Loss of cortactin causes endothelial barrier dysfunction via disturbed adrenomedullin secretion and actomyosin contractility

Plakoglobin does not participate in endothelial barrier stabilization mediated by cAMP

Critical for maintenance of endothelial barrier is the remodeling of the actin cytoskeleton and the precise control of junctional integrity. Plakoglobin (PG) is a structural and signaling protein involved in vascular permeability regulation together with key signaling molecules such as cAMP, Rho GTPases and actin-binding proteins. Here, we investigated the role of PG in cAMP-mediated endothelial barrier stabilization by establishing myocardial endothelial cells derived from wild type (WT) and PG knock-out (PG-KO) mice. Under basal conditions, TEER measurements showed increased barrier function of PG-KO, an effect associated with enhanced protein levels and junctional VE-cadherin and β-catenin accumulation. PG-KO cells also displayed more PECAM-1 and VE-PTP-phosphatase and less phosphorylated VE-cadherin, typically linked with modulation of junctional integrity. PG ablation neither changed the composition of VE-cadherin/β-catenin complex nor activities of Rac1 and RhoA but decreased the basal intracellular cAMP concentration. Remarkably, cAMP augmentation led to enhanced Rac1 activity and TEER in both cell lines, but the effect was less prominent in PG-KO. The tighter barrier in WT was paralleled with more VE-cadherin, β-catenin and cortactin, an actin-binding protein, towards junctions. Surprisingly, PG phosphorylation at Ser665 was not required for cAMP-mediated endothelial barrier integrity, which is different to cardiomyocyte and keratinocyte cell adhesion.

Plasma bioactive adrenomedullin predicts mortality and need for dialysis in critical COVID-19

COVID-19 is a severe respiratory disease affecting millions worldwide, causing significant morbidity and mortality. Adrenomedullin (bio-ADM) is a vasoactive hormone regulating the endothelial barrier and has been associated with COVID-19 mortality and other adverse events. This prospective cohort pilot study included 119 consecutive patients with verified SARS-CoV-2 infection admitted to two intensive care units (ICUs) in Southern Sweden. Bio-ADM was retrospectively analysed from plasma on ICU admission, and days 2 and 7. Information on comorbidities, adverse events and mortality was collected. The primary outcome was 90-day mortality, and secondary outcomes were markers of disease severity. The association between bio-ADM and outcomes was analysed using survival analysis and logistic regression. Bio-ADM on admission, day 2, and day 7 only moderately predicted 90-day mortality in univariate and multivariate Cox regression. The relative change in bio-ADM between sample times predicted 90-day mortality better even when adjusting for the SAPS3 score, with an HR of 1.09 (95% CI 1.04-1.15) and a C-index of 0.82 (95% CI 0.72-0.92) for relative change between day 2 and day 7. Bio-ADM had a good prediction of the need for renal replacement therapy in multivariate Cox regression adjusting for creatinine, where day 2 bio-ADM had an HR of 3.18 (95% CI 1.21-8.36) and C-index of 0.91 (95% CI 0.87-0.96). Relative changes did not perform better, possibly due to a small sample size. Admission and day 2 bio-ADM was associated with early acute kidney injury (AKI). Bio-ADM on ICU admission, day 2 and day 7 predicted 90-day mortality and dialysis needs, highlighting bio-ADM's importance in COVID-19 pathophysiology. Bio-ADM could be used to triage patients with a risk of adverse outcomes and as a potential target for clinical interventions.

Genetic and epigenetic regulation of cortactin (CTTN) by inflammatory factors and mechanical stress in human lung endothelial cells

RATIONALE

Cortactin, an actin-binding cytoskeletal protein, plays a crucial role in maintaining endothelial cell (EC) barrier integrity and regulating vascular permeability. The gene encoding cortactin, CTTN, is implicated in various lung inflammatory disorders. Despite this, the transcriptional regulation of CTTN by inflammatory stimuli and promoter SNPs remains unexplored.

METHODS

We transfected human lung ECs with a full-length CTTN promoters linked to a luciferase reporter to measure promoter activity. SNP-containing CTTN promoter was created via site-directed mutagenesis. Transfected ECs were exposed to LPS (PAMP), TNF-α (cytokine), cyclic stretch (CS), FG-4592 (HIF-inducer), NRF2 (anti-oxidant modulator), FTY-(S)-phosphate (endothelial barrier enhancer), and 5'-Aza (demethylation inducer). Immunohistochemistry was used to assess cortactin expression in mouse lungs exposed to LPS.

RESULTS

LPS, TNF-α, and 18%CS significantly increased CTTN promoter activities in a time-dependent manner (P<0.05). The variant rs34612166 (-212T/C) markedly enhanced LPS- and 18%CS- induced CTTN promoter activities (P<0.05). FG-4592 significantly boosted CTTN promoter activities (P<0.01), which were partially inhibited by HIF1α (KC7F2) and HIF2α (PT2385) inhibitors (P<0.05). NRF2 activator Bixin increased CTTN promoter activities, whereas NRF2 inhibitor Brusatol reduced them (P<0.05). 5'-Aza increased CTTN promoter activities by 2.9-fold (P<0.05). NF-κB response element mutations significantly reduced CTTN promoter activities response to LPS and TNFα. FTY-(S)-phosphate significantly increased CTTN promoter activities in 24 h. In vivo, cortactin levels were significantly elevated in inflammatory mouse lungs exposed to LPS for 18 h.

CONCLUSION

CTTN transcriptional is significantly influenced by inflammatory factors and promoter variants. Cortactin, essential in mitigating inflammatory edema, presents a promising therapeutic target to alleviate severe inflammatory disorders.

Arpin deficiency increases actomyosin contractility and vascular permeability

Arpin was discovered as an inhibitor of the Arp2/3 complex localized at the lamellipodial tip of fibroblasts, where it regulated migration steering. Recently, we showed that arpin stabilizes the epithelial barrier in an Arp2/3-dependent manner. However, the expression and functions of arpin in endothelial cells (EC) have not yet been described. Arpin mRNA and protein are expressed in EC and downregulated by pro-inflammatory cytokines. Arpin depletion in Human Umbilical Vein Endothelial Cells causes the formation of actomyosin stress fibers leading to increased permeability in an Arp2/3-independent manner. Instead, inhibitors of ROCK1 and ZIPK, kinases involved in the generation of stress fibers, normalize the loss-of-arpin effects on actin filaments and permeability. Arpin-deficient mice are viable but show a characteristic vascular phenotype in the lung including edema, microhemorrhage, and vascular congestion, increased F-actin levels, and vascular permeability. Our data show that, apart from being an Arp2/3 inhibitor, arpin is also a regulator of actomyosin contractility and endothelial barrier integrity.

The association of midregional pro-adrenomedullin (MR-proADM) at ICU admission and fluid overload in patients post elective cardiac surgery

Postoperative fluid overload (FO) after cardiac surgery is common and affects recovery. Predicting FO could help optimize fluid management. This post-hoc analysis of the HERACLES randomized controlled trial evaluated the predictive value of MR-proADM for FO post-cardiac surgery. MR-proADM levels were measured at four different timepoints in 33 patients undergoing elective cardiac surgery. Patients were divided into FO (> 5% weight gain) and no-FO at ICU discharge. The primary outcome was the predictive power of MR-proADM at ICU admission for FO at discharge. Secondary outcomes included the predictive value of MR-proADM for FO on day 6 post-surgery and changes over time. The association between MR-proADM and FO at ICU discharge or day 6 post-surgery was not significant (crude odds ratio (cOR): 4.3 (95% CI 0.5-40.9, p = 0.201) and cOR 1.1 (95% CI 0.04-28.3, p = 0.954)). MR-proADM levels over time did not differ significantly between patients with and without FO at ICU discharge (p = 0.803). MR-proADM at ICU admission was not associated with fluid overload at ICU discharge in patients undergoing elective cardiac surgery. MR-proADM levels over time were not significantly different between groups, although elevated levels were observed in patients with FO.

Ultrastructural Characterization of PBMCs and Extracellular Vesicles in Multiple Sclerosis: A Pilot Study

Growing evidence identifies extracellular vesicles (EVs) as important cell-to-cell signal transducers in autoimmune disorders, including multiple sclerosis (MS). If the etiology of MS still remains unknown, its molecular physiology has been well studied, indicating peripheral blood mononuclear cells (PBMCs) as the main pathologically relevant contributors to the disease and to neuroinflammation. Recently, several studies have suggested the involvement of EVs as key mediators of neuroimmune crosstalk in central nervous system (CNS) autoimmunity. To assess the role of EVs in MS, we applied electron microscopy (EM) techniques and Western blot analysis to study the morphology and content of plasma-derived EVs as well as the ultrastructure of PBMCs, considering four MS patients and four healthy controls. Through its exploratory nature, our study was able to detect significant differences between groups. Pseudopods and large vesicles were more numerous at the plasmalemma interface of cases, as were endoplasmic vesicles, resulting in an activated aspect of the PBMCs. Moreover, PBMCs from MS patients also showed an increased number of multivesicular bodies within the cytoplasm and amorphous material around the vesicles. In addition, we observed a high number of plasma-membrane-covered extensions, with multiple associated large vesicles and numerous autophagosomal vacuoles containing undigested cytoplasmic material. Finally, the study of EV cargo evidenced a number of dysregulated molecules in MS patients, including GANAB, IFI35, Cortactin, Septin 2, Cofilin 1, and ARHGDIA, that serve as inflammatory signals in a context of altered vesicular dynamics. We concluded that EM coupled with Western blot analysis applied to PBMCs and vesiculation can enhance our knowledge in the physiopathology of MS.

A Focus on the Pathophysiology of Adrenomedullin Expression: Endothelitis and Organ Damage in Severe Viral and Bacterial Infections

Adrenomedullin (ADM) is a peptide hormone produced primarily in the adrenal glands, playing a crucial role in various physiological processes. As well as improving vascular integrity and decreasing vascular permeability, ADM acts as a vasodilator, positive inotrope, diuretic, natriuretic and bronchodilator, antagonizing angiotensin II by inhibiting aldosterone secretion. ADM also has antihypertrophic, anti-apoptotic, antifibrotic, antioxidant, angiogenic and immunoregulatory effects and antimicrobial properties. ADM expression is upregulated by hypoxia, inflammation-inducing cytokines, viral or bacterial substances, strength of shear stress, and leakage of blood vessels. These pathological conditions are established during systemic inflammation that can result from infections, surgery, trauma/accidents or burns. The ability to rapidly identify infections and the prognostic, predictive power makes it a valuable tool in severe viral and bacterial infections burdened by high incidence and mortality. This review sheds light on the pathophysiological processes that in severe viral or bacterial infections cause endothelitis up to the development of organ damage, the resulting increase in ADM levels dosed through its more stable peptide mid-regional proadrenomedullin (MR-proADM), the most significant studies that attest to its diagnostic and prognostic accuracy in highlighting the severity of viral or bacterial infections and appropriate therapeutic insights.

Cortactin is in a complex with VE-cadherin and is required for endothelial adherens junction stability through Rap1/Rac1 activation

Vascular permeability is mediated by Cortactin (Cttn) and regulated by several molecules including cyclic-adenosine-monophosphate, small Rho family GTPases and the actin cytoskeleton. However, it is unclear whether Cttn directly interacts with any of the junctional components or if Cttn intervenes with signaling pathways affecting the intercellular contacts and the cytoskeleton. To address these questions, we employed immortalized microvascular myocardial endothelial cells derived from wild-type and Cttn-knock-out mice. We found that lack of Cttn compromised barrier integrity due to fragmented membrane distribution of different junctional proteins. Moreover, immunoprecipitations revealed that Cttn is within the VE-cadherin-based adherens junction complex. In addition, lack of Cttn slowed-down barrier recovery after Ca2+ repletion. The role of Cttn for cAMP-mediated endothelial barrier regulation was analyzed using Forskolin/Rolipram. In contrast to Cttn-KO, WT cells reacted with increased transendothelial electrical resistance. Absence of Cttn disturbed Rap1 and Rac1 activation in Cttn-depleted cells. Surprisingly, despite the absence of Cttn, direct activation of Rac1/Cdc42/RhoA by CN04 increased barrier resistance and induced well-defined cortical actin and intracellular actin bundles. In summary, our data show that Cttn is required for basal barrier integrity by allowing proper membrane distribution of junctional proteins and for cAMP-mediated activation of the Rap1/Rac1 signaling pathway.

Schisandrin A ameliorates increased pulmonary capillary endothelial permeability accompanied with sepsis through inhibition of RhoA/ROCK1/MLC pathways

BACKGROUND

Sepsis is a systemic inflammatory response, and vascular leakage associated with acute lung injury (ALI) is an important pathophysiological process during sepsis. Schisandrin A (SchA) is a bioactive lignan which has been reported to have the anti-inflammatory effects in many studies, while whether SchA can ameliorate ALI-related vascular leakage caused by sepsis is unknown.

OBJECTIVE

To evaluate the role and the underlying mechanism of SchA in increase of pulmonary vascular permeability induced by sepsis.

METHODS

The effect of SchA on pulmonary vascular permeability was examined in rat acute lung injury model. The effect of SchA on skin vascular permeability of mice was investigated through Miles assay. MTT assay was performed to detect the cell activity, and transwell assay was used to detect the effect of SchA on cell permeability. The effects of SchA on junction proteins and RhoA/ROCK1/MLC signaling pathway were manifested by immunofluorescence staining and western blot.

RESULTS

The administration of SchA alleviated rat pulmonary endothelial dysfunction, relieved increased permeability in the mouse skin and HUVECs induced by lipopolysaccharide (LPS). Meanwhile, SchA inhibited the formation of stress fibers, reversed the decrease of expression of ZO-1 and VE-cadherin. Subsequent experiments confirmed that SchA inhibited RhoA/ROCK1/MLC canonical pathway in rat lungs and HUVECs induced by LPS. Moreover, overexpression of RhoA reversed the inhibitory effect of SchA in HUVECs, which suggested that SchA protected the pulmonary endothelial barrier by inhibiting RhoA/ROCK1/MLC pathway.

CONCLUSION

In summary, our results indicate that SchA ameliorates the increase of pulmonary endothelial permeability induced by sepsis through inhibition of RhoA/ROCK1/MLC pathway, providing a potentially effective therapeutic strategy for sepsis.

Plasma bioactive adrenomedullin on intensive care unit admission is associated with acute respiratory distress syndrome: an observational study

BACKGROUND

Bioactive adrenomedullin (bio-ADM) is a vasoactive peptide with a key role in reducing vascular hyperpermeability and improving endothelial stability during infection, but it also has vasodilatory properties. Bioactive ADM has not been studied in conjunction with acute respiratory distress syndrome (ARDS), but it has recently been shown to correlate with outcomes after severe COVID-19. Therefore, this study investigated the association between circulating bio-ADM on intensive care unit (ICU) admission and ARDS. The secondary aim was the association between bio-ADM and ARDS mortality.

METHODS

We analysed bio-ADM levels and assessed the presence of ARDS in adult patients admitted to two general intensive care units in southern Sweden. Medical records were manually screened for the ARDS Berlin criteria. The association between bio-ADM levels and ARDS and mortality in ARDS patients was analysed using logistic regression and receiver-operating characteristics analysis. The primary outcome was an ARDS diagnosis within 72 h of ICU admission, and the secondary outcome was 30-day mortality.

RESULTS

Out of 1224 admissions, 11% (n = 132) developed ARDS within 72 h. We found that elevated admission bio-ADM level was associated with ARDS independently of sepsis status and of organ dysfunction as measured by the Sequential organ failure assessment (SOFA) score. Both lower levels (< 38 pg/L) and high (> 90 pg/L) levels of bio-ADM were independently (of the Simplified acute physiology score, SAPS-3) predictive of mortality. Patients with indirect mechanisms of lung injury had higher bio-ADM levels than those with a direct mechanism of injury, and bio-ADM increased with increasing ARDS severity.

CONCLUSIONS

High levels of bio-ADM on admission are associated with ARDS, and bio-ADM levels significantly differ depending on the injury mechanism. In contrast, both high and low levels of bio-ADM are associated with mortality, possibly due to the dual action of bio-ADM in stabilising the endothelial barrier and causing vasodilation. These findings could lead to improved diagnostic accuracy of ARDS and potentially lead to new therapeutic strategies.

APOLD1 loss causes endothelial dysfunction involving cell junctions, cytoskeletal architecture, and Weibel-Palade bodies, while disrupting hemostasis

Vascular homeostasis is impaired in various diseases thereby contributing to the progression of their underlying pathologies. The endothelial immediate early gene Apolipoprotein L domain-containing 1 (APOLD1) helps to regulate endothelial function. However, its precise role in endothelial cell biology remains unclear. We have localized APOLD1 to endothelial cell contacts and to Weibel-Palade bodies (WPB) where it associates with von Willebrand factor (VWF) tubules. Silencing of APOLD1 in primary human endothelial cells disrupted the cell junction-cytoskeletal interface, thereby altering endothelial permeability accompanied by spontaneous release of WPB contents. This resulted in an increased presence of WPB cargoes, notably VWF and angiopoietin-2 in the extracellular medium. Autophagy flux, previously recognized as an essential mechanism for the regulated release of WPB, was impaired in the absence of APOLD1. In addition, we report APOLD1 as a candidate gene for a novel inherited bleeding disorder across three generations of a large family in which an atypical bleeding diathesis was associated with episodic impaired microcirculation. A dominant heterozygous nonsense APOLD1:p.R49* variant segregated to affected family members. Compromised vascular integrity resulting from an excess of plasma angiopoietin-2, and locally impaired availability of VWF may explain the unusual clinical profile of APOLD1:p.R49* patients. In summary, our findings identify APOLD1 as an important regulator of vascular homeostasis and raise the need to consider testing of endothelial cell function in patients with inherited bleeding disorders without apparent platelet or coagulation defects.

TRIM40 is a pathogenic driver of inflammatory bowel disease subverting intestinal barrier integrity

The cortical actin cytoskeleton plays a critical role in maintaining intestinal epithelial integrity, and the loss of this architecture leads to chronic inflammation, as seen in inflammatory bowel disease (IBD). However, the exact mechanisms underlying aberrant actin remodeling in pathological states remain largely unknown. Here, we show that a subset of patients with IBD exhibits substantially higher levels of tripartite motif-containing protein 40 (TRIM40), a gene that is hardly detectable in healthy individuals. TRIM40 is an E3 ligase that directly targets Rho-associated coiled-coil-containing protein kinase 1 (ROCK1), an essential kinase involved in promoting cell-cell junctions, markedly decreasing the phosphorylation of key signaling factors critical for cortical actin formation and stabilization. This causes failure of the epithelial barrier function, thereby promoting a long-lived inflammatory response. A mutant TRIM40 lacking the RING, B-box, or C-terminal domains has impaired ability to accelerate ROCK1 degradation-driven cortical actin disruption. Accordingly, Trim40-deficient male mice are highly resistant to dextran sulfate sodium (DSS)-induced colitis. Our findings highlight that aberrant upregulation of TRIM40, which is epigenetically silenced under healthy conditions, drives IBD by subverting cortical actin formation and exacerbating epithelial barrier dysfunction.

TLR4 activation induces inflammatory vascular permeability via Dock1 targeting and NOX4 upregulation

The loss of vascular integrity is a cardinal feature of acute inflammatory responses evoked by activation of the TLR4 inflammatory cascade. Utilizing in vitro and in vivo models of inflammatory lung injury, we explored TLR4-mediated dysregulated signaling that results in the loss of endothelial cell (EC) barrier integrity and vascular permeability, focusing on Dock1 and Elmo1 complexes that are intimately involved in regulation of Rac1 GTPase activity, a well recognized modulator of vascular integrity. Marked reductions in Dock1 and Elmo1 expression was observed in lung tissues (porcine, rat, mouse) exposed to TLR4 ligand-mediated acute inflammatory lung injury (LPS, eNAMPT) in combination with injurious mechanical ventilation. Lung tissue levels of Dock1 and Elmo1 were preserved in animals receiving an eNAMPT-neutralizing mAb in conjunction with highly significant decreases in alveolar edema and lung injury severity, consistent with Dock1/Elmo1 as pathologic TLR4 targets directly involved in inflammation-mediated loss of vascular barrier integrity. In vitro studies determined that pharmacologic inhibition of Dock1-mediated activation of Rac1 (TBOPP) significantly exacerbated TLR4 agonist-induced EC barrier dysfunction (LPS, eNAMPT) and attenuated increases in EC barrier integrity elicited by barrier-enhancing ligands of the S1P1 receptor (sphingosine-1-phosphate, Tysiponate). The EC barrier-disrupting influence of Dock1 inhibition on S1PR1 barrier regulation occurred in concert with: 1) suppressed formation of EC barrier-enhancing lamellipodia, 2) altered nmMLCK-mediated MLC2 phosphorylation, and 3) upregulation of NOX4 expression and increased ROS. These studies indicate that Dock1 is essential for maintaining EC junctional integrity and is a critical target in TLR4-mediated inflammatory lung injury.

Lack of adducin impairs the stability of endothelial adherens and tight junctions and may be required for cAMP-Rac1-mediated endothelial barrier stabilization

Adducin (Add) is an actin binding protein participating in the stabilization of actin/spectrin networks, epithelial junctional turnover and cardiovascular disorders such as hypertension. Recently, we demonstrated that Add is required for adherens junctions (AJ) integrity. Here we hypothesized that Add regulates tight junctions (TJ) as well and may play a role in cAMP-mediated barrier enhancement. We evaluated the role of Add in MyEnd cells isolated from WT and Add-Knock-Out (KO) mice. Our results indicate that the lack of Add drastically alters the junctional localization and protein levels of major AJ and TJ components, including VE-Cadherin and claudin-5. We also showed that cAMP signaling induced by treatment with forskolin and rolipram (F/R) enhances the barrier integrity of WT but not Add-KO cells. The latter showed no junctional reorganization upon cAMP increase. The absence of Add also led to higher protein levels of the small GTPases Rac1 and RhoA. In vehicle-treated cells the activation level of Rac1 did not differ significantly when WT and Add-KO cells were compared. However, the lack of Add led to increased activity of RhoA. Moreover, F/R treatment triggered Rac1 activation only in WT cells. The function of Rac1 and RhoA per se was unaffected by the total ablation of Add, since direct activation with CN04 was still possible in both cell lines and led to improved endothelial barrier function. In the current study, we demonstrate that Add is required for the maintenance of endothelial barrier by regulating both AJ and TJ. Our data show that Add may act upstream of Rac1 as it is necessary for its activation via cAMP.

Respiratory syncytial virus disrupts the airway epithelial barrier by decreasing cortactin and destabilizing F-actin

Respiratory syncytial virus (RSV) infection is the leading cause of acute lower respiratory tract infection in young children worldwide. Our group recently revealed that RSV infection disrupts the airway epithelial barrier in vitro and in vivo. However, the underlying molecular pathways were still elusive. Here, we report the critical roles of the filamentous actin (F-actin) network and actin-binding protein cortactin in RSV infection. We found that RSV infection causes F-actin depolymerization in 16HBE cells, and that stabilizing the F-actin network in infected cells reverses the epithelial barrier disruption. RSV infection also leads to significantly decreased cortactin in vitro and in vivo. Cortactin-knockout 16HBE cells presented barrier dysfunction, whereas overexpression of cortactin protected the epithelial barrier against RSV. The activity of Rap1 (which has Rap1A and Rap1B forms), one downstream target of cortactin, declined after RSV infection as well as in cortactin-knockout cells. Moreover, activating Rap1 attenuated RSV-induced epithelial barrier disruption. Our study proposes a key mechanism in which RSV disrupts the airway epithelial barrier via attenuating cortactin expression and destabilizing the F-actin network. The identified pathways will provide new targets for therapeutic intervention toward RSV-related disease. This article has an associated First Person interview with the first author of the paper.

Estrogen modulation of the pronociceptive effects of serotonin on female rat trigeminal sensory neurons is timing dependent and dosage dependent and requires estrogen receptor alpha

ABSTRACT

The role of the major estrogen estradiol (E2) on orofacial pain conditions remains controversial with studies reporting both a pronociceptive and antinociceptive role of E2. E2 modulation of peripheral serotonergic activity may be one mechanism underlying the female prevalence of orofacial pain disorders. We recently reported that female rats in proestrus and estrus exhibit greater serotonin (5HT)-evoked orofacial nocifensive behaviors compared with diestrus and male rats. Further coexpression of 5HT 2A receptor mRNA in nociceptive trigeminal sensory neurons that express transient receptor potential vanilloid 1 ion channels contributes to pain sensitization. E2 may exacerbate orofacial pain through 5HT-sensitive trigeminal nociceptors, but whether low or high E2 contributes to orofacial pain and by what mechanism remains unclear. We hypothesized that steady-state exposure to a proestrus level of E2 exacerbates 5HT-evoked orofacial nocifensive behaviors in female rats, explored the transcriptome of E2-treated female rats, and determined which E2 receptor contributes to sensitization of female trigeminal sensory neurons. We report that a diestrus level of E2 is protective against 5HT-evoked orofacial pain behaviors, which increase with increasing E2 concentrations, and that E2 differentially alters several pain genes in the trigeminal ganglia. Furthermore, E2 receptors coexpressed with 5HT 2A and transient receptor potential vanilloid 1 and enhanced capsaicin-evoked signaling in the trigeminal ganglia through estrogen receptor α. Overall, our data indicate that low, but not high, physiological levels of E2 protect against orofacial pain, and we provide evidence that estrogen receptor α receptor activation, but not others, contributes to sensitization of nociceptive signaling in trigeminal sensory neurons.

Regulation and Dysregulation of Endothelial Permeability during Systemic Inflammation

Systemic inflammation can be triggered by infection, surgery, trauma or burns. During systemic inflammation, an overshooting immune response induces tissue damage resulting in organ dysfunction and mortality. Endothelial cells make up the inner lining of all blood vessels and are critically involved in maintaining organ integrity by regulating tissue perfusion. Permeability of the endothelial monolayer is strictly controlled and highly organ-specific, forming continuous, fenestrated and discontinuous capillaries that orchestrate the extravasation of fluids, proteins and solutes to maintain organ homeostasis. In the physiological state, the endothelial barrier is maintained by the glycocalyx, extracellular matrix and intercellular junctions including adherens and tight junctions. As endothelial cells are constantly sensing and responding to the extracellular environment, their activation by inflammatory stimuli promotes a loss of endothelial barrier function, which has been identified as a hallmark of systemic inflammation, leading to tissue edema formation and hypotension and thus, is a key contributor to lethal outcomes. In this review, we provide a comprehensive summary of the major players, such as the angiopoietin-Tie2 signaling axis, adrenomedullin and vascular endothelial (VE-) cadherin, that substantially contribute to the regulation and dysregulation of endothelial permeability during systemic inflammation and elucidate treatment strategies targeting the preservation of vascular integrity.

A cortactin CTTN coding SNP contributes to lung vascular permeability and inflammatory disease severity in African descent subjects

The cortactin gene (CTTN), encoding an actin-binding protein critically involved in cytoskeletal dynamics and endothelial cell (EC) barrier integrity, contains single nucleotide polymorphisms (SNPs) associated with severe asthma in Black patients. As loss of lung EC integrity is a major driver of mortality in the Acute Respiratory Distress Syndrome (ARDS), sepsis, and the acute chest syndrome (ACS), we speculated CTTN SNPs that alter EC barrier function will associate with clinical outcomes from these types of conditions in Black patients. In case-control studies, evaluation of a nonsynonymous CTTN coding SNP Ser484Asn (rs56162978, G/A) in a severe sepsis cohort (725 Black subjects) revealed significant association with increased risk of sepsis mortality. In a separate cohort of sickle cell disease (SCD) subjects with and without ACS (177 SCD Black subjects), significantly increased risk of ACS and increased ACS severity (need for mechanical ventilation) was observed in carriers of the A allele. Human lung EC expressing the cortactin S484N transgene exhibited: (i) delayed EC barrier recovery following thrombin-induced permeability; (ii) reduced levels of critical Tyr486 cortactin phosphorylation; (iii) inhibited binding to the cytoskeletal regulator, nmMLCK; and (iv) attenuated EC barrier-promoting lamellipodia dynamics and biophysical responses. ARDS-challenged Cttn+/- heterozygous mice exhibited increased lung vascular permeability (compared to wild-type mice) which was significantly attenuated by IV delivery of liposomes encargoed with CTTN WT transgene but not by CTTN S484N transgene. In summary, these studies suggest that the CTTN S484N coding SNP contributes to severity of inflammatory injury in Black patients, potentially via delayed vascular barrier restoration.

Unlocking the Untapped Potential of Endothelial Kinase and Phosphatase Involvement in Sepsis for Drug Treatment Design

Sepsis is a devastating clinical condition that can lead to multiple organ failure and death. Despite advancements in our understanding of molecular mechanisms underlying sepsis and sepsis-associated multiple organ failure, no effective therapeutic treatment to directly counteract it has yet been established. The endothelium is considered to play an important role in sepsis. This review highlights a number of signal transduction pathways involved in endothelial inflammatory activation and dysregulated endothelial barrier function in response to sepsis conditions. Within these pathways – NF-κB, Rac1/RhoA GTPases, AP-1, APC/S1P, Angpt/Tie2, and VEGF/VEGFR2 – we focus on the role of kinases and phosphatases as potential druggable targets for therapeutic intervention. Animal studies and clinical trials that have been conducted for this purpose are discussed, highlighting reasons why they might not have resulted in the expected outcomes, and which lessons can be learned from this. Lastly, opportunities and challenges that sepsis and sepsis-associated multiple organ failure research are currently facing are presented, including recommendations on improved experimental design to increase the translational power of preclinical research to the clinic.

Cortactin in Lung Cell Function and Disease

Cortactin (CTTN) is an actin-binding and cytoskeletal protein that is found in abundance in the cell cortex and other peripheral structures of most cell types. It was initially described as a target for Src-mediated phosphorylation at several tyrosine sites within CTTN, and post-translational modifications at these tyrosine sites are a primary regulator of its function. CTTN participates in multiple cellular functions that require cytoskeletal rearrangement, including lamellipodia formation, cell migration, invasion, and various other processes dependent upon the cell type involved. The role of CTTN in vascular endothelial cells is particularly important for promoting barrier integrity and inhibiting vascular permeability and tissue edema. To mediate its functional effects, CTTN undergoes multiple post-translational modifications and interacts with numerous other proteins to alter cytoskeletal structures and signaling mechanisms. In the present review, we briefly describe CTTN structure, post-translational modifications, and protein binding partners and then focus on its role in regulating cellular processes and well-established functional mechanisms, primarily in vascular endothelial cells and disease models. We then provide insights into how CTTN function affects the pathophysiology of multiple lung disorders, including acute lung injury syndromes, COPD, and asthma.

ROCK Inhibition as Potential Target for Treatment of Pulmonary Hypertension

Pulmonary hypertension (PH) is a cardiovascular disease caused by extensive vascular remodeling in the lungs, which ultimately leads to death in consequence of right ventricle (RV) failure. While current drugs for PH therapy address the sustained vasoconstriction, no agent effectively targets vascular cell proliferation and tissue inflammation. Rho-associated protein kinases (ROCKs) emerged in the last few decades as promising targets for PH therapy, since ROCK inhibitors demonstrated significant anti-remodeling and anti-inflammatory effects. In this review, current aspects of ROCK inhibition therapy are discussed in relation to the treatment of PH and RV dysfunction, from cell biology to preclinical and clinical studies.

Genome-wide landscape of mRNAs, microRNAs, lncRNAs, and circRNAs in hemorrhagic shock-induced ALI/ARDS in rats

BACKGROUND

Hemorrhagic shock (HS) can develop into multiple organ dysfunction syndrome, among which acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) usually lead to poor outcomes. The underlying molecular mechanisms of HS-induced ALI/ARDS remain unclear. This study sought to investigate gene expression profiles and predict competing endogenous RNA (ceRNA) regulatory networks in an HS-induced ALI/ARDS preclinical model.

METHODS

Sprague Dawley rats were subjected to a fixed volume of hemorrhage (HS, 40% estimated total blood volume) or not (sham) randomly. After 8 hours of observation, left lung tissue was harvested to evaluate lung injury. Right lung was collected for RNA sequencing. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway analyses were performed and the long noncoding RNA (lncRNA)/circular RNA (circRNA)-microRNA (miRNA)-messenger RNA (mRNA) linkages were predicted using the ceRNA theory. Quantitative real-time polymerase chain reaction was used to validate the RNA sequencing findings.

RESULTS

Hemorrhagic shock lungs showed noticeable ALI/ARDS features, and 437 mRNAs, 31 miRNAs, 734 lncRNAs, and 29 circRNAs were differentially expressed. In Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway analyses, the differentially expressed transcripts were enriched in the following terms: the metabolic pathways, signal transduction pathways, necroptosis, DNA damage recognition and repair, inflammatory cell migration and chemotaxis, the NOD-like receptor signaling pathway, the Janus kinase/signal transducer and activator of transcription signaling pathway, the mitogen-activated protein kinase signaling pathway, the phosphatidylinositol-3-kinase/protein kinase B signaling pathway, and so on. Also, this study identified lncRNA-miRNA-mRNA linkages with 12 lncRNAs, 5 miRNAs, 15 mRNAs, and circRNA-miRNA-mRNA linkages with 10 circRNAs, 16 miRNAs, 39 mRNAs. These networks might play important regulatory roles.

CONCLUSION

This is the first high-throughput analysis of gene expression profiles in HS-induced ALI/ARDS. It shows that metabolism, cell signaling, DNA damage and repair, and necroptosis-related RNAs altered, and inflammatory response-associated RNAs and pathways have pivotal roles in HS-induced ALI/ARDS progression. It also prompts some important RNAs and regulatory networks for future research.

LEVEL OF EVIDENCE

Basic science article.

Molecular Dambusters: What Is Behind Hyperpermeability in Bradykinin-Mediated Angioedema?

In the last few decades, a substantial body of evidence underlined the pivotal role of bradykinin in certain types of angioedema. The formation and breakdown of bradykinin has been studied thoroughly; however, numerous questions remained open regarding the triggering, course, and termination of angioedema attacks. Recently, it became clear that vascular endothelial cells have an integrative role in the regulation of vessel permeability. Apart from bradykinin, a great number of factors of different origin, structure, and mechanism of action are capable of modifying the integrity of vascular endothelium, and thus, may participate in the regulation of angioedema formation. Our aim in this review is to describe the most important permeability factors and the molecular mechanisms how they act on endothelial cells. Based on endothelial cell function, we also attempt to explain some of the challenging findings regarding bradykinin-mediated angioedema, where the function of bradykinin itself cannot account for the pathophysiology. By deciphering the complex scenario of vascular permeability regulation and edema formation, we may gain better scientific tools to be able to predict and treat not only bradykinin-mediated but other types of angioedema as well.

Cx43 and the Actin Cytoskeleton: Novel Roles and Implications for Cell-Cell Junction-Based Barrier Function Regulation

Barrier function is a vital homeostatic mechanism employed by epithelial and endothelial tissue. Diseases across a wide range of tissue types involve dynamic changes in transcellular junctional complexes and the actin cytoskeleton in the regulation of substance exchange across tissue compartments. In this review, we focus on the contribution of the gap junction protein, Cx43, to the biophysical and biochemical regulation of barrier function. First, we introduce the structure and canonical channel-dependent functions of Cx43. Second, we define barrier function and examine the key molecular structures fundamental to its regulation. Third, we survey the literature on the channel-dependent roles of connexins in barrier function, with an emphasis on the role of Cx43 and the actin cytoskeleton. Lastly, we discuss findings on the channel-independent roles of Cx43 in its associations with the actin cytoskeleton and focal adhesion structures highlighted by PI3K signaling, in the potential modulation of cellular barriers. Mounting evidence of crosstalk between connexins, the cytoskeleton, focal adhesion complexes, and junctional structures has led to a growing appreciation of how barrier-modulating mechanisms may work together to effect solute and cellular flux across tissue boundaries. This new understanding could translate into improved therapeutic outcomes in the treatment of barrier-associated diseases.

Epac1 Is Crucial for Maintenance of Endothelial Barrier Function through A Mechanism Partly Independent of Rac1

Epac1 (exchange protein activated by cAMP) stabilizes the endothelial barrier, but detailed studies are limited by the side effects of pharmacological Epac1 modulators and transient transfections. Here, we compare the key properties of barriers between endothelial cells derived from wild-type (WT) and Epac1-knockout (KO) mice myocardium. We found that KO cell layers, unlike WT layers, had low and cAMP-insensitive trans-endothelial resistance (TER). They also had fragmented VE-cadherin staining despite having augmented cAMP levels and increased protein expression of Rap1, Rac1, RhoA, and VE-cadherin. The simultaneous direct activation of Rac1 and RhoA by CN04 compensated Epac1 loss, since TER was increased. In KO-cells, inhibition of Rac1 activity had no additional effect on TER, suggesting that other mechanisms compensate the inhibition of the Rac1 function to preserve barrier properties. In summary, Epac1 is crucial for baseline and cAMP-mediated barrier stabilization through mechanisms that are at least partially independent of Rac1.

Cortactin Interacts with Hepatitis C Virus Core and NS5A Proteins: Implications for Virion Assembly

Hepatitis C virus (HCV) exploits cellular proteins to facilitate viral propagation. To identify the cellular factors involved in the HCV life cycle, we previously performed protein microarray assays using either HCV nonstructural 5A (NS5A) protein or core protein as a probe. Interestingly, cellular cortactin strongly interacted with both NS5A and core. Cortactin is an actin-binding protein critically involved in tumor progression by regulating the migration and invasion of cancerous cells. Protein interaction between cortactin and NS5A or core was confirmed by coimmunoprecipitation and immunofluorescence assays. We showed that cortactin interacted with NS5A and core via the N-terminal acidic domain of cortactin. Cortactin expression levels were not altered by HCV infection. Small interfering RNA (siRNA)-mediated knockdown of cortactin dramatically decreased HCV protein expression and infectivity levels, whereas overexpression of cortactin increased viral propagation. Ectopic expression of the siRNA-resistant cortactin recovered the viral infectivity, suggesting that cortactin was specifically required for HCV propagation. We further showed that cortactin was involved in the assembly step without affecting viral entry, HCV internal ribosome entry site (IRES)-mediated translation, and the replication steps of the HCV life cycle. Of note, silencing of cortactin markedly reduced both NS5A and core protein levels on the lipid droplets (LDs), and this effect was reversed by the overexpression of cortactin. Importantly, NS5A and core promoted cell migration by activating the phosphorylation of cortactin at tyrosine residues 421 and 466. Taken together, these data suggest that cortactin is not only involved in HCV assembly but also plays an important role in the cell migration.IMPORTANCE Cortactin is a cytoskeletal protein that regulates cell migration in response to a number of extracellular stimuli. The functional involvement of cortactin in the virus life cycle is not yet fully understood. The most significant finding is that cortactin strongly interacted with both hepatitis C virus (HCV) core and NS5A. Cortactin is involved in HCV assembly by tethering core and NS5A on the lipid droplets (LDs) with no effect on LD biogenesis. It was noteworthy that HCV NS5A and core activated cortactin by phosphorylation at tyrosines 421 and 466 to regulate cell migration. Collectively, our study shows that cortactin is a novel host factor involved in viral production and HCV-associated pathogenesis.

Molecular Mechanisms of Class B GPCR Activation: Insights from Adrenomedullin Receptors

Adrenomedullin (AM) is a 52 amino acid peptide that plays a regulatory role in the vasculature. Receptors for AM comprise the class B G protein-coupled receptor, the calcitonin-like receptor (CLR), in complex with one of three receptor activity-modifying proteins (RAMPs). The C-terminus of AM is involved in binding to the extracellular domain of the receptor, while the N-terminus is proposed to interact with the juxtamembranous portion of the receptor to activate signaling. There is currently limited information on the molecular determinants involved in AM signaling, thus we set out to define the importance of the AM N-terminus through five signaling pathways (cAMP production, ERK phosphorylation, CREB phosphorylation, Akt phosphorylation, and IP1 production). We characterized the three CLR:RAMP complexes through the five pathways, finding that each had a distinct repertoire of intracellular signaling pathways that it is able to regulate. We then performed an alanine scan of AM from residues 15-31 and found that most residues could be substituted with only small effects on signaling, and that most substitutions affected signaling through all receptors and pathways in a similar manner. We identify F18, T20, L26, and I30 as being critical for AM function, while also identifying an analogue (AM15-52 G19A) which has unique signaling properties relative to the unmodified AM. We interpret our findings in the context of new structural information, highlighting the complementary nature of structural biology and functional assays.

Actin-Binding Protein Cortactin Promotes Pathogenesis of Experimental Autoimmune Encephalomyelitis by Supporting Leukocyte Infiltration into the Central Nervous System

Leukocyte entry into the central nervous system (CNS) is essential for immune surveillance but is also the basis for the development of pathologic inflammatory conditions within the CNS, such as multiple sclerosis and its animal model, experimental autoimmune encephalomyelitis (EAE). The actin-binding protein, cortactin, in endothelial cells is an important player in regulating the interaction of immune cells with the vascular endothelium. Cortactin has been shown to control the integrity of the endothelial barrier and to support neutrophil transendothelial migration in vitro and in vivo in the skin. Here we use cortactin gene-inactivated male and female mice to study the role of this protein in EAE. Inducing EAE by immunization with a myelin oligodendrocyte glycoprotein peptide (MOG_35-55) revealed an ameliorated disease course in cortactin gene-deficient female mice compared with WT mice. However, proliferation capacity and expression of IL-17A and IFNγ by cortactin-deficient and WT splenocytes did not differ, suggesting that the lack of cortactin does not affect induction of the immune response. Rather, cortactin deficiency caused decreased vascular permeability and reduced leukocyte infiltration into the brains and spinal cords of EAE mice. Accordingly, cortactin gene-deficient mice had smaller numbers of proinflammatory cuffs, less extensive demyelination, and reduced expression levels of proinflammatory cytokines within the neural tissue compared with WT littermates. Thus, cortactin contributes to the development of neural inflammation by supporting leukocyte transmigration through the blood-brain barrier and, therefore, represents a potential candidate for targeting CNS autoimmunity.SIGNIFICANCE STATEMENT Multiple sclerosis is an autoimmune neuroinflammatory disorder, based on the entry of inflammatory leukocytes into the CNS where these cells cause demyelination and neurodegeneration. Here, we use a mouse model for multiple sclerosis, experimental autoimmune encephalomyelitis, and show that gene inactivation of cortactin, an actin binding protein that modulates actin dynamics and branching, protects against neuroinflammation in experimental autoimmune encephalomyelitis. Leukocyte infiltration into the CNS was inhibited in cortactin-deficient mice, and lack of cortactin in cultured primary brain endothelial cells inhibited leukocyte transmigration. Expression levels of proinflammatory cytokines in the CNS and induction of vascular permeability were reduced. We conclude that cortactin represents a novel potential target for the treatment of multiple sclerosis.

Vascular Effects of Adrenomedullin and the Anti-Adrenomedullin Antibody Adrecizumab in Sepsis

Sepsis remains a major scientific and medical challenge, for which, apart from significant refinements in supportive therapy, treatment has barely changed over the last few decades. During sepsis, both vascular tone and vascular integrity are compromised, and contribute to the development of shock. The free circulating peptide adrenomedullin (ADM) is involved in the regulation of the endothelial barrier function and tone of blood vessels. Several animal studies have shown that ADM administration improves outcome of sepsis. However, in higher dosages, ADM administration may cause hypotension, limiting its clinical applicability. Moreover, ADM has a very short half-life and easily adheres to surfaces, further hampering its clinical use. The non-neutralizing anti-ADM antibody Adrecizumab (HAM8101) which causes a long-lasting increase of plasma ADM has shown promising results in animal models of systemic inflammation and sepsis; it reduced inflammation, attenuated vascular leakage, and improved hemodynamics, kidney function, and survival. Combined with an excellent safety profile derived from animal and phase I human studies, Adrecizumab represents a promising candidate drug for the adjunctive treatment of sepsis. In this review, we first provide a brief overview of the currently available data on the role of adrenomedullin in sepsis and describe its effects on endothelial barrier function and vasodilation. Furthermore, we provide a novel hypothesis concerning the mechanisms of action through which Adrecizumab may exert its beneficial effects in sepsis.

Small GTPase Rap1A/B Is Required for Lymphatic Development and Adrenomedullin-Induced Stabilization of Lymphatic Endothelial Junctions

Objective- Maintenance of lymphatic permeability is essential for normal lymphatic function during adulthood, but the precise signaling pathways that control lymphatic junctions during development are not fully elucidated. The G_s-coupled AM (adrenomedullin) signaling pathway is required for embryonic lymphangiogenesis and the maintenance of lymphatic junctions during adulthood. Thus, we sought to elucidate the downstream effectors mediating junctional stabilization in lymphatic endothelial cells. Approach and Results- We knocked-down both Rap1A and Rap1B isoforms in human neonatal dermal lymphatic cells (human lymphatic endothelial cells) and genetically deleted the mRap1 gene in lymphatic endothelial cells by producing 2 independent, conditional Rap1a/b knockout mouse lines. Rap1A/B knockdown caused disrupted junctional formation with hyperpermeability and impaired AM-induced lymphatic junctional tightening, as well as rescue of histamine-induced junctional disruption. Less than 60% of lymphatic- Rap1a/b knockout embryos survived to E13.5 exhibiting interstitial edema, blood-filled lymphatics, disrupted lymphovenous valves, and defective lymphangiogenesis. Consistently, inducible lymphatic- Rap1a/b deletion in adult animals prevented AM-rescue of histamine-induced lymphatic leakage and dilation. Conclusions- Rap1 (Ras-related protein) serves as the dominant effector downstream of AM to stabilize lymphatic junctions. Rap1 is required for maintaining lymphatic permeability and driving normal lymphatic development.

Shear stress-induced endothelial adrenomedullin signaling regulates vascular tone and blood pressure

Hypertension is a primary risk factor for cardiovascular diseases including myocardial infarction and stroke. Major determinants of blood pressure are vasodilatory factors such as nitric oxide (NO) released from the endothelium under the influence of fluid shear stress exerted by the flowing blood. Several endothelial signaling processes mediating fluid shear stress-induced formation and release of vasodilatory factors have been described. It is, however, still poorly understood how fluid shear stress induces these endothelial responses. Here we show that the endothelial mechanosensitive cation channel PIEZO1 mediated fluid shear stress-induced release of adrenomedullin, which in turn activated its Gs-coupled receptor. The subsequent increase in cAMP levels promoted the phosphorylation of endothelial NO synthase (eNOS) at serine 633 through protein kinase A (PKA), leading to the activation of the enzyme. This Gs/PKA-mediated pathway synergized with the AKT-mediated pathways leading to eNOS phosphorylation at serine 1177. Mice with endothelium-specific deficiency of adrenomedullin, the adrenomedullin receptor, or Gαs showed reduced flow-induced eNOS activation and vasodilation and developed hypertension. Our data identify fluid shear stress-induced PIEZO1 activation as a central regulator of endothelial adrenomedullin release and establish the adrenomedullin receptor and subsequent Gs-mediated formation of cAMP as a critical endothelial mechanosignaling pathway regulating basal endothelial NO formation, vascular tone, and blood pressure.

High cortactin expression in B-cell acute lymphoblastic leukemia is associated with increased transendothelial migration and bone marrow relapse

Cancer is a major cause of death in children worldwide, with B-lineage cell acute lymphoblastic leukemia (B-ALL) being the most frequent childhood malignancy. Relapse, treatment failure and organ infiltration worsen the prognosis, warranting a better understanding of the implicated mechanisms. Cortactin is an actin-binding protein involved in cell adhesion and migration that is overexpressed in many solid tumors and in adult B-cell chronic lymphocytic leukemia. Here, we investigated cortactin expression and potential impact on infiltration and disease prognosis in childhood B-ALL. B-ALL cell lines and precursor cells from bone marrow (BM) and cerebrospinal fluid (CSF) of B-ALL patients indeed overexpressed cortactin. In CXCL12-induced transendothelial migration assays, transmigrated B-ALL cells had highest cortactin expression. In xenotransplantation models, only cortactinhigh-leukemic cells infiltrated lungs, brain, and testis; and they colonized more easily hypoxic BM organoids. Importantly, cortactin-depleted B-ALL cells were significantly less efficient in transendothelial migration, organ infiltration and BM colonization. Clinical data highlighted a significant correlation between high cortactin levels and BM relapse in drug-resistant high-risk B-ALL patients. Our results emphasize the importance of cortactin in B-ALL organ infiltration and BM relapse and its potential as diagnostic tool to identify high-risk patients and optimize their treatments.

Histidine-rich glycoprotein ameliorates endothelial barrier dysfunction through regulation of NF-κB and MAPK signal pathway

Background and Purpose

Microvascular barrier breakdown is a hallmark of sepsis that is associated with sepsis‐induced multiorgan failure. Histidine‐rich glycoprotein (HRG) is a 75‐kDa plasma protein that was demonstrated to improve the survival of septic mice through regulation of cell shape, spontaneous ROS production in neutrophils, and adhesion of neutrophils to vascular endothelial cells. We investigated HRG's role in the LPS/TNF‐α‐induced barrier dysfunction of endothelial cells in vitro and in vivo and the possible mechanism, to clarify the definitive roles of HRG in sepsis.

Experimental Approach

EA.hy 926 endothelial cells were pretreated with HRG or human serum albumin before stimulation with LPS/TNF‐α. A variety of biochemical assays were applied to explore the underlying molecular mechanisms on how HRG protected the barrier function of vascular endothelium.

Key Results

Immunostaining results showed that HRG maintains the endothelial monolayer integrity by inhibiting cytoskeleton reorganization, losses of VE‐cadherin and β‐catenin, focal adhesion kinase degradation, and cell detachment induced by LPS/TNF‐α. HRG also inhibited the cytokine secretion from endothelial cells induced by LPS/TNF‐α, which was associated with reduced NF‐κB activation. Moreover, HRG effectively prevented the LPS/TNF‐α‐induced increase in capillary permeability in vitro and in vivo. Finally, Western blot results demonstrated that HRG prevented the phosphorylation of MAPK family and RhoA activation, which are involved mainly in the regulation of cytoskeleton reorganization and barrier permeability.

Conclusions and Implications

Taken together, our results demonstrate that HRG has protective effects on vascular barrier function in vitro and in vivo, which may be due to the inhibition of MAPK family and Rho activation.

Chloride intracellular channel protein 2 in cancer and non-cancer human tissues: relationship with tight junctions

Chloride intracellular channel protein 2 (CLIC2) belongs to the CLIC family of conserved metazoan proteins. Although CLICs have been identified as chloride channels, they are currently considered multifunctional proteins. CLIC2 is the least studied family member. We investigated CLIC2 expression and localization in human hepatocellular carcinoma, metastatic colorectal cancer in the liver, and colorectal cancer. Significant expression of mRNAs encoding CLIC1, 2, 4, and 5 were found in the human tissues, but only CLIC2 was predominantly expressed in non-cancer tissues surrounding cancer masses. Fibrotic or dysfunctional (aspartate aminotransferase ≥40) non-cancer liver tissues and advanced stage HCC tissues expressed low levels of CLIC2. Endothelial cells lining blood vessels but not lymphatic vessels in non-cancer tissues expressed CLIC2 as well as high levels of the tight junction proteins claudins 1 and 5, occludin, and ZO-1. Most endothelial cells in blood vessels in cancer tissues had very low expressions of CLIC2 and tight junction proteins. CD31⁺/CD45⁻ endothelial cells isolated from non-cancer tissues expressed mRNAs encoding CLIC2, claudin 1, occludin and ZO-1, while similar cell fractions from cancer tissues had very low expressions of these molecules. Knockdown of CLIC2 expression in human umbilical vein endothelial cells (HUVECs) allowed human cancer cells to transmigrate through a HUVEC monolayer. These results suggest that CLIC2 may be involved in the formation and/or maintenance of tight junctions and that cancer tissue vasculature lacks CLIC2 and tight junctions, which allows the intravasation of cancer cells necessary for hematogenous metastasis.

Circulating adrenomedullin estimates survival and reversibility of organ failure in sepsis: the prospective observational multinational Adrenomedullin and Outcome in Sepsis and Septic Shock-1 (AdrenOSS-1) study

BACKGROUND

Adrenomedullin (ADM) regulates vascular tone and endothelial permeability during sepsis. Levels of circulating biologically active ADM (bio-ADM) show an inverse relationship with blood pressure and a direct relationship with vasopressor requirement. In the present prospective observational multinational Adrenomedullin and Outcome in Sepsis and Septic Shock 1 (, AdrenOSS-1) study, we assessed relationships between circulating bio-ADM during the initial intensive care unit (ICU) stay and short-term outcome in order to eventually design a biomarker-guided randomized controlled trial.

METHODS

AdrenOSS-1 was a prospective observational multinational study. The primary outcome was 28-day mortality. Secondary outcomes included organ failure as defined by Sequential Organ Failure Assessment (SOFA) score, organ support with focus on vasopressor/inotropic use, and need for renal replacement therapy. AdrenOSS-1 included 583 patients admitted to the ICU with sepsis or septic shock.

RESULTS

Circulating bio-ADM levels were measured upon admission and at day 2. Median bio-ADM concentration upon admission was 80.5 pg/ml [IQR 41.5-148.1 pg/ml]. Initial SOFA score was 7 [IQR 5-10], and 28-day mortality was 22%. We found marked associations between bio-ADM upon admission and 28-day mortality (unadjusted standardized HR 2.3 [CI 1.9-2.9]; adjusted HR 1.6 [CI 1.1-2.5]) and between bio-ADM levels and SOFA score (p < 0.0001). Need of vasopressor/inotrope, renal replacement therapy, and positive fluid balance were more prevalent in patients with a bio-ADM > 70 pg/ml upon admission than in those with bio-ADM ≤ 70 pg/ml. In patients with bio-ADM > 70 pg/ml upon admission, decrease in bio-ADM below 70 pg/ml at day 2 was associated with recovery of organ function at day 7 and better 28-day outcome (9.5% mortality). By contrast, persistently elevated bio-ADM at day 2 was associated with prolonged organ dysfunction and high 28-day mortality (38.1% mortality, HR 4.9, 95% CI 2.5-9.8).

CONCLUSIONS

AdrenOSS-1 shows that early levels and rapid changes in bio-ADM estimate short-term outcome in sepsis and septic shock. These data are the backbone of the design of the biomarker-guided AdrenOSS-2 trial.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT02393781 . Registered on March 19, 2015.

Cortical Actin Dynamics in Endothelial Permeability

The pulmonary endothelial cell forms a critical semi-permeable barrier between the vascular and interstitial space. As part of the blood-gas barrier in the lung, the endothelium plays a key role in normal physiologic function and pathologic disease. Changes in endothelial cell shape, defined by its plasma membrane, determine barrier integrity. A number of key cytoskeletal regulatory and effector proteins including non-muscle myosin light chain kinase, cortactin, and Arp 2/3 mediate actin rearrangements to form cortical and membrane associated structures in response to barrier enhancing stimuli. These actin formations support and interact with junctional complexes and exert forces to protrude the lipid membrane to and close gaps between individual cells. The current knowledge of these cytoskeletal processes and regulatory proteins are the subject of this review. In addition, we explore novel advancements in cellular imaging that are poised to shed light on the complex nature of pulmonary endothelial permeability.

Cortactin stabilization of actin requires actin-binding repeats and linker, is disrupted by specific substitutions, and is independent of nucleotide state

The actin-binding protein cortactin promotes the formation and maintenance of actin-rich structures, including lamellipodial protrusions in fibroblasts and neuronal dendritic spines. Cortactin cellular functions have been attributed to its activation of the Arp2/3 complex, which stimulates actin branch nucleation, and to its recruitment of Rho family GTPase regulators. Cortactin also binds actin filaments and significantly slows filament depolymerization, but the mechanism by which it does so and the relationship between actin binding and stabilization are unclear. Here we elucidated the cortactin regions that are necessary and sufficient for actin filament binding and stabilization. Using actin cosedimentation assays, we found that the cortactin repeat region binds actin but that the adjacent linker region is required for binding with the same affinity as full-length cortactin. Using total internal reflection fluorescence microscopy to measure the rates of single filament actin depolymerization, we observed that cortactin-actin interactions are sufficient to stabilize actin filaments. Moreover, conserved charged residues in repeat 4 were necessary for high-affinity actin binding, and substitution of these residues significantly impaired cortactin-mediated actin stabilization. Cortactin bound actin with higher affinity than did its paralog, hematopoietic cell-specific Lyn substrate 1 (HS1), and the effects on actin stability were specific to cortactin. Finally, cortactin stabilized ADP-actin filaments, indicating that the stabilization mechanism does not depend on the actin nucleotide state. Together, these results indicate that cortactin binding to actin is necessary and sufficient to stabilize filaments in a concentration-dependent manner, specific to conserved residues in the cortactin repeats, and independent of the actin nucleotide state.

Vav3-induced cytoskeletal dynamics contribute to heterotypic properties of endothelial barriers

Through multiple cell-cell and cell-matrix interactions, epithelial and endothelial sheets form tight barriers. Modulators of the cytoskeleton contribute to barrier stability and act as rheostats of vascular permeability. In this study, we sought to identify cytoskeletal regulators that underlie barrier diversity across vessels. To achieve this, we correlated functional and structural barrier features to gene expression of endothelial cells (ECs) derived from different vascular beds. Within a subset of identified candidates, we found that the guanosine nucleotide exchange factor Vav3 was exclusively expressed by microvascular ECs and was closely associated with a high-resistance barrier phenotype. Ectopic expression of Vav3 in large artery and brain ECs significantly enhanced barrier resistance and cortical rearrangement of the actin cytoskeleton. Mechanistically, we found that the barrier effect of Vav3 is dependent on its Dbl homology domain and downstream activation of Rap1. Importantly, inactivation of Vav3 in vivo resulted in increased vascular leakage, highlighting its function as a key regulator of barrier stability.

Cortactin expression in nasal polyps of Aspirin-Exacerbated Respiratory Disease (AERD) patients

PURPOSE

The term aspirin-exacerbated respiratory disease (AERD) refers to a combination of asthma, chronic rhinosinusitis with nasal polyposis (CRSwNP), and acute respiratory tract reactions to nonsteroidal anti-inflammatory drugs. AERD has now been included among the CRSwNP endotypes, and is considered one of the most aggressive in terms of disease recurrence. Cortactin is a multi-domain protein with a part in several cellular mechanisms involving actin assembly and cytoskeleton arrangement. Cortactin seems to have a role in inflammatory responses and to be implicated in human airway secretion and contraction mechanisms. The novel aim of the present study was to examine cortactin expression in nasal polyps of a consecutive cohort of AERD patients and in nasal mucosa of a control group of patients.

MATERIALS AND METHODS

Cortactin expression was assessed immunohistochemically in nasal polyps from 18 consecutive AERD patients who underwent endoscopic sinus surgery and in nasal mucosa of 19 patients without chronic rhinosinusitis.

RESULTS

Concomitant allergy was found in 11 AERD patients, most of them male (8 cases; p = 0.02). Cortactin expression in nasal polyps was definitely high (+3) in 17 out of 18 cases, in both epithelial cells (cytoplasmic and membranous immunoreactivity) and activated fibroblasts. A higher cortactin expression was seen in female than in male AERD patients (p = 0.05).

CONCLUSIONS

Given this preliminary evidence of cortactin upregulation in the polyps of AERD patients, prospective studies could further investigate the role of cortactin in the biology of AERD, and the potential role of cortactin-targeted approaches in integrated AERD treatments.

Adrenomedullin and Adrenomedullin-Targeted Therapy As Treatment Strategies Relevant for Sepsis

Sepsis remains a major medical challenge, for which, apart from improvements in supportive care, treatment has not relevantly changed over the last few decades. Vasodilation and vascular leakage play a pivotal role in the development of septic shock, with vascular leakage being caused by disrupted endothelial integrity. Adrenomedullin (ADM), a free circulating peptide involved in regulation of endothelial barrier function and vascular tone, is implicated in the pathophysiology of sepsis. ADM levels are increased during sepsis, and correlate with extent of vasodilation, as well as with disease severity and mortality. In vitro and preclinical in vivo data show that administration of ADM exerts anti-inflammatory, antimicrobial, and protective effects on endothelial barrier function during sepsis, but other work suggests that it may also decrease blood pressure, which could be detrimental for patients with septic shock. Work has been carried out to negate ADMs putative negative effects, while preserving or even potentiating its beneficial actions. Preclinical studies have demonstrated that the use of antibodies that bind to the N-terminus of ADM results in an overall increase of circulating ADM levels and improves sepsis outcome. Similar beneficial effects were obtained using coadministration of ADM and ADM-binding protein-1. It is hypothesized that the mechanism behind the beneficial effects of ADM binding involves prolongation of its half-life and a shift of ADM from the interstitium to the circulation. This in turn results in increased ADM activity in the blood compartment, where it exerts beneficial endothelial barrier-stabilizing effects, whereas its detrimental vasodilatory effects in the interstitium are reduced. Up till now, in vivo data on ADM-targeted treatments in humans are lacking; however, the first study in septic patients with an N-terminus antibody (Adrecizumab) is currently being conducted.

Relationship between G proteins coupled receptors and tight junctions

Tight junctions (TJs) are sites of cell-cell adhesion, constituted by a cytoplasmic plaque of molecules linked to integral proteins that form a network of strands around epithelial and endothelial cells at the uppermost portion of the lateral membrane. TJs maintain plasma membrane polarity and form channels and barriers that regulate the transit of ions and molecules through the paracellular pathway. This structure that regulates traffic between the external milieu and the organism is affected in numerous pathological conditions and constitutes an important target for therapeutic intervention. Here, we describe how a wide array of G protein-coupled receptors that are activated by diverse stimuli including light, ions, hormones, peptides, lipids, nucleotides and proteases, signal through heterotrimeric G proteins, arrestins and kinases to regulate TJs present in the blood-brain barrier, the blood-retinal barrier, renal tubular cells, keratinocytes, lung and colon, and the slit diaphragm of the glomerulus.

Adrenomedullin surges are linked to acute episodes of the systemic capillary leak syndrome (Clarkson disease)

BACKGROUND

Systemic Capillary Leak Syndrome (SCLS) is an extremely rare and life-threatening vascular disorder of unknown etiology. SCLS is characterized by abrupt and transient episodes of hypotensive shock and edema due to plasma leakage into peripheral tissues. The disorder has garnered attention recently because its initial presentation resembles more common vascular disorders including systemic anaphylaxis, sepsis, and acute infections with the Ebola/Marburg family of filoviruses. Although approximately 70-85% of patients with SCLS have a concurrent monoclonal gammopathy of unknown significance (MGUS), any contribution of the paraprotein to acute flares is unknown.

PROCEDURE

To identify circulating factors that might trigger acute SCLS crises, we profiled transcriptomes of paired peripheral blood mononuclear cell fractions obtained from patients during acute attacks and convalescent intervals by microarray.

RESULTS

This study uncovered 61 genes that were significantly up- or downregulated more than 2.5-fold in acute samples relative to respective baselines. One of the most upregulated genes was ADM, which encodes the vasoactive peptide adrenomedullin. A stable ADM protein surrogate (pro-ADM) was markedly elevated in SCLS acute sera compared to remission samples or sera from healthy controls. Monocytes and endothelial cells (ECs) from SCLS subjects expressed significantly more ADM in response to proinflammatory stimuli compared to healthy control cells. Application of ADM to ECs elicited protective effects on vascular barrier function, suggesting a feedback protective mechanism in SCLS.

CONCLUSIONS

Since ADM has established hypotensive effects, differentiating between these dual actions of ADM is crucial for therapeutic applications aimed at more common diseases associated with increased ADM levels.

Mind the gap: mechanisms regulating the endothelial barrier

The endothelial barrier consists of intercellular contacts localized in the cleft between endothelial cells, which is covered by the glycocalyx in a sievelike manner. Both types of barrier-forming junctions, i.e. the adherens junction (AJ) serving mechanical anchorage and mechanotransduction and the tight junction (TJ) sealing the intercellular space to limit paracellular permeability, are tethered to the actin cytoskeleton. Under resting conditions, the endothelium thereby builds a selective layer controlling the exchange of fluid and solutes with the surrounding tissue. However, in the situation of an inflammatory response such as in anaphylaxis or sepsis intercellular contacts disintegrate in post-capillary venules leading to intercellular gap formation. The resulting oedema can cause shock and multi-organ failure. Therefore, maintenance as well as coordinated opening and closure of interendothelial junctions is tightly regulated. The two principle underlying mechanisms comprise spatiotemporal activity control of the small GTPases Rac1 and RhoA and the balance of the phosphorylation state of AJ proteins. In the resting state, junctional Rac1 and RhoA activity is enhanced by junctional components, actin-binding proteins, cAMP signalling and extracellular cues such as sphingosine-1-phosphate (S1P) and angiopoietin-1 (Ang-1). In addition, phosphorylation of AJ components is prevented by junction-associated phosphatases including vascular endothelial protein tyrosine phosphatase (VE-PTP). In contrast, inflammatory mediators inhibiting cAMP/Rac1 signalling cause strong activation of RhoA and induce AJ phosphorylation finally leading to endocytosis and cleavage of VE-cadherin. This results in dissolution of TJs the outcome of which is endothelial barrier breakdown.

Cortactin in cancer cell migration and invasion

Cortactin, a substrate of sarcoma (Src) kinases, is an actin-binding protein that is involved in cytoskeletal regulation, and is frequently overexpressed in cancer cells. Binding to the actin related protein 2/3 (Arp2/3) complex stimulates cortactin activity, which promotes F-actin nucleation and assembly. Cortactin promotes cancer cell migration and invasion, and plays a pivotal role in invadopodia formation and extra cellular matrix degradation. Overexpression of cortactin, by amplification of the chromosomal band 11q13, increases tumor aggressiveness. In this review, we report on the current knowledge and potential mechanisms of action of cortactin as a critical mediator of cancer cell migration and invasion.

Cortactin deficiency causes increased RhoA/ROCK1-dependent actomyosin contractility, intestinal epithelial barrier dysfunction, and disproportionately severe DSS-induced colitis

The intestinal epithelium constitutes a first line of defense of the innate immune system. Epithelial dysfunction is a hallmark of intestinal disorders such as inflammatory bowel diseases (IBDs). The actin cytoskeleton controls epithelial barrier integrity but the function of actin regulators such as cortactin is poorly understood. Given that cortactin controls endothelial permeability, we hypothesized that cortactin is also important for epithelial barrier regulation. We found increased permeability in the colon of cortactin-KO mice that was accompanied by reduced levels of ZO-1, claudin-1, and E-cadherin. By contrast, claudin-2 was upregulated. Cortactin deficiency increased RhoA/ROCK1-dependent actomyosin contractility, and inhibition of ROCK1 rescued the barrier defect. Interestingly, cortactin deficiency caused increased epithelial proliferation without affecting apoptosis. KO mice did not develop spontaneous colitis, but were more susceptible to dextran sulfate sodium colitis and showed severe colon tissue damage and edema formation. KO mice with colitis displayed strong mucus deposition and goblet cell depletion. In healthy human colon tissues, cortactin co-localized with ZO-1 at epithelial cell contacts. In IBDs patients, we observed decreased cortactin levels and loss of co-localization with ZO-1. Thus, cortactin is a master regulator of intestinal epithelial barrier integrity in vivo and could serve as a suitable target for pharmacological intervention in IBDs.

Actin dynamics in the regulation of endothelial barrier functions and neutrophil recruitment during endotoxemia and sepsis

Sepsis is a leading cause of death worldwide. Increased vascular permeability is a major hallmark of sepsis. Dynamic alterations in actin fiber formation play an important role in the regulation of endothelial barrier functions and thus vascular permeability. Endothelial integrity requires a delicate balance between the formation of cortical actin filaments that maintain endothelial cell contact stability and the formation of actin stress fibers that generate pulling forces, and thus compromise endothelial cell contact stability. Current research has revealed multiple molecular pathways that regulate actin dynamics and endothelial barrier dysfunction during sepsis. These include intracellular signaling proteins of the small GTPases family (e.g., Rap1, RhoA and Rac1) as well as the molecules that are directly acting on the actomyosin cytoskeleton such as myosin light chain kinase and Rho kinases. Another hallmark of sepsis is an excessive recruitment of neutrophils that also involves changes in the actin cytoskeleton in both endothelial cells and neutrophils. This review focuses on the available evidence about molecules that control actin dynamics and regulate endothelial barrier functions and neutrophil recruitment. We also discuss treatment strategies using pharmaceutical enzyme inhibitors to target excessive vascular permeability and leukocyte recruitment in septic patients.

Regulation of endothelial and epithelial barrier functions by peptide hormones of the adrenomedullin family

The correct regulation of tissue barriers is of utmost importance for health. Barrier dysfunction accompanies inflammatory disorders and, if not controlled properly, can contribute to the development of chronic diseases. Tissue barriers are formed by monolayers of epithelial cells that separate organs from their environment, and endothelial cells that cover the vasculature, thus separating the blood stream from underlying tissues. Cells within the monolayers are connected by intercellular junctions that are linked by adaptor molecules to the cytoskeleton, and the regulation of these interactions is critical for the maintenance of tissue barriers. Many endogenous and exogenous molecules are known to regulate barrier functions in both ways. Proinflammatory cytokines weaken the barrier, whereas anti-inflammatory mediators stabilize barriers. Adrenomedullin (ADM) and intermedin (IMD) are endogenous peptide hormones of the same family that are produced and secreted by many cell types during physiologic and pathologic conditions. They activate certain G-protein-coupled receptor complexes to regulate many cellular processes such as cytokine production, actin dynamics and junction stability. In this review, we summarize current knowledge about the barrier-stabilizing effects of ADM and IMD in health and disease.