Endogenous IL-1α is a chromatin-associated protein in mouse macrophages

Proximity labelling of pro-interleukin-1α reveals evolutionary conserved nuclear interactions

Interleukin-1α is a suggested dual-function cytokine that diverged from interleukin-1β in mammals potentially by acquiring additional biological roles that relate to highly conserved regions in the pro-domain of interleukin-1α, including a nuclear localisation sequence and histone acetyltransferase-binding domains. Why evolution modified pro-interleukin-1α's subcellular location and protein interactome, and how this shaped interleukin-1α's intracellular role, is unknown. Here we show that TurboID proximity labelling with pro-interleukin-1α suggests a nuclear role for pro-interleukin-1α that involves interaction with histone acetyltransferases, including EP300. We also identify and validate inactivating mutations in the pro-interleukin-1α nuclear localisation sequence of multiple mammalian species, including toothed whales, castorimorpha and marsupials. However, histone acetyltransferase-binding domains are conserved in those species that have lost pro-interleukin-1α nuclear localisation. Together, these data suggest that histone acetyltransferase binding and nuclear localisation occurred together, and that while some species lost the nuclear localisation sequence in their pro-interleukin-1α, histone acetyltransferase binding ability was maintained. The nuclear localisation sequence was lost from several distinct species at different evolutionary times, suggesting convergent evolution, and that the loss of the nuclear localisation sequence confers some important biological outcome.

Tumor Cell-Associated IL-1α Affects Breast Cancer Progression and Metastasis in Mice through Manipulation of the Tumor Immune Microenvironment

IL-1α is a dual function cytokine that affects inflammatory and immune responses and plays a pivotal role in cancer. The effects of intracellular IL-1α on the development of triple negative breast cancer (TNBC) in mice were assessed using the CRISPR/Cas9 system to suppress IL-1α expression in 4T1 breast cancer cells. Knockout of IL-1α in 4T1 cells modified expression of multiple genes, including downregulation of cytokines and chemokines involved in the recruitment of tumor-associated pro-inflammatory cells. Orthotopical injection of IL-1α knockout (KO) 4T1 cells into BALB/c mice led to a significant decrease in local tumor growth and lung metastases, compared to injection of wild-type 4T1 (4T1/WT) cells. Neutrophils and myeloid-derived suppressor cells were abundant in tumors developing after injection of 4T1/WT cells, whereas more antigen-presenting cells were observed in the tumor microenvironment after injection of IL-1α KO 4T1 cells. This switch correlated with increased infiltration of CD3+CD8+ and NKp46+cells. Engraftment of IL-1α knockout 4T1 cells into immunodeficient NOD.SCID mice resulted in more rapid tumor growth, with increased lung metastasis in comparison to engraftment of 4T1/WT cells. Our results suggest that tumor-associated IL-1α is involved in TNBC progression in mice by modulating the interplay between immunosuppressive pro-inflammatory cells vs. antigen-presenting and cytotoxic cells.

Gene deletion of Interleukin-1α reduces ER stress-induced CHOP expression in macrophages and attenuates the progression of atherosclerosis in apoE-deficient mice

The pathophysiology of atherosclerosis initiation and progression involves many inflammatory cytokines, one of them is interleukin (IL)-1α that has been shown to be secreted by activated macrophages. We have previously shown that IL-1α from bone marrow-derived cells is critical for early atherosclerosis development in mice. It is known that endoplasmic reticulum (ER) stress in macrophages is involved in progression to more advanced atherosclerosis, but it is still unknown whether this effect is mediated through cytokine activation or secretion. We previously demonstrated that IL-1α is required in ER stress-induced activation of inflammatory cytokines in hepatocytes and in the associated induction of steatohepatitis. In the current study, we aimed to examine the potential role of IL-1α in ER stress-induced activation of macrophages, which is relevant to progression of atherosclerosis. First, we demonstrated that IL-1α is required for atherosclerosis development and progression in the apoE knockout (KO) mouse model of atherosclerosis. Next, we showed that ER stress in mouse macrophages results in the protein production and secretion of IL-1α in a dose-dependent manner, and that IL-1α is required in ER stress-induced production of the C/EBP homologous protein (CHOP), a critical step in ER stress-mediated apoptosis. We further demonstrated that IL-1α-dependent CHOP production in macrophages is specifically mediated through the PERK-ATF4 signaling pathway. Altogether, these findings highlight IL-1α as a potential target for prevention and treatment of atherosclerotic cardiovascular disease.

Diverse Control Mechanisms of the Interleukin-1 Cytokine Family

The majority of interleukin-1 (IL-1) family cytokines lack amino terminal secretion signals or transmembrane domains for secretion along the conventional biosynthetic pathway. Yet, these factors must be translocated from the cytoplasm across the plasma membrane into the extracellular space in order to regulate inflammation. Recent work has identified an array of mechanisms by which IL-1 family cytokines can be released into the extracellular space, with supramolecular organizing centers known as inflammasomes serving as dominant drivers of this process. In this review, we discuss current knowledge of the mechanisms of IL-1 family cytokine synthesis, processing, and release from cells. Using this knowledge, we propose a model whereby host metabolic state dictates the route of IL-1β secretion, with implications for microbial infection and sterile inflammation.

Nuclear localization of propiece IL-1α in HeLa cells

PURPOSE

The study aimed to examine the nuclear localization of propiece interleukin (IL)-1α (ppIL-1α) and extracellular release rates of ppIL-1α, pIL-1α, and mIL-1α.

METHODS

The subcellular localization of IL-1α molecules was observed in HeLa cells transfected with green fluorescent protein (GFP)-tagged IL-1α. Extracellular release efficiency was examined using N-terminal HiBiT-tagged IL-1α. The nuclear localization status of ppIL-1α was examined by incubating ppIL-1α transfectants with 0.1% Triton X-100 solution or with complete medium on ice.

RESULTS

The results indicated the diffuse cytoplasmic and nuclear localization for m and p and ppIL-1, respectively. All IL-1α forms were released from the cells even in the steady state, and the release efficiency was 25%, 13%, and 8% for mIL-1α, pIL-1α, and ppIL-1α, respectively. Under oxidative stress condition, GFP-mIL-1α was totally diminished, but weak staining of GFP-pIL-1α and GFP-ppIL-1α was detected; nuclear localization of GFP-ppIL-1α was completely abolished by 0.1% Triton X-100 treatment, however, it remained in the nucleus after culture in complete medium on ice.

CONCLUSION

The results of this study showed that ppIL-1α was localized in the nucleus and released extracellularly even in the steady state. Moreover, its cellular localization is not firm, and it is presumed to be floating in the nucleoplasm.

Augmented secretion of IL-1α from mouse oral squamous cell carcinoma (OSCC) cells caused by serum deprivation and hypoxia promotes immune suppressive activity of mesenchymal stromal cells

OBJECTIVES

We have previously reported that mouse oral squamous carcinoma (OSCC), Sq-1979-1, produces interleukin (IL)-1α, which specifically enhances the immunosuppressive activity of co-cultured mesenchymal stromal 10T1/2 cells. This study assessed the conditions promoting the production of IL-1α in Sq-1979-1 cells, which could further enhance the immunosuppressive function of 10T1/2 cells, and evaluated its expression in OSCC tissues.

METHODS

The expression of IL-1α was examined by RT-PCR, western blotting, and enzyme-linked immune sorbent assay (ELISA). The interferon (IFN)- γ-producing capability of anti-CD3 antibody-stimulated mouse spleen cells co-cultured with 10T1/2 cells and conditioned medium (CM) from Sq-1979-1 cells was examined by ELISA. The function of IL-1α was examined using an anti-IL1α antibody. Immunohistochemical analysis of the OSCC tissues was performed.

RESULTS

The production of IL-1α from Sq-1979-1 cells was synergistically enhanced in lower serum (0.5% or 1.0% FBS) at the transcriptional level, and under hypoxia (1.0% oxygen) at the release level compared to that in the control medium supplemented with 10% FBS under normoxia. The IFN-γ-producing capability of stimulated spleen cells co-cultured with 10T1/2 cells was significantly reduced in the CMs prepared with the lower serum or under hypoxia. These functions of CMs were completely abolished by the anti-IL-1α antibody. The expression of IL-1α in OSCC tissues was prominent in the midst of a carcinomatous cellular lesion or a nearby necrotic lesion, where a supply deficiency could occur.

CONCLUSIONS

IL-1α production by Sq-1979-1 cells was synergistically augmented under low serum and hypoxic conditions, which could promote the immunosuppressive activity of mesenchymal cells.

IL-1α Processing, Signaling and Its Role in Cancer Progression

Interleukin-1α (IL-1α) is a major alarmin cytokine which triggers and boosts the inflammatory responses. Since its discovery in the 1940s, the structure and bioactivity of IL-1α has been extensively studied and emerged as a vital regulator in inflammation and hematopoiesis. IL-1α is translated as a pro-form with minor bioactivity. The pro-IL-1α can be cleaved by several proteases to generate the N terminal and C terminal form of IL-1α. The C terminal form of IL-1α (mature form) has several folds higher bioactivity compared with its pro-form. IL-1α is a unique cytokine which could localize in the cytosol, membrane, nucleus, as well as being secreted out of the cell. However, the processing mechanism and physiological significance of these differentially localized IL-1α are still largely unknown. Accumulating evidence suggests IL-1α is involved in cancer pathogenesis. The role of IL-1α in cancer development is controversial as it exerts both pro- and anti-tumor roles in different cancer types. Here, we review the recent development in the processing and signaling of IL-1α and summarize the functions of IL-1α in cancer development.

Recruitment of pro-IL-1α to mitochondrial cardiolipin, via shared LC3 binding domain, inhibits mitophagy and drives maximal NLRP3 activation

The balance between NLRP3 inflammasome activation and mitophagy is essential for homeostasis and cellular health, but this relationship remains poorly understood. Here we found that interleukin-1α (IL-1α)-deficient macrophages have reduced caspase-1 activity and diminished IL-1β release, concurrent with reduced mitochondrial damage, suggesting a role for IL-1α in regulating this balance. LPS priming of macrophages induced pro-IL-1α translocation to mitochondria, where it directly interacted with mitochondrial cardiolipin (CL). Computational modeling revealed a likely CL binding motif in pro-IL-1α, similar to that found in LC3b. Thus, binding of pro-IL-1α to CL in activated macrophages may interrupt CL-LC3b-dependent mitophagy, leading to enhanced Nlrp3 inflammasome activation and more robust IL-1β production. Mutation of pro-IL-1α residues predicted to be involved in CL binding resulted in reduced pro-IL-1α-CL interaction, a reduction in NLRP3 inflammasome activity, and increased mitophagy. These data identify a function for pro-IL-1α in regulating mitophagy and the potency of NLRP3 inflammasome activation.

Acid-electrolyzed functional water-induces Interleukin-1α release from Intracellular Storage Sites in Oral Squamous Cell Carcinoma

The aim of this study was to examine the acid-electrolyzed functional water (FW)-mediated cytokine release in an oral squamous cell carcinoma-derived cell line (OSCC) following treatment with FW. FW is generated by the electrolysis of a sodium chloride solution and accelerate the burn wound healing. To elucidate the underlying mechanisms, the cytokine/chemokine secretion profile of HSC3 cells was examined using a cytokine array. FW treatment significantly induced interleukin (IL)-1α secretion, which was confirmed by enzyme-linked immunosorbent assay. Subsequently, the HSC3 cells were pre-treated with cycloheximide (CHX) for 1 h prior to FW stimulation to determine whether the augmented IL-1α secretion was due to enhanced protein synthesis. CHX pre-treatment did not affect IL-1α secretion suggesting that the secreted IL-1α might have been derived from intracellular storage sites. The amount of IL-1α in the cell lysate of the FW-treated HSC3 cells was significantly lower than that of the non-treated cells. Immunofluorescence staining using a polyclonal antibody against full-length IL-1α revealed a drastic reduction in IL-1α inside the FW- treated cells. IL-1α is synthesized in its precursor form (pIL-1α) and cleaved to produce pro-piece and mature IL-1α (ppIL-1α and mIL-1α) inside the cells. In the present study, only pIL-1α was detected within the HSC3 cells in its resting state. However, FW stimulation resulted in the release of the 33 kDa and two other smaller forms (about 19 kDa) of the protein. These results indicates that FW treatment induces IL-1α secretion, a typical alarmin, from the intracellular storage in OSCC cells.

Capping protein regulator and myosin 1 linker 3 regulates transcription of key cytokines in activated phagocytic cells

We have recently reported that capping protein regulator and myosin 1 linker 3 (CARMIL3), first identified as an oncofetal-like gene, is required for metastasis of breast and prostate cancer cells via regulating the actin cytoskeletal dynamics near the plasma membrane. Here, we demonstrate a novel function of CARMIL3 as an essential regulator of the transcription of several key proinflammatory cytokines in macrophages engulfing apoptotic cells and/or exposed to lipopolysaccharides (LPS). CARMIL3-deficient macrophages expressed strongly abrogated levels of interleukin (IL)-6, TNF-α, IL-1β and IL-23 in response to LPS, whereas IL-10 expression was enhanced. An RNA-seq analysis of CARMIL3-deficient and wild-type (WT) RAW264.7 cells stimulated with LPS revealed many differentially expressed genes, impacting several important inflammatory pathways. At the molecular level, CARMIL3 deficiency caused a strong impairment in LPS-activated nuclear factor-κB (NF-κB) signaling with decreased IKKα/β and IκBα phosphorylation and severely reduced p65 protein levels. This study uncovers a crucial role of CARMIL3 in impacting the balance between inflammation and tissue homeostasis via regulating major cytokines production in phagocytic cells.

Axl Deficiency Promotes the Neuroinvasion of Japanese Encephalitis Virus by Enhancing IL-1α Production from Pyroptotic Macrophages

Japanese encephalitis virus (JEV) is a mosquito-borne flavivirus that causes Japanese encephalitis (JE), the most commonly diagnosed viral encephalitis worldwide. The fatality rate of JE is 20%, and nearly half of the surviving patients develop neuropsychiatric sequelae. Axl is a receptor tyrosine kinase that plays multiple roles in flaviviral infections. Currently, the involvement of Axl in JEV infection remains enigmatic. In this study, we demonstrate that Axl impedes the pathogenesis of severe JE in mice by maintaining blood-brain-barrier (BBB) integrity and restricting viral neuroinvasion. Furthermore, serum IL-1α is a key mediator of this process and is primarily released by JEV-infected pyroptotic macrophages to elicit BBB breakdown, while an IL-1α antagonist can effectively reduce the incidence of severe JE. Our work uncovers the protective role of Axl in antagonizing severe JE and shows that the use of an IL-1α antagonist may be a promising tactic to prevent severe JE.

Japanese encephalitis virus (JEV) is a flavivirus that causes Japanese encephalitis (JE), which has an unclear pathogenesis. Despite vaccination, thousands of deaths attributed to JE are reported annually. In this study, we report that mice deficient for Axl, a receptor tyrosine kinase that plays multiple roles in flaviviral infection, displayed greater mortality upon JEV infection. The effect of Axl deficiency on JEV infection was mediated by markedly elevated serum interleukin-1α (IL-1α) levels, which devastated the blood-brain-barrier and promoted viral neuroinvasion within 24 h postinfection. Using an in situ infection model, we showed that dead macrophages were the primary source of observed increased serum IL-1α levels. Axl deficiency enhanced cell death and caused pyroptosis in 80% of JEV-infected macrophages by disrupting phosphatidylinositol 3-kinase (PI3K)-Akt signaling. Intriguingly, the primary effector released by pyroptotic macrophages in our model was IL-1α rather than IL-1β. Finally, we assessed the effect of an IL-1α antagonist and demonstrated that it effectively prevented the incidence of JE. Our results indicate that Axl plays a protective role in JEV infection, identify IL-1α released by pyroptotic macrophages as a crucial factor promoting JEV neuroinvasion, and suggest that an IL-1α antagonist may be a candidate for JE therapy.

IMPORTANCE Japanese encephalitis virus (JEV) is a mosquito-borne flavivirus that causes Japanese encephalitis (JE), the most commonly diagnosed viral encephalitis worldwide. The fatality rate of JE is 20%, and nearly half of the surviving patients develop neuropsychiatric sequelae. Axl is a receptor tyrosine kinase that plays multiple roles in flaviviral infections. Currently, the involvement of Axl in JEV infection remains enigmatic. In this study, we demonstrate that Axl impedes the pathogenesis of severe JE in mice by maintaining blood-brain-barrier (BBB) integrity and restricting viral neuroinvasion. Furthermore, serum IL-1α is a key mediator of this process and is primarily released by JEV-infected pyroptotic macrophages to elicit BBB breakdown, while an IL-1α antagonist can effectively reduce the incidence of severe JE. Our work uncovers the protective role of Axl in antagonizing severe JE and shows that the use of an IL-1α antagonist may be a promising tactic to prevent severe JE.

Amorphous nanosilica induced toxicity, inflammation and innate immune responses: A critical review

Nanoparticles are promising bioengineering platforms facilitating various consumer product formulations, including packaged food, electrical, biosensor and biomedical tools. The unique surface and physicochemical properties of amorphous nanosilica supports advanced nano-biomolecular applications for various manufacturing, biotechnology, and healthcare industries including cosmetics, packaging, implants, drug delivery systems and cancer diagnostics. The increased technological and economic benefits of amorphous nanosilica, raises concerns regarding their adverse biological effects on humans. The cellular mechanisms underlying amorphous nanosilica internalization, evasion of biological barriers, inadvertent nano-bio interactions and unexpected long term exposure effects must be taken into consideration from the diverse ecosystems and human safety aspects. Recent research studies reveal cytotoxic, inflammatory and immunomodulatory effects of amorphous nanosilica particles. Our review focuses on studies demonstrating hazardous impact of amorphous nanosilica/bio-systems interface on the cellular and biochemical processes. The review further seeks to evaluate amorphous nanosilica-induced cytotoxicity, innate immune responses, inflammation and immune related dysfunctions, and discuss open research questions related to the use of amorphous nanosilica in biomedicine.

MERS-CoV infection is associated with downregulation of genes encoding Th1 and Th2 cytokines/chemokines and elevated inflammatory innate immune response in the lower respiratory tract

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MERS-CoV infection downregulates Th1 and Th2 cytokines and chemokines.

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MERS-CoV infection provokes high levels of IL-1α, IL-1β and IL-8 (CXCL8).

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Inflammatory cytokines/chemokines correlate with MERS-CoV case fatality rate.

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Th1/Th2 downregulation may contribute to severe infection and evolution of ARDS.

MERS-CoV, a highly pathogenic virus in humans, is associated with high morbidity and case fatality. Inflammatory responses have a significant impact on MERS-CoV pathogenesis and disease outcome. However, CD4⁺ T-cell induced immune responses during acute MERS-CoV infection are barely detectable, with potent inhibition of effector T cells and downregulation of antigen presentation. The local pulmonary immune response, particularly the Th1 and Th2-related immune response during acute severe MERS-CoV infection is not fully understood. In this study, we offer the first insights into the pulmonary gene expression profile of Th1 and Th2-related cytokines/chemokines (Th1 & Th2 responses) during acute MERS-CoV infection using RT² Profiler PCR Arrays. We also quantified the expression level of primary inflammatory cytokines/chemokines. Our results showed a downregulation of Th2, inadequate (partial) Th1 immune response and high expression levels of inflammatory cytokines IL-1α and IL-1β and the neutrophil chemoattractant chemokine IL-8 (CXCL8) in the lower respiratory tract of MERS-CoV infected patients. Moreover, we identified a high viral load in all included patients. We also observed a correlation between inflammatory cytokines, Th1, and Th2 downregulation and the case fatality rate. Th1 and Th2 response downregulation, high expression of inflammatory cytokines, and high viral load may contribute to lung inflammation, severe infection, the evolution of pneumonia and ARDS, and a higher case fatality rate. Further study of the molecular mechanisms underlying the Th1 and Th2 regulatory pathways will be vital for active vaccine development and the identification of novel therapeutic strategies.

Critical role of IL-1α in IL-1β-induced inflammatory responses: cooperation with NF-κBp65 in transcriptional regulation

The IL-1 cytokines are considered among the first family of cytokines that orchestrate acute and chronic inflammatory diseases. Both IL-1β and IL-1α are members of the IL-1 family; however, their distinct roles in the inflammatory processes remain poorly understood. We explored the role of IL-1α in IL-1β-activated signaling pathways causing synovial inflammation in rheumatoid arthritis (RA). Using synovial fibroblasts isolated from RA joints, we found that IL-1β significantly stimulated IL-1α expression, which was selectively inhibited by blocking the NF-κB pathway. Knockdown of IL-1α using small interfering RNA abolished IL-1β-induced pro-IL-1α and pro-IL-1β expression and suppressed inflammation. Native and chromatin immunoprecipitation studies showed that IL-1α cooperates in NF-κBp65 binding to the distal region of IL-1α promoter and to the proximal region of IL-1β promoter upstream of the transcription start site to stabilize their gene transcription. Molecular dynamics simulation of IL-1α or IL-1β binding to IL-1 receptor showed distinct interaction sites that corroborate with the ability of IL-1α to differentially activate phosphorylation of signaling proteins compared with IL-1β. Our study highlights the importance of IL-1α in mediating IL-1β-induced inflammation in addition to maintaining its expression and providing a rationale for targeting IL-1α to minimize the role of IL-1β in inflammatory diseases like RA.-Singh, A. K., Fechtner, S., Chourasia, M., Sicalo, J., Ahmed, S. Critical role of IL-1α in IL-1β-induced inflammatory responses: cooperation with NF-κBp65 in transcriptional regulation.

Function and regulation of IL-1α in inflammatory diseases and cancer

The interleukin (IL)-1 family of cytokines is currently comprised of 11 members that have pleiotropic functions in inflammation and cancer. IL-1α and IL-1β were the first members of the IL-1 family to be described, and both signal via the same receptor, IL-1R. Over the last decade, much progress has been made in our understanding of biogenesis of IL-1β and its functions in human diseases. Studies from our laboratory and others have highlighted the critical role of nod-like receptors (NLRs) and multi-protein complexes known as inflammasomes in the regulation of IL-1β maturation. Recent studies have increased our appreciation of the role played by IL-1α in inflammatory diseases and cancer. However, the mechanisms that regulate the production of IL-1α and its bioavailability are relatively understudied. In this review, we summarize the distinctive roles played by IL-1α in inflammatory diseases and cancer. We also discuss our current knowledge about the mechanisms that control IL-1α biogenesis and activity, and the major unanswered questions in its biology.

Propiece IL-1α facilitates the growth of acute T-lymphocytic leukemia cells through the activation of NF-κB and SP1

Interleukin 1α (IL-1α) is a pro-inflammatory cytokine that possesses multiple immune-regulatory functions. It is mainly expressed as the cell-associated form and not actively secreted in healthy tissues. The intracellular IL-1α has been shown to be a chromatin-associated cytokine and can affect transcription. There are spontaneous expressions of IL-1α in acute lymphocytic leukemia (ALL) blasts. However, the role of nuclear-localized IL-1α in ALL is not clear. Here we showed that overexpression of the nuclear form of IL-1α (propiece IL-1α) could promote proliferation and reduce apoptosis of T-ALL cells. It also increased the ALL cells’ resistance to low serum concentration and cisplatin treatment. In vivo growth of the T-ALL cells overexpressing the propiece IL-1α were also enhanced compared to the control cells. Microarray analysis revealed many changes in gene expressions related to cell growth and stress, including a group of metallothionein genes. Moreover, the expressions of transcription factors, NFκB and specific protein 1 (SP1), were up-regulated by propiece IL-1α. Propiece IL-1α could bind to the promoter of SP1 and a binding sequence logo was identified. Therefore, nuclear expression of propiece IL-1α can facilitate the growth of T-ALL cells possibly through the activation of NFκB and SP1.

The Protective Role of PAC1-Receptor Agonist Maxadilan in BCCAO-Induced Retinal Degeneration

A number of studies have proven that pituitary adenylate cyclase activating polypeptide (PACAP) is protective in neurodegenerative diseases. Permanent bilateral common carotid artery occlusion (BCCAO) causes severe degeneration in the rat retina. In our previous studies, protective effects were observed with PACAP1-38, PACAP1-27, and VIP but not with their related peptides, glucagon, or secretin in BCCAO. All three PACAP receptors (PAC1, VPAC1, VPAC2) appear in the retina. Molecular and immunohistochemical analysis demonstrated that the retinoprotective effects are most probably mainly mediated by the PAC1 receptor. The aim of the present study was to investigate the retinoprotective effects of a selective PAC1-receptor agonist maxadilan in BCCAO-induced retinopathy. Wistar rats were used in the experiment. After performing BCCAO, the right eye was treated with intravitreal maxadilan (0.1 or 1 μM), while the left eye was injected with vehicle. Sham-operated rats received the same treatment. Two weeks after the operation, retinas were processed for standard morphometric and molecular analysis. Intravitreal injection of 0.1 or 1 μM maxadilan caused significant protection in the thickness of most retinal layers and the number of cells in the GCL compared to the BCCAO-operated eyes. In addition, 1 μM maxadilan application was more effective than 0.1 μM maxadilan treatment in the ONL, INL, IPL, and the entire retina (OLM-ILM). Maxadilan treatment significantly decreased cytokine expression (CINC-1, IL-1α, and L-selectin) in ischemia. In summary, our histological and molecular analysis showed that maxadilan, a selective PAC1 receptor agonist, has a protective role in BCCAO-induced retinal degeneration, further supporting the role of PAC1 receptor conveying the retinoprotective effects of PACAP.

Interleukin 1α and the inflammatory process

Inflammation occurs after disruption of tissue homeostasis by cell stress, injury or infection and ultimately involves the recruitment and retention of cells of hematopoietic origin, which arrive at the affected sites to resolve damage and initiate repair. Interleukin 1α (IL-1α) and IL-1β are equally potent inflammatory cytokines that activate the inflammatory process, and their deregulated signaling causes devastating diseases manifested by severe acute or chronic inflammation. Although much attention has been given to understanding the biogenesis of IL-1β, the biogenesis of IL-1α and its distinctive role in the inflammatory process remain poorly defined. In this review we examine key aspects of IL-1α biology and regulation and discuss its emerging importance in the initiation and maintenance of inflammation that underlie the pathology of many human diseases.

Endocytosis of indium-tin-oxide nanoparticles by macrophages provokes pyroptosis requiring NLRP3-ASC-Caspase1 axis that can be prevented by mesenchymal stem cells

The biological effects of indium-tin-oxide (ITO) are of considerable importance because workers exposed to indium compounds have been diagnosed with interstitial lung disease or pulmonary alveolar proteinosis; however, the pathophysiology of these diseases is undefined. Here, mice intraperitoneally inoculated with ITO-nanoparticles (ITO-NPs) resulted in peritonitis dependent in NLRP3 inflammasome, with neutrophils recruitment and interleukin-1β (IL-1β) production. Withal peritoneal macrophages exposed ex vivo to ITO-NPs caused IL-1β secretion and cytolysis. Further, alveolar macrophages exposed to ITO-NPs in vitro showed ITO-NP endocytosis and production of tumor necrosis factor-α (TNF-α) and IL-1β, ensued cell death by cytolysis. This cell death was RIPK1-independent but caspase1-dependent, and thus identified as pyroptosis. Endocytosis of ITO-NPs by activated THP-1 cells induced pyroptosis with IL-1β/TNF-α production and cytolysis, but not in activated THP-1 cells with knockdown of NLRP3, ASC, or caspase1. However, exposing activated THP-1 cells with NLRP3 or ASC knockdown to ITO-NPs resulted in cell death but without cytolysis, with deficiency in IL-1β/TNF-α, and revealing features of apoptosis. While, mesenchymal stem cells (MSCs) co-cultured with macrophages impaired both inflammation and cell death induced by ITO-NPs. Together, our findings provide crucial insights to the pathophysiology of respiratory diseases caused by ITO particles, and identify MSCs as a potent therapeutic.

Interleukin-1α deficiency attenuates endoplasmic reticulum stress-induced liver damage and CHOP expression in mice

BACKGROUND & AIMS

ER stress promotes liver fat accumulation and induction of inflammatory cytokines, which contribute to the development of steatohepatitis. Unresolved ER stress upregulates the pro-apoptotic CHOP. IL-1α is localized to the nucleus in apoptotic cells, but is released when these cells become necrotic and induce sterile inflammation. We investigated whether IL-1α is involved in ER stress-induced apoptosis and steatohepatitis.

METHODS

We employed WT and IL-1α-deficient mice to study the role of IL-1α in ER stress-induced steatohepatitis.

RESULTS

Liver CHOP mRNA was induced in a time dependent fashion in the atherogenic diet-induced steatohepatitis model, and was twofold lower in IL-1α deficient compared to WT mice. In the ER stress-driven steatohepatitis model, IL-1α deficiency decreased the elevation in serum ALT levels, the number of apoptotic cells (measured as caspase-3-positive hepatocytes), and the expression of IL-1β, IL-6, TNFα, and CHOP, with no effect on the degree of fatty liver formation. IL-1α was upregulated in ER-stressed-macrophages and the protein was localized to the nucleus. IL-1β mRNA and CHOP mRNA and protein levels were lower in ER-stressed-macrophages from IL-1α deficient compared to WT mice. ER stress induced the expression of IL-1α and IL-1β also in mouse primary hepatocytes. Recombinant IL-1α treatment in hepatocytes did not affect CHOP expression but upregulated both IL-1α and IL-1β mRNA levels.

CONCLUSION

We show that IL-1α is upregulated in response to ER stress and IL-1α deficiency reduces ER stress-induced CHOP expression, apoptosis and steatohepatitis. As a dual function cytokine, IL-1α may contribute to the induction of CHOP intracellularly, while IL-1α released from necrotic cells accelerates steatohepatitis via induction of inflammatory cytokines by neighboring cells.

Interleukin-1α activation and localization in lipopolysaccharide-stimulated human monocytes and macrophages

BACKGROUND

Interleukin-1α (IL-1α) is a proinflammatory cytokine belonging to the IL-1 family. It is synthesized as a 33kDa precursor peptide that is cleaved by a calpain-like protease to a 16 kDa propiece and a 17 kDa mature IL-1α peptide. In contrast to its close relative, IL-1β, the role of IL-1α in inflammation is only partly understood.

RESULTS

Human monocyte derived macrophages, stimulated with lipopolysaccharide (LPS) were analysed for production and localization of IL-1α by use of a monoclonal antibody (MAb) generated against recombinant precursor IL-1α. We found that the MAb detected IL-1α within the nuclei of the cells 2h (hours) after LPS stimulation and production continued for up to 20 h. At no time could we demonstrate cleavage of the IL-1α precursor. The MAb was conjugated to fluorescein isothiocyanate (FITC) for use in flow cytometry. Based on the flow cytometric analysis CD68 positive cells were positive for IL-1α in agreement with CD68 being a marker for monocytes.

CONCLUSIONS

Here, we demonstrate, for the first time, a method to visualize and measure the production of IL-1α in both human monocytes and macrophages.

Different Retinal Expression Patterns of IL-1α, IL-1β, and Their Receptors in a Rat Model of Type 1 STZ-Induced Diabetes

Diabetic retinopathy (DR), a common complication of diabetes, remains a major cause of blindness among population. Considerable amounts of evidences suggest the involvement of inflammatory process in this pathology. Increased levels of proinflammatory cytokines, including interleukin-1β (IL-1β), were found in the vitreous of diabetic patients and in the retina of diabetic rats. However, in this context, no attention has been given to the other main IL-1 family members: IL-1α, two transmembrane receptors IL-1RI and IL-1RII and the natural antagonist receptor IL-1Ra. Despite that they actively participate in the IL-1-mediated inflammation process, their implication in DR has not been described. Thus, we investigated by Western blot and confocal laser scanning microscopy analysis the effect of hyperglycemia on expression of IL-1 family members in retinal layers, using an in vivo model of type 1 diabetes. It was induced in adult rats by intraperitoneal injection of streptozotocin (STZ). Exposure to hyperglycemia induces a significant increase in the protein expression of IL-1β, IL-1RI, IL-RII and IL-1Ra but not of IL-1α. Moreover, high glucose alters their distribution pattern in the rat's retinal layers. Among these latter, the most compromised are the photoreceptor, the inner plexiform and ganglion cell layers. These findings support previous data demonstrating the involvement of inflammation in DR and suggest new pharmacological approaches for the treatment of this pathology.

The alarmin IL-1α is a master cytokine in acute lung inflammation induced by silica micro- and nanoparticles

Background

Inflammasome-activated IL-1β plays a major role in lung neutrophilic inflammation induced by inhaled silica. However, the exact mechanisms that contribute to the initial production of precursor IL-1β (pro-IL-1β) are still unclear. Here, we assessed the implication of alarmins (IL-1α, IL-33 and HMGB1) in the lung response to silica particles and found that IL-1α is a master cytokine that regulates IL-1β expression.

Methods

Pro- and mature IL-1β as well as alarmins were assessed by ELISA, Western Blot or qRT-PCR in macrophage cultures and in mouse lung following nano- and micrometric silica exposure. Implication of these immune mediators in the establishment of lung inflammatory responses to silica was investigated in knock-out mice or after antibody blockade by evaluating pulmonary neutrophil counts, CXCR2 expression and degree of histological injury.

Results

We found that the early release of IL-1α and IL-33, but not HMGB1 in alveolar space preceded the lung expression of pro-IL-1β and neutrophilic inflammation in silica-treated mice. In vitro, the production of pro-IL-1β by alveolar macrophages was significantly induced by recombinant IL-1α but not by IL-33. Neutralization or deletion of IL-1α reduced IL-1β production and neutrophil accumulation after silica in mice. Finally, IL-1α released by J774 macrophages after in vitro exposure to a range of micro- and nanoparticles of silica was correlated with the degree of lung inflammation induced in vivo by these particles.

Conclusions

We demonstrated that in response to silica exposure, IL-1α is rapidly released from pre-existing stocks in alveolar macrophages and promotes subsequent lung inflammation through the stimulation of IL-1β production. Moreover, we demonstrated that in vitro IL-1α release from macrophages can be used to predict the acute inflammogenic activity of silica micro- and nanoparticles.

Electronic supplementary material

The online version of this article (doi:10.1186/s12989-014-0069-x) contains supplementary material, which is available to authorized users.

Nanosilica-induced placental inflammation and pregnancy complications: Different roles of the inflammasome components NLRP3 and ASC

Despite the increasing commercial use of nanoparticles, little is known about their effects on placental inflammation and pregnancy complications. In this study, nanosilica (NS) particles upregulated the inflammasome component nucleotide-binding oligomerization domain-like receptor (NLR) family pyrin domain-containing 3 (NLRP3) and induced placental inflammation and reactive oxygen species (ROS) generation, resulting in pregnancy complications. Furthermore, NS-induced pregnancy complications were markedly improved in Nlrp3(-/-) mice but not in component apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC)-deficient (Asc(-/-)) mice, indicating the independence of NLRP3 inflammasomes. Pregnancy complications in Nlrp3(-/-) and Asc(-/-) mice phenotypes were dependent on the balance between interleukin (IL)-1α and IL-10. NS-induced pregnancy complications were completely prevented by either inhibition of ROS generation or forced expression of IL-10. Our findings provide important information about NS-induced placental inflammation and pregnancy complications and the novel pathophysiological roles of NLRP3 and ASC in pregnancy.

Interleukin-1α

Although the IL-1α molecule has long been recognized, information about its distinct role in various diseases is limited, since most clinical studies have focused on the role of IL-1β. Despite triggering the same IL-1 receptor as does IL-1β, there is, however, a distinct role for IL-1α in some inflammatory diseases. IL-1α is a unique cytokine since it is constitutively present intracellularly in nearly all resting non-hematopoietic cells in health as well as being up-regulated during hypoxia. During cell necrosis, IL-1α functions as an alarm molecule and thus plays a critical role early in inflammation. Following its release from damage tissue cells, IL-1α mediates neutrophil recruitment to the site of injury, inducing IL-1β, other cytokines and chemokines from surrounding resident cells. Another unique attribute of IL-1α is its nuclear localization sequence present in the N-terminal half of the precursor termed the propiece. The IL-1α propiece translocates into the nucleus and participates in the regulation of transcription. Therefore, IL-1α, like IL-1 family members IL-33 and IL-37, is a 'dual-function' cytokine binding to chromatin as well as to its cell surface receptor. Some cancer cells can express membrane IL-1α, which can increase immunogenicity of tumor cells and serve in anti-tumor immune surveillance and tumor regression. However, in the tumor microenvironment, precursor IL-1α released from dying tumor cells is inflammatory and, similar to IL-1β, increases tumor invasiveness and angiogenesis.