Control of mitochondrial function and cell growth by the atypical cadherin Fat1.

Mitochondrial products such as ATP, reactive oxygen species, and aspartate are key regulators of cellular metabolism and growth. Abnormal mitochondrial function compromises integrated growth-related processes such as development and tissue repair, as well as homeostatic mechanisms that counteract ageing and neurodegeneration, cardiovascular disease, and cancer. Physiologic mechanisms that control mitochondrial activity in such settings remain incompletely understood. Here we show that the atypical Fat1 cadherin acts as a molecular 'brake' on mitochondrial respiration that regulates vascular smooth muscle cell (SMC) proliferation after arterial injury. Fragments of Fat1 accumulate in SMC mitochondria, and the Fat1 intracellular domain interacts with multiple mitochondrial proteins, including critical factors associated with the inner mitochondrial membrane. SMCs lacking Fat1 (Fat1KO) grow faster, consume more oxygen for ATP production, and contain more aspartate. Notably, expression in Fat1KO cells of a modified Fat1 intracellular domain that localizes exclusively to mitochondria largely normalizes oxygen consumption, and the growth advantage of these cells can be suppressed by inhibition of mitochondrial respiration, which suggest that a Fat1-mediated growth control mechanism is intrinsic to mitochondria. Consistent with this idea, Fat1 species associate with multiple respiratory complexes, and Fat1 deletion both increases the activity of complexes I and II and promotes the formation of complex-I-containing supercomplexes. In vivo, Fat1 is expressed in injured human and mouse arteries, and inactivation of SMC Fat1 in mice potentiates the response to vascular damage, with markedly increased medial hyperplasia and neointimal growth, and evidence of higher SMC mitochondrial respiration. These studies suggest that Fat1 controls mitochondrial activity to restrain cell growth during the reparative, proliferative state induced by vascular injury. Given recent reports linking Fat1 to cancer, abnormal kidney and muscle development, and neuropsychiatric disease, this Fat1 function may have importance in other settings of altered cell growth and metabolism.

Reducing dermal exposure to agrochemical carcinogens using a fluorescent dye-based intervention among subsistence farmers in rural Honduras.

BACKGROUND: Occupational exposure to agrochemicals, some of which are known or suspected carcinogens, is a major health hazard for subsistence agricultural workers and their families. These impacts are more prevalent in low-and-middle income countries (LMIC) due to weak regulations, lack of awareness of the risks of contamination, predominant use of handheld backpack style spraying equipment, general lack of personal protective equipment (PPE), and low literacy about proper agrochemical application techniques. Reducing exposure to agrochemicals was identified as a paramount concern by rural Hondurans working with a community-engaged research initiative. Fluorescent tracer dyes have been described as a means of visualizing and quantifying dermal exposure to agricultural chemicals, and exposure models adapted for LMIC have been developed previously. Tracer dyes have also been used in educational simulations to promote pesticide safety. However, studies evaluating the effectiveness of these educational dye interventions in reducing future exposure have been lacking. AIM: To evaluate whether observing one's own chemical contamination after applying agrochemicals changed the amount of occupational dermal exposure during a subsequent chemical application. METHODS: We employed a multi-modal community intervention in a rural village in Honduras that incorporated chemical safety education and use of a fluorescent tracer dye during pesticide application on two consecutive occasions, and compared dermal exposure between the intervention group (previous dye experience and safety education, n = 6) and the control group (safety education only, n = 7). RESULTS: Mean total visual score (TVS) of the tracer dye, which accounts for both extent and intensity of whole-body contamination, was lower among those who had previously experienced the dye intervention (mean TVS = 41.3) than among participants who were dye-naïve (mean TVS = 78.4), with a difference between means of -37.10 (95% CI [-66.26, -7.95], p = 0.02). Stratifying by body part, contamination was significantly lower for the anterior left lower extremity and bilateral feet for the dye-experienced group vs. dye-naïve, with most other segments showing a trend toward decreased contamination as well. CONCLUSION: Participants who had previously experienced the dye intervention were significantly less contaminated than the dye-naïve control group during a subsequent spraying event. The findings of this small pilot study suggest that a multi-modal, community-based approach that utilizes fluorescence-augmented contamination for individualized learning (FACIL) may be effective in reducing dermal exposure to carcinogenic agrochemicals among subsistence farmers in Honduras and other LMIC.

Assessing Mental Health Concerns of Spanish-Speaking Dairy Farm Workers.

Background: Hispanic dairy farm workers have risk factors for mental health concerns. There is insufficient study of their mental health needs.Methods: We conducted focus groups at five farms. We quantified the burden of depressive symptoms with Patient Health Questionnaires (PHQ-2 and PHQ-9) during three seasons of mobile clinics on farm sites.Results: Focus groups revealed that sources of stress included working conditions, language barriers, fear of deportation, and distance from family. Depression screening found that the rate of mild depressive symptoms ranged from 0% to 3.2%. No individual scored higher than mild depression.Discussion: Rates of depressive symptoms were substantially lower than in the general US population, which may be explained by a population that self-selects for resilience. Our mixed qualitative and quantitative data acquisition provided us a more robust and comprehensive understanding of our population's mental health concerns than using one method alone.

ß-Catenin C-terminal signals suppress p53 and are essential for artery formation.

Increased activity of the tumour suppressor p53 is incompatible with embryogenesis, but how p53 is controlled is not fully understood. Differential requirements for p53 inhibitors Mdm2 and Mdm4 during development suggest that these control mechanisms are context-dependent. Artery formation requires investment of nascent endothelial tubes by smooth muscle cells (SMCs). Here, we find that embryos lacking SMC ß-catenin suffer impaired arterial maturation and die by E12.5, with increased vascular wall p53 activity. ß-Catenin-deficient SMCs show no change in p53 levels, but greater p53 acetylation and activity, plus impaired growth and survival. In vivo, SMC p53 inactivation suppresses phenotypes caused by loss of ß-catenin. Mechanistically, ß-catenin C-terminal interactions inhibit Creb-binding protein-dependent p53 acetylation and p53 transcriptional activity, and are required for artery formation. Thus in SMCs, the ß-catenin C-terminus indirectly represses p53, and this function is essential for embryogenesis. These findings have implications for angiogenesis, tissue engineering and vascular disease.

Cooperative signaling between Slit2 and Ephrin-A1 regulates a balance between angiogenesis and angiostasis.

Slit proteins induce cytoskeletal remodeling through interaction with roundabout (Robo) receptors, regulating migration of neurons and nonneuronal cells, including leukocytes, tumor cells, and endothelium. The role of Slit2 in vascular remodeling, however, remains controversial, with reports of both pro- and antiangiogenic activity. We report here that cooperation between Slit2 and ephrin-A1 regulates a balance between the pro- and antiangiogenic functions of Slit2. While Slit2 promotes angiogenesis in culture and in vivo as a single agent, Slit2 potently inhibits angiogenic remodeling in the presence of ephrin-A1. Slit2 stimulates angiogenesis through mTORC2-dependent activation of Akt and Rac GTPase, the activities of which are inhibited in the presence of ephrin-A1. Activated Rac or Akt partially rescues vascular assembly and motility in costimulated endothelium. Taken together, these data suggest that Slit2 differentially regulates angiogenesis in the context of ephrin-A1, providing a plausible mechanism for the pro- versus antiangiogenic functions of Slit2. Our results suggest that the complex roles of Slit-Robo signaling in angiogenesis involve context-dependent mechanisms.

Angiocrine factors modulate tumor proliferation and motility through EphA2 repression of Slit2 tumor suppressor function in endothelium.

It is well known that tumor-derived proangiogenic factors induce neovascularization to facilitate tumor growth and malignant progression. However, the concept of "angiocrine" signaling, in which signals produced by endothelial cells elicit tumor cell responses distinct from vessel function, has been proposed, yet remains underinvestigated. Here, we report that angiocrine factors secreted from endothelium regulate tumor growth and motility. We found that Slit2, which is negatively regulated by endothelial EphA2 receptor, is one such tumor suppressive angiocrine factor. Slit2 activity is elevated in EphA2-deficient endothelium. Blocking Slit activity restored angiocrine-induced tumor growth/motility, whereas elevated Slit2 impaired growth/motility. To translate our findings to human cancer, we analyzed EphA2 and Slit2 expression in human cancer. EphA2 expression inversely correlated with Slit2 in the vasculature of invasive human ductal carcinoma samples. Moreover, analysis of large breast tumor data sets revealed that Slit2 correlated positively with overall and recurrence-free survival, providing clinical validation for the tumor suppressor function for Slit2 in human breast cancer. Together, these data support a novel, clinically relevant mechanism through which EphA2 represses Slit2 expression in endothelium to facilitate angiocrine-mediated tumor growth and motility by blocking a tumor suppressive signal.