Low density lipoprotein (LDL) inhibits histamine release from human mast cells

Degranulation of human mast cells: modulation by P2 receptors' agonists

Since the late 1970s, there has been an alarming increase in the incidence of asthma and its morbidity and mortality. Acute obstruction and inflammation of allergic asthmatic airways are frequently caused by inhalation of exogenous substances such as allergens cross-linking IgE receptors expressed on the surface of the human lung mast cells (HLMC). The degree of constriction of human airways produced by identical amounts of inhaled allergens may vary from day to day and even hour to hour. Endogenous factors in the human mast cell (HMC)'s microenvironment during allergen exposure may markedly modulate the degranulation response. An increase in allergic responsiveness may significantly enhance bronchoconstriction and breathlessness. This review focuses on the role that the ubiquitous endogenous purine nucleotide, extracellular adenosine 5'-triphosphate (ATP), which is a component of the damage-associated molecular patterns, plays in mast cells' physiology. ATP activates P2 purinergic cell-surface receptors (P2R) to trigger signaling cascades resulting in heightened inflammatory responses. ATP is the most potent enhancer of IgE-mediated HLMC degranulation described to date. Current knowledge of ATP as it relates to targeted receptor(s) on HMC along with most recent studies exploring HMC post-receptor activation pathways are discussed. In addition, the reviewed studies may explain why brief, minimal exposures to allergens (e.g., dust, cat, mouse, and grass) can unpredictably lead to intense clinical reactions. Furthermore, potential therapeutic approaches targeting ATP-related enhancement of allergic reactions are presented.

Asthma and Obesity in Children

Asthma and obesity are two major chronic diseases in children and adolescents. Recent scientific evidence points out a causative role of obesity in asthma predisposition. However, studies assessing the real impact of excessive weight gain on lung function in children have shown heterogeneous results. In this review, the pathological mechanisms linking obesity and development of asthma in children are summarized and factors influencing this relationship are evaluated. Common disease modifying factors including age, sex, ethnicity, development of atopic conditions, and metabolic alterations significantly affect the onset and phenotypic characteristics of asthma. Given this, the impact of these several factors on the obesity–asthma link were considered, and from revision of the literature we suggest the possibility to define three main clinical subtypes on the basis of epidemiological data and physiological–molecular pathways: obese-asthmatic and atopy, obese-asthmatic and insulin-resistance, and obese-asthmatic and dyslipidemia. The hypothesis of the different clinical subtypes characterizing a unique phenotype might have an important impact for both future clinical management and research priorities. This might imply the necessity to study the obese asthmatic child with a “multidisciplinary approach”, evaluating the endocrinological and pneumological aspects simultaneously. This different approach might also make it possible to intervene earlier in a specific manner, possibly with a personalized and tailored treatment. Surely this hypothesis needs longitudinal and well-conducted future studies to be validated.

Delayed anaphylaxis to alpha-gal, an oligosaccharide in mammalian meat

IgE-mediated hypersensitivity refers to immune reactions that can be rapidly progressing and, in the case of anaphylaxis, are occasionally fatal. To that end, identification of the associated allergen is important for facilitating both education and allergen avoidance that are essential to long-term risk reduction. As the number of known exposures associated with anaphylaxis is limited, discovery of novel causative agents is crucial to evaluation and management of patients with idiopathic anaphylaxis. Within the last 10 years several apparently separate observations were recognized to be related, all of which resulted from the development of antibodies to a carbohydrate moiety on proteins. Interestingly, the exposure differed from airborne allergens but was nevertheless capable of producing anaphylactic and hypersensitivity reactions. Our recent work has identified these responses as being due to a novel IgE antibody directed against a mammalian oligosaccharide epitope, galactose-alpha-1,3-galactose (“alpha-gal”). This review will present the historical summary of the identification of cetuximab hypersensitivity due to alpha-gal IgE and discuss the non-primate mammalian meat food allergy as well as current goals and directions of our research programs.

The alpha-gal story: lessons learned from connecting the dots

Anaphylaxis is a severe allergic reaction that can be rapidly progressing and fatal, and therefore establishing its cause is pivotal to long-term risk management. Our recent work has identified a novel IgE antibody response to a mammalian oligosaccharide epitope, galactose-alpha-1,3-galactose (alpha-gal). IgE to alpha-gal has been associated with 2 distinct forms of anaphylaxis: (1) immediate-onset anaphylaxis during first exposure to intravenous cetuximab and (2) delayed-onset anaphylaxis 3 to 6 hours after ingestion of mammalian food products (eg, beef and pork). Results of our studies and those of others strongly suggest that tick bites are a cause, if not the only significant cause, of IgE antibody responses to alpha-gal in the southern, eastern, and central United States; Europe; Australia; and parts of Asia. Typical immune responses to carbohydrates are considered to be T-cell independent, whereas IgE antibody production is thought to involve sequential class-switching that requires input from T cells. Therefore, establishing the mechanism of the specific IgE antibody response to alpha-gal will be an important aspect to address as this area of research continues.

Novel relationship of serum cholesterol with asthma and wheeze in the United States

BACKGROUND

Cholesterol exerts complex effects on inflammation. There has been little investigation of whether serum cholesterol is associated with asthma, an inflammatory airways disease with great public health impact.

OBJECTIVE

To determine relationships between levels of 3 serum cholesterol measures (total cholesterol [TC], high-density lipoprotein cholesterol [HDL-C], and non-HDL-C) and asthma/wheeze in a sample representative of the US population.

METHODS

Cross-sectional study of 7005 participants age >or=6 years from the 2005 to 2006 National Health and Nutrition Examination Survey.

RESULTS

Serum TC and non-HDL-C were lower in patients with current asthma than in subjects without current asthma in the overall population (TC, 188.5 vs 192.2 mg/dL; non-HDL-C, 133.9 vs 137.7 mg/dL; P < .05 for both), whereas HDL-C was not different. Adjusted odds ratios (ORs) from multivariate logistic regression per 1-SD increase of TC and non-HDL-C for current asthma were 0.92 (95% CI, 0.86-0.98) and 0.91 (95% CI, 0.85-0.98), respectively. On racial/ethnic stratification, these relationships reflect marked reductions unique to Mexican Americans (MAs; TC, 171.4 vs 189.3 mg/dL; P < .001; OR, 0.62; 95% CI, 0.48-0.80; non-HDL-C, 119.8 vs 137.9 mg/dL; P < .001; OR, 0.62; 95% CI, 0.48-0.79). Among MAs, the adjusted OR for wheeze requiring medical attention was 0.57 (95% CI, 0.43-0.75) for TC and 0.53 (95% CI, 0.33-0.85) for non-HDL-C. Relationships between cholesterol and asthma/wheeze were independent of body mass index and serum C-reactive protein, and similar between atopic and nonatopic participants.

CONCLUSION

Serum TC and non-HDL-C are inversely related to asthma in the US population, chiefly reflecting a relationship among MAs.

The association of mast cells and atherosclerosis: a morphologic study of early atherosclerotic lesions in young people

Mast cell products, such as histamine, may contribute to the initiation and progression of the atherosclerotic plaque. To determine the relationship that may exist between early atherosclerotic plaques and mast cells we studied the aortas and coronary arteries of 115 young subjects aged 15 to 34 years who had traumatic deaths. Lesions were classified as normal intima, fatty streaks, fibro-fatty plaques, and fibrous plaques. Aortic and coronary artery segments with raised lesions had significantly greater numbers of mast cells in the adventitia (and occasionally intima and outer media) compared with those with a normal intima. In the aortic segments greater numbers of mast cells were located in the dorsal portion (lesion "prone") compared with the ventral half (lesion "resistant") (P < .05). These data support the concept that increased numbers of mast cells are associated with atherosclerosis and suggest a role for mast cell products in the evolution of the atherosclerotic plaque.