Major low-energy trauma results in non-specific immunoglobulin generation without evidence for specific autoantibody production: A prospective cohort study

Cellular debris resulting from large trauma might overwhelm the scavenger mechanisms and lead to autoimmune reactions. We analysed whether a major well-defined trauma in humans induces laboratory signs of transient autoimmunity in the months after the insult. We included 50 patients with pertrochanteric femur fracture undergoing intramedullary nail osteosynthesis in a prospective cohort study and followed them at 3-4 days, 6 weeks, 12 weeks and 12 months postoperatively. By standard techniques, we assessed levels of total immunoglobulins, anti-nuclear antibodies (ANA), anti-cardiolipin antibodies, anti-dsDNA antibodies and anti-C1q antibodies, as well as antibodies against cytomegalovirus (CMV) as a control. Blood leukocyte differential and lymphocyte subpopulations were determined at baseline and in the first two postoperative samples. The mean age of the patients reached 80.1 years, and 23 (46%) completed all visits. Serum concentrations of total IgG, IgM and IgA increased at all follow-up time points. The ANA fluorescence light intensity units increased at 12 weeks and 12 months postoperatively (p < 0.0001), but the proportion of ANA-positive patients did not change (35%). The values of anti-C1q mildly increased at all follow-up visits, but not the ratio to total IgG. Anti-dsDNA remained negative in all patients, and anti-cardiolipin IgG/IgM antibodies did not change. Anti-CMV IgG antibodies increased significantly at all follow-up visits, without change in the ratio to total IgG. Flow cytometry showed an increased proportion of B-cells 3-4 days postoperatively. In conclusion, major musculoskeletal trauma in elderly patients induces a generalized non-specific increase in immunoglobulin production without laboratory signs for enhanced systemic autoimmunity.

Intersection of Immunity, Metabolism, and Muscle Regeneration in an Autoimmune-Prone MRL Mouse Model

Due to the limited capacity of mammals to regenerate complex tissues, researchers have worked to understand the mechanisms of tissue regeneration in organisms that maintain that capacity. One example is the MRL/MpJ mouse strain with unique regenerative capacity in ear pinnae that is absent from other strains, such as the common C57BL/6 strain. The MRL/MpJ mouse has also been associated with an autoimmune phenotype even in the absence of the mutant Fas gene described in its parent strain MRL/lpr. Due to these findings, the differences between the responses of MRL/MpJ versus C57BL/6 strain are evaluated in volumetric muscle injury and subsequent material implantation. One salient feature of the MRL/MpJ response to injury is robust adipogenesis within the muscle. This is associated with a decrease in M2-like polarization in response to biologically derived extracellular matrix scaffolds. In pro-fibrotic materials, such as polyethylene, there are fewer foreign body giant cells in the MRL/MpJ mice. As there are reports of both positive and negative influences of adipose tissue and adipogenesis on wound healing, this model can provide an important lens to investigate the interplay between stem cells, adipose tissue, and immune responses in trauma and material implantation.

Burn Management in a Patient With Acute Exacerbation of Comorbid Systemic Lupus Erythematosus

A 28-year-old female presented to the burn unit with 2% total body surface area second-degree burns to the right flank and right breast after accidentally spilling coffee on herself while hospitalized for an acute exacerbation of systemic lupus erythematosus (SLE) in the form of neuromyelitis optica spectrum disorder. We document her inpatient management, which was challenging because of the contradictory relationship between typical management of SLE exacerbations (i.e., immunosuppressive medication regimens) and the body's post-burn healing process, which is inherently inflammatory in nature. Even with a high-dose immunosuppressive medication regimen, our patient's second-degree burns healed with non-operative management without significant adverse events. Adding to a small yet growing body of literature addressing the clinical presentation and management of burn wounds in the setting of an acute SLE exacerbation, our case suggests that clinicians must carefully weigh the risks of surgical intervention with those of non-operative management when approaching burn care during an acute rheumatologic disease flare up.

Aggregated and Hyperstable Damage-Associated Molecular Patterns Are Released During ER Stress to Modulate Immune Function

Chronic ER stress occurs when protein misfolding in the Endoplasmic reticulum (ER) lumen remains unresolved despite activation of the unfolded protein response. We have shown that traumatic injury such as a severe burn leads to chronic ER stress in vivo leading to systemic inflammation which can last for more than a year. The mechanisms linking chronic ER stress to systemic inflammatory responses are not clear. Here we show that induction of chronic ER stress leads to the release of known and novel damage-associated molecular patterns (DAMPs). The secreted DAMPs are aggregated and markedly protease resistant. ER stress-derived DAMPs activate dendritic cells (DCs) which are then capable of polarizing naïve T cells. Our findings indicate that induction of chronic ER stress may lead to the release of hyperstable DAMPs into the circulation resulting in persistent systemic inflammation and adverse outcomes.

The Absent in Melanoma 2-Like Receptor IFN-Inducible Protein 16 as an Inflammasome Regulator in Systemic Lupus Erythematosus: The Dark Side of Sensing Microbes

Absent in melanoma 2 (AIM2)-like receptors (ALRs) are a newly characterized class of pathogen recognition receptors (PRRs) involved in cytosolic and nuclear pathogen DNA recognition. In recent years, two ALR family members, the interferon (IFN)-inducible protein 16 (IFI16) and AIM2, have been linked to the pathogenesis of various autoimmune diseases, among which systemic lupus erythematosus (SLE) has recently gained increasing attention. SLE patients are indeed often characterized by constitutively high serum IFN levels and increased expression of IFN-stimulated genes due to an abnormal response to pathogens and/or incorrect self-DNA recognition process. Consistently, we and others have shown that IFI16 is overexpressed in a wide range of autoimmune diseases where it triggers production of specific autoantibodies. In addition, evidence from mouse models supports a model whereby ALRs are required for IFN-mediated host response to both exogenous and endogenous DNA. Following interaction with cytoplasmic or nuclear nucleic acids, ALRs can form a functional inflammasome through association with the adaptor ASC [apoptosis-associated speck-like protein containing a caspase recruitment domain (CARD)] and with procaspase-1. Importantly, inflammasome-mediated upregulation of IL-1β and IL-18 production positively correlates with SLE disease severity. Therefore, targeting ALR sensors and their downstream pathways represents a promising alternative therapeutic approach for SLE and other systemic autoimmune diseases.

Self-dsDNA in the pathogenesis of systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a systemic and poly-aetiological autoimmune disease characterized by the production of antibodies to autologous double-stranded DNA (dsDNA) which serve as diagnostic and prognostic markers. The defective clearance of apoptotic material, together with neutrophil extracellular traps (NETs), provides abundant chromatin or self-dsDNA to trigger the production of anti-dsDNA antibodies, although the mechanisms remain to be elucidated. In SLE patients, the immune complex (IC) of dsDNA and its autoantibodies trigger the robust type I interferon (IFN-I) production through intracellular DNA sensors, which drives the adaptive immune system to break down self-tolerance. In this review, we will discuss the potential resources of self-dsDNA, the mechanisms of self-dsDNA-mediated inflammation through various DNA sensors and its functions in SLE pathogenesis.

Autoimmune potential of perchloroethylene: Role of lipid-derived aldehydes

Tetrachloroethene (perchloroethylene, PCE), an ubiquitous environmental contaminant, has been implicated in inducing autoimmunity/autoimmune diseases (ADs), including systemic lupus erythematosus (SLE) and scleroderma in humans. However, experimental evidence suggesting the potential of PCE in mediating autoimmunity is lacking. This study was, therefore, undertaken to explore PCE's potential in inducing/exacerbating an autoimmune response. Six-week old female MRL+/+ mice, in groups of 6 each, were treated with PCE (0.5mg/ml) via drinking water for 12, 18 and 24weeks and markers of autoimmunity and oxidative stress were evaluated. PCE exposure led to significant increases in serum anti-nuclear antibodies (ANA), anti-dsDNA and anti-scleroderma-70 (anti-Scl-70) antibodies at 18weeks and, to a greater extent at 24weeks, suggesting that PCE exposure exacerbated autoimmunity in our animal model. The increases in autoantibodies were associated with time-dependent increases in malondialdehyde (MDA)-protein adducts and their antibodies, as well as significantly decreased levels of antioxidants GSH and SOD. The splenocytes isolated from mice treated with PCE for 18 and 24weeks showed greater Th17 cell proliferation and increased release of IL-17 in culture supernatants following stimulation with MDA-mouse serum albumin adducts, suggesting that MDA-modified proteins may act as an immunologic trigger by activating Th17 cells and contribute to PCE-mediated autoimmunity. Our studies thus provide an experimental evidence that PCE induces/exacerbates an autoimmune response and lipid-derived aldehydes (such as MDA) contribute to this response.

Lupus profundus limited to a site of trauma: Case report and review of the literature

Lupus erythematosus profundus (LEP) is a rare form of chronic cutaneous lupus erythematosus. We report on a case of a 56-year-old Caucasian woman who presented with a single, persistent, painful rash on the left hip and lateral aspect of the left upper thigh, which had been present for 2.5 years. The patient had a history of previous injury to this area before the rash started. Clinical findings showed an inflamed, hyperpigmented, and indurated plaque with a linear skin invagination and no associated systemic symptoms. A skin biopsy test result confirmed the diagnosis of LEP and the clinical and laboratory examinations ruled out systemic lupus erythematosus. After 2 months of treatment with methotrexate 20 mg weekly and 1 month of prednisolone 7.5 mg daily, the skin rash improved considerably. We also present a brief review of the epidemiology, etiology, clinical features, histopathology, laboratory findings, differential diagnosis, and treatment of LEP.

Association of Systemic Lupus Erythematosus and Beta Thalassaemia Trait- A Case Report

Systemic Lupus Erythematosus (SLE) is a multisystem chronic inflammatory disease of autoimmune aetiology. It has a predilection for female gender and presence of photosensitive rash over the sun exposed area gives a clue to the diagnosis. Diagnosis in a male patient with atypical manifestations is unusual and difficult. A 25-year-old male presented with fever, fatigue, vomiting, abdominal pain and loss of weight. He had sustained injury on his right arm following which he developed abscess at the trauma site and severe anaemia. Further evaluation revealed pancytopenia and peritonitis. Though peritonitis is rare in SLE, it was considered in the differential diagnosis after ruling out bacterial and tubercular peritonitis. Positive anti-dsDNA and antiSm antibodies confirmed the diagnosis. While evaluating for microcytic anaemia it was found that iron studies were normal and A2 fraction was raised in haemoglobin electrophoresis. The symptoms and laboratory parameters improved remarkably with steroid therapy. Beta thalassaemia trait is rare in patients with SLE, but when they co-exist the manifestations can be severe. High degree of suspicion is required to diagnose SLE in male patients in absence of typical photosensitive rash. Beta thalassaemia trait often does not require any treatment except genetic counseling. However empirical treatment with iron should be avoided.

iNOS null MRL+/+ mice show attenuation of trichloroethene-mediated autoimmunity: contribution of reactive nitrogen species and lipid-derived reactive aldehydes

Earlier studies from our laboratory in MRL+/+ mice suggest that free radicals, especially overproduction of reactive nitrogen species (RNS) and lipid-derived reactive aldehydes (LDRAs), are associated with trichloroethene (TCE)-mediated autoimmune response. The current study was undertaken to further assess the contribution of RNS and LDRAs in TCE-mediated autoimmunity by using iNOS-null MRL+/+ mice. iNOS-null MRL+/+ mice were obtained by backcrossing iNOS-null mice (B6.129P2-Nos2(tm1Lau)/J) to MRL +/+ mice. Female MRL+/+ and iNOS-null MRL+/+ mice were given TCE (10 mmol/kg, i.p., every 4(th) day) for 6 weeks; their respective controls received corn oil only. TCE exposure led to significantly increased iNOS mRNA in livers, iNOS protein in livers and sera, increased nitrotyrosine (NT) formation in both livers and sera, induction of MDA-/HNE-protein adducts in livers and their respective antibodies in sera along with significant increases in serum antinuclear antibodies (ANA) and anti-dsDNA in MRL+/+ mice. Even though in iNOS-null MRL+/+ mice, the iNOS and NT levels were negligible in both TCE-treated and untreated groups, TCE treatment still led to significant increases in MDA-/HNE-protein adducts and their respective antibodies along with increases in serum ANA and anti-dsDNA compared to controls. Most remarkably, the increases in serum ANA and anti-dsDNA induced by TCE in the iNOS-null MRL+/+ mice were significantly less pronounced compared to that in MRL+/+ mice. Our results provide further evidence that both RNS and LDRAs contribute to TCE-induced autoimmunity in MRL+/+ mice, and iNOS deficiency attenuates this autoimmune response.

Role of Fas and Treg cells in fracture healing as characterized in the fas-deficient (lpr) mouse model of lupus

Previous studies showed that loss of tumor necrosis factor α (TNFα) signaling delayed fracture healing by delaying chondrocyte apoptosis and cartilage resorption. Mechanistic studies showed that TNFα induced Fas expression within chondrocytes; however, the degree to which chondrocyte apoptosis is mediated by TNFα alone or dependent on the induction of Fas is unclear. This question was addressed by assessing fracture healing in Fas-deficient B6.MRL/Fas(lpr) /J mice. Loss of Fas delayed cartilage resorption but also lowered bone fraction in the calluses. The reduced bone fraction was related to elevated rates of coupled bone turnover in the B6.MRL/Fas(lpr) /J calluses, as evidenced by higher osteoclast numbers and increased osteogenesis. Analysis of the apoptotic marker caspase 3 showed fewer positive chondrocytes and osteoclasts in calluses of B6.MRL/Fas(lpr) /J mice. To determine if an active autoimmune state contributed to increased bone turnover, the levels of activated T cells and Treg cells were assessed. B6.MRL/Fas(lpr) /J mice had elevated Treg cells in both spleens and bones of B6.MRL/Fas(lpr) /J but decreased percentage of activated T cells in bone tissues. Fracture led to ∼30% to 60% systemic increase in Treg cells in both wild-type and B6.MRL/Fas(lpr) /J bone tissues during the period of cartilage formation and resorption but either decreased (wild type) or left unchanged (B6.MRL/Fas(lpr) /J) the numbers of activated T cells in bone. These results show that an active autoimmune state is inhibited during the period of cartilage resorption and suggest that iTreg cells play a functional role in this process. These data show that loss of Fas activity specifically in chondrocytes prolonged the life span of chondrocytes and that Fas synergized with TNFα signaling to mediate chondrocyte apoptosis. Conversely, loss of Fas systemically led to increased osteoclast numbers during later periods of fracture healing and increased osteogenesis. These findings suggest that retention of viable chondrocytes locally inhibits osteoclast activity or matrix proteolysis during cartilage resorption.

Differential oxidative modification of proteins in MRL+/+ and MRL/lpr mice: Increased formation of lipid peroxidation-derived aldehyde-protein adducts may contribute to accelerated onset of autoimmune response

Even though reactive oxygen species (ROS) have been implicated in SLE pathogenesis, the contributory role of ROS, especially the consequences of oxidative modification of proteins by lipid peroxidation-derived aldehydes (LPDAs) such as malondialdehyde (MDA) and 4-hydroxynonenal (HNE) in eliciting an autoimmune response and disease pathogenesis remains largely unexplored. MRL/lpr mice, a widely used model for SLE, spontaneously develop a condition similar to human SLE, whereas MRL+/+ mice with the same MRL background, show much slower onset of SLE. To assess if the differences in the onset of SLE in the two substrains could partly be due to differential expression of LPDAs and to provide evidence for the role of LPDA-modified proteins in SLE pathogenesis, we determined the serum levels of MDA-/HNE-protein adducts, anti-MDA-/HNE-protein adduct antibodies, MDA-/HNE-protein adduct specific immune complexes, and various autoantibodies in 6-, 12- and 18-week old mice of both substrains. The results show age-related increases in the formation of MDA-/HNE-protein adducts, their corresponding antibodies and MDA-/HNE-specific immune complexes, but MRL/lpr mice showed greater and more accelerated response. Interestingly, a highly positive correlation between increased anti-MDA-/HNE-protein adduct antibodies and autoantibodies was observed. More importantly, we further observed that HNE-MSA caused significant inhibition in antinuclear antibodies (ANA) binding to nuclear antigens. These findings suggest that LPDA-modified proteins could be important sources of autoantibodies and CICs in these mice, and thus contribute to autoimmune disease pathogenesis. The observed differential responses to LPDAs in MRL/lpr and MRL+/+ mice may, in part, be responsible for accelerated and delayed onset of the disease, respectively.

Aberrant macrophages mediate defective kidney repair that triggers nephritis in lupus-susceptible mice

CSF-1, required for macrophage (Mø) survival, proliferation, and activation, is upregulated in the tubular epithelial cells (TECs) during kidney inflammation. CSF-1 mediates Mø-dependent destruction in lupus-susceptible mice with nephritis and, paradoxically, Mø-dependent renal repair in lupus-resistant mice after transient ischemia/reperfusion injury (I/R). We now report that I/R leads to defective renal repair, nonresolving inflammation, and, in turn, early-onset lupus nephritis in preclinical MRL/MpJ-Faslpr/Fas(lpr) mice (MRL-Fas(lpr) mice). Moreover, defective renal repair is not unique to MRL-Fas(lpr) mice, as flawed healing is a feature of other lupus-susceptible mice (Sle 123) and MRL mice without the Fas(lpr) mutation. Increasing CSF-1 hastens renal healing after I/R in lupus-resistant mice but hinders healing, exacerbates nonresolving inflammation, and triggers more severe early-onset lupus nephritis in MRL-Fas(lpr) mice. Probing further, the time-related balance of M1 "destroyer" Mø shifts toward the M2 "healer" phenotype in lupus-resistant mice after I/R, but M1 Mø continue to dominate in MRL-Fas(lpr) mice. Moreover, hypoxic TECs release mediators, including CSF-1, that are responsible for stimulating the expansion of M1 Mø inherently poised to destroy the kidney in MRL-Fas(lpr) mice. In conclusion, I/R induces CSF-1 in injured TECs that expands aberrant Mø (M1 phenotype), mediating defective renal repair and nonresolving inflammation, and thereby hastens the onset of lupus nephritis.

Enhanced retinal pigment epithelium regeneration after injury in MRL/MpJ mice

Regenerative medicine holds the promise of restoring cells and tissues that are destroyed in human disease, including degenerative eye disorders. However, development of this approach in the eye has been limited by a lack of animal models that show robust regeneration of ocular tissue. Here, we test whether MRL/MpJ mice, which exhibit enhanced wound healing, can efficiently regenerate the retinal pigment epithelium (RPE) after an injury that mimics the loss of this tissue in age-related macular degeneration. The RPE of MRL/MpJ and control AKR/J mice was injured by retro-orbital injection of sodium iodate at 20 mg/kg body weight, which titration studies indicated was optimal for highlighting strain differences in the response to injury. Five days after sodium iodate injection at this dose, electroretinography of both strains revealed equivalent retinal responses that were significantly reduced compared to untreated mice. At one and two months post-injection, retinal responses were restored in MRL/MpJ but not AKR/J mice. Bright field and fluorescence microscopy of eyecup cryosections indicated an initial central loss of RPE cells and RPE65 immunostaining in MRL/MpJ and AKR/J mice, with preservation of peripheral RPE. Phalloidin staining of posterior eye whole mounts confirmed this pattern of RPE loss, and revealed a transition region characterized by RPE cell shedding and restructuring in both strains, suggesting a similar initial response to injury. At one month post-injection, central RPE cells, RPE65 immunostaining and phalloidin staining were restored in MRL/MpJ but not AKR/J mice. BrdU incorporation was observed throughout the RPE of MRL/MpJ but not AKR/J mice after one month of administration following sodium iodate treatment, consistent with RPE proliferation. These findings provide evidence for a dramatic regeneration of the RPE after injury in MRL/MpJ mice that supports full recovery of retinal function, which has not been observed previously in mammalian eyes. This model should prove useful for understanding molecular mechanisms that underlie regeneration, and for identifying factors that promote RPE regeneration in age-related macular degeneration and related diseases.

Wound trauma mediated inflammatory signaling attenuates a tissue regenerative response in MRL/MpJ mice

Background

Severe trauma can induce pathophysiological responses that have marked inflammatory components. The development of systemic inflammation following severe thermal injury has been implicated in immune dysfunction, delayed wound healing, multi-system organ failure and increased mortality.

Methods

In this study, we examined the impact of thermal injury-induced systemic inflammation on the healing response of a secondary wound in the MRL/MpJ mouse model, which was anatomically remote from the primary site of trauma, a wound that typically undergoes scarless healing in this specific strain. Ear-hole wounds in MRL/MpJ mice have previously displayed accelerated healing and tissue regeneration in the absence of a secondary insult.

Results

Severe thermal injury in addition to distal ear-hole wounds induced marked local and systemic inflammatory responses in the lungs and significantly augmented the expression of inflammatory mediators in the ear tissue. By day 14, 61% of the ear-hole wounds from thermally injured mice demonstrated extensive inflammation with marked inflammatory cell infiltration, extensive ulceration, and various level of necrosis to the point where a large percentage (38%) had to be euthanized early during the study due to extensive necrosis, inflammation and ear deformation. By day 35, ear-hole wounds in mice not subjected to thermal injury were completely closed, while the ear-hole wounds in thermally injured mice exhibited less inflammation and necrosis and only closed partially (62%). Thermal injury resulted in marked increases in serum levels of IL-6, TNFα, KC (CXCL1), and MIP-2α (CXCL2). Interestingly, attenuated early ear wound healing in the thermally injured mouse resulted in incomplete tissue regeneration in addition to a marked inflammatory response, as evidenced by the histological appearance of the wound and increased transcription of potent inflammatory mediators.

Conclusion

These findings suggest that the observed systemic inflammatory response of a severe thermal injury undoubtedly has an adverse effect on wound healing and tissue regeneration.