Advanced Glycation End-Products Acting as Immunomodulators for Chronic Inflammation, Inflammaging and Carcinogenesis in Patients with Diabetes and Immune-Related Diseases.

Increased production of advanced glycation end products (AGEs) among reducing sugars (glucose, fructose, galactose, or ribose) and amino acids/proteins via non-enzymatic Maillard reaction can be found in lifestyle-related disease (LSRD), metabolic syndrome (MetS), and obesity and immune-related diseases. Increased serum levels of AGEs may induce aging, diabetic complications, cardiovascular diseases (CVD), neurodegenerative diseases (NDD), cancer, and inflamm-aging (inflammation with immunosenescence). The Maillard reaction can also occur among reducing sugars and lipoproteins or DNAs to alter their structure and induce immunogenicity/genotoxicity for carcinogenesis. AGEs, as danger-associated molecular pattern molecules (DAMPs), operate via binding to receptor for AGE (RAGE) or other scavenger receptors on cell surface to activate PI3K-Akt-, P38-MAPK-, ERK1/2-JNK-, and MyD88-induced NF-κB signaling pathways to mediate various pathological effects. Recently, the concept of "inflamm-aging" became more defined, and we have unveiled some interesting findings in relation to it. The purpose of the present review is to dissect the potential molecular basis of inflamm-aging in patients with diabetes and immune-mediated diseases caused by different AGEs.

Risk of rituximab-induced hepatitis B flare after antiviral discontinuation in rheumatic patients with chronic hepatitis B virus.

OBJECTVES: Among immunosuppressants, rituximab is most strongly associated with the risk of hepatitis B virus (HBV) reactivation in chronic HBV individuals. Current guidelines recommending antiviral prophylaxis for these patients on rituximab are predominantly based on studies in oncology. However, limited data existed for the precise risk of HBV flares, effectiveness and optimal duration of antiviral prophylaxis in rituximab-treated rheumatic patients, whose immune status and treatment regimen differ significantly from those of oncology patients. Therefore, we aimed to assess the incidence and clinical outcome of HBV reactivation in HBsAg-positive patients receiving rituximab for various autoimmune diseases who discontinue the antiviral agents. METHODS: A retrospective analysis was performed on 95 hepatitis B surface antigen (HBsAg)-positive patients treated with rituximab for autoimmune diseases in a single centre in Taiwan. HBV related hepatitis, defined as alanine aminotransferase (ALT) more than 3 times of baseline level and concurrent HBV reactivation, after anti-viral discontinuation, was the primary endpoint. Factors associated with HBV hepatitis flare and off-antiviral hepatitis flare were also analysed. RESULTS: With nucleos(t)ide analogues (NA) prophylaxis, no hepatitis flares occurred. However, without prophylaxis, 59% had flare (24.5 per 100 person-years) and 8% experienced liver decompensation. Concurrent steroid use was a dose-dependent risk factor for flare. After NA discontinuation, rituximab "retreatment" led to flares in 75% of cases and liver decompensation in 63% of patients. Stopping NAs within one-year post-rituximab, even without further rituximab treatment, resulted in a 38% flare rate. CONCLUSIONS: This study offers the direct evidence for the necessity of universal antiviral prophylaxis in rheumatic patients with chronic HBV receiving rituximab. After NA discontinuation, rituximab "retreatment" led to even higher flare rate and worse outcome. Patients who completed rituximab treatment should also keep antiviral agents for at least one more year to prevent hepatitis flare.

Molecular Basis for Paradoxical Activities of Polymorphonuclear Neutrophils in Inflammation/Anti-Inflammation, Bactericide/Autoimmunity, Pro-Cancer/Anticancer, and Antiviral Infection/SARS-CoV-II-Induced Immunothrombotic Dysregulation.

Polymorphonuclear neutrophils (PMNs) are the most abundant white blood cells in the circulation. These cells act as the fast and powerful defenders against environmental pathogenic microbes to protect the body. In addition, these innate inflammatory cells can produce a number of cytokines/chemokines/growth factors for actively participating in the immune network and immune homeostasis. Many novel biological functions including mitogen-induced cell-mediated cytotoxicity (MICC) and antibody-dependent cell-mediated cytotoxicity (ADCC), exocytosis of microvesicles (ectosomes and exosomes), trogocytosis (plasma membrane exchange) and release of neutrophil extracellular traps (NETs) have been successively discovered. Furthermore, recent investigations unveiled that PMNs act as a double-edged sword to exhibit paradoxical activities on pro-inflammation/anti-inflammation, antibacteria/autoimmunity, pro-cancer/anticancer, antiviral infection/COVID-19-induced immunothrombotic dysregulation. The NETs released from PMNs are believed to play a pivotal role in these paradoxical activities, especially in the cytokine storm and immunothrombotic dysregulation in the recent SARS-CoV-2 pandemic. In this review, we would like to discuss in detail the molecular basis for these strange activities of PMNs.

Molecular Basis of Accelerated Aging with Immune Dysfunction-Mediated Inflammation (Inflamm-Aging) in Patients with Systemic Sclerosis.

Systemic sclerosis (SSc) is a chronic connective tissue disorder characterized by immune dysregulation, chronic inflammation, vascular endothelial cell dysfunction, and progressive tissue fibrosis of the skin and internal organs. Moreover, increased cancer incidence and accelerated aging are also found. The increased cancer incidence is believed to be a result of chromosome instability. Accelerated cellular senescence has been confirmed by the shortening of telomere length due to increased DNA breakage, abnormal DNA repair response, and telomerase deficiency mediated by enhanced oxidative/nitrative stresses. The immune dysfunctions of SSc patients are manifested by excessive production of proinflammatory cytokines IL-1, IL-6, IL-17, IFN-α, and TNF-α, which can elicit potent tissue inflammation followed by tissue fibrosis. Furthermore, a number of autoantibodies including anti-topoisomerase 1 (anti-TOPO-1), anti-centromere (ACA or anti-CENP-B), anti-RNA polymerase enzyme (anti-RNAP III), anti-ribonuclear proteins (anti-U1, U2, and U11/U12 RNP), anti-nucleolar antigens (anti-Th/T0, anti-NOR90, anti-Ku, anti-RuvBL1/2, and anti-PM/Scl), and anti-telomere-associated proteins were also found. Based on these data, inflamm-aging caused by immune dysfunction-mediated inflammation exists in patients with SSc. Hence, increased cellular senescence is elicited by the interactions among excessive oxidative stress, pro-inflammatory cytokines, and autoantibodies. In the present review, we will discuss in detail the molecular basis of chromosome instability, increased oxidative stress, and functional adaptation by deranged immunome, which are related to inflamm-aging in patients with SSc.

Progressive multifocal leukoencephalopathy in systemic lupus erythematosus managed with pembrolizumab: A case report with literature review.

Progressive multifocal leukoencephalopathy (PML) is one of the rare but lethal infectious complication in patients with SLE, manifesting progressive central nervous demyelination caused by JC virus (JCV). There have been no effective antiviral agents so far; however, immune checkpoint inhibitors (ICI) have been demonstrated as potential treatments by reinvigorating antiviral T-cell activity against JC virus. To date, sixteen PML cases treated with anti-PD-1 have been reported; however, there was no report addressing the use of ICI in patients with concomitant PML and rheumatic disease, possibly due to the concern for possible autoimmune disease flare-up. In addition, treatment outcomes of these ICI-treated cases were heterogeneous. Experiences from these cases suggested that high disease burden, JC viral load in CSF, and severe immunosuppression status at baseline may predict poor response to treatment. Our case, a 62-year-old woman with long-standing SLE, turned out to have a delayed but effective response to prolonged ICI treatment despite of her high JC viral load and immunosuppressed status caused by high-dose steroid and rituximab. To our knowledge, this is the first case report with SLE complicated with PML clinically improved by pembrolizumab treatment without consequent immune related adverse events (irAE). Considering the lethal nature of PML and absence of effective medication, ICI is a reasonable consideration in patients with SLE and progressive PML.

Cross-Talk among Polymorphonuclear Neutrophils, Immune, and Non-Immune Cells via Released Cytokines, Granule Proteins, Microvesicles, and Neutrophil Extracellular Trap Formation: A Novel Concept of Biology and Pathobiology for Neutrophils.

Polymorphonuclear neutrophils (PMNs) are traditionally regarded as professional phagocytic and acute inflammatory cells that engulf the microbial pathogens. However, accumulating data have suggested that PMNs are multi-potential cells exhibiting many important biological functions in addition to phagocytosis. These newly found novel activities of PMN include production of different kinds of cytokines/chemokines/growth factors, release of neutrophil extracellular traps (NET)/ectosomes/exosomes and trogocytosis (membrane exchange) with neighboring cells for modulating innate, and adaptive immune responses. Besides, PMNs exhibit potential heterogeneity and plasticity in involving antibody-dependent cellular cytotoxicity (ADCC), cancer immunity, autoimmunity, inflammatory rheumatic diseases, and cardiovascular diseases. Interestingly, PMNs may also play a role in ameliorating inflammatory reaction and wound healing by a subset of PMN myeloid-derived suppressor cells (PMN-MDSC). Furthermore, PMNs can interact with other non-immune cells including platelets, epithelial and endothelial cells to link hemostasis, mucosal inflammation, and atherogenesis. The release of low-density granulocytes (LDG) from bone marrow initiates systemic autoimmune reaction in systemic lupus erythematosus (SLE). In clinical application, identification of certain PMN phenotypes may become prognostic factors for severe traumatic patients. In the present review, we will discuss these newly discovered biological and pathobiological functions of the PMNs.

Increased heterogeneity of brain perfusion predicts the development of cerebrovascular accidents.

ABSTRACT: The heterogeneity of brain perfusion is related to the risk factors of thromboembolic events such as antiphospholipid syndrome. However, the effectiveness of brain perfusion heterogeneity as a marker to predict thromboembolic events has not been confirmed. Our objective was to evaluate the effectiveness of brain perfusion heterogeneity as a marker to predict the development of cerebrovascular accidents. In this retrospective cohort study, patients who underwent Tc-99m ECD brain SPECT from January 1, 2006 through December 31, 2008 were included. Each study was reoriented with the Talairach space provided by the NeuroGam Software package. Heterogeneity of brain perfusion was measured as the coefficient of variation. The study outcome was the risk of cerebral vascular accidents in patients with increased heterogeneity of brain perfusion between January 1, 2006 and December 31, 2015. A multiple Cox proportional hazards model was applied to evaluate the risk of cerebrovascular accidents. A total of 70 patients were included in this study. The median age was 39 years (range, 28 - 59 years). There were 55 (78.6%) women. For increased heterogeneity of brain perfusion, the hazard ratio of cerebrovascular accidents was 2.68 (95% CI, 1.41 - 5.09; P = .003) after adjusting for age, sex, hypertension, diabetes mellitus, and dyslipidemia. Our study suggests that increased heterogeneity of brain perfusion is associated with an increased risk of cerebrovascular accidents.

Trogocytosis between Non-Immune Cells for Cell Clearance, and among Immune-Related Cells for Modulating Immune Responses and Autoimmunity.

The term trogocytosis refers to a rapid bidirectional and active transfer of surface membrane fragment and associated proteins between cells. The trogocytosis requires cell-cell contact, and exhibits fast kinetics and the limited lifetime of the transferred molecules on the surface of the acceptor cells. The biological actions of trogocytosis include information exchange, cell clearance of unwanted tissues in embryonic development, immunoregulation, cancer surveillance/evasion, allogeneic cell survival and infectious pathogen killing or intercellular transmission. In the present review, we will extensively review all these aspects. In addition to its biological significance, aberrant trogocytosis in the immune system leading to autoimmunity and immune-mediated inflammatory diseases will also be discussed. Finally, the prospective investigations for further understanding the molecular basis of trogocytosis and its clinical applications will also be proposed.

The Potential Role of Genetics, Environmental Factors, and Gut Dysbiosis in the Aberrant Non-Coding RNA Expression to Mediate Inflammation and Osteoclastogenic/Osteogenic Differentiation in Ankylosing Spondylitis.

Ankylosing spondylitis (AS) or radiographic axial spondyloarthritis is a chronic immune-mediated rheumatic disorder characterized by the inflammation in the axial skeleton, peripheral joints, and soft tissues (enthesis, fascia, and ligament). In addition, the extra-skeletal complications including anterior uveitis, interstitial lung diseases and aortitis are found. The pathogenesis of AS implicates an intricate interaction among HLA (HLA-B27) and non-HLA loci [endoplasmic reticulum aminopeptidase 1 (ERAP1), and interleukin-23 receptor (IL23R), gut dysbiosis, immune plasticity, and numerous environmental factors (infections, heavy metals, stress, cigarette smoking, etc.) The latter multiple non-genetic factors may exert a powerful stress on epigenetic regulations. These epigenetic regulations of gene expression contain DNA methylation/demethylation, histone modifications and aberrant non-coding RNAs (ncRNAs) expression, leading to inflammation and immune dysfunctions. In the present review, we shall discuss these contributory factors that are involved in AS pathogenesis, especially the aberrant ncRNA expression and its effects on the proinflammatory cytokine productions (TNF-α, IL-17 and IL-23), T cell skewing to Th1/Th17, and osteoclastogenic/osteogenic differentiation. Finally, some potential investigatory approaches are raised for solving the puzzles in AS pathogenesis.

Systemic lupus erythematosus is associated with impaired autophagic degradation via interleukin-6 in macrophages.

Systemic lupus erythematosus (SLE) is an autoimmune disease associated with dysregulated interleukin (IL)-6 and autophagy. Although such disturbances are increasingly recognized in patients with SLE and animal models of the disease, little is known about the specific role of IL-6 and autophagy in SLE macrophages. Here, we investigated alterations in the IL-6 axis and autophagy in macrophages derived from patients with SLE and determined whether IL-6 modulates autophagy using human macrophage models. Serum IL-6 detected by ELISA was higher in SLE patients (n = 19) than in normal controls (n = 19, p < 0.001). Levels of the IL-6 receptor (IL-6R) and autophagic markers LC3B and p62 in SLE and normal macrophages were assessed by real-time PCR, western blotting, and immunofluorescence. Compared with normal macrophages, SLE macrophages not only overexpressed IL-6Rs but also exhibited impaired autophagic degradation as evidenced by elevated levels of LC3B and p62. In vitro analyses using macrophage models revealed that prolonged exposure to exogenous recombinant human IL-6 induced a marked impairment of autophagic degradation indicated by elevated levels of LC3B and p62 in both primary macrophages and transformed macrophages. Pretreatment with tocilizumab, a humanized anti-IL-6R monoclonal antibody, restored autophagic degradation and reversed p62 accumulation in a paracrine manner in macrophages. These findings demonstrate that SLE involves IL-6-induced impairment of autophagic degradation through augmentation of IL-6R in human macrophages.

Distinguishing lupus lymphadenitis from Kikuchi disease based on clinicopathological features and C4d immunohistochemistry.

OBJECTIVES: Distinguishing Kikuchi disease (KD) from lupus lymphadenitis (LL) histologically is nearly impossible. We applied C4d immunohistochemical (IHC) stain to develop diagnostic tools. METHODS: We retrospectively investigated clinicopathological features and C4d IHC staining in an LL-enriched development cohort (19 LL and 81 KD specimens), proposed risk stratification criteria and trained machine learning models, and validated them in an external cohort (2 LL and 55 KD specimens). RESULTS: Clinically, we observed that LL was associated with an older average age (33 vs 25 years; P=0.005), higher proportion of biopsy sites other than the neck [4/19 (21%) vs 1/81 (1%); P=0.004], and higher proportion of generalized lymphadenopathy compared with KD [9/16 (56%) vs 7/31 (23%); P=0.028]. Histologically, LL involved a larger tissue area than KD did (P=0.006). LL specimens exhibited more frequent interfollicular pattern [5/19 (26%) vs 3/81 (4%); P=0.001] and plasma cell infiltrates (P=0.002), and less frequent histiocytic infiltrates in the necrotic area (P=0.030). Xanthomatous infiltrates were noted in 6/19 (32%) LL specimens. Immunohistochemically, C4d endothelial staining in the necrotic area [11/17 (65%) vs 2/62 (3%); P<10-7], and capillaries/venules [5/19 (26%) vs 7/81 (9%); P=0.048] and trabecular/hilar vessels [11/18 (61%) vs 8/81 (10%); P<10-4] in the viable area was more common in LL. During validation, both the risk stratification criteria and machine learning models were superior to conventional histological criteria. CONCLUSIONS: Integrating clinicopathological and C4d findings could distinguish LL from KD.

The Cellular and Molecular Bases of Allergy, Inflammation and Tissue Fibrosis in Patients with IgG4-related Disease.

IgG4-related disease (IgG4-RD) is a spectrum of complex fibroinflammatory disorder with protean manifestations mimicking malignant neoplasms, infectious or non-infectious inflammatory process. The histopathologic features of IgG4-RD include lymphoplasmacytic infiltration, storiform fibrosis and obliterative phlebitis together with increased in situ infiltration of IgG4 bearing-plasma cells which account for more than 40% of all IgG-producing B cells. IgG4-RD can also be diagnosed based on an elevated serum IgG4 level of more than 110 mg/dL (normal < 86.5 mg/mL in adult) in conjunction with protean clinical manifestations in various organs such as pancreato-hepatobiliary inflammation with/without salivary/lacrimal gland enlargement. In the present review, we briefly discuss the role of genetic predisposition, environmental factors and candidate autoantibodies in the pathogenesis of IgG4-RD. Then, we discuss in detail the immunological paradox of IgG4 antibody, the mechanism of modified Th2 response for IgG4 rather than IgE antibody production and the controversial issues in the allergic reactions of IgG4-RD. Finally, we extensively review the implications of different immune-related cells, cytokines/chemokines/growth factors and Toll-like as well as NOD-like receptors in the pathogenesis of tissue fibro-inflammatory reactions. Our proposals for the future investigations and prospective therapeutic strategies for IgG4-RD are shown in the last part.

Pathogenic Roles of Autoantibodies and Aberrant Epigenetic Regulation of Immune and Connective Tissue Cells in the Tissue Fibrosis of Patients with Systemic Sclerosis.

Systemic sclerosis (SSc) is a multi-system autoimmune disease with tissue fibrosis prominent in the skin and lung. In this review, we briefly describe the autoimmune features (mainly autoantibody production and cytokine profiles) and the potential pathogenic contributors including genetic/epigenetic predisposition, and environmental factors. We look in detail at the cellular and molecular bases underlying tissue-fibrosis which include trans-differentiation of fibroblasts (FBs) to myofibroblasts (MFBs). We also state comprehensively the pro-inflammatory and pro-fibrotic cytokines relevant to MFB trans-differentiation, vasculopathy-associated autoantibodies, and fibrosis-regulating microRNAs in SSc. It is conceivable that tissue fibrosis is mainly mediated by an excessive production of TGF-ß, the master regulator, from the skewed Th2 cells, macrophages, fibroblasts, myofibroblasts, and keratinocytes. After binding with TGF-ß receptors on MFB, the downstream Wnt/ß-catenin triggers canonical Smad 2/3 and non-canonical Smad 4 signaling pathways to transcribe collagen genes. Subsequently, excessive collagen fiber synthesis and accumulation as well as tissue fibrosis ensue. In the later part of this review, we discuss limited data relevant to the role of long non-coding RNAs (lncRNAs) in tissue-fibrosis in SSc. It is expected that these lncRNAs may become the useful biomarkers and therapeutic targets for SSc in the future. The prospective investigations in the development of novel epigenetic modifiers are also suggested.

Preserved specific anti-viral T-cell response but associated with decreased lupus activity in SLE patients with cytomegalovirus infection.

OBJECTIVES: SLE is an autoimmune disease characterized by aberrant autoantibody production and immune dysfunctions. Whether the anti-CMV immunity is impaired in SLE patients is poorly understood. We investigated the specific anti-viral T-cell response in SLE patients with CMV infection and its possible impacts on clinical manifestations in lupus. METHODS: CD28 null T-cell percentages were measured by flow cytometry in 89 SLE patients and 58 healthy controls. A specific anti-CMV CD8 T-cell response was assessed ex vivo by the production of intracellular cytokines in response to CMV phosphoprotein 65 (pp65) by flow cytometry. Clinical manifestations and immune parameters were analysed in SLE patients according to their CMV serostatus. RESULTS: CD28 null T cells were significantly expanded in SLE patients. When the anti-CMV pp65 CD8 polyfunctional T cell response was analysed, as defined by production of at least three of four functional cytokines or effectors (intracellular IFN-γ, IL-2, TNF-α and surface CD107a), the results demonstrated that it was not impaired in SLE patients. In contrast, when comparing clinical manifestations, there were lower anti-ds-DNA levels and decreased SLEDAI in SLE patients with CMV infection. Furthermore, the expansion of CD4+CD28 null T cells was negatively associated with anti-ds-DNA levels and SLEDAI in these lupus patients. CONCLUSION: In SLE patients with CMV infection, the specific anti-CMV CD8 T-cell response is preserved but is associated with decreased disease activity and lower anti-DNA levels among these patients, suggesting CMV infection may mitigate lupus activity.

Advanced Glycation End Products of Bovine Serum Albumin Suppressed Th1/Th2 Cytokine but Enhanced Monocyte IL-6 Gene Expression via MAPK-ERK and MyD88 Transduced NF-κB p50 Signaling Pathways.

Advanced glycation end products (AGE), the most known aging biomarker, may cause "inflamm-aging" (i.e., chronic low-grade inflammation that develops with aging) in both aged and diabetes groups. However, the molecular bases of inflamm-aging remain obscure. We prepared AGE by incubating BSA (0.0746 mmol/L) + glucose (0.5 mol/L) at 37 °C in 5% CO2-95% air for 1-180 days. The lysine glycation in BSA-AGE reached 77% on day 30 and 100% after day 130, whereas the glycation of arginine and cysteine was minimal. The Nε-(carboxymethyl)-lysine content in BSA-AGE was also increased with increasing number of incubation days. The lectin-binding assay revealed that the glycation of BSA not only altered the conformational structure, but lost binding capacity with various lectins. An immunological functional assay showed that BSA-AGE > 8 µg/mL significantly suppressed normal human Th1 (IL-2 and IFN-γ) and Th2 (IL-10) mRNA expression, whereas AGE > 0.5 µg/mL enhanced monocyte IL-6 production irrelevant to cell apoptosis. The AGE-enhanced monocyte IL-6 production was via MAPK-ERK and MyD88-transduced NF-κBp50 signaling pathways. To elucidate the structure-function relationship of BSA-AGE-enhanced IL-6 production, we pre-preincubated BSA-AGE with different carbohydrate-degrading, protein-degrading, and glycoprotein-degrading enzymes. We found that trypsin and carboxypeptidase Y suppressed whereas ß-galactosidase enhanced monocyte IL-6 production. In conclusion, BSA-AGE exerted both immunosuppressive and pro-inflammatory effects that are the molecular basis of inflamm-aging in aged and diabetes groups.

Cumulative Burden of Glucocorticoid-related Adverse Events in Patients with Systemic Lupus Erythematosus: Findings from a 12-year Longitudinal Study.

OBJECTIVE: The aim of this population-based study is to examine the adverse events (AE) associated with longitudinal systemic glucocorticoid (GC) use among an ethnic Chinese systemic lupus erythematosus (SLE) cohort. METHODS: Our study subjects were patients with newly diagnosed SLE aged 18 and older who received at least 1 prescription of systemic GC between 2001 and 2012 from Taiwan's National Health Insurance Research Database (NHIRD). The earliest prescription date of systemic GC for each subject was defined as the index date. For each subject, we calculated the average prednisolone-equivalent dose and the medication possession ratio (MPR) of GC use every 90 days for each patient after the index date. Patients with a diagnosis of AE (defined by the International Classification of Diseases-9-Clinical Modification diagnosis code) during the followup were also identified from the NHIRD. Generalized estimating equations adjusted for propensity score were applied to examine the association between longitudinal GC use and risks of prespecified AE (musculoskeletal, gastrointestinal, ophthalmologic, infectious, cardiovascular, neuropsychiatric, metabolic, and dermatologic diseases). RESULTS: We identified 11,288 patients with SLE (mean followup: 6.28 yrs). Higher doses and higher MPR of GC were associated with increased risk of osteonecrosis [adjusted OR (aOR) 2.87-9.09]. Similar results were found regarding the risk of osteoporosis (aOR 1.71-3.67), bacterial infection (aOR 2.12-3.89), Cushingoid syndrome (aOR 6.51-62.03), and sleep disorder (aOR 1.42-3.59). CONCLUSION: To our knowledge, this is the first study to show that the dose and intensity of longitudinal use of GC were both associated with risk of AE among a nationwide Asian SLE cohort.

EGF receptor-dependent mechanism may be involved in the Tamm-Horsfall glycoprotein-enhanced PMN phagocytosis via activating Rho family and MAPK signaling pathway.

Our previous studies showed that urinary Tamm-Horsfall glycoprotein (THP) potently enhanced polymorphonuclear neutrophil (PMN) phagocytosis. However, the domain structure(s), signaling pathway and the intracellular events responsible for THP-enhanced PMN phagocytosis remain to be elucidated. THP was purified from normal human urine. The human promyelocytic leukemia cell line HL-60 was induced to differentiate into PMNs by all-trans retinoid acid. Pretreatment with different MAPK and PI3K inhibitors was used to delineate signaling pathways in THP-enhanced PMN phagocytosis. Phosphorylation of molecules responsible for PMN phagocytosis induced by bacterial lipopolysaccharide (LPS), THP, or human recombinant epidermal growth factor (EGF) was evaluated by western blot. A p38 MAPK inhibitor, SB203580, effectively inhibited both spontaneous and LPS- and THP-induced PMN phagocytosis. Both THP and LPS enhanced the expression of the Rho family proteins Cdc42 and Rac that may lead to F-actin re-arrangement. Further studies suggested that THP and EGF enhance PMN and differentiated HL-60 cell phagocytosis in a similar pattern. Furthermore, the EGF receptor inhibitor GW2974 significantly suppressed THP- and EGF-enhanced PMN phagocytosis and p38 and ERK1/2 phosphorylation in differentiated HL-60 cells. We conclude that EGF receptor-dependent signaling may be involved in THP-enhanced PMN phagocytosis by activating Rho family and MAP kinase.