Paigen diet-fed apolipoprotein E knockout mice develop severe pulmonary hypertension in an interleukin-1-dependent manner.

Inflammatory mechanisms are proposed to play a significant role in the pathogenesis of pulmonary arterial hypertension (PAH). Previous studies have described PAH in fat-fed apolipoprotein E knockout (ApoE(-/-)) mice. We have reported that signaling in interleukin-1-receptor-knockout (IL-1R1(-/-)) mice leads to a reduction in diet-induced systemic atherosclerosis. We subsequently hypothesized that double-null (ApoE(-/-)/IL-1R1(-/-)) mice would show a reduced PAH phenotype compared with that of ApoE(-/-) mice. Male IL-1R1(-/-), ApoE(-/-), and ApoE(-/-)/IL-1R1(-/-) mice were fed regular chow or a high-fat diet (Paigen diet) for 8 weeks before phenotyping for PAH. No abnormal phenotype was observed in the IL-1R1(-/-) mice. Fat-fed ApoE(-/-) mice developed significantly increased right ventricular systolic pressure and substantial pulmonary vascular remodeling. Surprisingly, ApoE(-/-)/IL-1R1(-/-) mice showed an even more severe PAH phenotype. Further molecular investigation revealed the expression of a putative, alternatively primed IL-1R1 transcript expressed within the lungs but not aorta of ApoE(-/-)/IL-1R1(-/-) mice. Treatment of ApoE(-/-) and ApoE(-/-)/IL-1R1(-/-) mice with IL-1-receptor antagonist prevented progression of the PAH phenotype in both strains. Blocking IL-1 signaling may have beneficial effects in treating PAH, and alternative IL-1-receptor signaling in the lung may be important in driving PAH pathogenesis.

A MitoTracker Green-based flow cytometric assay for natural killer cell activity: variability, the influence of platelets and a comparison of analytical approaches.

OBJECTIVE: A number of flow cytometric assays for natural killer (NK) cell cytotoxicity have been described, however, the relative merits of analytical approaches and the influence of platelets on measured responses have not been systematically evaluated. Information on the time-dependent variability in measured responses is also limited. MATERIALS AND METHODS: Human peripheral blood mononuclear cells were obtained using Nycoprep 1.077, or Nycoprep 1.077 followed by Nycoprep 1.068 (to remove platelets), and incubated for 3 hours with MitoTracker Green (MTG)-labeled K562 cells. Cells were stained with propidium iodide (PI) and the proportions of viable and nonviable target cells (MTG(+)PI(-), MTG(+)PI(+)) were determined by flow cytometry using quadrant and polygonal region analysis. RESULTS: Platelets inhibited NK cell cytotoxicity and the response was underestimated when the nonviable target cell population was not entirely enclosed within the nonviable target cell (upper right) flow cytometric quadrant. The variability in measured NK cell cytotoxic responses in samples obtained from five individuals on three occasions over a 3-week period was 28%, 24%, 26%, and 37%, and 19%, 23%, 27%, and 32% for the quadrant and region analyses (mean coefficient of variation at effector-to-target cell ratios of 100:1, 50:1, 25:1, and 12.5:1, respectively), and 24% and 20% when data were calculated as the area under the cytotoxic curve (AUCC). CONCLUSION: Polygonal regions and the calculation of data as the AUCC appear to be the best approach. This study will be of value to investigators that are wishing to incorporate an NK cell cytotoxicity assay into their portfolio of experimental techniques.

Administration of the stress protein gp96 prolongs rat cardiac allograft survival, modifies rejection-associated inflammatory events, and induces a state of peripheral T-cell hyporesponsiveness.

High-dose gp96 has been shown to inhibit experimental autoimmune disease by a mechanism that appears to involve immunoregulatory CD4+ T cells. This study tested the hypothesis that high-dose gp96 administration modifies allograft rejection and associated inflammatory events. Wistar cardiac allografts were transplanted into Lewis recipient rats and graft function was monitored daily by palpation. Intradermal administration of gp96 purified from Wistar rat livers (100 microg) at the time of transplantation and 3 days later significantly prolonged allograft survival (14 vs 8 days in phosphate-buffered saline [PBS]-treated recipients; P = 0.009). Rejected allografts from gp96-treated animals were significantly less enlarged than allografts from their PBS-treated counterparts (2.8 vs 4.3 g; P < 0.004). Gp96 was also effective when administered on days 1 and 8 (13 vs 7 days), but not if it was derived from recipient (Lewis) liver tissue or administered on days 0, 3, and 6. In parallel studies, CD3+ T cells from gp96-treated untransplanted animals secreted less interleukin (IL)-4, IL-10, and interferon (IFN)-gamma after in vitro polyclonal stimulation than CD3+ T cells from PBS-treated animals. Gp96 administration might therefore influence the induction of immunity to coencountered antigenic challenges and inflammatory events by inducing what appears to be a state of peripheral T-cell hyporesponsiveness.

Differential IL-1 signaling induced by BMPR2 deficiency drives pulmonary vascular remodeling.

Bone morphogenetic protein receptor type 2 (BMPR2) mutations are present in patients with heritable and idiopathic pulmonary arterial hypertension (PAH). Circulating levels of interleukin-1 (IL-1) are raised in patients and animal models. Whether interplay between BMP and IL-1 signaling can explain the local manifestation of PAH in the lung remains unclear. Cell culture, siRNA, and mRNA microarray analysis of RNA isolated from human pulmonary artery (PASMC) and aortic (AoSMC) smooth muscle cells were used. R899X+/- BMPR2 transgenic mice fed a Western diet for six weeks were given daily injections of IL-1ß prior to assessment for PAH and tissue collection. PASMC have reduced inflammatory activation in response to IL-1ß compared with AoSMCs; however, PASMC with reduced BMPR2 demonstrated an exaggerated response. Mice treated with IL-1ß had higher white blood cell counts and significantly raised serum protein levels of IL-6 and osteoprotegerin (OPG) plasma levels recapitulating in vitro data. Phenotypically, IL-1ß treated mice demonstrated increased pulmonary vascular remodeling. IL-1ß induces an exaggerated pulmonary artery specific transcriptomic inflammatory response when BMPR2 signaling is reduced.

The stress protein gp96 is not an activator of resting rat bone marrow-derived dendritic cells, but is a costimulator and activator of CD3+ T cells.

Although low doses of tumor-derived stress protein gp96 elicit protective immunity to the tumor from which it is isolated, protection is lost at high doses because of the induction of immunoregulatory CD4+ T cells. This study evaluated the influence of gp96 on resting rat bone marrow-derived dendritic cells (BMDCs) and purified CD3+ T cells. In contrast to previous reports, gp96 had no effect on adhesion and costimulatory molecule expression by BMDCs, nor did it influence interleukin (IL)-10 and IL-12 secretion or their allostimulatory capacity. Gp96 did not bind to BMDCs but dose-dependently bound to CD4+ and CD8+ T cells. At low concentrations (1 and 25 microg/mL), gp96 acted as a costimulator of CD3+ T cells, inducing proliferation and the secretion of interferon (IFN)-gamma- and IL-10. Gp96 also increased the proliferation of CD28-costimulated CD3+ T cells and their secretion of IFN-gamma, IL-4, and IL-10. Gp96 had no effect at higher concentrations (50 and 100 microg/mL), despite the occurrence of cell surface binding at these concentrations. These findings indicate that gp96 can act as a costimulatory molecule for CD3+ T cells, and an observed increase in the IL-10: IFN-gamma secretion ratio induced by gp96 suggests that it might, at appropriate concentrations, promote a regulatory T-helper 2 (Th2)-like phenotype.

Identification of a rat bone marrow-derived dendritic cell population which secretes both IL-10 and IL-12: evidence against a reciprocal relationship between IL-10 and IL-12 secretion.

The qualitative nature of immune responses induced by dendritic cells (DCs) is influenced by the balance of pro-inflammatory (e.g. IL-12) and anti-inflammatory (e.g. IL-10) cytokines that they secrete. Evidence to date suggests that IL-12 and IL-10 secretion is reciprocally regulated and that IL-10 inhibits IL-12 secretion. This study identifies a population of resting, immature rat bone marrow-derived DCs (BMDCs) which secretes IL-10, the IL-12(p70) heterodimer and the free IL-12(p40) subunit, the latter in vast excess of IL-12(p70). Counter-intuitively, activation with LPS induces the secretion of high and equivalent levels of IL-10 and IL-12(p40), but only quantitatively small increases in IL-12(p70). Neutralization of IL-10 increased the secretion of IL-12(p40) by resting BMDCs, but decreased IL-12(p40) secretion by LPS-activated BMDCs. Pre-incubation of resting BMDCs for 24h with neutralizing antibody to IL-10 reduced the subsequent secretion of IL-10 in allogeneic cultures of Lewis CD3(+) T cells with resting and LPS-activated Wistar BMDCs, and enhanced IL-12(p40) secretion in allogeneic cultures with LPS-activated BMDCs. IL-10 neutralization had no effect on the levels of IL-12(p70), IFN-gamma or IL-4 in allogeneic cultures. In summary, this study has identified a population of rat BMDCs that secretes low levels of bioactive IL-12(p70), but high levels of IL-10 and IL-12(p40). These findings argue against the concept that there is a reciprocal relationship between IL-10 and IL-12 secretion. They might also have implications for understanding the role of DCs in post-activation qualitative skewing of immune responses.

Improvement in nutritional status reduces the clinical impact of infections in older adults.

OBJECTIVES: To determine the effect of a dietary intervention and micronutrient supplementation on self-reported infections in older adults. DESIGN: A randomized, placebo-controlled intervention trial. SETTING: Community living older people in South Yorkshire, United Kingdom. PARTICIPANTS: Two-hundred seventeen older adults aged 65 to 85. INTERVENTION: Participants were randomized to a dietary intervention, a daily micronutrient supplement, or placebo for 3 months, with a 3-month follow-up. MEASUREMENTS: Self-reported measures of infection were reported over the 6-month study period. Secondary outcome measures were nutritional status, dietary intake, quality of life, and depression. RESULTS: Self-reported measures of infection over the 6-month duration of the study were significantly different between the treatment groups. The number of weeks in which illness affected life and the number of general practitioner and hospital visits were significantly lower in the food and micronutrient groups than in the placebo group. The number of weeks in which symptoms of an infection were described was significantly lower in the food group than the placebo and micronutrient groups. Significant improvements in biomarkers of micronutrient status were achieved in the food and micronutrient groups and showed significantly greater change than observed in the placebo group. Significant improvement in dietary intakes was observed in the food group only. CONCLUSION: Improving dietary intake and micronutrient status reduces the clinical impact of self-reported infections in older adults.

Serum osteoprotegerin is increased and predicts survival in idiopathic pulmonary arterial hypertension.

We previously reported that osteoprotegerin (OPG) is regulated by pathways associated with pulmonary arterial hypertension (PAH), and is present at elevated levels within pulmonary vascular lesions and sera from patients with idiopathic PAH (IPAH). Since OPG is a naturally secreted protein, we investigated the relationship between serum OPG and disease severity and outcome in patients with IPAH and animal models. OPG mRNA expression was measured in pulmonary artery smooth muscle cells (PASMC) from pulmonary arteries of patients with and without IPAH. Serum concentrations of OPG were measured in a retrospective and prospective group of patients. OPG levels were compared with phenotypic data and other putative PAH biomarkers. Prognostic significance was assessed and levels compared with healthy controls. Correlation of OPG and pulmonary vascular remodeling was also performed in rodent models of PAH. OPG mRNA was significantly increased 2-fold in PASMC isolated from explanted PAH lungs compared with control. Serum OPG concentrations were markedly elevated in IPAH compared with controls. In Cohort 1 OPG levels significantly correlated with mean right atrial pressure and cardiac index, while in Cohort 2 significant correlations existed between age-adjusted OPG levels and gas transfer. In both cohorts an OPG concentration above a ROC-derived threshold of 4728 pg/ml predicted poorer survival. In two rodent models, OPG correlated with the degree of pulmonary vascular remodeling. OPG levels are significantly elevated in patients with idiopathic PAH and are of prognostic significance. The role of OPG as a potential biomarker and therapeutic target merits further investigation.

A non-receptor-mediated mechanism for internalization of molecular chaperones.

The evolving realization that stress proteins, which have for many years been considered to be exclusively intracellular molecules under normal conditions, can be released from viable cells via a number of potential routes/pathways has prompted interest into their extracellular biology and intercellular signaling properties. That the stress proteins Hsp60, Hsp70 and gp96 can elicit both pro- and anti-inflammatory effects suggests that these molecules play a key role in the maintenance of immunological homeostasis, and a better understanding of the immunobiology of extracellular stress proteins might reveal new and more effective approaches for controlling and managing infectious disease, inflammatory disease and cancer. A number of cell surface receptors for stress proteins have been identified, and the intracellular consequences of these cell surface receptor-ligand interactions have been characterized. To date, studies into the intercellular signaling properties of stress proteins and their interactions with antigen presenting cells have focused on specific receptor-mediated uptake, and have not considered the fact that such cells can also take up proteins via non-specific endocytosis/pinocytosis. Herein we present a methodological approach for assessing receptor-mediated and non-receptor-mediated uptake of gp96 by rat bone marrow-derived dendritic cells.

FK409 inhibits both local and remote organ damage after intestinal ischaemia.

In addition to localized tissue injury, intestinal ischaemia-reperfusion (I/R) leads to remote organ damage, in particular to the lungs. Given that nitric oxide (NO) can attenuate I/R-induced tissue injury in many situations, this study evaluated the effects of the NO donor, FK409, on leukocyte adhesion in the microcirculation of the intestinal villus and also assessed pulmonary tissue damage after intestinal I/R injury. PVG rats were subjected to 30 min intestinal ischaemia and a sub-group of animals received the NO donor FK409 (10 mg/kg; i.v.) both 30 min prior to ischaemia and 30 min post-reperfusion. The intestinal mucosal surface was visualized via an incision made in an exteriorized ileal segment and leukocyte adhesion in the villous microcirculation was determined by in vivo microscopy. Total and differential leukocyte counts from peripheral blood were evaluated. Lungs were removed at the end for histological assessment. Six out of ten untreated I/R animals failed to survive the 2 h reperfusion period, whereas all ten FK409-treated animals survived. I/R induced a significant increase in villous leukocyte adhesion of untreated I/R animals (p<0.001) and this was significantly decreased by FK409 treatment (p<0.001). The total leukocyte count was significantly decreased in untreated I/R animals (p<0.001) and this primarily resulted from a reduction in circulating neutrophil numbers. This effect was not observed in FK409-treated animals. Collapsed alveoli, thickened interstitial walls, and a dense neutrophilic infiltrate were apparent in the lungs of untreated I/R animals, whereas lung histology was normal in FK409-treated animals. In conclusion, FK409 prevented mortality, significantly reduced villous leukocyte adhesion, maintained circulating leukocyte numbers, and prevented pulmonary tissue injury following intestinal I/R. FK409 may therefore be of value in reducing both local and remote tissue damage and improving outcome in situations where intestinal I/R injury is obligatory, such as small bowel transplantation.