The expression of RAGE and EN-RAGE in leprosy

Venestatin from parasitic helminths interferes with receptor for advanced glycation end products (RAGE)-mediated immune responses to promote larval migration

Parasitic helminths can reside in humans owing to their ability to disrupt host protective immunity. Receptor for advanced glycation end products (RAGE), which is highly expressed in host skin, mediates inflammatory responses by regulating the expression of pro-inflammatory cytokines and endothelial adhesion molecules. In this study, we evaluated the effects of venestatin, an EF-hand Ca²⁺-binding protein secreted by the parasitic helminth Strongyloides venezuelensis, on RAGE activity and immune responses. Our results demonstrated that venestatin bound to RAGE and downregulated the host immune response. Recombinant venestatin predominantly bound to the RAGE C1 domain in a Ca²⁺-dependent manner. Recombinant venestatin effectively alleviated RAGE-mediated inflammation, including footpad edema in mice, and pneumonia induced by an exogenous RAGE ligand. Infection experiments using S. venezuelensis larvae and venestatin silencing via RNA interference revealed that endogenous venestatin promoted larval migration from the skin to the lungs in a RAGE-dependent manner. Moreover, endogenous venestatin suppressed macrophage and neutrophil accumulation around larvae. Although the invasion of larvae upregulated the abundance of RAGE ligands in host skin tissues, mRNA expression levels of tumor necrosis factor-α, cyclooxygenase-2, endothelial adhesion molecules vascular cell adhesion protein-1, intracellular adhesion molecule-1, and E-selectin were suppressed by endogenous venestatin. Taken together, our results indicate that venestatin suppressed RAGE-mediated immune responses in host skin induced by helminthic infection, thereby promoting larval migration. The anti-inflammatory mechanism of venestatin may be targeted for the development of anthelminthics and immunosuppressive agents for the treatment of RAGE-mediated inflammatory diseases.

Parasitic helminths have evolved smart strategies to thrive in diverse hosts. For example, parasitic helminths secrete various immunomodulators in the host to establish successful tissue migration to their reproductive niche and chronic parasitism. Identification and functional analyses have revealed these immunomodulators may have potential therapeutic effects in the treatment of immune-related diseases. However, few immunomodulators from parasitic helminths have been identified and analyzed to date. In this study, we determined that venestatin, an EF-hand Ca²⁺-binding protein secreted by the parasitic nematode Strongyloides venezuelensis, bound to receptor for advanced glycation end products (RAGE), a host pro-inflammatory receptor, which downregulated RAGE-mediated inflammatory responses. S. venezuelensis larvae successfully migrated to their niche owing to the anti-inflammatory functions of venestatin. Venestatin could provide a novel therapeutic target for the treatment of RAGE-mediated inflammatory diseases, such as Alzheimer’s disease, rheumatoid arthritis, asthma, ulcerative colitis, and diabetes.

Involvement of RAGE and Oxidative Stress in Inflammatory and Infectious Skin Diseases

The surface receptor for advanced glycosylation end-products (RAGE) and its soluble (sRAGE) and endogenous secretory (EN-RAGE) forms belong to the superfamily of toll-like receptors and play important roles in inflammation and autoimmunity, directly or through binding with advanced glycosylation end-products (AGE) and advanced oxidation protein products (AOPP). We reviewed the literature on the role of RAGE in skin diseases. Research in this field is still rather limited (28 articles) but suggests the involvement of RAGE and RAGE-related pathways in chronic inflammatory diseases (lupus, psoriasis, atopic dermatitis, and lichen planus), infectious diseases (leprosy, Staphylococcus aureus-induced skin lesions), alterations of the repairing processes in diabetic skin, systemic sclerosis, and ulcers. These data prompt further research in this field, which not only will be useful to better understand the pathogenetic mechanisms of diseases, but is also likely to have intriguing clinical implications. Indeed, when their role in the complex and multifactorial inflammatory balance will be adequately defined, RAGE and related molecules could be used as markers of disease severity and/or response to treatment. Moreover, future promising therapeutic perspectives could be topical administration of some of these molecules (e.g., sRAGE) to modulate local inflammatory response and/or the development of anti-RAGE antibodies for systemic treatment.

Calcium Regulates S100A12 Zinc Sequestration by Limiting Structural Variations

Antimicrobial proteins such as S100A12 and S100A8/A9 are highly expressed and secreted by neutrophils during infection and participate in human immune response by sequestering transition metals. At neutral pH, S100A12 sequesters Zn2+ with nanomolar affinity, which is further enhanced upon calcium binding. We investigated the pH dependence of human S100A12 zinc sequestration by using Co2+ as a surrogate. Apo-S100A12 exhibits strong Co2+ binding between pH 7.0 and 10.0 that progressively diminishes as the pH is decreased to 5.3. Ca2+ -S100A12 can retain nanomolar Co2+ binding up to pH 5.7. NMR spectroscopic measurements revealed that calcium binding does not alter the side-chain protonation of the Co2+ /Zn2+ binding histidine residues. Instead, the calcium-mediated modulation is achieved by restraining pH-dependent conformational changes to EF loop 1, which contains Co2+ /Zn2+ binding Asp25. This calcium-induced enhancement of Co2+ /Zn2+ binding might assist in the promotion of antimicrobial activities in humans by S100 proteins during neutrophil activation under subneutral pH conditions.

Application of new host biomarker profiles in quantitative point-of-care tests facilitates leprosy diagnosis in the field

BACKGROUND

Transmission of Mycobacterium leprae, the pathogen causing leprosy, is still persistent. To facilitate timely (prophylactic) treatment and reduce transmission it is vital to both early diagnose leprosy, and identify infected individuals lacking clinical symptoms. However, leprosy-specific biomarkers are limited, particularly for paucibacillary disease. Therefore, our objective was to identify new biomarkers for leprosy and assess their applicability in point-of-care (POC) tests.

METHODS

Using multiplex-bead-arrays, 60 host-proteins were measured in a cross-sectional approach in 24-h whole blood assays (WBAs) collected in Bangladesh (79 patients; 54 contacts; 51 endemic controls (EC)). Next, 17 promising biomarkers were validated in WBAs of a separate cohort (55 patients; 27 EC). Finally, in a third cohort (36 patients; 20 EC), five candidate markers detectable in plasma were assessed for application in POC tests.

FINDINGS

This study identified three new biomarkers for leprosy (ApoA1, IL-1Ra, S100A12), and confirmed five previously described biomarkers (CCL4, CRP, IL-10, IP-10, αPGL-I IgM). Overnight stimulation in WBAs provided increased specificity for leprosy and was required for IL-10, IL-1Ra and CCL4. The remaining five biomarkers were directly detectable in plasma, hence suitable for rapid POC tests. Indeed, lateral flow assays (LFAs) utilizing this five-marker profile detected both multi- and paucibacillary leprosy patients with variable immune responses.

INTERPRETATION

Application of novel host-biomarker profiles to rapid, quantitative LFAs improves leprosy diagnosis and allows POC testing in low-resource settings. This platform can thus aid diagnosis and classification of leprosy and also provides a tool to detect M.leprae infection in large-scale contact screening in the field.

Antimicrobial peptides as an alternative to anti-tuberculosis drugs

Tuberculosis (TB) presently accounts for high global mortality and morbidity rates, despite the introduction four decades ago of the affordable and efficient four-drugs (isoniazid, rifampicin, pyrazinamide and ethambutol). Thus, a strong need exists for new drugs with special structures and uncommon modes of action to effectively overcome M. tuberculosis. Within this scope, antimicrobial peptides (AMPs), which are small, cationic and amphipathic peptides that comprise a section of the innate immune system, are currently the leading potential agents for the treatment of TB. Many studies have recently illustrated the capability of anti-mycobacterial peptides to disrupt the normal mycobacterial cell wall function through various modes, thereby interacting with the intracellular targets, as well as encompassing nucleic acids, enzymes and organelles. This review presents a wide array of antimicrobial activities, alongside the associated properties of the AMPs that could be utilized as potential agents in therapeutic tactics for TB treatment.

The effects of advanced glycation end products (AGEs) on dermal wound healing and scar formation: a systematic review

Introduction:

With ageing, the skin gradually loses its youthful appearance and functions like wound healing and scar formation. The pathophysiological theory of Advanced Glycation End products (AGEs) has gained traction during the last decade. This review aims to document the influence of AGEs on the mechanical and physiologic properties of the skin, how they affect dermal wound healing and scar formation in high-AGE populations like elderly patients and diabetics, and potential therapeutic strategies.

Methods:

This systematic literature study involved a structured search in Pubmed and Web of Science with qualitative analysis of 14 articles after a three-staged selection process with the use of in- and exclusion criteria.

Results:

Overall, AGEs cause shortened, thinned, and disorganized collagen fibrils, consequently reducing elasticity and skin/scar thickness with increased contraction and delayed wound closure. Documented therapeutic strategies include dietary AGE restriction, sRAGE decoy receptors, aminoguanidine, RAGE-blocking antibodies, targeted therapy, thymosin β4, anti-oxidant agents and gold nanoparticles, ethyl pyruvate, Gal-3 manipulation and metformin.

Discussion:

With lack of evidence concerning scars, no definitive conclusions can yet be made about the role of AGEs on possible appearance or function of scar tissue. However, all results suggest that scars tend to be more rigid and contractile with persistent redness and reduced tendency towards hypertrophy as AGEs accumulate.

Conclusion:

Abundant evidence supports the pathologic role of AGEs in ageing and dermal wound healing and the effectiveness of possible therapeutic agents. More research is required to conclude its role in scar formation and scar therapy.

Our skin is the body’s first line of defense. It is the barrier that protects us from chemical and biological threats such as viruses, bacteria or corrosive liquids. It is the sensor that allows us to detect physical threats like extreme temperatures, pressure and pain. And when these preventative measures fail, the skin has yet another property: the ability to heal.

Skin changes visibly with age, most notably with the appearance of wrinkles. However, there is more to ageing than meets the eye; invisible alterations cause the decline of various functions of the skin, such as wound healing and scar formation. An array of non-conclusive research has been done in this field. One theory that has gained traction during the last decade is the Advanced Glycation End products (AGEs) theory. The theory states that AGEs play an important role in skin aging, wound healing and the effectiveness of different therapeutic options. Their presence supposedly indicates a diminished ability for wound healing and scar formation.

AGEs are proteins to which sugar molecule is bound. The sugar molecule inhibits the original protein from functioning properly. As skin contains many proteins like collagen, the formation of these AGEs could be a viable explanation for the diminished functioning with ageing. In this review, we investigated whether the accumulation of AGEs affects wound healing and scar formation.

Normal scar formation results in a thin scar. However, it may happen that scarring results in thick, large, painful and itchy scars. We investigated whether people with a high AGE content in their skin, like diabetics and elderly, have difficulties forming aesthetically pleasing scars. Secondly, we investigated which therapies reduce the AGE content and, if so, whether these therapies can improve wound healing and scarring. This literature study involved research in scientific databases with qualitative analysis of 14 articles after a three-staged selection process with the use of set criteria.

We found the different ways in which AGEs affect skin properties and wound healing. Collagen, one of the most important proteins in the skin, is affected by these AGEs. Once a sugar binds to it, the collagen strings becomes thinner and shorter, and the different collagen proteins cross-link with each other in an unstructured way. The result of these alterations is a reduced elasticity, i.e. the skin becomes stiffer. The scar will be thinner and the time for wounds to close is longer. We also found strategies to diminish the AGE content, including dietary AGE restriction and Metformin, a drug used in diabetes.

We can conclude that there is proof of AGEs playing an important role in skin ageing, wound healing and the effectiveness of different therapeutic options. However, more research is required to conclude the exact role of AGEs in scar formation and scar therapy.

Quantitative lateral flow strip assays as User-Friendly Tools To Detect Biomarker Profiles For Leprosy

Leprosy is a debilitating, infectious disease caused by Mycobacterium leprae. Despite the availability of multidrug therapy, transmission is unremitting. Thus, early identification of M. leprae infection is essential to reduce transmission. The immune response to M. leprae is determined by host genetics, resulting in paucibacillary (PB) and multibacillary (MB) leprosy associated with dominant cellular or humoral immunity, respectively. This spectral pathology of leprosy compels detection of immunity to M. leprae to be based on multiple, diverse biomarkers. In this study we have applied quantitative user friendly lateral flow assays (LFAs) for four immune markers (anti-PGL-I antibodies, IL-10, CCL4 and IP-10) for whole blood samples from a longitudinal BCG vaccination field-trial in Bangladesh. Different biomarker profiles, in contrast to single markers, distinguished M. leprae infected from non-infected test groups, patients from household contacts (HHC) and endemic controls (EC), or MB from PB patients. The test protocol presented in this study merging detection of innate, adaptive cellular as well as humoral immunity, thus provides a convenient tool to measure specific biomarker profiles for M. leprae infection and leprosy utilizing a field-friendly technology.

S100A12 Is Part of the Antimicrobial Network against Mycobacterium leprae in Human Macrophages

Triggering antimicrobial mechanisms in macrophages infected with intracellular pathogens, such as mycobacteria, is critical to host defense against the infection. To uncover the unique and shared antimicrobial networks induced by the innate and adaptive immune systems, gene expression profiles generated by RNA sequencing (RNAseq) from human monocyte-derived macrophages (MDMs) activated with TLR2/1 ligand (TLR2/1L) or IFN-γ were analyzed. Weighed gene correlation network analysis identified modules of genes strongly correlated with TLR2/1L or IFN-γ that were linked by the “defense response” gene ontology term. The common TLR2/1L and IFN-γ inducible human macrophage host defense network contained 16 antimicrobial response genes, including S100A12, which was one of the most highly induced genes by TLR2/1L. There is limited information on the role of S100A12 in infectious disease, leading us to test the hypothesis that S100A12 contributes to host defense against mycobacterial infection in humans. We show that S100A12 is sufficient to directly kill Mycobacterium tuberculosis and Mycobacterium leprae. We also demonstrate that S100A12 is required for TLR2/1L and IFN-γ induced antimicrobial activity against M. leprae in infected macrophages. At the site of disease in leprosy, we found that S100A12 was more strongly expressed in skin lesions from tuberculoid leprosy (T-lep), the self-limiting form of the disease, compared to lepromatous leprosy (L-lep), the progressive form of the disease. These data suggest that S100A12 is part of an innate and adaptive inducible antimicrobial network that contributes to host defense against mycobacteria in infected macrophages.

Macrophage antimicrobial activity induced by innate and adaptive immune stimuli is crucial for controlling infection against intracellular pathogens. In order to characterize host defense pathways, we activated human macrophages with innate and adaptive immune stimuli known to induce antimicrobial activity against mycobacteria, identifying a set of 16 antimicrobial response genes. One of these, S100A12, is present in humans, but not mice, has limited studies in infectious disease. By studying leprosy as a model, we found that expression of S100A12 was greater in skin lesions from patients with the self-limiting versus the progressive form of the disease. Furthermore, we show that S100A12 is sufficient to kill mycobacteria and is required for decreasing the relative viability of M. leprae in infected macrophages.

Etiologies of Sarcoidosis

Since sarcoidosis was first described more than a century ago, the etiologic determinants causing this disease remain uncertain. Studies suggest that genetic, host immunologic, and environmental factors interact together to cause sarcoidosis. Immunologic characteristics of sarcoidosis include non-caseating granulomas, enhanced local expression of T helper-1 (and often Th17) cytokines and chemokines, dysfunctional regulatory T-cell responses, dysregulated Toll-like receptor signaling, and oligoclonal expansion of CD4+ T cells consistent with chronic antigenic stimulation. Multiple environmental agents have been suggested to cause sarcoidosis. Studies from several groups implicate mycobacterial or propionibacterial organisms in the etiology of sarcoidosis based on tissue analyses and immunologic responses in sarcoidosis patients. Despite these studies, there is no consensus on the nature of a microbial pathogenesis of sarcoidosis. Some groups postulate sarcoidosis is caused by an active viable replicating infection while other groups contend there is no clinical, pathologic, or microbiologic evidence for such a pathogenic mechanism. The authors posit a novel hypothesis that proposes that sarcoidosis is triggered by a hyperimmune Th1 response to pathogenic microbial and tissue antigens associated with the aberrant aggregation of serum amyloid A within granulomas, which promotes progressive chronic granulomatous inflammation in the absence of ongoing infection.

Clinical significance of serum S100A12 in acute otitis media in young children

BACKGROUND

S100A12 is a calcium-binding protein predominantly expressed in neutrophil granulocytes in response to infections or inflammation. Acute otitis media (AOM) is a local infection mainly caused by Streptococcus pneumoniae (Spn), nontypeable Haemophilus influenzae (NTHi), and/or Moraxella catarrhalis (Mcat).

METHODS

To study if S100A12 values could serve as a diagnostic marker, serum S100A12 concentrations were tested in young children before, at onset, and after recovery from AOM.

RESULTS

Among 116 children with AOM, we found that serum S100A12 concentrations were significantly increased at onset of AOM compared with before infection (P = 0.0001), and returned to normal levels when the children recovered from the infection (P = 0.01). Elevation of S100A12 correlated with the presence of Spn (P = 0.004) or NTHi (P = 0.04) in the middle ear, but not with Mcat or upper respiratory viral infection. Change in serum value of S100A12 at onset of AOM was not related to the frequency of occurrence of AOM or the age of the child.

CONCLUSION

S100A12 may be a useful biomarker for onset of AOM due to Spn and NTHi, and for following children with AOM.

Phagocyte-specific S100 proteins in the local response to the Echinococcus granulosus larva

Infection by larval Echinococcus granulosus is usually characterized by tight inflammatory control. However, various degrees of chronic granulomatous inflammation are also observed, reaching a high point in infection of cattle by the most prevalent parasite strain worldwide, which is not well adapted to this host species. In this context, epithelioid and multinucleated giant macrophages surround the parasite, and the secreted products of these cells often associate with the larval wall. The phagocyte-specific S100 proteins, S100A8, S100A9 and S100A12, are important non-conventionally secreted amplifiers of inflammatory responses. We have analysed by proteomics and immunohistochemistry the presence of these proteins at the E. granulosus larva-host interface. We found that, in the context of inflammatory control as observed in human infections, the S100 proteins are not abundant, but S100A9 and S100A8 can be expressed by eosinophils distal to the parasite. In the granulomatous inflammation context as observed in cattle infections, we found that S100A12 is one of the most abundant host-derived, parasite-associated proteins, while S100A9 and S100A8 are not present at similarly high levels. As expected, S100A12 derives mostly from the epithelioid and multinucleated giant cells. S100A12, as well as cathepsin K and matrix metalloproteinase-9, also expressed by E. granulosus-elicited epithelioid cells, are connected to the Th17 arm of immunity, which may therefore be involved in this granulomatous response.

Immunohistochemical localization of receptor for advanced glycation end (RAGE) products in the R6/2 mouse model of Huntington's disease

The receptor for advanced glycation end (RAGE) products is a multi-ligand receptor that belongs to the immunoglobulin superfamily of cell surface receptors, whose ligands are known to be upregulated in neuropathological conditions. RAGE upregulation has been described in neurodegenerative diseases, such as Alzheimer's disease, Creutzfeldt-Jakob's disease and Huntington's disease (HD). To analyze in detail the implication of RAGE in HD, we studied the immunohistochemical distribution of RAGE in the striatum of the R6/2 mouse model of HD, with particular attention to the neuronal subpopulations and their relative vulnerability to HD neurodegeneration. We show that RAGE immunoreactivity is evenly distributed to the cytoplasm of neurons in the wild type mouse, while it is finely granular in the cytoplasm of striatal neurons of R6/2 mouse. RAGE is distributed in 98% of spiny projection neurons, both in the normal mouse and in the R6/2. RAGE co-localizes with all of the striatal interneuron subsets both in the wild-type and in the R6/2 mouse. However, the intensity of RAGE immunoreactivity is significantly higher in the spiny neurons and in the PARV neurons of R6/2 mouse, whereas it is comparable between R6/2 and wild-type in the cholinergic and somatostatinergic interneurons. These data support the concept that RAGE is upregulated in the neurodegenerative process of HD, and suggests that its activation is related to the individual vulnerability of the striatal neuronal subtype.

C-reactive protein (CRP) up-regulates expression of receptor for advanced glycation end products (RAGE) and its inflammatory ligand EN-RAGE in THP-1 cells: inhibitory effects of atorvastatin

BACKGROUND

Receptor for advanced glycation end products (RAGE) may play an important role in inflammatory processes and endothelial activation. Extracellular newly identified RAGE binding protein (EN-RAGE), natural pro-inflammatory ligand for RAGE. The role of C-reactive protein (CRP) as a mediator in inflammation and atherosclerosis is the subject of recent investigations worldwide. In the present study, we investigated the effect of CRP on RAGE and EN-RAGE gene expression in THP-1 monocytic cell line. MAP kinases (ERK, p38 and JNK) were exploited as possible signaling pathways involved in the signal transduction by CRP. Further, atorvastatin was used as a therapeutic modality for modulation of these genes in the presence of CRP.

MATERIALS AND METHODS

Time and dose-dependent experiments were carried out in the presence of CRP. Specific MAPK pathways inhibitors were used to elucidate the signaling pathways involved. Effect of atorvastatin was also determined in the presence of CRP on the expression of these genes.

RESULTS

Time and dose-dependent experiments revealed that, treatment of THP-1 cells with 100 microg of CRP/ml/10(6) cells for 24 h, augmented the expression of RAGE and EN-RAGE genes by 2.5-3.5 folds and 3.5-4.5 folds respectively. CRP acted via FcgammaRII and utilized ERK, p38 and JNK pathways to transduce signals. Atorvastatin in a dose of 20 muM, was able to attenuate up-regulation of CRP-induced genes (p<0.01) and effects were both dose and time-dependent.

CONCLUSION

Our data strongly suggests that blockade of RAGE-EN-RAGE by statins at an early stage may prevent inflammation in atherosclerosis and counteract the harmful effects mediated by CRP.

Hypoxia mediated release of endothelial microparticles and increased association of S100A12 with circulating neutrophils

Microparticles are released from the endothelium under normal homeostatic conditions and have been shown elevated in disease states, most notably those characterised by endothelial dysfunction. The endothelium is sensitive to oxidative stress/status and vascular cell adhesion molecule-1 (VCAM-1) expression is upregulated upon activated endothelium, furthermore the presence of VCAM-1 on microparticles is known. S100A12, a calcium binding protein part of the S100 family, is shown to be present on circulating leukocytes and is thought a sensitive marker to local inflammatory process, which may be driven by oxidative stress. Eight healthy males were subjected to breathing hypoxic air (15% O(2), approximately equivalent to 3000 metres altitude) for 80 minutes in a temperature controlled laboratory and venous blood samples were processed immediately for VCAM-1 microparticles (VCAM-1 MP) and S100A12 association with leukocytes by flow cytometry. A pre-hypoxic blood sample was used for comparison. Both VCAM-1 MP and S100A12 association with neutrophils were significantly elevated post hypoxic breathing later declining to levels observed in the pre-test samples. A similar trend was observed in both cases and a correlation may exist between these two markers in response to hypoxia. These data offer evidence using novel markers of endothelial and circulating blood responses to hypoxia.