Macropinosome formation is M-CSF dependent.

<p>A and B. Wild-type macrophages were differentiated with M-CSF for 7 days and visualized by phase-contrast microscopy following the treatments described below. Macrophages differentiated with M-CSF were pretreated 30 min with DMSO drug vehicle (A), or 5 µM of cFMS (i.e., M-CSF receptor) tyrosine kinase inhibitor, GW2580 (B). Pretreatment was carried out without either serum or M-CSF. Withdrawal of M-CSF caused disappearance of the macrophage vacuoles. Subsequently, these macrophage cultures were treated 30 min with fresh serum-free medium containing M-CSF (50 ng/ml) without (A) or with GW2580 (B). Macrophages treated with M-CSF without GW2580 showed numerous vacuoles shown to be macropinosomes in Video S1. In contrast, there was complete inhibition of macropinosome formation when macrophage cultures were treated with GW2580 (also see Video S2). Scale bar in B = 75 µm and also applies to A. (C) Wild-type macrophages were incubated 24 h with 1 mg/ml LDL without or with 5 µM GW2580, and then cholesterol accumulation was assessed. Macrophages incubated without LDL had 111±3 nmol cholesterol/mg protein. ** = <i>p</i><0.01.</p

LDL-derived cholesterol accumulation occurs independently of class I PI3K isoforms.

<p>Cholesterol accumulation after 24 h-incubation without or with 1 mg/ml LDL was assessed in M-CSF differentiated macrophages cultured from wild-type, PI3Kγ-KI, PI3Kβ-KI, and PI3Kδ-KI mice.</p

Fluid-phase pinocytosis mediates LDL uptake.

<p>(A) Wild-type macrophages were incubated 6 h with either 25 µg/ml ¹²⁵I-LDL alone, or 25 µg/ml ¹²⁵I-LDL and 500 µg/ml unlabeled LDL. CD36 KO macrophages (ΔCD36) and SRA KO macrophages (ΔSRA) macrophages were incubated 6 h with 25 µg/ml ¹²⁵I-LDL alone. (B) Wild-type macrophages were incubated 6 h with either 25 µg/ml ¹²⁵I-AcLDL alone, or 25 µg/ml ¹²⁵I-AcLDL and 500 µg/ml unlabeled AcLDL. CD36 KO macrophages (ΔCD36) and SRA KO macrophages (ΔSRA) macrophages were incubated 6 h with 25 µg/ml ¹²⁵I-AcLDL alone. Incubations were performed in serum-free medium containing 50 ng/ml M-CSF. Uptake values represent the sum of cell-associated and degraded ¹²⁵I-labeled lipoprotein. The range of cell-associated and degraded ¹²⁵I-LDL was 17–21% and 79–83%, respectively. The range of cell-associated and degraded ¹²⁵I-AcLDL was 16–18% and 82–84%, respectively. ¹²⁵I-LDL uptake was not competed with excess unlabeled LDL consistent with fluid-phase pinocytosis mediating uptake. Statistical tests compare each treatment group with wild-type macrophages incubated with 25 µg/ml ¹²⁵I-AcLDL. * = <i>p</i><0.05. ** = <i>p</i><0.01. *** = <i>p</i><0.001. There was no statistical difference between macrophage groups incubated with ¹²⁵I-LDL.</p

The effect of PI3K inhibitors and cytochalasin D on LDL uptake and net cholesterol accumulation in LDLR −/− macrophages.

<p>LDLR−/− bone marrow-derived macrophages were pretreated 1 h with either drug vehicle, 50 µM LY294002, 100 nm wortmannin, or 4 µg/ml cytochalasin D. For cholesterol accumulation, macrophages then were incubated with 1 mg/ml LDL and inhibitor for 24 h. For ¹²⁵I-LDL uptake, macrophages then were incubated 5 h with 200 µg/ml ¹²⁵I-LDL and inhibitor. All incubations were performed in serum-free medium containing 50 ng/ml M-CSF. The percent inhibition of net cholesterol accumulation compares macrophages treated with LDL alone and LDL with inhibitor after basal cholesterol values were subtracted from each. The percent inhibition of ¹²⁵I-LDL uptake compares macrophages treated with ¹²⁵I-LDL alone and ¹²⁵I-LDL with inhibitor. ** = <i>p</i><0.01. *** = <i>p</i><0.001. All inhibitors showed almost complete inhibition of macropinosome formation as assessed by phase-microscopy. For LY294002 and wortmannin experiments, control macrophages incubated with LDL or ¹²⁵I-LDL alone showed net cholesterol accumulation and ¹²⁵I-LDL uptake values of 226±8 nmole/mg cell protein and 2.7±0.1 µg/mg cell protein, respectively. For cytochalasin D experiments, control macrophages incubated with LDL or ¹²⁵I-LDL alone showed net cholesterol accumulation and ¹²⁵I-LDL uptake values of 230±2 nmole/mg cell protein and 3.4±0.1 µg/mg cell protein, respectively. The range of cell-associated and degraded ¹²⁵I-LDL for all treatments was 19–33% and 67–81%, respectively.</p

Macrophage uptake of ¹²⁵I-LDL is non-saturable.

<p>A. LDLR−/− macrophages were incubated with 1 mg/ml of LDL for 0–24 h and cholesterol accumulation was then assessed. B. LDLR−/− macrophages were incubated 24 h with increasing concentrations of ¹²⁵I-LDL, and then ¹²⁵I-LDL uptake was assessed. Uptake values represent the sum of cell-associated and degraded ¹²⁵I-LDL. The range of cell-associated and degraded ¹²⁵I-LDL was 7–13% and 87–93%, respectively.</p

The effect of possible inhibitors of fluid-phase pinocytosis on LDL uptake and net cholesterol accumulation in wild-type M-CSF-differentiated macrophages.

<p>Wild-type bone marrow-derived macrophages were pretreated 1 h with drug vehicle or the indicated drug. For cholesterol accumulation, macrophages then were incubated with 1 mg/ml LDL and inhibitor for 6 h. For ¹²⁵I-LDL uptake, macrophages then were incubated with 200 µg/ml ¹²⁵I-LDL and inhibitor for 6 h. All incubations were performed in serum-free medium containing 50 ng/ml M-CSF. The percent inhibition of net cholesterol accumulation compares macrophages treated with LDL alone and LDL with inhibitor (except the experiment that compares macrophages treated with LDL and dynamin peptide inhibitor with LDL and control peptide) after basal cholesterol values were subtracted from each. The percent inhibition of ¹²⁵I-LDL uptake compares macrophages treated with ¹²⁵I-LDL alone and ¹²⁵I-LDL with inhibitor. Control values for macrophages incubated with LDL alone or ¹²⁵I-LDL alone are indicated in parentheses. For cholesterol accumulation, control values are expressed as nmol net cholesterol accumulation/mg cell protein. For ¹²⁵I-LDL uptake, control values are expressed as µg ¹²⁵I-LDL uptake/mg cell protein. The range of cell-associated and degraded ¹²⁵I-LDL for all treatments except bafilomycin A1-treated macrophages was 15–19% and 82–86%, respectively. Cell-associated and degraded ¹²⁵I-LDL for bafilomycin A1-treated macrophages was 91% and 9%, respectively. * = <i>p</i><0.05. ** = <i>p</i><0.01. *** = <i>p</i><0.001. ND = not determined. “+” indicates a decrease in the number of macropinosomes and “−” indicates no effect on macropinosomes. “−” in percent inhibition columns indicates stimulation rather than inhibition.</p

The effect of PI3K inhibitors and cytochalasin D on net cholesterol accumulation in wild-type macrophages.

<p>Wild-type bone marrow-derived macrophages were pretreated 1 h with either drug vehicle, 50 µM LY294002, 100 nm wortmannin, or 4 µg/ml cytochalasin D. Macrophages then were incubated with 1 mg/ml LDL and inhibitor for 6 h. Incubations were performed in serum-free medium containing 50 ng/ml M-CSF. The percent inhibition of net cholesterol accumulation compares macrophages treated with LDL alone and LDL with inhibitor after basal cholesterol values were subtracted from each. ** = <i>p</i><0.01. *** = <i>p</i><0.001. All inhibitors almost completely inhibited macropinosome formation as assessed by phase-microscopy. For the LY294002 experiment, control macrophages incubated with LDL alone showed net cholesterol accumulation of 31±2 nmole/mg cell protein. For the wortmannin and cytochalasin D experiments, control macrophages incubated with LDL alone showed net cholesterol accumulation of 78±2 nmole/mg cell protein.</p

Wild-type and LDL−/− macrophages incubated with LDL accumulate similar levels of cholesterol.

<p>Wild-type and LDLR−/− macrophages were incubated with 1 mg/ml LDL for 24 h and then total cholesterol accumulation was assessed. The baseline cholesterol levels for wild-type and LDLR−/− macrophages were 107±10 nmol cholesterol/mg protein and 122±9 nmol cholesterol/mg protein, respectively.</p

Cytokines Induced Neutrophil Extracellular Traps Formation: Implication for the Inflammatory Disease Condition

<div><p>Neutrophils (PMNs) and cytokines have a critical role to play in host defense and systemic inflammatory response syndrome (SIRS). Neutrophil extracellular traps (NETs) have been shown to extracellularly kill pathogens, and inflammatory potential of NETs has been shown. Microbial killing inside the phagosomes or by NETs is mediated by reactive oxygen and nitrogen species (ROS/RNS). The present study was undertaken to assess circulating NETs contents and frequency of NETs generation by isolated PMNs from SIRS patients. These patients displayed significant augmentation in the circulating myeloperoxidase (MPO) activity and DNA content, while PMA stimulated PMNs from these patients, generated more free radicals and NETs. Plasma obtained from SIRS patients, if added to the PMNs isolated from healthy subjects, enhanced NETs release and free radical formation. Expressions of inflammatory cytokines (IL-1β, TNFα and IL-8) in the PMNs as well as their circulating levels were significantly augmented in SIRS subjects. Treatment of neutrophils from healthy subjects with TNFα, IL-1β, or IL-8 enhanced free radicals generation and NETs formation, which was mediated through the activation of NADPH oxidase and MPO. Pre-incubation of plasma from SIRS with TNFα, IL-1β, or IL-8 antibodies reduced the NETs release. Role of IL-1β, TNFα and IL-8 thus seems to be involved in the enhanced release of NETs in SIRS subjects.</p> </div

Circulating DNA content, MPO activity and NETs formation in healthy subjects and SIRS patients.

<p>(<b>A</b>) DNA content in the plasma of SIRS patients and control samples (***p<0.001 vs control). (<b>B</b>) MPO activity in plasma of SIRS patients and control subjects (***p<0.001 vs control). (<b>C</b>) MPO activity in PMNs of SIRS patients and control subject. (<b>D</b>) PCR of mitochondrial genes [ATP synthase subunit 6 (atp6), cytochrome oxidase c subunit 1 (co1)], and (<b>E</b>) nuclear genes [Glyceraldehyde-3-phosphate dehydrogenase (gapdh), and β-actin]. (<b>F</b>) Bar diagram representing NETs formation in neutrophils from healthy subjects and SIRS patients following PMA treatment (*p<0.05, ***p<0.001 vs control; ^$$p<0.01, ^$$$p<0.001 vs PMA stimulated cells of healthy volunteer).</p