Apoptosis and Bax, Bcl-2, Mcl-1 expression in neutrophils of Crohn's disease patients

Catalase inhibition can modulate the ability of peripheral blood T cells to undergo apoptosis in Crohn's disease

Crohn's disease (CD) is a chronic relapsing inflammatory disorder in which defective apoptosis of mucosal T cells is postulated to produce sustained inflammation and reactive oxygen species accumulation. Whether CD T cells are intrinsically resistant to apoptosis or whether this resistance is acquired at the intestinal site needs to be clarified, as the cellular mechanisms modulate the impaired apoptosis in these cells. Here, we analysed peripheral blood T cells from patients naïve to specific CD treatment at the onset and from healthy controls. Non-activated freshly purified lymphocytes were cultured and submitted to in vitro protocols for activation (CD3/CD28 antibodies) and apoptosis (Fas antibody). Cells were analysed by flow cytometry. Caspases (3, 8, and 9) and catalase activity were measured; protein levels of bax, Bcl-2, and NF-kB were detected by western blotting, and cytokines by Luminex-based assays. The results showed that CD4 T cells from CD patients are less prone to apoptosis before they can migrate to the intestinal mucosa. Caspase-9, FasR, sIL-2Rα, IL-17A, IFNγ, IL-6, TNF-α, and IL-10 were shown to be significantly different in CD but not for the rest of the analysed biological elements. Catalase activity was significantly reduced in CD T cells, which was confirmed in ex vivo experiments in which catalase inhibition in T cells from healthy controls triggered apoptosis inhibition in a dose-dependent manner. In conclusion, apoptosis inhibition of CD T cells is a feature of these cells before they can migrate to the intestinal mucosa. Noteworthy, the impaired apoptosis of T cells can be directly influenced by catalase inhibition.

Intrinsic Apoptotic Pathway Genes of Circulating Blood Neutrophils Triggered during HIV Infection and Remained Stimulated in ART Patients

BACKGROUND

The intrinsic apoptotic pathway of neutrophils in Human Immunodeficiency Virus (HIV) infection results in spontaneous neutrophil death. There is a scarcity of data regarding the gene expression of an intrinsic apoptotic pathway of neutrophils in HIV patients.

OBJECTIVE

The objective of this study was to observe the differential expression of some important genes involved in the intrinsic apoptotic pathway of HIV patients, including those who were receiving antiretroviral therapy (ART).

METHODS

Blood samples were collected from asymptomatic, symptomatic, ART receiver HIV patients, and healthy individuals. Total RNA was extracted from neutrophils and subjected to quantitative real-time PCR assay. CD4+T cells and an automated complete blood count were performed.

RESULTS

Among the asymptomatic, symptomatic, and ART receiver HIV patients (n=20 in each group), median CD4+T counts were 633, 98, and 565 cells/ml, and the length of HIV infection in months (± SD) was 24.06 ± 21.36, 62.05 ± 25.51, and 69.2 ± 39.67, respectively. Compared with healthy controls, intrinsic apoptotic pathway genes, i.e., BAX, BIM, Caspase-3, Caspase-9, MCL-1, and Calpain-1, were upregulated to 1.21 ± 0.33, 1.8 ± 0.25, 1.24 ± 0.46, 1.54 ± 0.21, 1.88 ± 0.30, and 5.85 ± 1.34 fold in the asymptomatic group, and even more significantly, i.e., 1.51 ± 0.43, 2.09 ± 1.13, 1.85 ± 1.22, 1.72 ± 0.85, 2.26 ± 1.34, and 7.88 ± 3.31 fold in symptomatic patients, respectively. Despite CD4+ T-cell levels increased in the ART receiver group, these genes did not approach the level of healthy or asymptomatic and remained significantly upregulated.

CONCLUSION

The genes involved in the intrinsic apoptotic pathway in circulating neutrophils during HIV infection were stimulated in vivo, and ART reduced the expression of those upregulated genes but did not return to the level of asymptomatic or healthy individuals.

Circular RNA expression alterations in colon tissues of Crohn's disease patients

Genetic factors are crucial in the development of Crohn's disease (CD). Circular RNAs (circRNAs) are known to function as microRNA (miRNA) sponges and regulate a number of signalling pathways via circRNA‑miRNA interactions. As competing endogenous RNAs, the functions of circRNAs in CD should be investigated. In the present study, colon biopsy tissues were collected from ileocolon (L3)‑active CD patients and healthy controls. circRNA microarrays were performed with colon tissues from 3 CD patients and 3 controls. Subsequently, the candidate circRNAs were verified via reverse transcription‑quantitative polymerase chain reaction using colon tissues from a further 10 CD patients and 10 controls. Targeted miRNAs, genes and pathways of candidate circRNAs were predicted and analysed. Arraystar circRNA microarrays demonstrated that there were 163 upregulated circRNAs targeting 435 miRNAs and 55 downregulated circRNAs targeting 207 miRNAs (fold‑change >2 and P<0.01) in CD patients. As a candidate circRNA, hsa‑circRNA‑102685 was observed to putatively target hsa‑miR‑146b‑5p, hsa‑miR‑182‑5p and hsa‑miR‑146a‑5p. Furthermore, Kyoto Encyclopaedia of Genes and Genomes pathway analysis predicted that hsa‑circRNA‑102685 potentially participated in apoptosis, and in the Toll‑like receptor and p53 signalling pathways. Overall, the current study suggested that circRNA alterations serve an important role in the pathogenesis of CD. circRNAs, such as hsa‑circRNA‑102685, are involved in certain important signalling pathways of CD, and may be novel targets for diagnosis or treatment in this disease.

Diagnostic Value of Neutrophil-to-Lymphocyte Ratio and Platelet-to-Lymphocyte Ratio in Crohn's Disease

The aim of this study is to investigate the diagnostic efficacy of neutrophil-to-lymphocyte ratio (NLR), neutrophil-to-monocyte ratio (NMR), lymphocyte-to-monocyte ratio (LMR), and platelet-to-lymphocyte ratio (PLR) in patients with Crohn's disease (CD) and non-CD controls. These ratios were all derived from complete blood counts. Two hundred and six participants including CD inpatients and non-CD controls were retrospectively enrolled. We found statistically higher NLR and PLR and lower LMR in CD patients than in non-CD controls (all P < 0.01). However, NMR was not different between the two groups (P = 0.18). In addition, NLR, PLR, and LMR were associated with CRP and ESR. Optimal cutoffs for NLR and PLR were 2.72 (sensitivity: 68.3%, specificity: 75.9%, and overall accuracy: 70.1%) and 132.88 (sensitivity: 76.7%, specificity: 84.8%, and overall accuracy: 80.8%), respectively. In conclusion, the NLR and PLR might be effective, readily available, and low-cost biomarkers for differentiating CD patients from non-CD controls.

Possible Mechanisms of Ethanol-Mediated Colorectal Carcinogenesis: The Role of Cytochrome P4502E1, Etheno-DNA Adducts, and the Anti-Apoptotic Protein Mcl-1

BACKGROUND

Chronic alcohol consumption is a risk factor for colorectal cancer. The mechanisms by which ethanol (EtOH) exerts its carcinogenic effect on the colorectal mucosa are not clear and may include oxidative stress with the action of reactive oxygen species (ROS) generated through EtOH metabolism via cytochrome P4502E1 (CYP2E1) leading to carcinogenic etheno-DNA adducts. ROS may also induce apoptosis. However, the effect of chronic EtOH consumption on CYP2E1, etheno-DNA adducts as well as anti-apoptotic proteins in the colorectal mucosa of heavy drinkers without colorectal inflammation is still not known.

METHODS

Rectal biopsies from 32 alcoholics (>60 g EtOH/d) and from 12 controls (<20 g EtOH/d) were histologically examined, and immunohistochemistry for CYP2E1 and etheno-DNA adducts was performed. Apoptosis (cleaved PARP) as well as anti-apoptotic proteins including Bcl-x_L , Bcl-2, and Mcl-1 were immunohistochemically determined.

RESULTS

No significant difference in mucosal CYP2E1 or etheno-DNA adducts was observed between alcoholics and control patients. However, CYP2E1 and etheno-DNA adducts correlated significantly when both groups were combined (p < 0.001). In addition, although apoptosis was found not to be significantly affected by EtOH, the anti-apoptotic protein Mcl-1, but neither Bcl-x_L nor Bcl-2, was found to be significantly increased in heavy drinkers as compared to controls (p = 0.014).

CONCLUSIONS

Although colorectal CYP2E1 was not found to be significantly increased in alcoholics, CYP2E1 correlated overall with the level of etheno-DNA adducts in the colorectal mucosa, which identifies CYP2E1 as an important factor in colorectal carcinogenesis. Most importantly, however, is the up-regulation of the anti-apoptotic protein Mcl-1 in heavy drinkers counteracting apoptosis and possibly stimulating cancer development.

Association Studies of the GPR103 and BCL2L15 Genes in Autoimmune Thyroid Disease in the Japanese Population

While the past genome-wide association study (GWAS) for autoimmune thyroid diseases (AITDs) was done in Caucasians, a recent GWAS in Caucasian patients with both AITD and type 1 diabetes [a variant of autoimmune polyglandular syndrome type 3 (APS3v)] identified five non-HLA genes: BCL2L15, MAGI3, PHTF1, PTPN22, and GPR103. The aim of our study was to replicate these associations with AITD in a Japanese population. Since analyzing the rs2476601 single-nucleotide polymorphism (SNP) within the PTPN22 gene revealed no polymorphism in the Japanese, we analyzed four SNPs, rs2358994 (in BCL2L15), rs2153977 (in MAGI3), rs1111695 (in PHTF1), and rs7679475 (in GPR103) genotypes in a case-control study based on 447 Japanese AITD patients [277 Graves' disease (GD) and 170 Hashimoto's thyroiditis (HT) patients] and 225 matched Japanese controls using the high-resolution melting and unlabeled probe methods. Case-control association studies were performed using the χ(2) and Fisher's exact tests with Yates correction. The G allele of rs7679475 (A/G) was associated with HT compared with controls [P = 0.022, odds ratio (OR) = 0.69]. GD showed no significant associations with any SNPs. However, when patients with GD were stratified according to Graves' ophthalmopathy (GO), the G allele of rs2358994 (A/G) was associated with GO vs. controls (P = 0.018, OR = 1.52). These findings suggest that in the Japanese population the GPR103 gene may contribute to the pathogenesis of HT. Moreover, this study demonstrated that the SNP rs2358994 within BCL2L15 gene is associated with GO in the Japanese population.

Involvement of heat shock protein a4/apg-2 in refractory inflammatory bowel disease

BACKGROUND

Expression of heat shock protein A4 (HSPA4, also called Apg-2), a member of the HSP110 family, is induced by several forms of stress. The physiological and pathological functions of HSPA4 in the intestine remain to be elucidated.

METHODS

We assessed HSPA4 expression and function by generating HSPA4-deficient mice and using 214 human intestinal mucosa samples from patients with inflammatory bowel disease (IBD).

RESULTS

In the colonic mucosa of patients with IBD, a significant correlation was observed between the expression of HSPA4 and antiapoptotic protein Bcl-2, a T-cell-derived cytokine IL-17 or stem cell markers, such as Sox2. In refractory ulcerative colitis, a condition associated with increased cancer risk, expression of HSPA4 and Bcl-2 was increased in inflammatory cells of colonic mucosae. HSPA4 was overexpressed both in cancer cells and immune cells of human colorectal cancers. Patients with high expression of HSPA4 or Bmi1 showed significantly lower response rates upon subsequent steroid therapy as compared with patients with low expression of each gene. HSPA4-deficient mice exhibit more apoptosis and less expression of IL-17/IL-23 in inflammatory cells and less number of Sox2 cells after administration of dextran sodium sulfate than control mice. Transduction of HspaA4 bone marrow into wild-type mice reduced the immune response.

CONCLUSIONS

Upregulation of Bcl-2 and IL-17 by HSPA4 would control apoptosis of inflammatory cells and immune response in the gut, which might develop treatment resistance in IBD. HSPA4 and Bmi1 would be a useful biomarker for refractory clinical course and a promising approach for a therapeutic strategy in patients with IBD.

Defective apoptosis in intestinal and mesenteric adipose tissue of Crohn's disease patients

BACKGROUND

Crohn's disease (CD) is associated with complex pathogenic pathways involving defects in apoptosis mechanisms. Recently, mesenteric adipose tissue (MAT) has been associated with CD ethiopathology, since adipose thickening is detected close to the affected intestinal area. However, the potential role of altered apoptosis in MAT of CD has not been addressed.

AIMS

To evaluate apoptosis in the intestinal mucosa and MAT of patients with CD.

METHODS

Samples of intestinal mucosa and MAT from patients with ileocecal CD and from non-inflammatory bowel diseases patients (controls) were studied. Apoptosis was assessed by TUNEL assay and correlated with the adipocytes histological morphometric analysis. The transcriptional and protein analysis of selected genes and proteins related to apoptosis were determined.

RESULTS

TUNEL assay showed fewer apoptotic cells in CD, when compared to the control groups, both in the intestinal mucosa and in MAT. In addition, the number of apoptotic cells (TUNEL) correlated significantly with the area and perimeter of the adipose cells in MAT. Transcriptomic and proteomic analysis reveal a significantly lower transcript and protein levels of Bax in the intestinal mucosa of CD, compared to the controls; low protein levels of Bax were found localized in the lamina propria and not in the epithelium of this tissue. Furthermore, higher level of Bcl-2 and low level of Caspase 3 were seen in the MAT of CD patients.

CONCLUSION

The defective apoptosis in MAT may explain the singular morphological characteristics of this tissue in CD, which may be implicated in the pathophysiology of the disease.

Toll-like receptor 9 signaling delays neutrophil apoptosis by increasing transcription of Mcl-1

Neutrophils detect bacterial constituents, including bacterial DNA (CpG DNA), which elicits innate immunity and prolongs the functional life span of neutrophils through suppression of apoptosis. Both the anti-apoptotic protein Mcl-1 and activation of NF-κB have been implicated in neutrophil survival, but there is no evidence that these are linked in neutrophils. We hypothesized that CpG DNA could simultaneously activate these pathways. High purity CpG DNA (0.4–3.2 µg/ml) extended the life span of human neutrophils in vitro by delaying apoptosis through altering the rate of Mcl-1 turnover. CpG DNA slightly decreased Mcl-1 protein level in the presence of cyclohexmide and the proteasome inhibitor MG132 had little effect on Mcl-1 expression in CpG DNA-treated neutrophils. In contrast, CpG DNA evoked rapid increases in DNA binding by NF-κB/p65 and Mcl-1 mRNA. NF-κB inhibitors and the telomere-derived TLR9 inhibitory oligonucleotide 5′-TTT AGG GTT AGG GTT AGG G-3′ markedly reduced Mcl-1 protein levels and subsequently abrogated suppression of apoptosis by CpG DNA. Furthermore, CpG DNA attenuated the decreases in Mcl-1 in both cell lysate and nucleus of neutrophils undergoing spontaneous apoptosis and increased Mcl-1 translocation to the mitochondria, leading to preservation of mitochondrial transmembrane potential. These results demonstrate that CpG DNA through toll-like receptor 9 links two survival signaling pathways by delaying apoptosis through induction of NF-κB-mediated Mcl-1 gene transcription and promoting Mcl-1 translocation to the mitochondria.

Modulation of Neutrophil Apoptosis and the Resolution of Inflammation through β2 Integrins

Precise control of the neutrophil death program provides a balance between their defense functions and safe clearance, whereas impaired regulation of neutrophil death is thought to contribute to a wide range of inflammatory pathologies. Apoptosis is essential for neutrophil functional shutdown, removal of emigrated neutrophils, and timely resolution of inflammation. Neutrophils receive survival and pro-apoptosis cues from the inflammatory microenvironment and integrate these signals through surface receptors and common downstream mechanisms. Among these receptors are the leukocyte-specific membrane receptors β2 integrins that are best known for regulating adhesion and phagocytosis. Accumulating evidence indicate that outside-in signaling through the β2 integrin Mac-1 can generate contrasting cues in neutrophils, leading to promotion of their survival or apoptosis. Binding of Mac-1 to its ligands ICAM-1, fibrinogen, or the azurophilic granule enzyme myeloperoxidase suppresses apoptosis, whereas Mac-1-mediated phagocytosis of bacteria evokes apoptotic cell death. Mac-1 signaling is also target for the anti-inflammatory, pro-resolving mediators, including lipoxin A4, aspirin-triggered lipoxin A4, and resolvin E1. This review focuses on molecular mechanisms underlying Mac-1 regulation of neutrophil apoptosis and highlights recent advances how hierarchy of survival and pro-apoptosis signals can be harnessed to facilitate neutrophil apoptosis and the resolution of inflammation.

Imaging inflammation: molecular strategies to visualize key components of the inflammatory cascade, from initiation to resolution

Dysregulation of inflammation is central to the pathogenesis of innumerable human diseases. Understanding and tracking the critical events in inflammation are crucial for disease monitoring and pharmacological drug discovery and development. Recent progress in molecular imaging has provided novel insights into spatial associations, molecular events and temporal sequelae in the inflammatory process. While remaining a burgeoning field in pre-clinical research, increasing application in man affords researchers the opportunity to study disease pathogenesis in humans in situ thereby revolutionizing conventional understanding of pathophysiology and potential therapeutic targets. This review provides a description of commonly used molecular imaging modalities, including optical, radionuclide and magnetic resonance imaging, and details key advances and translational opportunities in imaging inflammation from initiation to resolution.

A differential concentration-dependent effect of IVIg on neutrophil functions: relevance for anti-microbial and anti-inflammatory mechanisms

BACKGROUND

Polymorphonuclear neutrophils (PMN) play a key role in host defences against invading microorganisms but can also potentiate detrimental inflammatory reactions in case of excessive or misdirected responses. Intravenous immunoglobulins (IVIg) are used to treat patients with immune deficiencies and, at higher doses, in autoimmune, allergic and systemic inflammatory disorders.

METHODOLOGY/PRINCIPAL FINDINGS

We used flow cytometry to examine the effects of IVIg on PMN functions and survival, using whole-blood conditions in order to avoid artifacts due to isolation procedures. IVIg at low concentrations induced PMN activation, as reflected by decreased L-selectin and increased CD11b expression at the PMN surface, oxidative burst enhancement, and prolonged cell survival. In contrast, IVIg at higher concentrations inhibited LPS-induced CD11b degranulation and oxidative burst priming, and counteracted LPS-induced PMN lifespan prolongation.

CONCLUSIONS/SIGNIFICANCE

IVIg appears to have differential, concentration-dependent effects on PMN, possibly supporting the use of IVIg as either an anti-microbial or an anti-inflammatory agent.

Regulation of neutrophil survival/apoptosis by Mcl-1

Neutrophil granulocytes have the shortest lifespan among leukocytes in the circulation and die via apoptosis. At sites of infection or tissue injury, prolongation of neutrophil lifespan is critical for effective host defense. Apoptosis of inflammatory neutrophils and their clearance are critical control points for termination of the inflammatory response. Evasion of neutrophil apoptosis aggravates local injury and leads to persistent tissue damage. The short-lived prosurvival Bcl-2 family protein, Mcl-1 (myeloid cell leukemia-1), is instrumental in controlling apoptosis and consequently neutrophil lifespan in response to rapidly changing environmental cues during inflammation. This paper will focus on multiple levels of control of Mcl-1 expression and function and will discuss targeting Mcl-1 as a potential therapeutic strategy to enhance the resolution of inflammation through accelerating neutrophil apoptosis.

Selectively induced apoptosis in human neutrophils in the presence of oxidative phenoxazines, 2-amino-4,4α-dihydryo-4α-7H-phenoxazine-3-one and 2-aminophenoxazine-3-one, preceded by decrease of intracellular pH, depolarization of the mitochondria, and inhibition of superoxide generation

The present research investigated the effect of the oxidative phenoxazines, 2-amino-4,4α-dihydryo-4α-7H-phenoxazine-3-one (Phx-1) and 2-amino-phenoxazine-3-one (Phx-3) on apoptosis induction and apoptosis-related early events in human neutrophils. When Phx-1 or Phx-3 was administered to freshly drawn human blood for 18 h, these phenoxazines caused apoptotic cell death morphologically characterized by condensation of the nucleus in neutrophils, without causing it in lymphocytes and monocytes. Apoptosis, which was detectable by microscopic analysis and by using flow-cytometry, occurred significantly in human neutrophils isolated from freshly drawn blood, 6 h after the administration of 50 µM Phx-1 and Phx-3. After 24 h, every isolated neutrophil treated with Phx-1 or Phx-3 fell into apoptosis or lost its morphology, while many of the neutrophils without these phenoxazines remained alive, with normal morphology. Apoptosis-related early events including a decrease in intracellular pH (pHi) and depolarization of the mitochondria occurred in the isolated neutrophils, 30 min and 6 h after the administration of Phx-1 or Phx-3, respectively. Superoxide generation from the isolated neutrophils mimicked by phorbol myristate acetate (PMA) was very markedly inhibited by 100 µM Phx-1 or Phx-3. This result could be explained, in part, by the fact that the insufficient supply of NADPH (nicotinamide adenine dinucleotide phosphate, reduced form) was caused by pHi decrease in neutrophils treated with Phx-1 or Phx, because NADPH is necessary for NADPH oxidase responsible for generating superoxide in the cells. The present results suggest that Phx-1 and Phx-3 have the capacity of selectively inducing apoptosis in human neutrophils and that these phenoxazines may be useful as specific drugs to induce apoptotic cell death of human neutrophils and thereby prevent inflammation caused by these phagocytic cells.

Effective caspase inhibition blocks neutrophil apoptosis and reveals Mcl-1 as both a regulator and a target of neutrophil caspase activation

Human tissue inflammation is terminated, at least in part, by the death of inflammatory neutrophils by apoptosis. The regulation of this process is therefore key to understanding and manipulating inflammation resolution. Previous data have suggested that the short-lived pro-survival Bcl-2 family protein, Mcl-1, is instrumental in determining neutrophil lifespan. However, Mcl-1 can be cleaved following caspase activity, and the possibility therefore remains that the observed fall in Mcl-1 levels is due to caspase activity downstream of caspase activation, rather than being a key event initiating apoptosis in human neutrophils.We demonstrate that apoptosis in highly purified neutrophils can be almost completely abrogated by caspase inhibition with the highly effective di-peptide caspase inhibitor, Q-VD.OPh, confirming the caspase dependence of neutrophil apoptosis. Effective caspase inhibition does not prevent the observed fall in Mcl-1 levels early in ultrapure neutrophil culture, suggesting that this fall in Mcl-1 levels is not a consequence of neutrophil apoptosis. However, at later timepoints, declines in Mcl-1 can be reversed with effective caspase inhibition, suggesting that Mcl-1 is both an upstream regulator and a downstream target of caspase activity in human neutrophils.

Delayed human neutrophil apoptosis by Trichomonas vaginalis lysate

Neutrophils play an important role in the human immune system for protection against such microorganisms as a protozoan parasite, Trichomonas vaginalis; however, the precise role of neutrophils in the pathogenesis of trichomoniasis is still unknown. Moreover, it is thought that trichomonal lysates and excretory-secretory products (ESP), as well as live T. vaginalis, could possibly interact with neutrophils in local tissues, including areas of inflammation induced by T. vaginalis in humans. The aim of this study was to investigate the influence of T. vaginalis lysate on the fate of neutrophils. We found that T. vaginalis lysate inhibits apoptosis of human neutrophils as revealed by Giemsa stain. Less altered mitochondrial membrane potential (MMP) and surface CD16 receptor expression also supported the idea that neutrophil apoptosis is delayed after T. vaginalis lysate stimulation. In contrast, ESP stimulated-neutrophils were similar in apoptotic features of untreated neutrophils. Maintained caspase-3 and myeloid cell leukemia-1 (Mcl-1) in neutrophils co-cultured with trichomonad lysate suggest that an intrinsic mitochondrial pathway of apoptosis was involved in T. vaginalis lysate-induced delayed neutrophil apoptosis; this phenomenon may contribute to local inflammation in trichomoniasis.

Diminished macrophage apoptosis and reactive oxygen species generation after phorbol ester stimulation in Crohn's disease

BACKGROUND

Crohn's Disease (CD) is a chronic relapsing disorder characterized by granulomatous inflammation of the gastrointestinal tract. Although its pathogenesis is complex, we have recently shown that CD patients have a systemic defect in macrophage function, which results in the defective clearance of bacteria from inflammatory sites.

METHODOLOGY/PRINCIPAL FINDINGS

Here we have identified a number of additional macrophage defects in CD following diacylglycerol (DAG) homolog phorbol-12-myristate-13-acetate (PMA) activation. We provide evidence for decreased DNA fragmentation, reduced mitochondrial membrane depolarization, impaired reactive oxygen species production, diminished cytochrome c release and increased IL-6 production compared to healthy subjects after PMA exposure. The observed macrophage defects in CD were stimulus-specific, as normal responses were observed following p53 activation and endoplasmic reticulum stress.

CONCLUSION

These findings add to a growing body of evidence highlighting disordered macrophage function in CD and, given their pivotal role in orchestrating inflammatory responses, defective apoptosis could potentially contribute to the pathogenesis of CD.

Granulocyte-macrophage colony-stimulating factor autoantibodies in murine ileitis and progressive ileal Crohn's disease

BACKGROUND & AIMS

Genetic variations that affect innate immunity increase risk of ileal Crohn's disease (CD). However, the penetrance of susceptibility genes, including NOD2, is low, suggesting additional risk factors. Neutralizing autoantibodies (Ab) against granulocyte-macrophage colony-stimulating factor (GM-CSF Ab) reduce neutrophil antimicrobial function in patients with primary alveolar proteinosis (PAP). We investigated whether GM-CSF Ab regulates neutrophil function in CD.

METHODS

Serum samples from 354 adult and pediatric patients with inflammatory bowel disease (IBD) were analyzed for GM-CSF Ab and IBD markers. Levels of GM-CSF Ab were compared with patients' CD features and neutrophil function. Intestinal barrier function and nonsteroidal anti-inflammatory drug (NSAID)-induced injury were assessed in GM-CSF-null and NOD2-null mice.

RESULTS

Median GM-CSF Ab levels increased from 0.4 microg/mL in control serum to 2.4 microg/mL in pediatric CD and 11.7 microg/mL in adult CD serum and were associated with ileal involvement (P<.001). Ileal location, duration of disease, and increased GM-CSF Ab levels were associated with stricturing/penetrating behavior (odds ratio, 2.2; P=.018). The positive and negative predictive values of GM-CSF Ab for stricturing/penetrating behavior were comparable with that of other IBD serum markers. CD patients with increased GM-CSF Ab had reduced neutrophil phagocytic capacity and increased accumulation of pSTAT3+ neutrophils in the affected ileum. GM-CSF-null mice and NOD2-null mice in which GM-CSF was neutralized had defects in mucosal barrier function and developed a transmural ileitis following NSAID exposure.

CONCLUSIONS

GM-CSF regulates ileal homeostasis in CD and in mouse models. CD patients with increases in serum GM-CSF Ab might benefit from GM-CSF administration.