Objective-The aim of this study was to determine whether macrophages dispersed throughout perivascular fat are crucial to the loss of anticontractile function when healthy adipose tissue becomes inflamed and to gain an understanding of the mechanisms involved. Methods and Results-Pharmacological studies on in vitro small arterial segments from a mouse model of inducible macrophage ablation and on wild-type animals were carried out with and without perivascular fat using 2 physiological stimuli of inflammation: aldosterone and hypoxia. Both inflammatory insults caused a similar loss of anticontractile capacity of perivascular fat and increased macrophage activation. Aldosterone receptor antagonism and free radical scavengers were able to restore this capacity and reduce macrophage activation. However, in a mouse deficient of macrophages CD11b-diptheria toxin receptor (CD11b-DTR), there was no increase in contractility of arteries following aldosterone incubation or hypoxia. Conclusion-The presence and activation of macrophages in adipose tissue is the key modulator of the increase in contractility in arteries with perivascular fat following induction of inflammation. Despite multiple factors that may be involved in bringing about the vascular consequences of obesity, the ability of eplerenone to ameliorate the inflammatory effects of both aldosterone and hypoxia may be of potential therapeutic interest. Key Words: hypoxia Ⅲ microcirculation Ⅲ obesity Ⅲ inflammation O besity is set to reach epidemic levels in many countries, 1 predisposing individuals to an increased risk of type II diabetes, hypertension, and the inevitable consequences of circulatory disease. 2 The hallmark of this phenotype is an increase in the size of individual adipocytes as excess energy is stored, together with the recruitment and activation of macrophages and the release of cytokines as local inflammation ensues. 3,4 The effect on the vasculature can be profound, with loss of vasodilator adipokine bioavailability, increased tone, 5,6 and the development of the metabolic syndrome. 7

Interleukin-1 receptor antagonist-deficient (Il1rn-/-) BALB/c mice developed inflammation localized to the skin of the ear pinna in 64% of the cases examined. Histopathologically, the disease had many features resembling human psoriasis, suggesting that it might be a useful disease model. The epidermis became thickened and hypertrophic, and expressed the immature keratin, K6, throughout. The stratum corneum showed parakeratotsis. Large epidermal projections formed into a grossly thickened dermis and both tissues were infiltrated by leukocytes. Neutrophil-rich microabscesses formed beneath the stratum corneum. Dendritic cells and activated T cells of both helper classes were identified in both the dermis and epidermis, while a high density of macrophages was seen in the dermis, where mast cells were also prominent. Dense patterns of apparently activated small dermal vessels were seen in the diseased dermis. Cutaneous inflammation, along with arterial inflammation and arthritis, is the third site-specific, inflammatory disease to be found to affect Il1rn-/- BALB/c mice. None of the diseases affected Il1rn-/- C57BL/6. In F2 hybrids of Il1rn-/- BALB/c and C57BL/6, cutaneous inflammation was absent, aortic inflammation was common, and arthritis was rare, indicating that the sets of background modifier genes that cause susceptibility to each disease are not fully overlapping.

Resistance to the intestinal parasitic helminth Trichuris muris requires T-helper 2 (TH2) cellular and associated IgG1 responses, with expulsion typically taking up to 4 weeks in mice. Here, we show that the time-of-day of the initial infection affects efficiency of worm expulsion, with strong TH2 bias and early expulsion in morning-infected mice. Conversely, mice infected at the start of the night show delayed resistance to infection, and this is associated with feeding-driven metabolic cues, such that feeding restriction to the day-time in normally nocturnal-feeding mice disrupts parasitic expulsion kinetics. We deleted the circadian regulator BMAL1 in antigen-presenting dendritic cells (DCs) in vivo and found a loss of time-of-day dependency of helminth expulsion. RNAseq analyses revealed that IL-12 responses to worm antigen by circadian-synchronised DCs were dependent on BMAL1. Therefore, we find that circadian machinery in DCs contributes to the TH1/TH2 balance, and that environmental, or genetic perturbation of the DC clock results in altered parasite expulsion kinetics.

The large intestine is a major site of infection and disease yet little is known about how immunity is initiated within this site and the role of dendritic cells (DCs) in this process. We used the well-established model of Trichuris muris infection to investigate the innate response of colonic DCs in mice that are inherently resistant or susceptible to infection. One day post-infection, there was a significant increase in the number of immature colonic DCs in resistant but not susceptible mice. This increase was sustained at day 7 post-infection in resistant mice when the majority of the DCs were mature. There was no increase in DC numbers in susceptible mice until day 13 post-infection. In resistant mice, most colonic DCs were located in or adjacent to the epithelium post-infection. There were also marked differences in the expression of colonic epithelial chemokines in resistant mice and susceptible mice. Resistant mice had significantly increased levels of epithelium-derived CCL2, CCL3, CCL5 and CCL20 compared with susceptible mice. Furthermore, administering neutralizing CCL5 and CCL20 antibodies to resistant mice prevented DC recruitment. This study provides clear evidence of differences in the kinetics of DC responses in hosts inherently resistant and susceptible to infection. DC responses in the colon correlate with resistance to infection. Differences in the production of DC chemotactic chemokines by colonic epithelial cells in response to infection in resistant versus susceptible mice may explain the different kinetics of the DC response.