Fatty acid binding proteins (FABPs) are known central regulators of both metabolic and inflammatory pathways, but their role in tumor development remains largely unexplored. Here, we report that host expression of epidermal FABP (E-FABP) protects against mammary tumor growth. We find that E-FABP is highly expressed in macrophages, particularly in a specific subset, promoting their antitumor activity. In the tumor stroma E-FABP-expressing tumor-associated macrophages (TAMs) produce high levels of interferon β (IFNβ) through upregulation of lipid droplet (LD) formation in response to tumors. E-FABP-mediated IFNβ signaling can further enhance recruitment of tumoricidal effector cells, in particular NK cells, to the tumor stroma for antitumor activity. These findings identify E-FABP as a new protective factor to strengthen IFNβ responses against tumor growth.

SUMMARY Defining specific cellular and molecular mechanisms in most obesity-related diseases remains an important challenge. Here we report a serendipitous finding that consumption of a high-fat diet (HFD) greatly increased the occurrence of skin lesions in C57BL/6 mice. We demonstrated that HFD induced the accumulation of a specific type of CD11c+ macrophages in skin preceding detectable lesions. These cells primed skin to induce IL-1β and IL-18 signaling, which further promoted the cytokines IFNγ- and IL-17-mediated skin inflammation. Mechanistically, epidermal fatty acid binding protein (E-FABP) was significantly upregulated in skin of obese mice, which coupled lipid droplet formation and NLRP3 inflammasome activation. Deficiency of E-FABP in obese mice decreased recruitment of CD11c+ macrophages in skin tissues, reduced production of IL-1β and IL-18, and consequently dampened activation of effector T cells. Furthermore, E-FABP deficient mice are completely resistant to HFD-induced skin lesions. Collectively, E-FABP represents a molecular sensor triggering HFD-induced skin inflammation.

It is clear that obesity increases the risk of many types of cancer, including breast cancer. However, the underlying molecular mechanisms by which obesity is linked to cancer risk remain to be defined. Herein, we report that circulating adipose fatty acid binding protein (A-FABP) promotes obesity-associated breast cancer development. Using clinical samples, we demonstrated that circulating A-FABP levels were significantly increased in obese patients with breast cancer in comparison with those without breast cancer. Circulating A-FABP released by adipose tissue directly targeted mammary tumor cells, enhancing tumor stemness and aggressiveness through activation of the IL-6/STAT3/ALDH1 pathway. Importantly, genetic deletion of A-FABP successfully reduced tumor ALHD1 activation and obesity-associated mammary tumor growth and development in different mouse models. Collectively, these data suggest circulating A-FABP as a new link between obesity and breast cancer risk, thereby revealing A-FABP as a potential new therapeutic target for treatment of obesity-associated cancers.

A luminescent europium-organic framework with tubular channels based on the H4BTMIPA ligand (H4BTMIPA = 5,5'-methylenebis(2,4,6-trimethylisophthalic acid)) was assembled and characterized. The [H2N(CH3)2](+) ions as counterions are located in the channels. The cation exchange between [H2N(CH3)2](+) and metal ions resulted in complex that can selectively sense Fe(3+) and Al(3+) ions through fluorescence quenching and enhancement, respectively.

Yersinia pestis causes an acute infection known as the plague. Conventional techniques to enumerate Y. pestis can be labor intensive and do not lend themselves to high throughput assays. In contrast, bioluminescent bioreporters produce light that can be detected using plate readers or optical imaging platforms to monitor bacterial populations as a function of luminescence. Here, we describe the development of two Y. pestis chromosomal-based luxCDABE bioreporters, LuxPtolC and LuxPcysZK. These bioreporters use constitutive promoters to drive expression of luxCDABE that allow for sensitive detection of bacteria via bioluminescence in vitro. Importantly, both bioreporters demonstrate a direct correlation between bacterial numbers and bioluminescence, which allows for bioluminescence to be used to compare bacterial numbers. We demonstrate the use of these bioreporters to test antimicrobial inhibitors (LuxPtolC) and monitor intracellular survival (LuxPtolC and LuxPcysZK) in vitro. Furthermore, we show that Y. pestis infection of the mouse model can be monitored using whole animal optical imaging in real time. Using optical imaging, we observed Y. pestis dissemination and differentiated between virulence phenotypes in live animals via bioluminescence. Finally, we demonstrate that whole animal optical imaging can identify unexpected colonization patterns in mutant-infected animals.

Tumor-associated macrophages (TAM) play a critical role in cancer development and progression. However, the heterogeneity of TAM presents a major challenge to identify clinically relevant markers for protumor TAM. Here, we report that expression of adipocyte/macrophage fatty acid-binding protein (A-FABP) in TAM promotes breast cancer progression. Although upregulation of A-FABP was inversely associated with breast cancer survival, deficiency of A-FABP significantly reduced mammary tumor growth and metastasis. Furthermore, the protumor effect of A-FABP was mediated by TAM, in particular, in a subset of TAM with a CD11bF4/80MHCIILy6C phenotype. A-FABP expression in TAM facilitated protumor IL6/STAT3 signaling through regulation of the NFκB/ pathway. Collectively, our results suggest A-FABP as a new functional marker for protumor TAM. These findings identify A-FABP as a functional marker for protumor macrophages, thus offering a new target for tumor immunotherapy. .

Macrophages play a critical role in obesity-associated chronic inflammation and disorders. However, the molecular mechanisms underlying the response of macrophages to elevated fatty acids (FAs) and their contribution to metabolic inflammation in obesity remain to be fully elucidated. Here, we report a new mechanism by which dietary FAs, in particular saturated FAs, are able to directly trigger macrophage cell death. We demonstrated that excess saturated FAs, but not unsaturated FAs, induced the production of cytotoxic ceramides in macrophage cell lines. Most importantly, expression of adipose fatty acid binding protein (A-FABP) in macrophages facilitated metabolism of excess saturated FAs for ceramide synthesis. Inhibition or deficiency of A-FABP in macrophage cell lines decreased saturated FA-induced ceramide production, thereby resulting in reduced cell death. Furthermore, we validated the role of A-FABP in promoting saturated FA-induced macrophage cell death with primary bone-marrow derived macrophages and high-fat diet-induced obese mice. Altogether, our data reveal that excess dietary saturated FAs may serve as direct triggers in induction of ceramide production and macrophage cell death through elevated expression of A-FABP, thus establishing A-FABP as a new molecular sensor in triggering macrophage-associated sterile inflammation in obesity.

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