Extracellular pressure stimulates macrophage phagocytosis by inhibiting a pathway involving FAK and ERK

Matrix stiffness affects tumor-associated macrophage functional polarization and its potential in tumor therapy

The extracellular matrix (ECM) plays critical roles in cytoskeletal support, biomechanical transduction and biochemical signal transformation. Tumor-associated macrophage (TAM) function is regulated by matrix stiffness in solid tumors and is often associated with poor prognosis. ECM stiffness-induced mechanical cues can activate cell membrane mechanoreceptors and corresponding mechanotransducers in the cytoplasm, modulating the phenotype of TAMs. Currently, tuning TAM polarization through matrix stiffness-induced mechanical stimulation has received increasing attention, whereas its effect on TAM fate has rarely been summarized. A better understanding of the relationship between matrix stiffness and macrophage function will contribute to the development of new strategies for cancer therapy. In this review, we first introduced the overall relationship between macrophage polarization and matrix stiffness, analyzed the changes in mechanoreceptors and mechanotransducers mediated by matrix stiffness on macrophage function and tumor progression, and finally summarized the effects of targeting ECM stiffness on tumor prognosis to provide insight into this new field.

A novel drug-like water-soluble small molecule Focal Adhesion Kinase (FAK) activator promotes intestinal mucosal healing

Non-steroidal anti-inflammatory drugs (NSAIDs) injure the proximal and distal gut by different mechanisms. While many drugs reduce gastrointestinal injury, no drug directly stimulates mucosal wound healing. Focal adhesion kinase (FAK), a non-receptor tyrosine kinase, induces epithelial sheet migration. We synthesized and evaluated a water-soluble FAK-activating small molecule, M64HCl, with drug-like properties. Monolayer wound closure and Western blots measured migration and FAK phosphorylation in Caco-2 ​cells, in vitro kinase assays established FAK activation, and pharmacologic tests assessed drug-like properties. 30 ​mg/kg/day M64HCl was administered in two murine small intestine injury models for 4 days. M64HCl (0.1-1000 ​nM) dose-dependently increased Caco-2 FAK-Tyr 397 phosphorylation, without activating Pyk2 and accelerated Caco-2 monolayer wound closure. M64HCl dose-responsively activates the FAK kinase domain vs. the non-salt M64, increasing the V_max of ATP-binding. Pharmacologic tests suggested M64HCl has drug-like properties and is enterally absorbed. M64HCl 25 ​mg/kg/day continuous infusion promoted healing of ischemic jejunal ulcers and indomethacin-induced small intestinal injury in C57Bl/6 mice. M64HCl-treated mice exhibited smaller ulcers 4 days after ischemic ulcer induction or indomethacin injury. Renal histology and plasma creatinine were normal. Mild hepatic inflammatory changes and ALT elevation were similar among M64HCl-treated mice and controls. M64HCl was concentrated in kidney and gastrointestinal mucosa and functional nephrectomy studies suggested predominantly urinary excretion. Little toxicity was observed in vitro or in single-dose mouse toxicity studies until >1000x higher than effective concentrations. M64HCl, a water-soluble FAK activator, promotes epithelial restitution and intestinal mucosal healing and may be useful to treat gut mucosal injury.

In vivo spatiotemporal dynamics of astrocyte reactivity following neural electrode implantation

Brain computer interfaces (BCIs), including penetrating microelectrode arrays, enable both recording and stimulation of neural cells. However, device implantation inevitably causes injury to brain tissue and induces a foreign body response, leading to reduced recording performance and stimulation efficacy. Astrocytes in the healthy brain play multiple roles including regulating energy metabolism, homeostatic balance, transmission of neural signals, and neurovascular coupling. Following an insult to the brain, they are activated and gather around the site of injury. These reactive astrocytes have been regarded as one of the main contributors to the formation of a glial scar which affects the performance of microelectrode arrays. This study investigates the dynamics of astrocytes within the first 2 weeks after implantation of an intracortical microelectrode into the mouse brain using two-photon microscopy. From our observation astrocytes are highly dynamic during this period, exhibiting patterns of process extension, soma migration, morphological activation, and device encapsulation that are spatiotemporally distinct from other glial cells, such as microglia or oligodendrocyte precursor cells. This detailed characterization of astrocyte reactivity will help to better understand the tissue response to intracortical devices and lead to the development of more effective intervention strategies to improve the functional performance of neural interfacing technology.

Persistent Acidic Environment Induces Impaired Phagocytosis via ERK in Microglia

Acidic environment evoked by stroke, traumatic brain injury, and Alzheimer's disease may change the functional properties of microglia. Nevertheless, the underlying mechanisms of functional changes in microglia remain unclear. In this study, we found that acidic stimuli (pH 6.8) increased rapidly interleukin (IL)-1β and IL-6 mRNA levels and subsequently reduced IL-10, transforming growth factor (TGF)-β1, Cx3cr1, and P2ry12 as the exposure time to acidic environment increase in BV2 cells. In addition, persistent acidic environment (pH 6.8 for 6 h) induced impaired phagocytic function in BV2 cells. Short-term acidic exposure (pH 6.8 for 30 min) increased cyclic AMP (cAMP) and phospho-protein kinase A (PKA) but inhibited phospho-extracellular signal-regulated kinase (p-ERK). However, under persistent acidic environment (pH 6.8 for 6 h), cyclic AMP and PKA were normalized and p-ERK was increased with TDAG8 (T cell death associated gene 8; GPR65) reduction. FR 180,204, an ERK inhibitor, rescued the persistent acidic environment-induced functional changes in BV2 cells and its effect was recapitulated in primary neonatal microglia. Thus, we propose that ERK targeting may be an alternative strategy to restore microglial dysfunction in the central nervous system (CNS) acidic environment in various neurological disorders.

Mechanotransduction at the Plasma Membrane-Cytoskeleton Interface

Mechanical cues are crucial for survival, adaptation, and normal homeostasis in virtually every cell type. The transduction of mechanical messages into intracellular biochemical messages is termed mechanotransduction. While significant advances in biochemical signaling have been made in the last few decades, the role of mechanotransduction in physiological and pathological processes has been largely overlooked until recently. In this review, the role of interactions between the cytoskeleton and cell-cell/cell-matrix adhesions in transducing mechanical signals is discussed. In addition, mechanosensors that reside in the cell membrane and the transduction of mechanical signals to the nucleus are discussed. Finally, we describe two examples in which mechanotransduction plays a significant role in normal physiology and disease development. The first example is the role of mechanotransduction in the proliferation and metastasis of cancerous cells. In this system, the role of mechanotransduction in cellular processes, including proliferation, differentiation, and motility, is described. In the second example, the role of mechanotransduction in a mechanically active organ, the gastrointestinal tract, is described. In the gut, mechanotransduction contributes to normal physiology and the development of motility disorders.

ZINC40099027 Promotes Gastric Mucosal Repair in Ongoing Aspirin-Associated Gastric Injury by Activating Focal Adhesion Kinase

Nonsteroidal anti-inflammatory drugs cause gastric ulcers and gastritis. No drug that treats GI injury directly stimulates mucosal healing. ZINC40099027 (ZN27) activates focal adhesion kinase (FAK) and heals acute indomethacin-induced small bowel injury. We investigated the efficacy of ZN27 in rat and human gastric epithelial cells and ongoing aspirin-associated gastric injury. ZN27 (10 nM) stimulated FAK activation and wound closure in rat and human gastric cell lines. C57BL/6J mice were treated with 300 mg/kg/day aspirin for five days to induce ongoing gastric injury. One day after the initial injury, mice received 900 µg/kg/6 h ZN27, 10 mg/kg/day omeprazole, or 900 µg/kg/6 h ZN27 plus 10 mg/kg/day omeprazole. Like omeprazole, ZN27 reduced gastric injury vs. vehicle controls. ZN27-treated mice displayed better gastric architecture, with thicker mucosa and less hyperemia, inflammation, and submucosal edema, and lost less weight than vehicle controls. Gastric pH, serum creatinine, serum alanine aminotransferase (ALT), and renal and hepatic histology were unaffected by ZN27. Blinded scoring of pFAK-Y-397 immunoreactivity at the edge of ZN27-treated lesions demonstrated increased FAK activation, compared to vehicle-treated lesions, confirming target activation in vivo. These results suggest that ZN27 ameliorates ongoing aspirin-associated gastric mucosal injury by a pathway involving FAK activation. ZN27-derivatives may be useful to promote gastric mucosal repair.

Review on experimental study and clinical application of low-intensity pulsed ultrasound in inflammation

Low-intensity pulsed ultrasound (LIPUS), as physical therapy, is widely used in both research and clinical settings. It induces multiple bioeffects, such as alleviating pain, promoting tissue repair, and shortening disease duration. LIPUS can also mediate inflammation. This paper reviews the application of LIPUS in inflammation and discusses the underlying mechanism. In basic experiments, LIPUS can regulate inflammatory responses at the cellular level by affecting some signaling pathways. In a clinical trial, LIPUS has been shown to alleviate inflammatory responses efficiently. As a cheap, safe, and convenient physical method, LIPUS is promising as anti-inflammatory therapy.

Squeezing in a Meal: Myosin Functions in Phagocytosis

Phagocytosis is a receptor-mediated, actin-dependent process of internalization of large extracellular particles, such as pathogens or apoptotic cells. Engulfment of phagocytic targets requires the activity of myosins, actin-dependent molecular motors, which perform a variety of functions at distinct steps during phagocytosis. By applying force to actin filaments, the plasma membrane, and intracellular proteins and organelles, myosins can generate contractility, directly regulate actin assembly to ensure proper phagocytic internalization, and translocate phagosomes or other cargo to appropriate cellular locations. Recent studies using engineered microenvironments and phagocytic targets have demonstrated how altering the actomyosin cytoskeleton affects phagocytic behavior. Here, we discuss how studies using genetic and biochemical manipulation of myosins, force measurement techniques, and live-cell imaging have advanced our understanding of how specific myosins function at individual steps of phagocytosis.

Small molecule FAK activator promotes human intestinal epithelial monolayer wound closure and mouse ulcer healing

GI mucosal healing requires epithelial sheet migration. The non-receptor tyrosine kinase focal adhesion kinase (FAK) stimulates epithelial motility. A virtual screen identified the small drug-like FAK mimic ZINC40099027, which activates FAK. We assessed whether ZINC40099027 promotes FAK-Tyr-397 phosphorylation and wound healing in Caco-2 monolayers and two mouse intestinal injury models. Murine small bowel ulcers were generated by topical serosal acetic acid or subcutaneous indomethacin in C57BL/6J mice. One day later, we began treatment with ZINC40099027 or DMSO, staining the mucosa for phosphorylated FAK and Ki-67 and measuring mucosal ulcer area, serum creatinine, ALT, and body weight at day 4. ZINC40099027 (10–1000 nM) dose-dependently activated FAK phosphorylation, without activating Pyk2-Tyr-402 or Src-Tyr-419. ZINC40099027 did not stimulate proliferation, and stimulated wound closure independently of proliferation. The FAK inhibitor PF-573228 prevented ZINC40099027-stimulated wound closure. In both mouse ulcer models, ZINC40099027accelerated mucosal wound healing. FAK phosphorylation was increased in jejunal epithelium at the ulcer edge, and Ki-67 staining was unchanged in jejunal mucosa. ZINC40099027 serum concentration at sacrifice resembled the effective concentration in vitro. Weight, creatinine and ALT did not differ between groups. Small molecule FAK activators can specifically promote epithelial restitution and mucosal healing and may be useful to treat gut mucosal injury.

Mechanical stretch promotes tumoricidal M1 polarization via the FAK/NF-κB signaling pathway

Macrophages (Mφs) can be used as a part of cell-based cancer immunotherapy. However, they may be hampered by a failure to effectively and stably regulate their polarization state to enhance their tumoricidal effects. In this work, mechanical stretch (MS), as a biology-free modulatory method, was shown to enhance M1 polarization and tumoricidal effects. By using an in vitro Flexcell Tension system, we found that murine Mφ RAW264.7 cells showed higher M1 polarization-related mRNA expression and cytokine release after MS. Further molecular analyses found that focal adhesion kinase and NF-κB activation occurred in the MS-induced M1 polarization. Coculture of MS-preconditioned Mφ with B16F10 skin melanoma cells in vitro showed that the proliferation of B16F10 cells decreased, whereas caspase-3-induced apoptosis increased. Importantly, the injection of MS-preconditioned Mφ into murine skin melanomas in vivo impeded tumor growth; lesions were characterized by increased amounts of M1 Mφ, decreased tumor cell proliferation, and increased tumor cell apoptosis in the tumor microenvironment. Together, our results suggest that MS could be used as a simple preconditioning approach to prepare tumoricidal M1 Mφ for cancer immunotherapy.-Shan, S., Fang, B., Zhang, Y., Wang, C., Zhou, J., Niu, C., Gao, Y., Zhao, D., He, J., Wang, J., Zhang, X., Li, Q. Mechanical stretch promotes tumoricidal M1 polarization via the FAK/NF-κB signaling pathway.

Phagocytosis by macrophages depends on histamine H2 receptor signaling and scavenger receptor 1

The histamine H2 receptor (H2R) is a G protein‐coupled receptor that mediates cyclic AMP production, protein kinase A activation, and MAP kinase signaling. In order to explore the multifaceted effects of histamine signaling on immune cells, phagocytosis was evaluated using primary mouse‐derived macrophages. Phagocytosis is initiated by signaling via surface‐bound scavenger receptors and can be regulated by autophagy. Absence of H2R signaling resulted in diminished phagocytosis of live bacteria and synthetic microspheres by primary macrophages from histamine H2 receptor gene (Hrh2)‐deficient mice. Flow cytometry and immunofluorescence microscopy were used to quantify phagocytosis of phylogenetically diverse bacteria as well as microspheres of defined chemical composition. Autophagy and scavenger receptor gene expression were quantified in macrophages after exposure to Escherichia coli. Expression of the autophagy genes, Becn1 and Atg12, was increased in Hrh2^−/− macrophages, indicating upregulation of autophagy pathways. Expression of the Macrophage Scavenger Receptor 1 gene (Msr1) was diminished in Hrh2‐deficient macrophages, supporting the possible importance of histamine signaling in scavenger receptor abundance and macrophage function. Flow cytometry confirmed diminished MSR1 surface abundance in Hrh2^−/− macrophages. These data suggest that H2R signaling is required for effective phagocytosis by regulating the process of autophagy and scavenger receptor MSR1 abundance in macrophages.

The Autoimmune Susceptibility Gene C5orf30 Regulates Macrophage-Mediated Resolution of Inflammation

Genetic variants in C5orf30 have been associated with development of the autoimmune conditions primary biliary cirrhosis and rheumatoid arthritis. In rheumatoid arthritis, C5orf30 expression is cell-specific, with highest expression found in macrophages and synovial fibroblasts. C5orf30 is highly expressed in inflamed joints and is a negative regulator of tissue damage in a mouse model of inflammatory arthritis. Transcriptomic analysis from ultrasound-guided synovial biopsy of inflamed joints in a well characterized clinical cohort of newly diagnosed, disease-modifying antirheumatic drugs-naive rheumatoid arthritis patients was used to determine the clinical association of C5orf30 expression with disease activity. A combined molecular and computational biology approach was used to elucidate C5orf30 function in macrophages both in vitro and in vivo. Synovial expression of C5orf30 is inversely correlated with both clinical measures of rheumatoid arthritis disease activity and with synovial TNF mRNA expression. C5orf30 plays a role in regulating macrophage phenotype and is differentially turned over in inflammatory and anti-inflammatory macrophages. Inhibition of C5orf30 reduces wound healing/repair-associated functions of macrophages, reduces signaling required for resolution of inflammation, and decreases secretion of anti-inflammatory mediators. In an animal model of wound healing (zebrafish), C5orf30 inhibition increases the recruitment of macrophages to the wound site. Finally, we demonstrate that C5orf30 skews macrophage immunometabolism, demonstrating a mechanism for C5orf30-mediated immune regulation.

Outer Membrane Vesicles Prime and Activate Macrophage Inflammasomes and Cytokine Secretion In Vitro and In Vivo

Outer membrane vesicles (OMVs) are proteoliposomes blebbed from the surface of Gram-negative bacteria. Chronic periodontitis is associated with an increase in subgingival plaque of Gram-negative bacteria, Porphyromonas gingivalis, Treponema denticola, and Tannerella forsythia. In this study, we investigated the immune-modulatory effects of P. gingivalis, T. denticola, and T. forsythia OMVs on monocytes and differentiated macrophages. All of the bacterial OMVs were phagocytosed by monocytes, M(naïve) and M(IFNγ) macrophages in a dose-dependent manner. They also induced NF-κB activation and increased TNFα, IL-8, and IL-1β cytokine secretion. P. gingivalis OMVs were also found to induce anti-inflammatory IL-10 secretion. Although unprimed monocytes and macrophages were resistant to OMV-induced cell death, lipopolysaccharide or OMV priming resulted in a significantly reduced cell viability. P. gingivalis, T. denticola, and T. forsythia OMVs all activated inflammasome complexes, as monitored by IL-1β secretion and ASC speck formation. ASC was critical for OMV-induced inflammasome formation, while AIM2-/- and Caspase-1-/- cells had significantly reduced inflammasome formation and NLRP3-/- cells exhibited a slight reduction. OMVs were also found to provide both priming and activation of the inflammasome complex. High-resolution microscopy and flow cytometry showed that P. gingivalis OMVs primed and activated macrophage inflammasomes in vivo with 80% of macrophages exhibiting inflammasome complex formation. In conclusion, periodontal pathogen OMVs were found to have significant immunomodulatory effects upon monocytes and macrophages and should therefore influence pro-inflammatory host responses associated with disease.

Inhibition of pressure-activated cancer cell adhesion by FAK-derived peptides

Forces within the surgical milieu or circulation activate cancer cell adhesion and potentiate metastasis through signaling requiring FAK-Akt1 interaction. Impeding FAK-Akt1 interaction might inhibit perioperative tumor dissemination, facilitating curative cancer surgery without global FAK or AKT inhibitor toxicity. Serial truncation and structurally designed mutants of FAK identified a seven amino acid, short helical structure within FAK that effectively competes with Akt1-FAK interaction. Adenoviral overexpression of this FAK-derived peptide inhibited pressure-induced FAK phosphorylation and AKT-FAK coimmunoprecipitation in human SW620 colon cancer cells briefly exposed to 15mmHg increased pressure, consistent with laparoscopic or post-surgical pressures. Adenoviral FAK-derived peptide expression prevented pressure-activation of SW620 adhesion not only to collagen-I-coated plates but also to murine surgical wounds. A scrambled peptide did not. Finally, we modeled operative shedding of tumor cells before irrigation and closure by transient cancer cell adhesion to murine surgical wounds before irrigation and closure. Thirty minute preincubation of SW620 cells at 15mmHg increased pressure impaired subsequent tumor free survival in mice exposed to cells expressing the scrambled peptide. The FAK-derived sequence prevented this. These results suggest that blocking FAK-Akt1 interaction may prevent perioperative tumor dissemination and that analogs or mimics of this 7 amino acid FAK-derived peptide could impair metastasis.

Elasticity in Macrophage-Synthesized Biocrystals

Supramolecular crystalline assembly constitutes a rational approach to bioengineer intracellular structures. Here, biocrystals of clofazimine (CFZ) that form in vivo within macrophages were measured to have marked curvature. Isolated crystals, however, showed reduced curvature suggesting that intracellular forces bend these drug crystals. Consistent with the ability of biocrystals to elastically deform, the inherent crystal structure of the principal molecular component of the biocrystals-the hydrochloride salt of CFZ (CFZ-HCl)-has a corrugated packing along the (001) face and weak dispersive bonding in multiple directions. These characteristics were previously found to be linked to the elasticity of other organic crystals. Internal stress in bent CFZ-HCl led to photoelastic effects on the azimuthal orientation of polarized light transmittance. We propose that elastic, intracellular crystals can serve as templates to construct functional microdevices with different applications.

Role for Mechanotransduction in Macrophage and Dendritic Cell Immunobiology

Tissue homeostasis is not only controlled by biochemical signals but also through mechanical forces that act on cells. Yet, while it has long been known that biochemical signals have profound effects on cell biology, the importance of mechanical forces has only been recognized much more recently. The types of mechanical stress that cells experience include stretch, compression, and shear stress, which are mainly induced by the extracellular matrix, cell-cell contacts, and fluid flow. Importantly, macroscale tissue deformation through stretch or compression also affects cellular function.Immune cells such as macrophages and dendritic cells are present in almost all peripheral tissues, and monocytes populate the vasculature throughout the body. These cells are unique in the sense that they are subject to a large variety of different mechanical environments, and it is therefore not surprising that key immune effector functions are altered by mechanical stimuli. In this chapter, we describe the different types of mechanical signals that cells encounter within the body and review the current knowledge on the role of mechanical signals in regulating macrophage, monocyte, and dendritic cell function.

Skin perfusion responses under normal and combined loadings: Comparisons between legs with venous stasis ulcers and healthy legs

BACKGROUND

Venous ulcers, also known as stasis ulcers, are skin wounds often found at the medial surface of the lower leg. These wounds are related to chronic venous insufficiencies and affect almost 2.5 million patients every year in the United States.

METHOD

Eighteen participants with venous stasis ulcers on at least one leg and twenty healthy participants were tested. Normal and combined normal and shear loadings were applied to each lower leg and local blood perfusion was monitored. Basal perfusion, post-occlusive reactive hyperemia as well as changes in perfusion due to different loadings were compared.

FINDINGS

Legs with existing venous stasis ulcers ("wounded legs") had the highest reactive hyperemia and basal perfusion values. Legs without ulcers but from participants with venous stasis ulcers ("non-wounded legs") had intermediate reactive hyperemia, and healthy legs exhibited the lowest values. Wounded legs also exhibited the largest decrease in blood perfusion under both normal and combined loadings. Non-wounded legs decreased perfusion similarly to healthy legs under normal loadings; however, non-wounded legs exhibited larger decreases in blood flow than healthy legs in response to shear and normal loading together.

INTERPRETATION

These results suggest that patients with venous stasis disease have abnormal responses to tissue loading and raise the possibility that this technique may have the potential to identify patients at risk for developing a venous stasis ulcer. Moreover, they emphasize the importance of studying shear loading in addition to normal loading in attempting to understand the pathophysiology of this disease.

Hyperbaric oxygen enhances neutrophil apoptosis and their clearance by monocyte-derived macrophages

Neutrophil apoptosis and clearance by macrophages are essential for wound healing. Evidence suggests that hyperbaric oxygen (HBO) exposure may enhance neutrophil apoptosis, but HBO effects leading to neutrophil clearance by macrophages are still unclear. In the current study, bovine neutrophils and monocyte-derived macrophages (MDMΦ) were co-cultured under HBO (97.9% O2, 2.1% CO2 at 2.4 atm absolute (ATA)) (1 atm = 101.325 kPa), hyperbaric normoxia (8.8% O2 at 2.4 ATA), normobaric hyperoxia (95% O2, 5% CO2), normoxia (air), and normobaric hypoxia (5% O2, 5% CO2). Phagocytosis of fresh and 22 h aged neutrophils by MDMΦ was increased after HBO pre-treatment, assessed using flow cytometry and light microscopy. Enhanced clearance of neutrophils was accompanied by an increase in H2O2 levels following HBO pre-treatment with upregulation of IL-10 (anti-inflammatory cytokine) mRNA expression in LPS-stimulated MDMΦ that had ingested aged neutrophils. TNF-α (pro-inflammatory cytokine) gene expression did not change in LPS-stimulated MDMΦ that had ingested fresh or aged neutrophils after HBO, pressure, and hyperoxia. These findings suggest that HBO-activated MDMΦ participate in the clearance of apoptotic cells. Uptake of neutrophils by MDMΦ exposed to HBO may contribute to resolution of inflammation, because HBO induced up-regulation of IL-10 mRNA expression.

Beluga (Delphinapterus leucas) granulocytes and monocytes display variable responses to in vitro pressure exposures

While it is widely known that marine mammals possess adaptations which allow them to make repetitive and extended dives to great depths without suffering ill effects seen in humans, the response of marine mammal immune cells to diving is unknown. Renewed interest in marine mammal dive physiology has arisen due to reports of decompression sickness-like symptoms and embolic damage in stranded and by-caught animals, and there is concern over whether anthropogenic activities can impact marine mammal health by disrupting adaptive dive responses and behavior. This work addresses the need for information concerning marine mammal immune function during diving by evaluating granulocyte and monocyte phagocytosis, and granulocyte activation in belugas (n = 4) in comparison with humans (n = 4), with and without in vitro pressure exposures. In addition, the potential for additional stressors to impact immune function was investigated by comparing the response of beluga cells to pressure between baseline and stressor conditions. Granulocyte and monocyte phagocytosis, as well as granulocyte activation, were compared between pressure exposed and non-exposed cells for each condition, between different pressure profiles and between conditions using mixed generalized linear models (α = 0.05). The effects of pressure varied between species as well by depth, compression/decompression rates, and length of exposures, and condition for belugas. Pressure induced changes in granulocyte and monocyte function in belugas could serve a protective function against dive-related pathologies and differences in the response between humans and belugas could reflect degrees of dive adaptation. The alteration of these responses during physiologically challenging conditions may increase the potential for dive-related in jury and disease in marine mammals.

Increased extracellular pressure stimulates tumor proliferation by a mechanosensitive calcium channel and PKC-β

Large tumors exhibit high interstitial pressure heightened by growth against the constraining stroma. Such pressures could stimulate tumor proliferation via a mechanosensitive ion channel. We studied the effects of 0-80 mmHg increased extracellular pressure for 24 h on proliferation of SW620, Caco-2, and CT-26 colon; MCF-7 breast; and MLL and PC3 prostate cancer cells, and delineated its mechanism in SW620 cells with specific inhibitors and siRNA. Finally, we compared NF-kB, phospho-IkB and cyclin D1 immunoreactivity in the high pressure centers and low pressure peripheries of human tumors. Pressure-stimulated proliferation in all cells. Pressure-driven SW620 proliferation required calcium influx via the T-type Ca(2+) channel Cav3.3, which stimulated PKC-β to invoke the IKK-IkB-NF-kB pathway to increase proliferation and S-phase fraction. The mitotic index and immunoreactivity of NF-kB, phospho-IkB, and cyclin D1 in the center of 28 large human colon, lung, and head and neck tumors exceeded that in tumor peripheries. Extracellular pressure increases [Ca(2+)]i via Cav3.3, driving a PKC-β- IKK- IkB-NF-kB pathway that stimulates cancer cell proliferation. Rapid proliferation in large stiff tumors may increase intratumoral pressure, activating this pathway to stimulate further proliferation in a feedback cycle that potentiates tumor growth. Targeting this pathway may inhibit proliferation in large unresectable tumors.

Cytokine deposition alters leukocyte morphology and initial recruitment of monocytes and γδT cells after corneal injury

PURPOSE

An in vivo mouse model reproducibly induces recurrent epithelial erosions in wild-type mice spontaneously 2 weeks after a single 1.5-mm corneal debridement wound made with a dulled blade. When 1.5-mm wounds are made by a rotating burr so that the corneal epithelial basement membrane is removed, corneas heal without developing erosions. Here, we characterize differences in cytokine deposition and changes in leukocytes between 0 and 6 hours after dulled-blade and rotating-burr wounding.

METHODS

BALB/c mice were used to study 1.5-mm corneal wounds made using a dulled blade or a rotating burr. Mice were studied immediately after wounding (0 hour) and at 6 hours in vivo and in vitro in organ culture. Corneas, corneal extracts, and collagenase digests from naïve and wounded mice were used for three-dimensional (3D) confocal imaging, cytokine arrays, and flow cytometry.

RESULTS

Confocal imaging showed CD45, a protein derived from leukocytes, accumulates at the wound edge by 3 and 6 hours after wounding in vivo but not in vitro with more CD45 accumulating after dulled-blade compared with rotating-burr wounds. Morphologic changes occurred in CD45+ leukocytes and higher levels for several cytokines were detected in the stromal wound bed within minutes following dulled-blade wounds. Flow cytometry showed significantly more monocytes (CD45+/CD11b+/Ly6C+) and γδT cells (CD45+/GL3+) recruited into the corneas of mice with dulled-blade wounds by 6 hours.

CONCLUSIONS

Differences in cytokine-driven leukocyte responses are seen after dulled-blade debridement compared with rotating-burr injury.

Conditional deletion of FAK in mice endothelium disrupts lung vascular barrier function due to destabilization of RhoA and Rac1 activities

Loss of lung-fluid homeostasis is the hallmark of acute lung injury (ALI). Association of catenins and actin cytoskeleton with vascular endothelial (VE)-cadherin is generally considered the main mechanism for stabilizing adherens junctions (AJs), thereby preventing disruption of lung vascular barrier function. The present study identifies endothelial focal adhesion kinase (FAK), a nonreceptor tyrosine kinase that canonically regulates focal adhesion turnover, as a novel AJ-stabilizing mechanism. In wild-type mice, induction of ALI by intraperitoneal administration of lipopolysaccharide or cecal ligation and puncture markedly decreased FAK expression in lungs. Using a mouse model in which FAK was conditionally deleted only in endothelial cells (ECs), we show that loss of EC-FAK mimicked key features of ALI (diffuse lung hemorrhage, increased transvascular albumin influx, edema, and neutrophil accumulation in the lung). EC-FAK deletion disrupted AJs due to impairment of the fine balance between the activities of RhoA and Rac1 GTPases. Deletion of EC-FAK facilitated RhoA's interaction with p115-RhoA guanine exchange factor, leading to activation of RhoA. Activated RhoA antagonized Rac1 activity, destabilizing AJs. Inhibition of Rho kinase, a downstream effector of RhoA, reinstated normal endothelial barrier function in FAK-/- ECs and lung vascular integrity in EC-FAK-/- mice. Our findings demonstrate that EC-FAK plays an essential role in maintaining AJs and thereby lung vascular barrier function by establishing the normal balance between RhoA and Rac1 activities.

β-Glucans are involved in immune-modulation of THP-1 macrophages

SCOPE

We aimed to examine different immunological aspects of β-glucans derived from different food sources (oat, barley and shiitake) on phorbol myristate acetate (PMA)-differentiated THP-1 macrophages. Commercially purified barley β-glucan (commercial BG) and lentinan were included to compare β-glucans from the same origin but different degree of purity and processing.

METHODS AND RESULTS

Chemical composition and molecular weight distribution of β-glucan samples were determined. Inflammation-related gene expression kinetics (IL-1β, IL-8, nuclear factor kappa B [NF-κB] and IL-10) after 3, 6 and 24 h of stimulation with 100 μg/mL β-glucan were investigated. All tested β-glucans mildly upregulated the observed inflammation-related genes with differential gene expression patterns. Similar gene expression kinetics, but different fold induction values, was found for the crude β-glucan extracts and their corresponding commercial forms. Pre-incubation of THP-1 macrophages with β-glucans prior to lipopolysaccharide (LPS) exposure decreased the induction of inflammation-related genes compared to LPS treatment. No production of nitric oxide (NO) and hydrogen peroxide (H₂O₂) was detected in β-glucan stimulated THP-1 macrophages. Phagocytic activity was not different after stimulation by β-glucan samples.

CONCLUSION

Based on these in vitro analyses, it can be concluded that the analysed β-glucans have varying levels of immunomodulating properties, which are likely related to structure, molecular weight and compositional characteristic of β-glucan.

Impaired phagocytosis in macrophages from patients affected by lysinuric protein intolerance

Lysinuric Protein Intolerance (LPI, MIM 222700) is a recessive aminoaciduria caused by defective cationic amino acid transport in epithelial cells of intestine and kidney. SLC7A7, the gene mutated in LPI, codifies for the y+LAT1 subunit of system y(+)L amino acid transporter. LPI patients frequently display severe complications, such as pulmonary disease, haematological abnormalities and disorders of the immune response. The transport defect may explain only a part of the clinical aspects of the disease, while the mechanisms linking the genetic defect to the clinical features of the patients remain thus far obscure. The aim of the study is to investigate the consequences of SLC7A7 mutations on specific macrophage functions, so as to evaluate if a macrophage dysfunction may have a role in the development of pulmonary and immunological complications of LPI. The results presented 1) confirm previous data obtained in one LPI patient, demonstrating that arginine influx through system y(+)L is markedly compromised in LPI macrophages; 2) demonstrate that also system y(+)L-mediated arginine efflux is significantly lower in LPI macrophages than in normal cells and 3) demonstrate that the phagocytic activity of LPI macrophages is severely impaired. In conclusion, SLC7A7/y+LAT1 mutations lead to a defective phenotype of macrophages, supporting the pathogenetic role of these cells in the development of LPI-associated complications.

Propofol's effects on phagocytosis, proliferation, nitrate production, and cytokine secretion in pressure-stimulated microglial cells

BACKGROUND

Intracranial hypertension complicates severe traumatic brain injury frequently and might be associated with poor outcomes. Traumatic brain injury induces a neuroinflammatory response by microglial activation and upregulation of proinflammatory cytokines, such as interleukin-1β, tumor necrosis factor alpha, and interleukin-6. To elucidate the effect of increased intracranial pressure on microglial function, we studied the effects of increased extracellular pressure on primary human microglial cell phagocytosis, proliferation, cytokine secretion, and total nitrate production. In addition, because many patients receive propofol during anesthesia or intensive care unit sedation, we evaluated whether propofol alters the effects of pressure.

METHODS

Human microglial cells were pretreated with (2.5-20 μg/mL) propofol or Intralipid as a vehicle control were incubated at ambient atmospheric pressure or at 15 or 30 mm Hg increased pressure for 2 h for phagocytosis assays or 24 h for proliferation, cytokine secretion, and total nitrate production studies. Phagocytosis was determined by incorporation of intracellular fluorescent latex beads. Tumor necrosis factor alpha, interleukin-1β, and interleukin-6 were assayed by sandwich enzyme-linked immunosorbent assay and total nitrate by Greiss reagent.

RESULTS

Increased extracellular pressure stimulated phagocytosis versus untreated microglial cells or cells treated with an Intralipid vehicle control. Propofol also stimulated microglial phagocytosis at ambient pressure. Increased pressure, however, decreased phagocytosis in the presence of propofol. Pressure also increased microglial tumor necrosis factor-α and interleukin-1β secretion and propofol pretreatment blocked the pressure-stimulated effect. Interleukin-6 production was not altered either by pressure or by propofol. Pressure also induced total nitrate secretion, and propofol pretreatment decreased basal as well as pressure-induced microglial nitrate production.

CONCLUSION

Extracellular pressures consistent with increased intracranial pressure after a head injury activate inflammatory signals in human primary microglial cells in vitro, stimulating phagocytosis, proliferation, tumor necrosis factor-α, interleukin-1β, and total nitrate secretion but not affecting interleukin-6. Such inflammatory events may contribute to the worsened prognosis of traumatic brain injury after increased intracranial pressure. Because propofol alleviated these potentially proinflammatory effects, these results suggest that the inflammatory cascade activated by intracranial pressure might be targeted by propofol in patients with increased intracranial pressure after traumatic brain injury.

The PPE18 protein of Mycobacterium tuberculosis inhibits NF-κB/rel-mediated proinflammatory cytokine production by upregulating and phosphorylating suppressor of cytokine signaling 3 protein

Mycobacterium tuberculosis bacteria are known to suppress proinflammatory cytokines like IL-12 and TNF-α for a biased Th2 response that favors a successful infection and its subsequent intracellular survival. However, the signaling pathways targeted by the bacilli to inhibit production of these cytokines are not fully understood. In this study, we demonstrate that the PPE18 protein of M. tuberculosis inhibits LPS-induced IL-12 and TNF-α production by blocking nuclear translocation of p50, p65 NF-κB, and c-rel transcription factors. We found that PPE18 upregulates the expression as well as tyrosine phosphorylation of suppressor of cytokine signaling 3 (SOCS3), and the phosphorylated SOCS3 physically interacts with IκBα-NF-κB/rel complex, inhibiting phosphorylation of IκBα at the serine 32/36 residues by IκB kinase-β, and thereby prevents nuclear translocation of the NF-κB/rel subunits in LPS-activated macrophages. Specific knockdown of SOCS3 by small interfering RNA enhanced IκBα phosphorylation, leading to increased nuclear levels of NF-κB/rel transcription factors vis-a-vis IL-12 p40 and TNF-α production in macrophages cotreated with PPE18 and LPS. The PPE18 protein did not affect the IκB kinase-β activity. Our study describes a novel mechanism by which phosphorylated SOCS3 inhibits NF-κB activation by masking the phosphorylation site of IκBα. Also, this study highlights the possible mechanisms by which the M. tuberculosis suppresses production of proinflammatory cytokines using PPE18.

Alum interaction with dendritic cell membrane lipids is essential for its adjuvanticity

As an approved vaccine adjuvant for use in humans, alum has vast health implications, but, as it is a crystal, questions remain regarding its mechanism. Furthermore, little is known about the target cells, receptors, and signaling pathways engaged by alum. Here we report that, independent of inflammasome and membrane proteins, alum binds dendritic cell (DC) plasma membrane lipids with substantial force. Subsequent lipid sorting activates an abortive phagocytic response that leads to antigen uptake. Such activated DCs, without further association with alum, show high affinity and stable binding with CD4(+) T cells via the adhesion molecules intercellular adhesion molecule-1 (ICAM-1) and lymphocyte function-associated antigen-1 (LFA-1). We propose that alum triggers DC responses by altering membrane lipid structures. This study therefore suggests an unexpected mechanism for how this crystalline structure interacts with the immune system and how the DC plasma membrane may behave as a general sensor for solid structures.

beta(1)-integrin mediates pressure-stimulated phagocytosis

BACKGROUND

Extracellular pressure alterations in infection, inflammation, or positive pressure ventilation may influence macrophage phagocytosis. We hypothesized that pressure modulates beta1-integrins to stimulate phagocytosis.

METHODS

We assayed fibroblast phagocytosis of fluorescent latex beads at ambient or 20 mm Hg increased pressure, and macrophage integrin phosphorylation by Western blot.

RESULTS

Pressure did not alter phagocytosis in beta(1)-integrin null GD25 fibroblasts, but stimulated phagocytosis in fibroblasts expressing wild-type beta(1)-integrin. In phorbol myristate acetate-differentiated THP-1 macrophages, pressure stimulated beta(1)-integrin T788/789 phosphorylation, but not S785 phosphorylation. Furthermore, pressure stimulated phagocytosis in cells expressing an inactivating S785A point mutation or a T788D substitution to mimic a constitutively phosphorylated threonine, but not in cells expressing an inactivating TT788/9AA mutation.

CONCLUSIONS

The effects of pressure on phagocytosis are not limited to macrophages but generalize to other phagocytic cells. These results suggest that pressure stimulates phagocytosis via increasing beta(1)-integrin T789 phosphorylation. Interventions that target beta(1)-integrin threonine 789 phosphorylation may modulate phagocytic function.

The effects of mechanical forces on intestinal physiology and pathology

The epithelial and non-epithelial cells of the intestinal wall experience a myriad of physical forces including strain, shear, and villous motility during normal gut function. Pathologic conditions alter these forces, leading to changes in the biology of these cells. The responses of intestinal epithelial cells to forces vary with both the applied force and the extracellular matrix proteins with which the cells interact, with differing effects on proliferation, differentiation, and motility, and the regulation of these effects involves similar but distinctly different signal transduction mechanisms. Although normal epithelial cells respond to mechanical forces, malignant gastrointestinal epithelial cells also respond to forces, most notably by increased cell adhesion, a critical step in tumor metastasis. This review will focus on the phenomenon of mechanical forces influencing cell biology and the mechanisms by which the gut responds these forces in both the normal as well as pathophysiologic states when forces are altered. Although more is known about epithelial responses to force, information regarding mechanosensitivity of vascular, neural, and endocrine cells within the gut wall will also be discussed, as will, the mechanism by which forces can regulate epithelial tumor cell adhesion.

Elevated hydrostatic pressure activates sodium/hydrogen exchanger-1 in rat optic nerve head astrocytes

Optic nerve head astrocytes become abnormal in eyes that have elevated intraocular pressure, and cultured astrocytes display altered protein expression after being subjected for > or = 1 days to elevated hydrostatic pressure. Here we show that 2-h elevated hydrostatic pressure (15 or 30 mmHg) causes phosphorylation of ERK1/2, ribosomal S6 protein kinase (p90(RSK)), and Na/H exchanger (NHE)1 in cultured rat optic nerve head astrocytes as judged by Western blot analysis. The MEK/ERK inhibitor U0126 abolished phosphorylation of NHE1 and p90(RSK) as well as ERK1/2. To examine NHE1 activity, cytoplasmic pH (pH(i)) was measured with BCECF and, in some experiments, cells were acidified by 5-min exposure to 20 mM ammonium chloride. Although baseline pH(i) was unaltered, the rate of pH(i) recovery from acidification was fourfold higher in pressure-treated astrocytes. In the presence of either U0126 or dimethylamiloride (DMA), an NHE inhibitor, hydrostatic pressure did not change the rate of pH(i) recovery. The findings are consistent with NHE1 activation due to phosphorylation of ERK1/2, p90(RSK), and NHE1 that occurs in response to hydrostatic pressure. These responses may precede long-term changes of protein expression known to occur in pressure-stressed astrocytes.

Propofol inhibits pressure-stimulated macrophage phagocytosis via the GABAA receptor and dysregulation of p130cas phosphorylation

Surgical stress and anesthesia result in systemic immunosuppression. Propofol, a commonly used anesthetic agent, alters immune cell functions. Previously, we demonstrated that extracellular pressure increases macrophage phagocytosis. We hypothesized that propofol might influence pressure-induced macrophage phagocytosis in monocytes from patients undergoing surgery. Pressure (20 mmHg above ambient pressure) augmented phagocytosis in monocytes from non-propofol-anesthetized patients but reduced phagocytosis in monocytes from propofol-anesthetized patients. In vitro, propofol stimulated phagocytosis but reversed pressure-induced phagocytosis in THP-1 macrophages and monocytes from healthy volunteers. The GABA(A) receptor antagonists picrotoxin and SR-95531 did not affect basal THP-1 phagocytosis or prevent pressure-stimulated phagocytosis. However, picrotoxin and SR-95531 negated the inhibitory effect of pressure in propofol-treated cells without altering propofol-induced phagocytosis. Phosphorylation of the adaptor protein p130cas was inversely related to phagocytosis: it was inhibited by pressure or propofol but increased by pressure + propofol compared with propofol alone. Reduction of p130cas by small interfering RNA in THP-1 macrophages increased basal phagocytosis and prevented pressure and propofol effects. In conclusion, propofol may alter macrophage responses to pressure via the GABA(A) receptor and p130cas, whereas pressure also acts via p130cas but independently of GABA(A) receptors. p130cas may be an important target for modulation of macrophage function in anesthetized patients.

Alphavbeta3/alphavbeta5 integrins-FAK-RhoB: a novel pathway for hypoxia regulation in glioblastoma

The presence of hypoxic areas in glioblastoma is an important determinant in tumor response to therapy and, in particular, to radiotherapy. Here we have explored the involvement of integrins, up to now known as regulators of angiogenesis and invasion, in the regulation of tumor hypoxia driven from the tumor cell. We first show that hypoxia induces the recruitment of alpha(v)beta(3) and alpha(v)beta(5) integrins to the cellular membrane of U87 and SF763 glioblastoma cells, thereby activating the focal adhesion kinase (FAK). We then show that inhibiting alpha(v)beta(3) or alpha(v)beta(5) integrins in hypoxic cells with a specific inhibitor or with siRNA decreases the hypoxia-inducible factor 1alpha (HIF-1alpha) intracellular level. This integrin-dependent regulation of HIF-1alpha is mediated through the regulation of FAK, which in turn activates the small GTPase RhoB, leading to the inhibition of GSK3-beta. Furthermore, silencing this pathway in glioma cells of established xenografts dramatically reduces glioma hypoxia, associated with a significant decrease in vessel density. Our present results unravel a new mechanism of hypoxia regulation by establishing the existence of an alpha(v)beta(3)/alpha(v)beta(5) integrin-dependent loop of hypoxia autoregulation in glioma. Targeting this hypoxia loop may be crucial to optimizing radiotherapy efficiency.

Phagocytosis of bacteria is enhanced in macrophages undergoing nutrient deprivation

Phagocytosis represents a mechanism used by macrophages to remove pathogens and cellular debris. Recent evidence suggests that phagocytosis is stimulated under specific conditions of stress, such as extracellular pressure and hypoxia. In the present study, we show that amino acid or glucose deprivation caused an increase in the phagocytosis of heat-inactivated Escherichia coli and Staphylococcus aureus by macrophages, but not the uptake of platelets, apoptotic cells or beads. Increased phagocytosis of bacteria could be blocked by phagocytosis inhibitors and was found to be dependent on p38 mitogen-activated protein kinase activity and scavenger receptor A. Although nutrient deprivation is a strong stimulus of autophagy, autophagosome formation was not critical for the uptake of bacteria because phagocytic clearance was not inhibited after down-regulation of the autophagy essential gene Atg7. Moreover, enhanced uptake of bacteria should not be considered as a general stress response because phagocytosis of bacteria was not stimulated after exposure of macrophages to the genotoxic agent camptothecin, heat (40 degrees C) or thapsigargin-induced endoplasmic reticulum stress. Overall, the results obtained in the present study indicate that nutrient deprivation can stimulate macrophages to fight bacterial infections.

Cancer chemotherapy: not only a direct cytotoxic effect, but also an adjuvant for antitumor immunity

Treatment of metastatic cancer mainly relies on chemotherapy. Chemotherapeutic agents kill tumor cells by direct cytotoxicity, thus leading to tumor regression. However, emerging data focus on another side of cancer chemotherapy: its antitumor immunity effect. Although cancer chemotherapy was usually considered as immunosuppressive, some chemotherapeutic agents have recently been shown to activate an anticancer immune response, which is involved in the curative effect of these treatments. Cancer development often leads to the occurrence of an immune tolerance that prevents cancer rejection by the immune system and hinders efficacy of immunotherapy. Cancer cells induce proliferation and local accumulation of immunosuppressive cells such as regulatory T cells and immature myeloid cells, and prevent the maturation of dendritic cells and their capacity to present tumor antigens to T lymphocytes. Many anticancer cytotoxic agents interfere with the molecular and cellular mechanisms leading to tumor-induced tolerance. They can restore an efficient immune response that contributes to the therapeutic effects of chemotherapy. These findings open a novel field of investigations for future clinical trial design, taking into account the immunostimulatory capacity of chemotherapeutic agents, and using them in combined chemo-immunotherapy strategies when tumor-induced tolerance is overcome.

Alphavbeta3 and alphavbeta5 integrins control glioma cell response to ionising radiation through ILK and RhoB

Integrins are extracellular matrix receptors involved in tumour invasion and angiogenesis. Although there is evidence that inhibiting integrins might enhance the efficiency of radiotherapy, little is known about the exact mechanisms involved in the integrin-dependent modulation of tumor radiosensitivity. The purpose of this study was to investigate the role of alphavbeta3 and alphavbeta5 integrins in glioblastoma cell radioresistance and overall to decipher the downstream biological pathways. We first demonstrated that silencing alphavbeta3 and alphavbeta5 integrins with specific siRNAs significantly reduced the survival after irradiation of 2 glioblastoma cell lines: U87 and SF763. We then showed that integrin activity and integrin signalling pathways controlled the glioma cell radiosensitivity. This regulation of glioma cell response to ionising radiation was mediated through the integrin-linked kinase, ILK, and the small GTPase, RhoB, by two mechanisms. The first one, independent of ILK, consists in the regulation of the intracellular level of RhoB by alphavbeta3 or alphavbeta5 integrin. The second pathway involved in cell radiosensitivity consists in RhoB activation by ionising radiation through ILK. Furthermore, we demonstrated that the alphavbeta3/alphavbeta5 integrins/ILK/RhoB pathway controlled the glioma cells radiosensitivity by regulating radiation-induced mitotic cell death. This work identifies a new biological pathway controlling glioblastoma cells radioresistance, activated from the membrane through alphavbeta3 and/or alphavbeta5 integrins via ILK and RhoB. Our results are clues that downstream effectors of alphavbeta3 and alphavbeta5 integrins as ILK and RhoB might also be promising candidate targets for improving the efficiency of radiotherapy and thus the clinical outcome of patients with glioblastoma.

Increased pressure stimulates aberrant dendritic cell maturation

Patients with malignancy typically exhibit abnormal dendritic cell profiles. Interstitial tumor pressure is increased 20-50mmHg over that in normal tissue. We hypothesized that elevated pressure in the tumor microenvironment may influence dendritic cell (DC) phenotype and function. Monocyte-derived immature and mature DC isolated from healthy human donors were exposed to either ambient or 40 mmHg increased pressure at 37°C for 12 hours, then assessed for expression of CD80, CD86, CD83, CD40, MHC-I and MHC-II. IL-12 production and phagocytosis of CFSE-labeled tumor lysate were assessed in parallel. Elevated pressure significantly increased expression of all co-stimulatory and MHC molecules on mature DC. Immature DC significantly increased expression of CD80, CD86, CD83 and MHC-II, but not MHC-I and CD40, versus ambient pressure controls. Pressure-treated immature DC phenotypically resembled mature DC controls, but produced low IL-12. Phenotypic maturation correlated with decreased phagocytic capacity. These results suggest increased extracellular pressure may cause aberrant DC maturation and impair tumor immunosurveillance.

Akt2, but not Akt1 or Akt3 mediates pressure-stimulated serum-opsonized latex bead phagocytosis through activating mTOR and p70 S6 kinase

Monocytes and macrophages play critical roles in innate host defense and are sensitive to mechanical stimuli. Tissue pressure is often altered in association with inflammation or infection. Low pressure (20 mmHg), equivalent to normal tissue pressure, increases phagocytosis by primary monocytes and PMA-differentiated THP-1 macrophages, in part by FAK and ERK inhibition and p38 activation. PI-3K is required for macrophage phagocytosis, but whether PI-3K mediates pressure-stimulated phagocytosis is not known. Furthermore, little is known about the role played by the PI-3K downstream Kinases, Akt, and p70 S6 kinase (p70S6K) in modulating macrophage phagocytosis. Thus, we studied the contribution of PI-3K, Akt, and p70S6K to pressure-increased serum-opsonized bead phagocytosis. Pressure-induced p85 PI-3K translocation from cytosolic to membrane fractions and increased Akt activation by 36.1 +/- 12.0% in THP-1 macrophages. LY294002 or Akt inhibitor IV abrogated pressure-stimulated but not basal phagocytosis. Basal Akt activation was inhibited 90% by LY294002 and 70% by Akt inhibitor IV. Each inhibitor prevented Akt activation by pressure. SiRNA targeted to Akt1, Akt2, or Akt3 reduced Akt1, Akt2, and Akt3 expression by 50%, 45%, and 40%, respectively. However, only Akt2SiRNA abrogated the pressure-stimulated phagocytosis without affecting basal. Pressure also activated mTOR and p70S6K. mTORSiRNA and p70S6K inhibition by rapamycin or p70S6KSiRNA blocked pressure-induced, but not basal, phagocytosis. Changes in tissue pressure during inflammation may regulate macrophage phagocytosis by activation of PI-3K, which activates Akt2, mTOR, and p70S6K.

Low intensity pulsed ultrasound accelerates macrophage phagocytosis by a pathway that requires actin polymerization, Rho, and Src/MAPKs activity

Phagocytosis is an essential event in the complex process of tissue repair. Here we examined the effect of low intensity pulsed ultrasound (US), which promotes fracture and wound healing, on phagocytosis by mouse macrophage cell line J774A.1 and human monocyte-derived macrophages. First, 10 to 40 min low intensity pulsed US increased uptake of serum opsonized E. coli by J774A.1 cells during a 50 min phagocytosis period. In addition, when the E. coli exposure time was varied between 35 to 80 min, the maximum increase in phagocytosis was observed in the first 35 min upon US exposure. In parallel, US induced robust actin polymerization in a time dependent manner in J774A.1 cells, showing the peak effect 30 min after stimulation. Interestingly, a low concentration of cytochalasin D (0.25-0.5 microM) prevented US-induced phagocytosis of E. coli. Furthermore, we demonstrated US enhanced activation of RhoA. Blocking its downstream effector Rho associated kinase (ROCK) with Y27632 abrogated US-induced phagocytosis. We also show that US induced activation of ERK and p38 MAPK. Pretreatment of the cells with the corresponding inhibitors PD98059 and SB203580 reduced US-induced phagocytosis. In addition, activity of tyrosine kinase Src was required for US-induced phagocytosis. Here Src represents an upstream activator of ERK and p38 MAPK. Depolymerization of actin by cytochalasin D prevented US-induced Src, ERK, and p38 activation. Our data provide a new insight into the cellular and molecular mechanisms by which low intensity pulsed US promotes tissue repair.

Involvement of MGr1-Ag/37LRP in the vincristine-induced HIF-1 expression in gastric cancer cells

Drug resistance is a major obstacle in the development of effective cancer therapy. It was reported that many chemotherapeutic drugs such as vincristine (VCR), a potent anti-tumor agent that associates with microtubules and disrupts the microtubular system, was found in acquisition of drug-resistance associated with an increase of HIF-1 expression via activating the NF-gammaB signal pathway. However, the multifactorial mechanism responsible for VCR increased HIF-1alpha expression remains to be fully elucidated. MGr1-Ag was previously reported by our laboratory as an upregulated protein in VCR-resistant cell lines SGC7901/VCR. In our study, detection of HIF-1 expression in SGC7901 cells and SGC7901/VCR cell or VCR-treated SGC7901cells showed that VCR could induce a significant expression of HIF-1alpha and VCR-resistant SGC7901/VCR cells had much higher expression of HIF-1alpha. Under nonhypoxic condition, VCR could enhance DNA binding activity and transcriptional activity of HIF-1alpha by 5.42- and 9.42-fold, respectively. Further study showed that forced expression of MGr1-Ag/37LRP upregulated HIF-1alpha protein expression and transcriptional activity in gastric cancer cell under nonhypoxic condition whereas siRNA targeting MGr1-Ag showed a markedly decreased VCR-induced HIF-1alpha expression and transcriptional activity (P < 0.05). SiRNA targeting FAK or inhibitors of phosphatidylinositol 3-kinase (PI3K) and MAPK could inhibit VCR-induced HIF-1alpha expression, suggesting FAK-PI3K and p42/44MAPK (Erk1/2) may be the major signaling molecules in MGr1-Ag/37LRP-induced HIF-1alpha expression and activity. These data support a model in which MGr1-Ag was a focal point for the convergence of VCR-mediated signaling events leading to HIF-1Alpha induction, thus revealing a novel aspect of HIF-1alpha regulation.