chronic infarct group was generated from hearts which had their LAD coronary artery occluded in vivo. Four weeks later, hearts were excised, perfused and imaged to generate metabolic maps of infused pyruvate and its metabolites lactate and bicarbonate. Myocardial perfusion and energetics were assessed by first‐pass perfusion imaging and ³¹P MRS, respectively. In both acute and chronically infarcted hearts, perfusion was reduced to the infarct region, as revealed by reduced gadolinium influx and lower signal intensity in the hyperpolarised pyruvate images. In the acute infarct region, there were significant alterations in the lactate (increased) and bicarbonate (decreased) signal ratios. In the chronically infarcted region, there was a significant reduction in both bicarbonate and lactate signals. ³¹P‐derived energetics revealed a significant decrease between control and chronic infarcted hearts. Significant decreases in contractile function between control and both acute and chronic infracted hearts were also seen. In conclusion, we have demonstrated that hyperpolarised pyruvate can detect reduced perfusion in the rat heart following both acute and chronic infarction. Changes in lactate and bicarbonate ratios indicate increased anaerobic metabolism in the acute infarct, which is not observed in the chronic infarct. Thus, this study has successfully demonstrated a novel imaging approach to assess altered metabolism in the isolated perfused rat heart. © 2013 The Authors. NMR in Biomedicine published by John Wiley & Sons Ltd     

Novel function of histamine signaling in hyperlipidemia‐induced atherosclerosis: Histamine H1 receptors protect and H2 receptors accelerate atherosclerosis

Histamine is not only essential for acute inflammatory reactions, but it also participates in a chronic inflammatory disorder. We generated apolipoprotein E (apoE) and histamine receptors (HHRs), including the major H1 and H2 receptors (HH1R, HH2R) double knockout mice (DKO) to clarify the role of HHRs in hyperlipidemia‐induced atherosclerosis, in which apoE‐KO and DKO mice were fed a high cholesterol diet. We found that pronounced hyperlipidemia‐induced atherosclerotic progression occurred in HH1R/apoE‐DKO mice, but in HH2R/apoE‐DKO mice less atherosclerosis, despite pro‐atherogenic serum cholesterol levels compared with apoE‐KO mice. Furthermore, the increased expressions of scavenger receptors (SRs), such as SR‐A, CD36 and lectin‐like oxidized low‐density lipoprotein receptor 1 (LOX‐1), nuclear factor‐kappa B (NFκB), monocyte chemoattractant protein (MCP‐1), matrix metalloproteinases (MMPs) or liver X receptor (LXR)‐related inflammatory signaling factors, were consistent with the pro‐atherogenic phenotype of HH2R/apoE‐DKO mice. We hypothesize that histamine/HH1R and HH2R signaling has conflicting innate functions, inflammatory/atherogenic and anti‐inflammatory/anti‐atherogenic actions, and that there are innate links between histamine signaling and hyperlipidemia‐induced atherosclerosis, independently of serum cholesterol metabolism. Specific histamine signaling blockers, in particular, HH2R blockers, are a possible novel therapeutic target for hyperlipidemia‐induced atherosclerosis.     

Detection of lung transplant rejection in a rat model using hyperpolarized [1‐13C] pyruvate‐based metabolic imaging

The current standard for noninvasive imaging of acute rejection consists of X‐ray/CT, which derive their contrast from changes in ventilation, inflammation and edema, as well as remodeling during rejection. We propose the use of hyperpolarized [1‐¹³C] pyruvate MRI—which provides real‐time metabolic assessment of tissue—as an early biomarker for tissue rejection. In this preliminary study, we used μCT‐derived parameters and HP ¹³C MR‐derived biomarkers to predict rejection in an orthotopic left lung transplant model in both allogeneic and syngeneic rats. On day 3, the normalized lung density—a parameter that accounts for both lung volume (mL) and density (HU)—was ?0.335 (CI: ‐0.598, ?0.073) and ? 0.473 (CI: ‐0.726, ?0.220) for the allograft and isograft, respectively (not significant, 0.40). The lactate‐to‐pyruvate ratios—derived from the HP ¹³C MRI—for the allograft and isograft were 0.200 (CI: 0.161, 0.240) and 0.114 (CI: 0.074, 0.153), respectively (significant, 0.020). Both techniques showed tissue rejection on day 7. A separate sub‐study revealed CD8+ cells as the primary source of the lactate‐to‐pyruvate signal. Our study suggests that hyperpolarized (HP) [1‐¹³C] pyruvate MRI is a promising early biomarker for tissue rejection that provides metabolic assessment in real time based on changes in cellularity and metabolism of lung tissue and the infiltrating inflammatory cells, and may be able to predict tissue rejection earlier than X‐ray/CT.