Actin polymerization stabilizes α4β1 integrin anchors that mediate monocyte adhesion

Leukocytes arrested on inflamed endothelium via integrins are subjected to force imparted by flowing blood. How leukocytes respond to this force and resist detachment is poorly understood. Live-cell imaging with Lifeact-transfected U937 cells revealed that force triggers actin polymerization at upstream α4β1 integrin adhesion sites and the adjacent cortical cytoskeleton. Scanning electron microscopy revealed that this culminates in the formation of structures that anchor monocyte adhesion. Inhibition of actin polymerization resulted in cell deformation, displacement, and detachment. Transfection of dominant-negative constructs and inhibition of function or expression revealed key signaling steps required for upstream actin polymerization and adhesion stabilization. These included activation of Rap1, phosphoinositide 3-kinase γ isoform, and Rac but not Cdc42. Thus, rapid signaling and structural adaptations enable leukocytes to stabilize adhesion and resist detachment forces

. DS-70, a novel and potent \uf0614 integrin antagonist, is an effective treatment for experimental allergic conjunctivitis in guinea pigs

BACKGROUND AND PURPOSE Allergic conjunctivitis is an eye inflammation that involves the infiltration of immune cells into the conjunctiva via cell surfaceadhesion receptors, such as integrin \u3b14\u3b21. These receptors interact with adhesion molecules expressed on the conjunctival endothelium and may be a target to treat this disease. We synthesized DS-70, a novel \u3b1/\u3b2-peptidomimetic \u3b14 integrin antagonist, to prevent the conjunctival infiltration of immune cells and clinical symptoms in a model of allergic conjunctivitis. EXPERIMENTAL APPROACH In vitro, DS-70 was pharmacologically characterized using a scintillation proximity procedure to measure its affinity for \u3b14\u3b21 integrin, and its effect on cell adhesion mediated by different integrins was also evaluated. The effects of DS-70 on vascular cell adhesion molecule-1 (VCAM-1)-mediated degranulation of a human mast cell line and an eosinophilic cell line, which both express \u3b14\u3b21, and on VCAM-1-mediated phosphorylation of ERK 1/2 in Jurkat E6.1 cells were investigated. Effects of DS-70 administered in the conjunctival fornix of ovalbumin-sensitized guinea pigs were evaluated. KEY RESULTS DS-70 bound to integrin \u3b14\u3b21 with nanomolar affinity, prevented the adhesion of \u3b14 integrin-expressing cells, antagonized VCAM-1- mediated degranulation of mast cells and eosinophils and ERK 1/2 phosphorylation. Only 20% was degraded after an 8 h incubation with serum. DS-70 dose-dependently reduced the clinical symptoms of allergic conjunctivitis, conjunctival \u3b14 integrin expression and conjunctival levels of chemokines and cytokines in ovalbumin-sensitized guinea pigs. CONCLUSIONS AND IMPLICATIONS These findings highlight the role of \u3b14 integrin in allergic conjunctivitis and suggest that DS-70 is a potential treatment for this condition

Hypoxia and dehydroepiandrosterone in old age: a mouse survival study

BACKGROUND: Survival remains an issue in pulmonary hypertension, a chronic disorder that often affects aged human adults. In young adult mice and rats, chronic 50% hypoxia (11% FIO2 or 0.5 atm) induces pulmonary hypertension without threatening life. In this framework, oral dehydroepiandrosterone was recently shown to prevent and reverse pulmonary hypertension in rats within a few weeks. To evaluate dehydroepiandrosterone therapy more globally, in the long term and in old age, we investigated whether hypoxia decreases lifespan and whether dehydroepiandrosterone improves survival under hypoxia. METHODS: 240 C57BL/6 mice were treated, from the age of 21 months until death, by normobaric hypoxia (11% FIO2) or normoxia, both with and without dehydroepiandrosterone sulfate (25 mg/kg in drinking water) (4 groups, N = 60). Survival, pulmonary artery and heart remodeling, weight and blood patterns were assessed. RESULTS: In normoxia, control mice reached the median age of 27 months (median survival: 184 days). Hypoxia not only induced cardiopulmonary remodeling and polycythemia in old animals but also induced severe weight loss, trembling behavior and high mortality (p < 0.001, median survival: 38 days). Under hypoxia however, dehydroepiandrosterone not only significantly reduced cardiopulmonary remodeling but also remarkably extended survival (p < 0.01, median survival: 126 days). Weight loss and trembling behavior at least partially remained, and polycythemia completely, the latter possibly favorably participating in blood oxygenation. Interestingly, at the dose used, dehydroepiandrosterone sulfate was detrimental to long-term survival in normoxia (p < 0.05, median survival: 147 days). CONCLUSION: Dehydroepiandrosterone globally reduced what may be called an age-related frailty induced by hypoxic pulmonary hypertension. This interestingly recalls an inverse correlation found in the prospective PAQUID epidemiological study, between dehydroepiandrosterone blood levels and mortality in aged human smokers and former smokers

Calcium Flux in Neutrophils Synchronizes β2 Integrin Adhesive and Signaling Events that Guide Inflammatory Recruitment

Intracellular calcium flux is an early step in the signaling cascade that bridges ligation of selectin and chemokine receptors to activation of adhesive and motile functions during recruitment on inflamed endothelium. Calcium flux was imaged in real time and provided a means of correlating signaling events in neutrophils rolling on E-selectin and stimulated by chemokine in a microfluidic chamber. Integrin dependent neutrophil arrest was triggered by E-selectin tethering and ligation of IL-8 seconds before a rapid rise in intracellular calcium, which was followed by the onset of pseudopod formation. Calcium flux on rolling neutrophils increased in a shear dependent manner, and served to link integrin adhesion and signaling of cytoskeletally driven cell polarization. Abolishing calcium influx through membrane expressed store operated calcium channels inhibited activation of high affinity β2 integrin and subsequent cell arrest. We conclude that calcium influx at the plasma membrane integrates chemotactic and adhesive signals, and functions to synchronize signaling of neutrophil arrest and migration in a shear stress dependent manner

The role of pulmonary arterial stiffness in COPD

AbstractCOPD is the second most common cause of pulmonary hypertension, and is a common complication of severe COPD with significant implications for both quality of life and mortality. However, the use of a rigid diagnostic threshold of a mean pulmonary arterial pressure (mPAP) of ≥25mHg when considering the impact of the pulmonary vasculature on symptoms and disease is misleading. Even minimal exertion causes oxygen desaturation and elevations in mPAP, with right ventricular hypertrophy and dilatation present in patients with mild to moderate COPD with pressures below the threshold for diagnosis of pulmonary hypertension. This has significant implications, with right ventricular dysfunction associated with poorer exercise capability and increased mortality independent of pulmonary function tests.The compliance of the pulmonary artery (PA) is a key component in decoupling the right ventricle from the pulmonary bed, allowing the right ventricle to work at maximum efficiency and protecting the microcirculation from large pressure gradients. PA stiffness increases with the severity of COPD, and correlates well with the presence of exercise induced pulmonary hypertension. A curvilinear relationship exists between PA distensibility and mPAP and pulmonary vascular resistance (PVR) with marked loss of distensibility before a rapid rise in mPAP and PVR occurs with resultant right ventricular failure. This combination of features suggests PA stiffness as a promising biomarker for early detection of pulmonary vascular disease, and to play a role in right ventricular failure in COPD. Early detection would open this up as a potential therapeutic target before end stage arterial remodelling occurs

Integrins as therapeutic targets: lessons and opportunities.

The integrins are a large family of cell adhesion molecules that are essential for the regulation of cell growth and function. The identification of key roles for integrins in a diverse range of diseases, including cancer, infection, thrombosis and autoimmune disorders, has revealed their substantial potential as therapeutic targets. However, so far, pharmacological inhibitors for only three integrins have received marketing approval. This article discusses the structure and function of integrins, their roles in disease and the chequered history of the approved integrin antagonists. Recent advances in the understanding of integrin function, ligand interaction and signalling pathways suggest novel strategies for inhibiting integrin function that could help harness their full potential as therapeutic targets

The underpinning biology relating to multiple sclerosis disease modifying treatments during the COVID-19 pandemic

Since January 2020 Elsevier has created a COVID-19 resource centre with free information in English and Mandarin on the novel coronavirus COVID-19. The COVID-19 resource centre is hosted on Elsevier Connect, the company's public news and information website. Elsevier hereby grants permission to make all its COVID-19-related research that is available on the COVID-19 resource centre - including this research content - immediately available in PubMed Central and other publicly funded repositories, such as the WHO COVID database with rights for unrestricted research re-use and analyses in any form or by any means with acknowledgement of the original source. These permissions are granted for free by Elsevier for as long as the COVID-19 resource centre remains active

Occurrence of Diadema Antillarum in South Florida and Caribbean National Parks from 2008-2018

Diadema antillarum, frequently referred to as the long-spined black sea urchin, is a common herbivorous echinoid that can be found in almost all marine habitats within their native range. (Ogden & Carpenter, 1987). They serve as a keystone grazer by preferentially feeding on algae that can overgrow and kill coral (Jeremy & Kaufmann, 1987). Between 1983 and 1984 a mass mortality event swept through D. antillarum populations, which caused a phase shift from coral-dominated to algal-dominated on many reefs throughout the Caribbean (Weil et al., 2005). This analysis sought to understand the occurrence of Diadema antillarum within national parks served by the South Florida/Caribbean Inventory and Monitoring Network (SFCN) division of the National Park Service (NPS) from 2008 to 2018. SFCN began monitoring urchins in 2008 in conjunction with the development of their benthic coral monitoring protocol. The abundances of D. antillarum are monitored along each transect at which coral monitoring takes place. Individuals are visually counted within a 2-meter swath of the targeted coral transect and recorded on the datasheet (Miller et al., 2017). Abundance counts inside the Research National Area (RNA) in Dry Tortugas National Park (DRTO) were compared, and occurrence data were compared between Biscayne National Park and Dry Tortugas National Park in Florida and Buck Island Reef National Monument, Salt River National Historical Park and Ecological Preserve, and Virgin Islands National Park in the United States Virgin Islands. Occurrence was highest at two subsites outside the RNA in DRTO, followed by two index sites in Biscayne National Park. Due to a high number of observations with zero urchins at many sites, the data were transformed using a negative binomial regression and delta lognormal transformation (Lo et al., 1992; Maunder & Punt 2004). The combined delta lognormal index determined that the probability of presence was the same between the zones inside the RNA and outside the RNA, but the abundance when present was different. When expanded to analyze urchins between Florida and Caribbean parks, the combined delta lognormal index again determined that the probability of presence was the same between the two regions, but the abundance when present was different. Weak correlations were found with depth and percent coral cover using Spearman’s rank coefficient and Kendall’s Tau correlation tests, but no firm trends could be determined. The delta lognormal index indicated that the urchins are unaffected by the presence of the RNA, and are faring similarly in national parks located in both Florida and the Caribbean. Abundance counts indicated that D. antillarum are recovering very slowly, if at all, within Florida and Caribbean national parks. Close monitoring of this keystone species should continue to search for clues as to why they have not recovered within these national parks.</p