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Exercise changes the tumor microenvironment by remodeling blood vessels and increasing infiltration by cytotoxic immune cells. The mechanisms driving these changes remain unclear. Herein, we demonstrate that exercise normalizes tumor vasculature and upregulates endothelial expression of VCAM1 in YUMMER 1.7 and B16F10 murine models of melanoma but differentially regulates tumor growth, hypoxia, and the immune response. We found that exercise suppressed tumor growth and increased CD8+ T-cell infiltration in YUMMER but not in B16F10 tumors. Single-cell RNA sequencing and flow cytometry revealed exercise modulated the number and phenotype of tumor-infiltrating CD8+ T cells and myeloid cells. Specifically, exercise caused a phenotypic shift in the tumor-associated macrophage population and increased the expression of MHC class II transcripts. We further demonstrated that ERK5 S496A knock-in mice, which are phosphorylation deficient at the S496 residue, mimicked the exercise effect when unexercised, yet when exercised, these mice displayed a reversal in the effect of exercise on tumor growth and macrophage polarization compared with wild-type mice. Taken together, our results reveal tumor-specific differences in the immune response to exercise and show that ERK5 signaling via the S496 residue plays a crucial role in exercise-induced tumor microenvironment changes. See related Spotlight by Betof Warner, p. 1158.

[This corrects the article DOI: 10.3389/fcvm.2020.542485.].

Previously, we reported that post-translational modifications (PTMs) of MAGI1, including S741 phosphorylation and K931 de-SUMOylation, both of which are regulated by p90RSK activation, lead to endothelial cell (EC) activation. However, roles for p90RSK and MAGI1-PTMs in regulating EC permeability remain unclear despite MAGI1 being a junctional molecule. Here, we show that thrombin (Thb)-induced EC permeability, detected by the electric cell-substrate impedance sensing (ECIS) based system, was decreased by overexpression of dominant negative p90RSK or a MAGI1-S741A phosphorylation mutant, but was accelerated by overexpression of p90RSK, siRNA-mediated knockdown of magi1, or the MAGI1-K931R SUMOylation mutant. MAGI1 depletion also increased the mRNA and protein expression of the large tumor suppressor kinases 1 and 2 (LATS1/2), which inhibited YAP/TAZ activity and increased EC permeability. Because the endothelial barrier is a critical mediator of tumor hypoxia, we also evaluated the role of p90RSK activation in tumor vessel leakiness by using a relatively low dose of the p90RSK specific inhibitor, FMK-MEA. FMK-MEA significantly inhibited tumor vessel leakiness at a dose that does not affect morphology and growth of tumor vessels in vivo. These results provide novel insights into crucial roles for p90RSK-mediated MAGI1 PTMs and the Hippo pathway in EC permeability, as well as p90RSK activation in tumor vessel leakiness.

The interplay among signaling events for endothelial cell (EC) senescence, apoptosis, and activation and how these pathological conditions promote atherosclerosis in the area exposed to disturbed flow (d-flow) in concert remain unclear. The aim of this study was to determine whether telomeric repeat-binding factor 2-interacting protein (TERF2IP), a member of the shelterin complex at the telomere, can regulate EC senescence, apoptosis, and activation simultaneously, and if so, by what molecular mechanisms. We found that d-flow induced p90RSK and TERF2IP interaction in a p90RSK kinase activity-dependent manner. An in vitro kinase assay revealed that p90RSK directly phosphorylated TERF2IP at the serine 205 (S205) residue, and d-flow increased TERF2IP S205 phosphorylation as well as EC senescence, apoptosis, and activation by activating p90RSK. TERF2IP phosphorylation was crucial for nuclear export of the TERF2IP-TRF2 complex, which led to EC activation by cytosolic TERF2IP-mediated NF-κB activation and also to senescence and apoptosis of ECs by depleting TRF2 from the nucleus. Lastly, using EC-specific TERF2IP-knockout (TERF2IP-KO) mice, we found that the depletion of TERF2IP inhibited d-flow-induced EC senescence, apoptosis, and activation, as well as atherosclerotic plaque formation. These findings demonstrate that TERF2IP is an important molecular switch that simultaneously accelerates EC senescence, apoptosis, and activation by S205 phosphorylation.

Disturbed blood flow (d-flow) causes endothelial cell (EC) dysfunction, leading to atherosclerotic plaque formation. We have previously shown that d-flow increases SUMOylation of p53 and ERK5 through downregulation of sentrin/SUMO-specific protease 2 (SENP2) function; however, it is not known how SENP2 itself is regulated by d-flow. Here, we determined that d-flow activated the serine/threonine kinase p90RSK, which subsequently phosphorylated threonine 368 (T368) of SENP2. T368 phosphorylation promoted nuclear export of SENP2, leading to downregulation of eNOS expression and upregulation of proinflammatory adhesion molecule expression and apoptosis. In an LDLR-deficient murine model of atherosclerosis, EC-specific overexpression of p90RSK increased EC dysfunction and lipid accumulation in the aorta compared with control animals; however, these pathologic changes were not observed in atherosclerotic mice overexpressing dominant negative p90RSK (DN-p90RSK). Moreover, depletion of SENP2 in these mice abolished the protective effect of DN-p90RSK overexpression. We propose that p90RSK-mediated SENP2-T368 phosphorylation is a master switch in d-flow-induced signaling, leading to EC dysfunction and atherosclerosis.

BackgroundDiabetes mellitus is a major risk factor for cardiovascular mortality by increasing endothelial cell (EC) dysfunction and subsequently accelerating atherosclerosis. Extracellular-signal regulated kinase 5 (ERK5) is activated by steady laminar flow and regulates EC function by increasing endothelial nitric oxide synthase expression and inhibiting EC inflammation. However, the role and regulatory mechanisms of ERK5 in EC dysfunction and atherosclerosis are poorly understood. Here, we report the critical role of the p90 ribosomal S6 kinase (p90RSK)/ERK5 complex in EC dysfunction in diabetes mellitus and atherosclerosis.Methods and resultsInducible EC-specific ERK5 knockout (ERK5-EKO) mice showed increased leukocyte rolling and impaired vessel reactivity. To examine the role of endothelial ERK5 in atherosclerosis, we used inducible ERK5-EKO-LDLR(-/-) mice and observed increased plaque formation. When activated, p90RSK associated with ERK5, and this association inhibited ERK5 transcriptional activity and upregulated vascular cell adhesion molecule 1 expression. In addition, p90RSK directly phosphorylated ERK5 S496 and reduced endothelial nitric oxide synthase expression. p90RSK activity was increased in diabetic mouse vessels, and fluoromethyl ketone-methoxyethylamine, a specific p90RSK inhibitor, ameliorated EC-leukocyte recruitment and diminished vascular reactivity in diabetic mice. Interestingly, in ERK5-EKO mice, increased leukocyte rolling and impaired vessel reactivity were resistant to the beneficial effects of fluoromethyl ketone-methoxyethylamine, suggesting a critical role for endothelial ERK5 in mediating the salutary effects of fluoromethyl ketone-methoxyethylamine on endothelial dysfunction. Fluoromethyl ketone-methoxyethylamine also inhibited atherosclerosis formation in ApoE(-/-) mice.ConclusionsOur study highlights the importance of the p90RSK/ERK5 module as a critical mediator of EC dysfunction in diabetes mellitus and atherosclerosis formation, thus revealing a potential new target for therapeutic intervention.

Background: Cardio‐oncology and emergency medicine are closely collaborative, as many cardiac events in cancer patients require evaluation and treatment in the emergency department (ED). Immune checkpoint inhibitors (ICIs) have become a common treatment for patients with head and neck cancer (HNC). However, the immune‐related adverse events (irAEs) from ICIs can be clinically significant. Methods: We reviewed and analyzed cardiovascular diagnoses among HNC patients who received ICI during the period April 1, 2016–December 31, 2020 in a large tertiary cancer center. Demographics, clinical and cancer‐related data were abstracted, and billing databases were queried for cardiovascular disease (CVD)‐related diagnosis using International Classification of Disease‐version10 (ICD‐10) codes. We recorded receipt of care at the ED as one of the outcome variables. Results: A total of 610 HNC patients with a median follow‐up time of 12.3 months (median, interquartile range = 5–30 months) comprised our study cohort. Overall, 25.7% of patients had pre‐existing CVD prior to ICI treatment. Of the remaining 453 patients without pre‐existing CVD, 31.5% (n = 143) had at least one CVD‐related diagnosis after ICI initiation. Tachyarrhythmias (91 new events) was the most frequent CVD‐related diagnosis after ICI. The time to diagnosis of myocarditis from initiation of ICI occurred the earliest (median 2.5 months, 1.5–6.8 months), followed by myocardial infarction (3.7, 0.5–9), cardiomyopathy (4.5, 1.6–7.3), and tachyarrhythmias (4.9, 1.2–11.4). Patients with myocarditis and tachyarrhythmias mainly presented to the ED for care. Conclusion: The use of ICI in HNC is still expanding and the spectrum of delayed manifestation of ICI‐induced cardiovascular toxicities is yet to be fully defined in HNC survivors. [ABSTRACT FROM AUTHOR]