Up-Regulation of Secretory Leukocyte Protease Inhibitor (SLPI) in the Brain after Ischemic Stroke: Adenoviral Expression of SLPI Protects Brain from Ischemic Injury

An interpretable machine learning-based cerebrospinal fluid proteomics clock for predicting age reveals novel insights into brain aging

Machine learning can be used to create "biologic clocks" that predict age. However, organs, tissues, and biofluids may age at different rates from the organism as a whole. We sought to understand how cerebrospinal fluid (CSF) changes with age to inform the development of brain aging-related disease mechanisms and identify potential anti-aging therapeutic targets. Several epigenetic clocks exist based on plasma and neuronal tissues; however, plasma may not reflect brain aging specifically and tissue-based clocks require samples that are difficult to obtain from living participants. To address these problems, we developed a machine learning clock that uses CSF proteomics to predict the chronological age of individuals with a 0.79 Pearson correlation and mean estimated error (MAE) of 4.30 years in our validation cohort. Additionally, we analyzed proteins highly weighted by the algorithm to gain insights into changes in CSF and uncover novel insights into brain aging. We also demonstrate a novel method to create a minimal protein clock that uses just 109 protein features from the original clock to achieve a similar accuracy (0.75 correlation, MAE 5.41). Finally, we demonstrate that our clock identifies novel proteins that are highly predictive of age in interactions with other proteins, but do not directly correlate with chronological age themselves. In conclusion, we propose that our CSF protein aging clock can identify novel proteins that influence the rate of aging of the central nervous system (CNS), in a manner that would not be identifiable by examining their individual relationships with age.

The secretory leukocyte protease inhibitor (SLPI) in pathophysiology of non-communicable diseases: Evidence from experimental studies to clinical applications

Non-communicable diseases (NCDs) are a worldwide health issue because of their prevalence, negative impacts on human welfare, and economic costs. Protease enzymes play important roles in viral and NCD diseases. Slowing disease progression by inhibiting proteases using small-molecule inhibitors or endogenous inhibitory peptides appears to be crucial. Secretory leukocyte protease inhibitor (SLPI), an inflammatory serine protease inhibitor, maintains protease/antiprotease balance. SLPI is produced by host defense effector cells during inflammation to prevent proteolytic enzyme-induced tissue damage. The etiology of noncommunicable illnesses is linked to SLPI's immunomodulatory and tissue regeneration roles. Disease phases are associated with SLPI levels and activity changes in regional tissue and circulation. SLPI has been extensively evaluated in inflammation, but rarely in NCDs. Unfortunately, the thorough evaluation of SLPI's pathophysiological functions in NCDs in multiple research models has not been published elsewhere. In this review, data from PubMed from 2014 to 2023 was collected, analysed, and categorized into in vitro, in vivo, and clinical studies. According to the review, serine protease inhibitor (SLPI) activity control is linked to non-communicable diseases (NCDs) and other illnesses. Overexpression of the SLPI gene and protein may be a viable diagnostic and therapeutic target for non-communicable diseases (NCDs). SLPI is also cytoprotective, making it a unique treatment. These findings suggest that future research should focus on these pathways using advanced methods, reliable biomarkers, and therapy approaches to assess susceptibility and illness progression. Implications from this review will help pave the way for a new therapeutic target and diagnosis marker for non-communicable diseases.

Evaluation of a gene signature related to thrombotic manifestations in antiphospholipid syndrome

Thrombotic primary antiphospholipid syndrome (t-PAPS) is an acquired condition characterized by heterogeneous thrombotic manifestations, which is intriguing since venous and arterial thrombosis appear to have distinct pathogenesis. Gene expression analysis may constitute a new approach to evaluate potential similarities or differences between the clinical manifestations of t-PAPS. Recently, dysregulation of the ANXA3, TNFAIP6, TXK, BACH2, and SERPINB2 genes has been associated with both arterial and venous thrombosis in the general population. Therefore, the aim of this study was to examine whether ANXA3, TNFAIP6, TXK, BACH2, and SERPINB2 expression was associated with t-PAPS. Gene expression was quantified by qPCR of total leukocyte mRNA. In this case-control study, 102 t-PAPS patients, 17 asymptomatic antiphospholipid (aPL) carriers and 100 controls were evaluated. Increased expression of ANXA3 (P = 0.008) and TNFAIP6 (P = 0.001) and decreased expression of the TXK gene (P = 0.0001) were associated with an increased risk of t-PAPS compared to the control. ANXA3 upregulation was more evident in cases of arterial thrombosis and multiple thrombotic events. There was no difference in the expression of these genes between triple and non-triple aPL positivity. ANXA3, TNFAIP6, TXK, BACH2, and SERPINB2 expression levels were also similar between aPL carriers and controls (P = 0.77; P = 0.48; P = 0.08; P = 0.73, and P = 0.13, respectively). In conclusion, our results showed that genes related to hemostasis (ANXA3) and immunity (TNFAIP6, TXK) are dysregulated in t-PAPS compared to controls. Gene dysregulation was not detected in aPL carriers and was not related to the aPL profile, suggesting that this gene signature is related to thrombotic manifestations rather than to aPL burden. Our results suggest that innate immunity and hemostasis pathways are associated with t-PAPS at a molecular level and may play a role in disease severity.

Secretory Leukocyte Proteinase Inhibitor Protects Acute Kidney Injury Through Immune and Non-Immune Pathways

ABSTRACT

Acute kidney injury (AKI) is characterized by rapid loss of excretory function and is the clinical manifestation of several disorders affecting the kidney. The aim of the present study was to investigate the mechanism of action of Secretory Leukocyte Proteinase Inhibitor (SLPI) that protects the kidneys form AKI. In vivo and in vitro experiments were performed to assess the effect of SLPI on kidney injury. Animal models of kidney injury was generated by 40 min obstruction of kidney artery and vein (ischemia-reperfusion injury model) or daily administration of 60 mg/kg/day of gentamicine for 5 day (gentamicin-associated AKI model). For in vitro assessment, human renal epithelium HK-2 cells were cultured under serum starvation conditions or with tacrolimus. The administration of SLPI (250 μg/kg, i.p.) reduced elevated plasma creatinine and blood urea nitrogen levels, tissue myeloperoxidase content, and acute tubular necrosis induced by kidney damage. Furthermore, SLPI treatment reduced CD86, CD68, CD14, CCL2, TNFα, and IL-10 transcripts in kidney biopsies. To further analyze a direct effect of SLPI on renal epithelial cells, HK-2 cells from human renal epithelium were cultured under serum starvation conditions or with tacrolimus. Both conditions induced apoptosis of HK-2 cells which was reduced when SLPI was present in the culture medium. Furthermore, SLPI favored the proliferation and migration of HK-2 cells. An analysis of the gene profiles of HK-2 cells treated with calcineurin inhibitors affected inflammatory and non-inflammatory pathways that were reversed by SLPI. Among them, SLPI down modulated the expression of CCL2, SLC5A3, and BECN1 but up-regulated the expression of TLR4, ATF4, ATF6, HSP90B, BBC3 SLC2A1, and TNFRSF10B. Overall, these results suggest that SLPI, in addition to its activity on immune cells, may directly target tubular epithelial cells of the kidney to mediate the nephroprotective activity in AKI.

Working from within: how secretory leukocyte protease inhibitor regulates the expression of pro-inflammatory genes

Secretory leukocyte protease inhibitor (SLPI) is a small but powerful member of the serine protease inhibitor family, which includes proteins such as elafin and α1-antitrypsin. These proteins all have similar structures and antiprotease abilities, but SLPI has been found to have an additional role as an anti-inflammatory factor. It can inhibit the production of pro-inflammatory cytokines in cells stimulated with lipopolysaccharide, prevent neutrophil infiltration in murine models of lung and liver injury, and regulate the activity of the transcription factor NF-κB. In this review, we will revisit SLPI's unique biochemistry, and then explore how its anti-inflammatory functions can be linked to more recent findings showing that SLPI can localize to the nuclei of cells, bind DNA, and act as a regulator of gene expression.

Identification of common and divergent gene expression signatures in patients with venous and arterial thrombosis using data from public repositories

STRENGTHS AND LIMITATIONS OF THIS STUDY

Our results represent the first comparison of venous and arterial thrombosis at the transcriptomic level.Our main result was the demonstration that immunothrombosis pathways are important to the pathophysiology of these conditions, also at the transcriptomic level.A specific signature for venous and arterial thrombosis was described, and validated in independent cohorts.The limited number of public repositories with gene expression data from patients with venous thromboembolism limits the representation of these patients in our analyses.In order to gather a meaningful number of studies with gene expression data we had to include patients in different time-points since the index thrombotic event, which might have increased the heterogeneity of our population.

Functional circuitry of neuro-immune communication in the mesenteric lymph node and spleen

The peripheral nervous system is an active participant in immune responses capable of blocking aberrant activation of a variety of immune cells. As one of these neuro-immune circuits, the cholinergic anti-inflammatory pathway has been well established to reduce the severity of several immunopathologies. While the activation of this pathway by vagal nerve stimulation requires sympathetic innervation of the spleen, the neuro-immune circuitry remains highly controversial. Neuro-immune pathways in other lymphoid tissues such as mesenteric lymph nodes (MLN) that are critical to the surveillance of the small intestine and proximal colon have not been assessed. Using conditionally expressed Channelrhodopsin, selective stimulation of sympathetic post-ganglionic neurons in the superior mesenteric ganglion (SMG) prevented macrophage activation and LPS-induced TNFα production in the spleen and MLN, but not in the inguinal LN. Site selective stimulation of the SMG induced the release of norepinephrine, resulting in β2AR dependent acetylcholine release in the MLN and spleen. VNS-evoked release of norepinephrine and acetylcholine in the MLN and spleen was significantly reduced using selective optogenetic blockade applied at the SMG. Additionally, this optogenetic blockade restored LPS-induced TNFα production, despite VNS. These studies identify the superior mesenteric ganglion as a critical node in a neuro-immune circuit that can inhibit immune function in the MLN and the spleen.

Overexpression and pre-treatment of recombinant human Secretory Leukocyte Protease Inhibitor (rhSLPI) reduces an in vitro ischemia/reperfusion injury in rat cardiac myoblast (H9c2) cell

One of the major causes of cardiac cell death during myocardial ischemia is the oversecretion of protease enzymes surrounding the ischemic tissue. Therefore, inhibition of the protease activity could be an alternative strategy for preventing the expansion of the injured area. In the present study, we investigated the effects of Secretory Leukocyte Protease Inhibitor (SLPI), by means of overexpression and treatment of recombinant human SLPI (rhSLPI) in an in vitro model. Rat cardiac myoblast (H9c2) cells overexpressing rhSLPI were generated by gene delivery using pCMV2-SLPI-HA plasmid. The rhSLPI-H9c2 cells, mock transfected cells, and wild-type (WT) control were subjected to simulated ischemia/reperfusion (sI/R). Moreover, the treatment of rhSLPI in H9c2 cells was also performed under sI/R conditions. The results showed that overexpression of rhSLPI in H9c2 cells significantly reduced sI/R-induced cell death and injury, intracellular ROS level, and increased Akt phosphorylation, when compared to WT and mock transfection (p <0.05). Treatment of rhSLPI prior to sI/R reduced cardiac cell death and injury, and intra-cellular ROS level. In addition, 400 ng/ml rhSLPI treatment, prior to sI, significantly inhibited p38 MAPK phosphorylation and rhSLPI at 400-1000 ng/ml could increase Akt phosphorylation.

Elevated Levels of Adhesion Proteins Are Associated With Low Ankle-Brachial Index

Inflammation plays a pivotal role in peripheral artery disease (PAD). Cellular adhesion proteins mediate the interaction of leukocytes with endothelial cells during inflammation. To determine the association of cellular adhesion molecules with ankle-brachial index (ABI) and ABI category (≤1.0 vs >1.0) in a diverse population, 15 adhesion proteins were measured in the Multi-Ethnic Study of Atherosclerosis (MESA). To assess multivariable associations of each protein with ABI and ABI category, linear and logistic regression was used, respectively. Among 2364 participants, 23 presented with poorly compressible arteries (ABI > 1.4) and were excluded and 261 had ABI ≤ 1.0. Adjusting for traditional risk factors, elevated levels of soluble P-selectin, hepatocyte growth factor, and secretory leukocyte protease inhibitor were associated with lower ABI ( P = .0004, .001, and .002, respectively). Per each standard deviation of protein, we found 26%, 20%, and 19% greater odds of lower ABI category ( P = .001, .01, and .02, respectively). Further investigation into the adhesion pathway may shed new light on biological mechanisms implicated in PAD.

Destination Brain: the Past, Present, and Future of Therapeutic Gene Delivery

Neurological diseases and disorders (NDDs) present a significant societal burden and currently available drug- and biological-based therapeutic strategies have proven inadequate to alleviate it. Gene therapy is a suitable alternative to treat NDDs compared to conventional systems since it can be tailored to specifically alter select gene expression, reverse disease phenotype and restore normal function. The scope of gene therapy has broadened over the years with the advent of RNA interference and genome editing technologies. Consequently, encouraging results from central nervous system (CNS)-targeted gene delivery studies have led to their transition from preclinical to clinical trials. As we shift to an exciting gene therapy era, a retrospective of available literature on CNS-associated gene delivery is in order. This review is timely in this regard, since it analyzes key challenges and major findings from the last two decades and evaluates future prospects of brain gene delivery. We emphasize major areas consisting of physiological and pharmacological challenges in gene therapy, function-based selection of a ideal cellular target(s), available therapy modalities, and diversity of viral vectors and nanoparticles as vehicle systems. Further, we present plausible answers to key questions such as strategies to circumvent low blood-brain barrier permeability and most suitable CNS cell types for targeting. We compare and contrast pros and cons of the tested viral vectors in the context of delivery systems used in past and current clinical trials. Gene vector design challenges are also evaluated in the context of cell-specific promoters. Key challenges and findings reported for recent gene therapy clinical trials, assessing viral vectors and nanoparticles are discussed from the perspective of bench to bedside gene therapy translation. We conclude this review by tying together gene delivery challenges, available vehicle systems and comprehensive analyses of neuropathogenesis to outline future prospects of CNS-targeted gene therapies.

Secretory leukocyte protease inhibitor promising protective roles in obesity-associated atherosclerosis

Secretory leukocyte protease inhibitor (SLPI), a serine protease inhibitor, which was most commonly examined in mucosal fluids such as saliva, is a versatile molecule and plays non-redundant roles. In addition to its anti-protease activity, SLPI has been shown to express anti-bacterial, anti-viral, anti-fungal, and anti-inflammatory properties as well as participating in innate and adaptive immune responses, most of which has been well documented. Recently, it is reported that SLPI is expressed in adipocytes and adipose tissue where it could play an important feedback role in the resolution of inflammation. Furthermore, circulating SLPI has been shown to correlate with progressive metabolic dysfunction. Moreover, adenoviral gene delivery of elafin and SLPI attenuates nuclear factor-κB-dependent inflammatory responses of human endothelial cells and macrophages to atherogenic stimuli. This review contributes to unraveling the protective role of SLPI in obesity-related atherosclerosis development, and the potential role in preventing arterial plaque rupture.

Regulation of Dipeptidyl Peptidase IV in the Post-stroke Rat Brain and In Vitro Ischemia: Implications for Chemokine-Mediated Neural Progenitor Cell Migration and Angiogenesis

Cerebral ischemia evokes abnormal release of proteases in the brain microenvironment that spatiotemporally impact angio-neurogenesis. Dipeptidyl peptidase IV (DPPIV), a cell surface and secreted protease, has been implicated in extracellular matrix remodeling by regulating cell adhesion, migration, and angiogenesis through modifying the functions of the major chemokine stromal-derived factor, SDF1. To elucidate the possible association of DPPIV in ischemic brain, we examined the expression of DPPIV in the post-stroke rat brain and under in vitro ischemia by oxygen glucose deprivation (OGD). We further investigated the effects of DPPIV on SDF1 mediated in vitro chemotactic and angiogenic functions. DPPIV protein and mRNA levels were significantly upregulated during repair phase in the ischemic cortex of the rat brain, specifically in neurons, astrocytes, and endothelial cells. In vitro exposure of Neuro-2a neuronal cells and rat brain endothelial cells to OGD resulted in upregulation of DPPIV. In vitro functional analysis showed that DPPIV decreases the SDF1-mediated angiogenic potential of rat brain endothelial cells and inhibits the migration of Neuro-2a and neural progenitor cells. Western blot analyses revealed decreased levels of phosphorylated ERK1/2 and AKT in the presence of DPPIV. DPPIV inhibitor restored the effects of SDF1. Proteome profile array screening further revealed that DPPIV decreases matrix metalloproteinase-9, a key downstream effector of ERK-AKT signaling pathways. Overall, delayed induction of DPPIV in response to ischemia/reperfusion suggests that DPPIV may play an important role in endogenous brain tissue remodeling and repair processes. This may be mediated through modulation of SDF1-mediated cell migration and angiogenesis.

Secretory leukocyte protease inhibitor (SLPI), a multifunctional protein in the host defense response

Secretory leukocyte protease inhibitor (SLPI), a ∼12kDa nonglycosylated cationic protein, is emerging as an important regulator of innate and adaptive immunity and as a component of tissue regenerative programs. First described as an inhibitor of serine proteases such as neutrophil elastase, this protein is increasingly recognized as a molecule that benefits the host via its anti-proteolytic, anti-microbial and immunomodulatory activities. Here, we discuss the diverse functions of SLPI. Moreover, we review several novel layers of SLPI-mediated control that protect the host from excessive/dysregulated inflammation typical of infectious, allergic and autoinflammatory diseases and that support healing responses through affecting cell proliferation, differentiation and apoptosis.

Looking downstream: the role of cyclic AMP-regulated genes in axonal regeneration

Elevation of intracellular cyclic AMP (cAMP) levels has proven to be one of the most effective means of overcoming inhibition of axonal regeneration by myelin-associated inhibitors such as myelin-associated glycoprotein (MAG), Nogo, and oligodendrocyte myelin glycoprotein. Pharmacological manipulation of cAMP through the administration of dibutyryl cAMP or rolipram leads to enhanced axonal growth both in vivo and in vitro, and importantly, upregulation of cAMP within dorsal root ganglion neurons is responsible for the conditioning lesion effect, which indicates that cAMP plays a significant role in the endogenous mechanisms that promote axonal regeneration. The effects of cAMP are transcription-dependent and are mediated through the activation of protein kinase A (PKA) and the transcription factor cyclic AMP response element binding protein (CREB). This leads to the induction of a variety of genes, several of which have been shown to overcome myelin-mediated inhibition in their own right. In this review, we will highlight the pro-regenerative effects of arginase I (ArgI), interleukin (IL)-6, secretory leukocyte protease inhibitor (SLPI), and metallothionein (MT)-I/II, and discuss their potential for therapeutic use in spinal cord injury.

Wild-type bone marrow transplant partially reverses neuroinflammation in progranulin-deficient mice

Frontotemporal dementia (FTD) is a neurodegenerative disease with devastating changes in behavioral performance and social function. Mutations in the progranulin gene (GRN) are one of the most common causes of inherited FTD due to reduced progranulin expression or activity, including in brain where it is expressed primarily by neurons and microglia. Thus, efforts aimed at enhancing progranulin levels might be a promising therapeutic strategy. Bone marrow (BM)-derived cells are able to engraft in the brain and adopt a microglial phenotype under myeloablative irradiation conditioning. This ability makes BM-derived cells a potential cellular vehicle for transferring therapeutic molecules to the central nervous system. Here, we utilized BM cells from Grn(+/+) (wild type or wt) mice labeled with green fluorescence protein for delivery of progranulin to progranulin-deficient (Grn(-/-)) mice. Our results showed that wt bone marrow transplantation (BMT) partially reconstituted progranulin in the periphery and in cerebral cortex of Grn(-/-) mice. We demonstrated a pro-inflammatory effect in vivo and in ex vivo preparations of cerebral cortex of Grn(-/-) mice that was partially to fully reversed 5 months after BMT. Our findings suggest that BMT can be administered as a stem cell-based approach to prevent or to treat neurodegenerative diseases.

Secretory Leukocyte Protease Inhibitor (SLPI): Emerging Roles in CNS Trauma and Repair

At first glance, secretory leukocyte protease inhibitor (SLPI) would appear to have little relevance to the central nervous system (CNS). This serine protease inhibitor is most commonly found in mucosal fluids such as saliva and is best known for its anti-inflammatory and antimicrobial properties. It has been shown to promote wound healing by reducing expression of pro-inflammatory cytokines, and it can also inhibit bacterial growth and block HIV infection of macrophages. In the past 10 years, however, several studies have reported that SLPI is strongly up-regulated in response to CNS injury and that exogenous administration of SLPI is neuroprotective. It has also been shown that SLPI can overcome inhibition by CNS myelin and promote axonal regeneration. In this review, we will discuss these studies, examine the molecular mechanisms underlying SLPI's effects, and consider SLPI's potential for therapeutic use in cerebral ischemia, spinal cord injury, and multiple sclerosis.

Genital herpes simplex virus type 2 infection in humanized HIV-transgenic mice triggers HIV shedding and is associated with greater neurological disease

BACKGROUND

Epidemiological studies consistently demonstrate synergy between herpes simplex virus type 2 (HSV-2) and human immunodeficiency virus type 1 (HIV-1). Higher HIV-1 loads are observed in coinfected individuals, and conversely, HIV-1 is associated with more-severe herpetic disease. A small animal model of coinfection would facilitate identification of the biological mechanisms underlying this synergy and provide the opportunity to evaluate interventions.

METHODS

Mice transgenic for HIV-1 provirus and human cyclin T1 under the control of a CD4 promoter (JR-CSF/hu-cycT1) were intravaginally infected with HSV-2 and evaluated for disease progression, HIV shedding, and mucosal immune responses.

RESULTS

HSV-2 infection resulted in higher vaginal HIV loads and genital tissue expression of HIV RNA, compared with HSV-uninfected JR-CSF/hu-cycT1 mice. There was an increase in genital tract inflammatory cells, cytokines, chemokines, and interferons in response to HSV-2, although the kinetics of the response were delayed in HIV-transgenic, compared with control mice. Moreover, the JR-CSF/hu-cycT1 mice exhibited earlier and more-severe neurological disease. The latter was associated with downregulation of secretory leukocyte protease inhibitor expression in neuronal tissue, a molecule with antiinflammatory, antiviral, and neuroprotective properties.

CONCLUSIONS

JR-CSF/hu-cycT1 mice provide a valuable model to study HIV/HSV-2 coinfection and identify potential mechanisms by which HSV-2 facilitates HIV-1 transmission and HIV modulates HSV-2-mediated disease.

Secretory leukocyte protease inhibitor reverses inhibition by CNS myelin, promotes regeneration in the optic nerve, and suppresses expression of the transforming growth factor-β signaling protein Smad2

After CNS injury, axonal regeneration is limited by myelin-associated inhibitors; however, this can be overcome through elevation of intracellular cyclic AMP (cAMP), as occurs with conditioning lesions of the sciatic nerve. This study reports that expression of secretory leukocyte protease inhibitor (SLPI) is strongly upregulated in response to elevation of cAMP. We also show that SLPI can overcome inhibition by CNS myelin and significantly enhance regeneration of transected retinal ganglion cell axons in rats. Furthermore, regeneration of dorsal column axons does not occur after a conditioning lesion in SLPI null mutant mice, indicating that expression of SLPI is required for the conditioning lesion effect. Mechanistically, we demonstrate that SLPI localizes to the nuclei of neurons, binds to the Smad2 promoter, and reduces levels of Smad2 protein. Adenoviral overexpression of Smad2 also blocked SLPI-induced axonal regeneration. SLPI and Smad2 may therefore represent new targets for therapeutic intervention in CNS injury.

Inhibition of SLPI ameliorates disease activity in experimental autoimmune encephalomyelitis

Background

The secretory leukocyte protease inhibitor (SLPI) exerts wide ranging effects on inflammatory pathways and is upregulated in EAE but the biological role of SLPI in EAE, an animal model of multiple sclerosis is unknown

Methods

To investigate the pathophysiological effects of SLPI within EAE, we induced SLPI-neutralizing antibodies in mice and rats to determine the clinical severity of the disease. In addition we studied the effects of SLPI on the anti-inflammatory cytokine TGF-β.

Results

The induction of SLPI neutralizing antibodies resulted in a milder disease course in mouse and rat EAE. SLPI neutralization was associated with increased serum levels of TGF-β and increased numbers of FoxP3+ CD4+ T cells in lymph nodes. In vitro, the addition of SLPI significantly decreased the number of functional FoxP3+ CD25^hi CD4+ regulatory T cells in cultures of naive human CD4+ T cells. Adding recombinant TGF-β to SLPI-treated human T cell cultures neutralized SLPI's inhibitory effect on regulatory T cell differentiation.

Conclusion

In EAE, SLPI exerts potent pro-inflammatory actions by modulation of T-cell activity and its neutralization may be beneficial for the disease.

WAP domain proteins as modulators of mucosal immunity

WAP (whey acidic protein) is an important whey protein present in milk of mammals. This protein has characteristic domains, rich in cysteine residues, called 4-DSC (four-disulfide core domain). Other proteins, mainly present at mucosal surfaces, have been shown to also possess these characteristic WAP-4-DSC domains. The present review will focus on two WAP-4-DSC containing proteins, namely SLPI (secretory leucocyte protease inhibitor) and trappin-2/elafin. Although first described as antiproteases able to inhibit in particular host neutrophil proteases [NE (neutrophil elastase), cathepsin-G and proteinase-3] and as such, able to limit maladaptive tissue damage during inflammation, it has become apparent that these molecules have a variety of other functions (direct antimicrobial activity, bacterial opsonization, induction of adaptive immune responses, promotion of tissue repair, etc.). After providing information about the 'classical' antiproteasic role of these molecules, we will discuss the evidence pertaining to their pleiotropic functions in inflammation and immunity.

Inflammatory pathways in spinal cord injury

Injury to the spinal cord results in direct damage to axons, neuronal cell bodies, and glia that cause functional loss below the site of injury. In addition, the injury also triggers an inflammatory response that contributes to secondary tissue damage that leads to further functional loss. Reducing inflammation after spinal cord injury (SCI) is therefore a worthy therapeutic goal. Inflammation in the injured spinal cord is a complex response that involves resident cells of the central nervous system as well as infiltrating immune cells, and is mediated by a variety of molecular pathways and signaling molecules. Here, we discuss approaches we have used to identify novel therapeutic targets to modulate the inflammatory response after SCI to reduce tissue damage and promote recovery. Effective treatments for SCI will likely require a combination of approaches to reduce inflammation and secondary damage with those that promote axon regeneration.

Loss of function mutations in the progranulin gene are related to pro-inflammatory cytokine dysregulation in frontotemporal lobar degeneration patients

The progranulin gene (PGRN) encodes a pleiotropic molecule with anti-inflammatory actions and neuronal protective effects. Accordingly, PGRN-deficient mice have been demonstrated to develop enhanced inflammation and progressive neurodegeneration. Loss of function mutations of the PGRN gene have been also reported to cause frontotemporal lobar degeneration (FTLD), a neurodegenerative disease leading to dementia generally in the presenium. Since neurodegeneration might be negatively impacted by chronic inflammation, the possible influence of PGRN defects on inflammatory pathways appears to be of great relevance for the understanding of neurodegeneration pathogenic processes in those patients. However, no data about the inflammatory profile of PGRN-defective subjects have been so far provided.

In this study, we analyzed serum levels of the pro-inflammatory mediators IL-6, TNF-α and IL-18 in FTLD patients with or without PGRN mutations, at both pre-symptomatic and symptomatic stages. We provide evidence that circulating IL-6 is increased in PGRN-mutated FTLD patients, as compared to both PGRN non-mutated FTLD patients and controls. In contrast, levels of IL-6 were not altered in asymptomatic subjects carrying the PGRN mutations. Finally, TNF-α and IL-18 serum levels did not differ among all groups of included subjects.

We conclude that the profile of circulating pro-inflammatory cytokines is altered in PGRN-related symptomatic FTLD. Thus, our findings point to IL-6 as a possible specific mediator and a potential therapeutic target in this monogenic disease, suggesting that an enhanced inflammatory response might be indeed involved in its progression.

Micro-encapsulated secretory leukocyte protease inhibitor decreases cell-mediated immune response in autoimmune orchitis

AIMS

We previously reported that recombinant human Secretory Leukocyte Protease Inhibitor (SLPI) inhibits mitogen-induced proliferation of human peripheral blood mononuclear cells. To determine the relevance of this effect in vivo, we investigated the immuno-regulatory role of SLPI in an experimental autoimmune orchitis (EAO) model.

MAIN METHODS

In order to increase SLPI half life, poly-ε-caprolactone microspheres containing SLPI were prepared and used for in vitro and in vivo experiments. Multifocal orchitis was induced in Sprague-Dawley adult rats by active immunization with testis homogenate and adjuvants. Microspheres containing SLPI (SLPI group) or vehicle (control group) were administered s.c. to rats during or after the immunization period.

KEY FINDINGS

In vitro SLPI-release microspheres inhibited rat lymphocyte proliferation and retained trypsin inhibitory activity. A significant decrease in EAO incidence was observed in the SLPI group (37.5%) versus the control group (93%). Also, SLPI treatment significantly reduced severity of the disease (mean EAO score: control, 6.33±0.81; SLPI, 2.72±1.05). In vivo delayed-type hypersensitivity and ex vivo proliferative response to testicular antigens were reduced by SLPI treatment compared to control group (p<0.05).

SIGNIFICANCE

Our results highlight the in vivo immunosuppressive effect of released SLPI from microspheres which suggests its feasible therapeutic use.

The paradox of the neutrophil's role in tissue injury

The neutrophil is an essential component of the innate immune system, and its function is vital to human life. Its production increases in response to virtually all forms of inflammation, and subsequently, it can accumulate in blood and tissue to varying degrees. Although its participation in the inflammatory response is often salutary by nature of its normal interaction with vascular endothelium and its capability to enter tissues and respond to chemotactic gradients and to phagocytize and kill microrganisms, it can contribute to processes that impair vascular integrity and blood flow. The mechanisms that the neutrophil uses to kill microorganisms also have the potential to injure normal tissue under special circumstances. Its paradoxical role in the pathophysiology of disease is particularly, but not exclusively, notable in seven circumstances: 1) diabetic retinopathy, 2) sickle cell disease, 3) TRALI, 4) ARDS, 5) renal microvasculopathy, 6) stroke, and 7) acute coronary artery syndrome. The activated neutrophil's capability to become adhesive to endothelium, to generate highly ROS, and to secrete proteases gives it the potential to induce local vascular and tissue injury. In this review, we summarize the evidence for its role as a mediator of tissue injury in these seven conditions, making it or its products potential therapeutic targets.

Identification of stage biomarkers for human African trypanosomiasis

Human African trypanosomiasis (HAT), caused by infection with sub-species of Trypanosoma brucei (T. b.), manifests as a hemolymphatic stage followed by an encephalitic stage. The distinction of the two stages needs improvement as drugs used for the late stage are highly toxic. Transcripts encoding 16 secreted proteins differentially expressed in the brains of mice at late stage T. b. brucei infection when the early stage drug suramin is no longer effective and different to immunoglobulins, chemokines, and cytokines, were selected by microarray analysis. Lipocalin 2 and secretory leukocyte peptidase inhibitor (SLPI) mRNA showed the highest differential expression in mice. These transcripts were also upregulated in brains from infected rats. Lipocalin 2 was increased in cerebrospinal fluid (CSF) from rats during late stage T. b. brucei infection. Protein levels of lipocalin 2, SLPI, and the chemokine CXCL10 were found increased in CSF from Trypanosoma brucei gambiense and Trypanosoma brucei rhodesiense late stage HAT compared to early stage.

Beneficial effects of secretory leukocyte protease inhibitor after spinal cord injury

Secretory leukocyte protease inhibitor is a serine protease inhibitor produced by various cell types, including neutrophils and activated macrophages, and has anti-inflammatory properties. It has been shown to promote wound healing in the skin and other non-neural tissues, however, its role in central nervous system injury was not known. We now report a beneficial role for secretory leukocyte protease inhibitor after spinal cord injury. After spinal cord contusion injury in mice, secretory leukocyte protease inhibitor is expressed primarily by astrocytes and neutrophils but not macrophages. We show, using transgenic mice over-expressing secretory leukocyte protease inhibitor, that this molecule has an early protective effect after spinal cord contusion injury. Furthermore, wild-type mice treated for the first week after spinal cord contusion injury with recombinant secretory leukocyte protease inhibitor exhibit sustained improvement in locomotor control and reduced secondary tissue damage. Recombinant secretory leukocyte protease inhibitor injected intraperitoneally localizes to the nucleus of circulating leukocytes, is detected in the injured spinal cord, reduces activation of nuclear factor-kappaB and expression of tumour necrosis factor-alpha. Administration of recombinant secretory leukocyte protease inhibitor might therefore be useful for the treatment of acute spinal cord injury.

Innate immunity and disorders of the female reproductive tract

Sexually transmitted infections, and their associated sequelae, such as tubal infertility, ectopic pregnancy and preterm labour, are a major worldwide health problem. Chlamydia trachomatis infection is thought to be the leading global cause of tubal infertility and tubal ectopic pregnancy. Preterm birth occurs in around 10% of all deliveries, and nearly 30% of preterm deliveries are associated with intrauterine infection. The mucosal innate immune system of the female reproductive tract has evolved to eliminate such sexually transmitted pathogens whilst maintaining its ability to accommodate specialized physiological functions that include menstruation, fertilization, implantation, pregnancy and parturition. The aim of this review was to describe the role and distribution of key mediators of the innate immune system, the natural antimicrobial peptides (secretory leukocyte protease inhibitor, elafin and the defensins) and the pattern recognition toll-like receptors in the normal female reproductive tract and in the context of these pathological processes.

Novel role for SLPI in MOG-induced EAE revealed by spinal cord expression analysis

Background

Experimental autoimmune encephalomyelitis (EAE) induced by myelin oligodendrocyte protein (MOG) in female Dark Agouti (DA) rats is a chronic demyelinating animal model of multiple sclerosis (MS). To identify new candidate molecules involved in the evolution or repair of EAE-lesions we used Affymetrix oligonucleotide microarrays to compare the spinal cord transcriptome at the peak of EAE, during remission and at the first relapse with healthy DA rats.

Methods

Untreated DA rats and DA rats immunised with MOG protein were sacrificed at defined time points. Total RNA was isolated from spinal cord tissue and used for hybridization of Affymetrix rat genome arrays RG U34 A-C. Selected expression values were confirmed by RealTime PCR.

Adult neural stem cells were incubated with recombinant secretory leukocyte protease inhibitor (SLPI). Proliferation was assessed by BrdU incorporation, cyclin D1 and HES1 expression by RealTime PCR, cell differentiation by immunofluorescence analysis and IkappaBalpha degradation by Western blot.

Results

Among approximately 26,000 transcripts studied more than 1,100 were differentially regulated. Focussing on functional themes, we noticed a sustained downregulation of most of the transcripts of the cholesterol biosynthesis pathway. Furthermore, we found new candidate genes possibly contributing to regenerative processes in the spinal cord. Twelve transcripts were solely upregulated in the recovery phase, including genes not previously associated with repair processes. Expression of SLPI was upregulated more than hundredfold during EAE attack. Using immunohistochemistry, SLPI was identified in macrophages, activated microglia, neuronal cells and astrocytes. Incubation of adult neural stem cells (NSC) with recombinant SLPI resulted in an increase of cell proliferation and of differentiation towards oligodendrocytes. These processes were paralleled by an upregulation of the cell-cycle promotor cyclin D1 and a suppression of the cell differentiation regulator HES1. Finally, SLPI prevented the degradation of IkappaBalpha, which may explain the suppression of the cell differentiation inhibitor HES1 suggesting a possible mechanism of oligodendroglial differentiation.

Conclusion

We identified novel features of gene expression in the CNS during EAE, in particular the suppression of genes of cholesterol biosynthesis and a strong upregulation of SLPI, a gene which is for the first time associated with autoimmune inflammation. The capacity of SLPI to increase proliferation of adult NSC and of oligodendroglial differentiation suggests a novel role for SLPI in the promotion of tissue repair, beyond its known functions in the prevention of tissue damages by protease inhibition damage and modulation of inflammatory reactions.

Progranulin in frontotemporal lobar degeneration and neuroinflammation

Progranulin (PGRN) is a pleiotropic protein that has gained the attention of the neuroscience community with recent discoveries of mutations in the gene for PGRN that cause frontotemporal lobar degeneration (FTLD). Pathogenic mutations in PGRN result in null alleles, and the disease is likely the result of haploinsufficiency. Little is known about the normal function of PGRN in the central nervous system apart from a role in brain development. It is expressed by microglia and neurons. In the periphery, PGRN is involved in wound repair and inflammation. High PGRN expression has been associated with more aggressive growth of various tumors. The properties of full length PGRN are distinct from those of proteolytically derived peptides, referred to as granulins (GRNs). While PGRN has trophic properties, GRNs are more akin to inflammatory mediators such as cytokines. Loss of the neurotrophic properties of PGRN may play a role in selective neuronal degeneration in FTLD, but neuroinflammation may also be important. Gene expression studies suggest that PGRN is up-regulated in a variety of neuroinflammatory conditions, and increased PGRN expression by microglia may play a pivotal role in the response to brain injury, neuroinflammation and neurodegeneration.

Helicobacter pylori-induced downregulation of the secretory leukocyte protease inhibitor (SLPI) in gastric epithelial cell lines and its functional relevance for H. pylori-mediated diseases

The secretory leukocyte protease inhibitor (SLPI) exerts antiproteolytic activity towards serine proteases, as well as anti-microbial and anti-inflammatory effects. To investigate its role in H. pylori-mediated diseases, SLPI expression was analyzed by RT-PCR, ELISA and immunohistochemistry in clinical samples and gastric tumor cell lines. Determination of the mucosal SLPI levels in 126 patients confirmed the previously reported downregulation of SLPI in H. pylori-infected patients. The lower SLPI levels in antral biopsies of H. pylori-positive subjects were associated with a 30-fold increase (p<0.01) in neutrophil elastase activity, and a significant negative correlation was demonstrated for both parameters (R=-0.63, p=0.0002). Eradication of the bacterium in a long-term study (5-7 years) led to a recovery of mucosal SLPI expression. In vitro experiments using four gastric tumor cell lines (AGS, MKN-28, MKN-45, NCI-N87) generally confirmed the clinical findings. While the co-incubation of these cell lines with H. pylori resulted in lower or unchanged SLPI protein levels, the corresponding SLPI mRNA amounts were upregulated by up to five-fold (p=0.006) in all cell lines. Taken together, these results indicate that the reduction in antral SLPI levels in H. pylori-infected subjects has a functional relevance for gastric mucosa and the H. pylori-induced decrease in SLPI is primarily regulated at the posttranslational level.

SLPI and elafin: one glove, many fingers

Elafin and SLPI (secretory leucocyte protease inhibitor) have multiple important roles both in normal homoeostasis and at sites of inflammation. These include antiprotease and antimicrobial activity as well as modulation of the response to LPS (lipopolysaccharide) stimulation. Elafin and SLPI are members of larger families of proteins secreted predominantly at mucosal sites, and have been shown to be modulated in multiple pathological conditions. We believe that elafin and SLPI are important molecules in the controlled functioning of the innate immune system, and may have further importance in the integration of this system with the adaptive immune response. Recent interest has focused on the influence of inflamed tissues on the recruitment and phenotypic modulation of cells of the adaptive immune system and, indeed, the local production of elafin and SLPI indicate that they are ideally placed in this regard. Functionally related proteins, such as the defensins and cathelicidins, have been shown to have direct effects upon dendritic cells with potential alteration of their phenotype towards type I or II immune responses. This review addresses the multiple functions of elafin and SLPI in the inflammatory response and discusses further their roles in the development of the adaptive immune response.

Secretory leukocyte protease inhibitor expression in various types of gastritis: a specific role of Helicobacter pylori infection

OBJECTIVES

Secretory leukocyte protease inhibitor (SLPI) represents a multifunctional protein of the gastrointestinal mucosa exerting antimicrobial and anti-inflammatory effects. SLPI expression is generally induced during inflammation; however, Helicobacter pylori-mediated gastritis is associated with significantly decreased antral SLPI levels. The aim of the study was to investigate whether SLPI downregulation of gastric mucosa represents a specific phenomenon of H. pylori infection or is generally linked to gastric inflammation.

METHODS

SLPI expression was retrospectively analysed by immunohistochemistry in 85 paraffin-embedded samples: H. pylori-induced (n=13), non-steroidal anti-inflammatory drug (NSAID)-enhanced (n=18), autoimmune (n=11), lymphocytic gastritis (n=26) and H. pylori-negative controls (n=17). The intensity of the staining was semiquantitatively analysed using an immunoreactivity score. Statistical analysis of differences was performed using an analysis of variance test.

RESULTS

In comparison with the control group, the SLPI expression of antral mucosa in H. pylori-mediated and lymphocytic gastritis was significantly lower (P<0.001), whereas epithelial SLPI expression was not affected in NSAID-enhanced and autoimmune gastritis either in the antrum or corpus, respectively. Both the H. pylori-mediated and lymphocytic gastritis revealed a significantly lower expression of SLPI in infiltrating immune cells (P<0.01), whereas immune cells infiltrating the corpus in autoimmune gastritis showed higher SLPI levels than the immune cells of other groups (P<0.03).

CONCLUSION

The local downregulation of SLPI in antral mucosa is specifically linked to H. pylori infection and is not a general phenomenon of gastric inflammation.

Helicobacter pylori infection, but not low-dose aspirin, results in a local reduction of the secretory leukocyte protease inhibitor in gastroduodenal mucosa

BACKGROUND

The secretory leukocyte protease inhibitor (SLPI) represents a multifunctional protein with mucosa-protective features. Helicobacter pylori and the usage of low-dose aspirin are two independent risk factors for the development of gastrointestinal diseases. Therefore, the effect of low-dose aspirin on gastrointestinal SLPI expression was analyzed in the context of H. pylori infection.

MATERIAL AND METHODS

The study included 20 volunteers (H. pylori positive and negative: n = 10) who received 2 x 50 mg aspirin/day for 7 days. H. pylori-positive subjects underwent eradication therapy and repeated the protocol. Gastroduodenoscopy was performed at day 0, 1, 3, and 7, and biopsies were obtained each from antrum, corpus, and duodenal bulb. SLPI expression was determined by quantitative reverse transcription-polymerase chain reaction (RT-PCR) and enzyme-linked immunosorbent assay (ELISA).

RESULTS

A reduction of antral SLPI levels, ranging between 582 (day 0) and 941 pg/10 microg protein (day 7), was determined in H. pylori-positive compared to H. pylori-negative and -eradicated subjects (1600-2050 pg/10 microg protein, ANOVA: p = .001-.045). No differences concerning aspirin were observed within the groups. SLPI levels in corpus and duodenal mucosa were neither affected by H. pylori nor low-dose aspirin. There was an inverse correlation between SLPI and H. pylori-induced inflammation (activity: r = -0.575, -0.69 to -0.43, p < .0001; chronicity: r = -0.54, -0.66 to -0.39, p < .0001) in antral mucosa only, whereas other locations as well as the usage of low-dose aspirin did not show an association between SLPI and inflammation.

CONCLUSIONS

H. pylori infection, but not the usage of low-dose aspirin, has a role in the down-regulation of antral SLPI levels.

Recent advances in the pharmacology of neurological gene therapy

The choice of vectors, transgenes, regulatory elements, delivery approaches and the capacity to transduce the appropriate target cell type all influence the effectiveness of gene therapy for neurological diseases. Furthermore, even if many strategies are sound and effective in experimental animals, issues relating to side effects of gene therapy, longevity of therapeutic transgene expression and diffusion throughout the brain can limit the clinical potential of gene therapy. During the past 12-18 months, there have been significant advances in the following areas: the capacity to target vectors to predetermined cells types; the development of gene therapy approaches for the treatment of dominant inherited and neurodegenerative diseases; the capacity to achieve systemic delivery of viral vectors to the brain; and the development of viral vectors to model neurological diseases.