Deficiency of P-selectin or P-selectin glycoprotein ligand-1 leads to accelerated development of glomerulonephritis and increased expression of CC chemokine ligand 2 in lupus-prone mice

Targeting the PSGL-1 Immune Checkpoint Promotes Immunity to PD-1 Resistant Melanoma

Immune checkpoint inhibitors have had impressive efficacy in some cancer patients, reinvigorating long-term durable immune responses against tumors. Despite the clinical success of these therapies, most cancer patients continue to be unresponsive to these treatments, highlighting the need for novel therapeutic options. Although P-selectin glycoprotein ligand-1 (PSGL-1) has been shown to inhibit immune responses in a variety of disease models, previous work has yet to address whether PSGL-1 can be targeted therapeutically to promote antitumor immunity. Using an aggressive melanoma tumor model, we targeted PSGL-1 in tumor-bearing mice and found increased effector CD4+ and CD8+ T-cell responses and decreased regulatory T cells (Tregs) in tumors. T cells exhibited increased effector function, activation, and proliferation, which delayed tumor growth in mice after anti-PSGL-1 treatment. Targeting PD-1 in PSGL-1-deficient, tumor-bearing mice led to an increased frequency of mice with complete tumor eradication. Targeting both PSGL-1 and PD-1 in wild-type tumor-bearing mice also showed enhanced anti-tumor immunity and slowed melanoma tumor growth. Our findings showed that therapeutically targeting the PSGL-1 immune checkpoint can reinvigorate anti-tumor immunity and suggest that targeting PSGL-1 may represent a new therapeutic strategy for cancer treatment.

Tetraspanin CD53 modulates lymphocyte trafficking but not systemic autoimmunity in Lyn-deficient mice

The leukocyte-restricted tetraspanin CD53 has been shown to promote lymphocyte homing to lymph nodes (LNs) and myeloid cell recruitment to acutely inflamed peripheral organs, and accelerate the onset of immune-mediated disease. However, its contribution in the setting of chronic systemic autoimmunity has not been investigated. We made use of the Lyn^-/- autoimmune model, generating Cd53^-/- Lyn^-/- mice, and compared trafficking of immune cells into secondary lymphoid organs and systemic autoimmune disease development with mice lacking either gene alone. Consistent with previous observations, absence of CD53 led to reduced LN cellularity via reductions in both B and T cells, a phenotype also observed in Cd53^-/- Lyn^-/- mice. In some settings, Cd53^-/- Lyn^-/- lymphocytes showed greater loss of surface L-selectin and CD69 upregulation above that imparted by Lyn deficiency alone, indicating that absence of these two proteins can mediate additive effects in the immune system. Conversely, prototypical effects of Lyn deficiency including splenomegaly, plasma cell expansion, elevated serum immunoglobulin M and anti-nuclear antibodies were unaffected by CD53 deficiency. Furthermore, while Lyn^-/- mice developed glomerular injury and showed elevated glomerular neutrophil retention above than that in wild-type mice, absence of CD53 in Lyn^-/- mice did not alter these responses. Together, these findings demonstrate that while tetraspanin CD53 promotes lymphocyte trafficking into LNs independent of Lyn, it does not make an important contribution to development of autoimmunity, plasma cell dysfunction or glomerular injury in the Lyn^-/- model of systemic autoimmunity.

PSGL-1 Immune Checkpoint Inhibition for CD4+ T Cell Cancer Immunotherapy

Immune checkpoint inhibition targeting T cells has shown tremendous promise in the treatment of many cancer types and are now standard therapies for patients. While standard therapies have focused on PD-1 and CTLA-4 blockade, additional immune checkpoints have shown promise in promoting anti-tumor immunity. PSGL-1, primarily known for its role in cellular migration, has also been shown to function as a negative regulator of CD4+ T cells in numerous disease settings including cancer. PSGL-1 is highly expressed on T cells and can engage numerous ligands that impact signaling pathways, which may modulate CD4+ T cell differentiation and function. PSGL-1 engagement in the tumor microenvironment may promote CD4+ T cell exhaustion pathways that favor tumor growth. Here we highlight that blocking the PSGL-1 pathway on CD4+ T cells may represent a new cancer therapy approach to eradicate tumors.

Relevance of PSGL-1 Expression in B Cell Development and Activation

PSGL-1 is expressed in all plasma cells, but only in a small percentage of circulating B cells. Patients with systemic sclerosis (SSc) show reduced expression of PSGL-1 in B cells and increased prevalence of pulmonary arterial hypertension. PSGL-1 deficiency leads to a SSc-like syndrome and SSc-associated pulmonary hypertension in female mice. In this work, the expression of PSGL-1 was assessed during murine B cell development in the bone marrow and in several peripheral and spleen B cell subsets. The impact of PSGL-1 absence on B cell biology was also evaluated. Interestingly, the percentage of PSGL-1 expressing cells and PSGL-1 expression levels decreased in the transition from common lymphoid progenitors to immature B cells. PSGL-1^−/− mice showed reduced frequencies of peripheral B cells and reduced B cell lineage-committed precursors in the bone marrow. In the spleen of WT mice, the highest percentages of PSGL-1⁺ populations were shown by Breg (90%), B1a (34.7%), and B1b (19.1%), while only 2.5–8% of B2 cells expressed PSGL-1; however, within B2 cells, the class-switched subsets showed the highest percentages of PSGL-1⁺ cells. Interestingly, PSGL-1^−/− mice had increased IgG⁺ and IgD⁺ subsets and decreased IgA⁺ population. Of note, the percentage of PSGL-1⁺ cells was increased in all the B cell subclasses studied in peritoneal fluid. Furthermore, PSGL-1 engagement during in vitro activation with anti-IgM and anti-CD40 antibodies of human peripheral B cells, blocked IL-10 expression by activated human B cells. Remarkably, PSGL-1 expression in circulating plasma cells was reduced in pulmonary arterial hypertension patients. In summary, although the expression of PSGL-1 in mature B cells is low, the lack of PSGL-1 compromises normal B cell development and it may also play a role in the maturation and activation of peripheral naïve B cells.

P-selectin blockade ameliorates lupus nephritis in MRL/lpr mice through improving renal hypoxia and evaluation using BOLD-MRI

BACKGROUND

Lupus nephritis is one of the most common and severe complications of systemic lupus erythematosus, of which poor prognosis is indicated by aggravated renal hypoxia and tubulointerstitial fibrosis. Cell adhesion molecules play a key role in the progression of lupus nephritis tubulointerstitial lesion, including P-selectin, which mediates the rolling of leukocytes and subsequent adhesion and infiltration and then initiates the inflammatory immune response and ischemia and hypoxia injury. However, the effects and mechanisms of P-selectin in lupus nephritis remain to be investigated, and a noninvasive measurement of lupus nephritis tubulointerstitial hypoxia and fibrosis remains to be explored.

METHODS

Thirty-four MRL/lpr mice were randomly divided into the following three groups: MRL/lpr, saline, and anti-P-selectin, which consisted of no treatment, treatment with normal saline, and treatment with anti-P-selectin monoclonal antibody (mAb) from 12 to 16 weeks of age, respectively. Ten male C57BL/6 mice of the same age served as normal controls. 24-h urinary protein, urinary albumin-creatinine ratio, and periodic acid-Schiff were used to assess kidney damage; Western blot or immunohistochemical staining of the hypoxia probe Hypoxyprobe™-1, hypoxia-inducible factor 1α (HIF-1α), and CD31 were used to evaluate hypoxia in renal tissue; and NADPH oxidase subunit gp91phox and p22phox were used to examine renal oxidative stress. The correlation between kidney injury and blood oxygen level-dependent magnetic resonance imaging (BOLD-MRI) was calculated to assess the clinical value of BOLD-MRI.

RESULTS

P-selectin is upregulated in lupus nephritis. Blocking P-selectin with mAb alleviated renal tubulointerstitial fibrosis, renal hypoxia, and peritubular capillary loss, without alteration of the levels of lupus activity indicators, anti-dsDNA antibody, or complement C3. BOLD-MRI showed that the reduced R2* values in the renal cortex and medulla of lupus mice were increased when treated with anti-P-selectin mAb as compared with those treated with normal saline, which were negatively correlated with Hypoxyprobe™-1 hypoxia probe and the expression of HIF-1α.

CONCLUSIONS

Early intervention of lupus nephritis with anti-P-selectin mAb can significantly improve the hypoxic state of the kidney and reduce the severity of tubulointerstitial lesions. BOLD-MRI techniques are noninvasive and can dynamically evaluate the changes in renal lesions and intrarenal oxygenation levels before and after treatment in lupus nephritis.

Spontaneous Pulmonary Hypertension Associated With Systemic Sclerosis in P-Selectin Glycoprotein Ligand 1-Deficient Mice

OBJECTIVE

Pulmonary arterial hypertension (PAH), one of the major complications of systemic sclerosis (SSc), is a rare disease with unknown etiopathogenesis and noncurative treatments. As mice deficient in P-selectin glycoprotein ligand 1 (PSGL-1) develop a spontaneous SSc-like syndrome, we undertook this study to analyze whether they develop PAH and to examine the molecular mechanisms involved.

METHODS

Doppler echocardiography was used to estimate pulmonary pressure, immunohistochemistry was used to assess vascular remodeling, and myography of dissected pulmonary artery rings was used to analyze vascular reactivity. Angiotensin II (Ang II) levels were quantified by enzyme-linked immunosorbent assay, and Western blotting was used to measure Ang II type 1 receptor (AT1 R), AT2 R, endothelial cell nitric oxide synthase (eNOS), and phosphorylated eNOS expression in lung lysates. Flow cytometry allowed us to determine cytokine production by immune cells and NO production by endothelial cells. In all cases, there were 4-8 mice per experimental group.

RESULTS

PSGL-1-/- mice showed lung vessel wall remodeling and a reduced mean ± SD expression of pulmonary AT2 R (expression ratio [relative to β-actin] in female mice age >18 months: wild-type mice 0.799 ± 0.508 versus knockout mice 0.346 ± 0.229). With aging, female PSGL-1-/- mice had impaired up-regulation of estrogen receptor α (ERα) and developed lung vascular endothelial dysfunction coinciding with an increase in mean ± SEM pulmonary Ang II levels (wild-type 48.70 ± 5.13 pg/gm lung tissue versus knockout 78.02 ± 28.09 pg/gm lung tissue) and a decrease in eNOS phosphorylation, leading to reduced endothelial NO production. These events led to a reduction in the pulmonary artery acceleration time:ejection time ratio in 33% of aged female PSGL-1-/- mice, indicating pulmonary hypertension. Importantly, we found expanded populations of interferon-γ-producing PSGL-1-/- T cells and B cells and a reduced presence of regulatory T cells.

CONCLUSION

The absence of PSGL-1 induces a reduction in Treg cells, NO production, and ERα expression and causes an increase in Ang II in the lungs of female mice, favoring the development of PAH.

Targeting P-selectin glycoprotein ligand-1/P-selectin interactions as a novel therapy for metabolic syndrome

Obesity-induced insulin resistance and metabolic syndrome continue to pose an important public health challenge worldwide as they significantly increase the risk of type 2 diabetes and atherosclerotic cardiovascular disease. Advances in the pathophysiologic understanding of this process has identified that chronic inflammation plays a pivotal role. In this regard, given that both animal models and human studies have demonstrated that the interaction of P-selectin glycoprotein ligand-1 (PSGL-1) with P-selectin is not only critical for normal immune response but also is upregulated in the setting of metabolic syndrome, PSGL-1/P-selectin interactions provide a novel target for preventing and treating resultant disease. Current approaches of interfering with PSGL-1/P-selectin interactions include targeted antibodies, recombinant immunoglobulins that competitively bind P-selectin, and synthetic molecular therapies. Experimental models as well as clinical trials assessing the role of these modalities in a variety of diseases have continued to contribute to the understanding of PSGL-1/P-selectin interactions and have demonstrated the difficulty in creating clinically relevant therapeutics. Most recently, however, computational simulations have further enhanced our understanding of the structural features of PSGL-1 and related glycomimetics, which are responsible for high-affinity selectin interactions. Leveraging these insights for the design of next generation agents has thus led to development of a promising synthetic method for generating PSGL-1 glycosulfopeptide mimetics for the treatment of metabolic syndrome.

P-Selectin preserves immune tolerance in mice and is reduced in human cutaneous lupus

Mice deficient in P-Selectin presented altered immunity/tolerance balance. We have observed that the absence of P-Selectin promotes splenomegaly with reduced naïve T cell population, elevated activated/effector T cell subset, increased germinal center B and Tfh populations and high production of autoreactive antibodies. Moreover, 1.5-3-month-old P-selectin KO mice showed reduced IL-10-producing leukocytes in blood and a slightly reduced Treg population in the skin. With aging and, coinciding with disease severity, there is an increase in the IL17⁺ circulating and dermal T cell subpopulations and reduction of dermal Treg. As a consequence, P-Selectin deficient mice developed a progressive autoimmune syndrome showing skin alterations characteristic of lupus prone mice and elevated circulating autoantibodies, including anti-dsDNA. Similar to human SLE, disease pathogenesis was characterized by deposition of immune complexes in the dermoepidermal junction and renal glomeruli, and a complex pattern of autoantibodies. More important, skin biopsies of cutaneous lupus erythematosus patients did not show increased expression of P-Selectin, as described for other inflammatory diseases, and the number of vessels expressing P-Selectin was reduced.

Live Imaging of Immune Responses in Experimental Models of Multiple Sclerosis

Experimental autoimmune encephalomyelitis (EAE) is the most common animal model of multiple sclerosis (MS), a chronic inflammatory autoimmune disease of the central nervous system (CNS) characterized by multifocal perivascular infiltrates that predominantly comprise lymphocytes and macrophages. During EAE, autoreactive T cells first become active in the secondary lymphoid organs upon contact with antigen-presenting cells (APCs), and then gain access to CNS parenchyma, through a compromised blood–brain barrier, subsequently inducing inflammation and demyelination. Two-photon laser scanning microscopy (TPLSM) is an ideal tool for intravital imaging because of its low phototoxicity, deep tissue penetration, and high resolution. In the last decade, TPLSM has been used to visualize the behavior of T cells and their contact with APCs in the lymph nodes (LNs) and target tissues in several models of autoimmune diseases. The leptomeninges and cerebrospinal fluid represent particularly important points for T cell entry into the CNS and reactivation following contact with local APCs during the preclinical phase of EAE. In this review, we highlight recent findings concerning the pathogenesis of EAE and MS, emphasizing the use of TPLSM to characterize T cell activation in the LNs and CNS, as well as the mechanisms of tolerance induction. Furthermore, we discuss how advanced imaging unveils disease mechanisms and helps to identify novel therapeutic strategies to treat CNS autoimmunity and inflammation.

Psgl-1 Deficiency is Protective against Stroke in a Murine Model of Lupus

Systemic lupus erythematosus (SLE) is associated with an elevated risk of vascular complications, including premature stroke. Therapies targeting leukocyte recruitment may be beneficial in reducing vascular complications associated with SLE. Lupus was induced in female wild-type (WT) and P-selectin glycoprotein ligand-1 deficient (Psgl-1^−/−) mice with pristane. Stroke was induced following photochemical injury to the middle cerebral artery (MCA). Stroke size was increased in pristane-treated WT mice compared to non-pristane-treated WT controls. However, stroke size was not increased in pristane-treated Psgl-1^−/− mice compared to controls, despite evidence of increased nephritis in Psgl-1^−/− mice. Pristane-treated WT mice showed elevated anti-dsDNA, anti-snRNP, CXCL1, and MCP-1 levels compared to untreated mice; however levels of anti-snRNP, MCP-1, and CXCL1 were reduced in pristane-treated Psgl-1^−/− mice compared to pristane-treated WT mice. Infiltration of neutrophils and macrophages at the cerebral infarction site were reduced in pristane-treated Psgl-1^−/− mice compared to pristane-treated WT mice. In conclusion, the increase in stroke size associated with lupus is prevented by Psgl-1 deficiency while nephritis is exacerbated. Therapies targeting Psgl-1 may be useful in the management of SLE patients at high risk of acute vascular complications although elucidation of downstream pathways will be necessary to identify targets that do not promote nephritis.

Cholesterol-Independent Suppression of Lymphocyte Activation, Autoimmunity, and Glomerulonephritis by Apolipoprotein A-I in Normocholesterolemic Lupus-Prone Mice

Apolipoprotein (Apo)A-I, the major lipid-binding protein of high-density lipoprotein, can prevent autoimmunity and suppress inflammation in hypercholesterolemic mice by attenuating lymphocyte cholesterol accumulation and removing tissue-oxidized lipids. However, whether ApoA-I mediates immune-suppressive or anti-inflammatory effects under normocholesterolemic conditions and the mechanisms involved remain unresolved. We transferred bone marrow from systemic lupus erythematosus (SLE)-prone Sle123 mice into normal, ApoA-I-knockout (ApoA-I(-/-)) and ApoA-I-transgenic (ApoA-I(tg)) mice. Increased ApoA-I in ApoA-I(tg) mice suppressed CD4(+) T and B cell activation without changing lymphocyte cholesterol levels or reducing major ApoA-I-binding oxidized fatty acids. Unexpectedly, oxidized fatty acid peroxisome proliferator-activated receptor γ ligands 13- and 9-hydroxyoctadecadienoic acid were increased in lymphocytes of autoimmune ApoA-I(tg) mice. ApoA-I reduced Th1 cells independently of changes in CD4(+)Foxp3(+) regulatory T cells or CD11c(+) dendritic cell activation and migration. Follicular helper T cells, germinal center B cells, and autoantibodies were also lower in ApoA-I(tg) mice. Transgenic ApoA-I also improved SLE-mediated glomerulonephritis. However, ApoA-I deficiency did not have the opposite effects on autoimmunity or glomerulonephritis, possibly as the result of compensatory increases in ApoE on high-density lipoprotein. We conclude that, although compensatory mechanisms prevent the proinflammatory effects of ApoA-I deficiency in normocholesterolemic mice, increasing ApoA-I can attenuate lymphocyte activation and autoimmunity in SLE independently of cholesterol transport, possibly through oxidized fatty acid peroxisome proliferator-activated receptor γ ligands, and it can reduce renal inflammation in glomerulonephritis.

Development of an autoimmune syndrome affecting the skin and internal organs in P-selectin glycoprotein ligand 1 leukocyte receptor-deficient mice

OBJECTIVE

To define and characterize the progression of the spontaneous autoimmune disease that develops in mice in the absence of the leukocyte adhesion receptor P-selectin glycoprotein ligand 1 (PSGL-1).

METHODS

Skin-resident immune cells from PSGL-1-deficient mice and C57BL/6 control mice of different ages were isolated and analyzed by flow cytometry. Biochemical parameters were analyzed in mouse serum and urine, and the presence of serum autoantibodies was investigated. Skin and internal organs were extracted, and their structure was analyzed histologically.

RESULTS

Skin-resident innate and adaptive immune cells from PSGL-1(-/-) mice had a proinflammatory phenotype with an imbalanced T effector cell:Treg cell ratio. Sera from PSGL-1(-/-) mice had circulating autoantibodies commonly detected in connective tissue-related human autoimmune diseases. Biochemical and histologic analysis of skin and internal organs revealed skin fibrosis and structural and functional abnormalities in the lungs and kidneys. Furthermore, PSGL-1(-/-) mice exhibited vascular alterations, showing loss of dermal vessels, small vessel medial layer remodeling in the lungs and kidneys, and ischemic processes in the kidney that promote renal infarcts.

CONCLUSION

Our study demonstrates that immune system overactivation due to PSGL-1 deficiency triggers an autoimmune syndrome with characteristics similar to systemic sclerosis, including skin fibrosis, vascular alterations, and systemic organ involvement. These results suggest that PSGL-1 expression contributes to the maintenance of the homeostasis of the immune system and could act as a barrier for autoimmunity in mice.

Regulatory T cells suppress the late phase of the immune response in lymph nodes through P-selectin glycoprotein ligand-1

Regulatory T cells (Tregs) maintain tolerance toward self-antigens and suppress autoimmune diseases, although the underlying molecular mechanisms are unclear. In this study, we show that mice deficient for P-selectin glycoprotein ligand-1 (PSGL-1) develop a more severe form of experimental autoimmune encephalomyelitis than wild type animals do, suggesting that PSGL-1 has a role in the negative regulation of autoimmunity. We found that Tregs lacking PSGL-1 were unable to suppress experimental autoimmune encephalomyelitis and failed to inhibit T cell proliferation in vivo in the lymph nodes. Using two-photon laser-scanning microscopy in the lymph node, we found that PSGL-1 expression on Tregs had no role in the suppression of early T cell priming after immunization with Ag. Instead, PSGL-1-deficient Tregs lost the ability to modulate T cell movement and failed to inhibit the T cell-dendritic cell contacts and T cell clustering essential for sustained T cell activation during the late phase of the immune response. Notably, PSGL-1 expression on myelin-specific effector T cells had no role in T cell locomotion in the lymph node. Our data show that PSGL-1 represents a previously unknown, phase-specific mechanism for Treg-mediated suppression of the persistence of immune responses and autoimmunity induction.

ICAM-1 deficiency exacerbates sarcoid-like granulomatosis induced by Propionibacterium acnes through impaired IL-10 production by regulatory T cells

Propionibacterium acnes has been implicated as one of the suggested causative antigens for sarcoidosis, a systemic granulomatous disease. By injecting heat-killed P. acnes into the dorsal skin of C57BL/6J mice on days 1, 3, 5, and 14, sarcoid-like granulomatosis was induced in skin and lungs of these mice on day 28. To clarify the role of cell adhesion molecules in cutaneous sarcoidosis, we induced sarcoid-like granulomatosis in mice deficient of intercellular adhesion molecule (ICAM)-1, L-selectin, P-selectin, or E-selectin via repeated P. acnes injection. Histopathologic analysis revealed that granuloma formation was aggravated in the skin and lungs of ICAM-1-deficient mice compared with wild-type mice. Within skin granulomas of ICAM-1-deficient mice, P. acnes immunization up-regulated mRNA expression of tumor necrosis factor-α, although it failed to induce IL-10 mRNA expression in contrast to wild-type mice. Infiltration of regulatory T cells into skin granuloma was similar between wild-type mice and ICAM-1-deficient mice. P. acnes immunization induced IL-10 production by CD4(+)CD25(+)Foxp3(+) regulatory T cells in lymph nodes of wild-type mice in vivo, which was absent in regulatory T cells of ICAM-1-deficient mice. Our results indicate that ICAM-1 is imperative for inducing regulatory T cells to produce IL-10 in vivo, which would prevent granuloma formation.

Endothelial nitric oxide synthase inhibits the development of autoimmune-mediated vasculitis in mice

OBJECTIVE

Many different genes or mediators have been implicated in promoting the development of vasculitis, although little is known regarding the mechanisms that normally act to suppress lesion formation. Endothelial nitric oxide synthase (eNOS) has been shown to inhibit vascular inflammation in many different model systems, but its roles in the pathogenesis of vasculitis have not been elucidated. This study was undertaken to determine the functions of eNOS in the initiation and progression of vasculitic lesion formation.

METHODS

MRL/MpJ-Fas(lpr) mice lacking the gene for eNOS (Nos3(-/-) ) were generated and comprehensively evaluated and compared to controls with regard to the development of autoimmune disease, including vasculitic lesion formation and glomerulonephritis.

RESULTS

Nos3(-/-) MRL/MpJ-Fas(lpr) mice exhibited accelerated onset and increased incidence of renal vasculitis compared to Nos3(+/+) controls. In contrast, no significant differences in severity of glomerulonephritis were observed between groups. Vasculitis was also observed in other organs of eNOS-deficient mice, including in the lungs of several of these animals. Ultrastructural analyses of renal lesions revealed the presence of electron-dense deposits in affected arteries, and IgG, IgA, and C3 deposition was observed in some vessels in the kidneys of Nos3(-/-) mice. In addition, Nos3(-/-) MRL/MpJ-Fas(lp) mice showed increased levels of circulating IgG-IgA immune complexes at 20 weeks of age, compared to Nos3(+/+) MRL/MpJ-Fas(lpr) and Nos3(-/-) C57BL/6 mice.

CONCLUSION

These findings strongly indicate that eNOS serves as a negative regulator of vasculitis in MRL/MpJ-Fas(lpr) mice and further suggest that NO produced by this enzyme may be critical for inhibiting lesion formation and vascular damage in human vasculitic diseases.

Fli-1 transcription factor affects glomerulonephritis development by regulating expression of monocyte chemoattractant protein-1 in endothelial cells in the kidney

Expression of transcription factor Fli-1 is implicated in the development of glomerulonephritis. Fli-1 heterozygous knockout (Fli1(+/-)) NZM2410 mice, a murine model of lupus, had significantly improved survival and reduced glomerulonephritis. In this study, we found that infiltrated inflammatory cells were significantly decreased in the kidneys from Fli-1(+/-) NZM2410 mice. The expression of monocyte chemoattractant protein-1 (MCP-1) was significantly decreased in kidneys from Fli-1(+/-) NZM2410 mice. The primary endothelial cells isolated from the kidneys of Fli-1(+/-) NZM2410 mice produced significantly less MCP-1. In endothelial cells transfected with specific Fli-1 siRNA the production of MCP-1 was significantly reduced compared to cells transfected with negative control siRNA. By Chromatin Immunoprecipitation (ChIP) assay, we further demonstrated that Fli-1 directly binds to the promoter of the MCP-1 gene. Our data indicate that Fli-1 impacts glomerulonephritis development by regulating expression of inflammatory chemokine MCP-1 and inflammatory cell infiltration in the kidneys in the NZM2410 mice.

Complement factor H deficiency accelerates development of lupus nephritis

Complement factor H (CfH) is a key regulator of the alternative pathway, and its presence on mouse platelets and podocytes allows the processing of immune complexes. Because of the role of immune complexes in the pathophysiology of lupus nephritis, we studied the role of CfH in the development of nephritis in MRL-lpr mice, an animal model of lupus. At 12 weeks, CfH-deficient MRL-lpr mice had significantly more albuminuria and higher BUN levels than MRL-lpr controls. Cfh-deficient MRL-lpr mice also experienced earlier mortality: at 14 weeks, 6 of 9 CfH-deficient MRL-lpr mice had died of renal failure, whereas all 11 littermate CfH-sufficient MRL-lpr mice were alive (P ≤ 0.001). Histologically, CfH-deficient MRL-lpr mice developed severe diffuse lupus nephritis by 12 weeks (glomerulonephritis scores of 2.6 ± 0.4 versus 0.4 ± 0.2 in littermate controls, P = 0.001). Similar to other CfH-deficient mouse models on nonautoimmune backgrounds, immunofluorescence staining showed extensive linear C3 staining along glomerular capillary walls. IgG was present in the mesangium and peripheral capillary walls along with excessive infiltration of macrophages and neutrophils. Ultrastructurally, there were subendothelial and subepithelial immune deposits and extensive podocyte foot process effacement. In summary, the loss of CfH accelerates the development of lupus nephritis and recapitulates the functional and structural features of the human disease. This illustrates the critical role of complement regulation and metabolism of immune complexes in the pathogenesis of lupus nephritis.

Oxidative stress in anxiety and comorbid disorders

Anxiety disorders, depression, and alcohol use disorder are common neuropsychiatric diseases that often occur together. Oxidative stress has been suggested to contribute to their etiology. Oxidative stress is a consequence of either increased generation of reactive oxygen species or impaired enzymatic or non-enzymatic defense against it. When excessive it leads to damage of all major classes of macromolecules, and therefore affects several fundamentally important cellular functions. Consequences that are especially detrimental to the proper functioning of the brain include mitochondrial dysfunction, altered neuronal signaling, and inhibition of neurogenesis. Each of these can further contribute to increased oxidative stress, leading to additional burden to the brain. In this review, we will provide an overview of recent work on oxidative stress markers in human patients with anxiety, depressive, or alcohol use disorders, and in relevant animal models. In addition, putative oxidative stress-related mechanisms important for neuropsychiatric diseases are discussed. Despite the considerable interest this field has obtained, the detailed mechanisms that link oxidative stress to the pathogenesis of neuropsychiatric diseases remain largely unknown. Since this pathway may be amenable to pharmacological intervention, further studies are warranted.

Cell adhesion molecules regulate fibrotic process via Th1/Th2/Th17 cell balance in a bleomycin-induced scleroderma model

Mice s.c. injected with bleomycin, an experimental model for human systemic sclerosis, develop skin and lung fibrosis, which is mediated by inflammatory cell infiltration. This process is highly regulated by multiple adhesion molecules and does not require Ag sensitization. To assess the role of adhesion molecules in this pathogenetic process, bleomycin-induced fibrosis was examined in mice lacking adhesion molecules. L-selectin and/or ICAM-1 deficiency inhibited skin and lung fibrosis with decreased Th2 and Th17 cytokines and increased Th1 cytokines. In contrast, P-selectin deficiency, E-selectin deficiency with or without P-selectin blockade, or P-selectin glycoprotein ligand 1 (PSGL-1) deficiency augmented the fibrosis in parallel with increased Th2 and Th17 cytokines and decreased Th1 cytokines. Furthermore, loss of L-selectin and/or ICAM-1 reduced Th2 and Th17 cell numbers in bronchoalveolar lavage fluid, whereas loss of P-selectin, E-selectin, or PSGL-1 reduced Th1 cell numbers. Moreover, Th1 cells exhibited higher PSGL-1 expression and lower expression of LFA-1, a ligand for ICAM-1, whereas Th2 and Th17 cells showed higher LFA-1 and lower PSGL-1 expression. This study suggests that L-selectin and ICAM-1 regulate Th2 and Th17 cell accumulation into the skin and lung, leading to the development of fibrosis, and that P-selectin, E-selectin, and PSGL-1 regulate Th1 cell infiltration, resulting in the inhibition of fibrosis.

Neutrophils: game changers in glomerulonephritis?

Glomerulonephritides represent a diverse array of diseases that have in common immune cell-mediated effector mechanisms that cause organ damage. The contribution of neutrophils to the pathogenesis of proliferative glomerulonephritis (GN) is not well recognized. Most equate neutrophils with killing pathogens and causing collateral tissue damage during acute inflammation. However, these phagocytes are endowed with additional characteristics that have been traditionally reserved for cells of the adaptive immune system. They communicate with other cells, exhibit plasticity in their responses and have the potential to coordinate and inform the subsequent immune response, thus countering the notion that they arrive, destroy and then disappear. Therefore, neutrophils, which are the first to arrive at a site of inflammation, are potential game changers in GN.

Mild calorie restriction induces fat accumulation in female C57BL/6J mice

This study investigated the effects of mild calorie restriction (CR) (5%) on body weight, body composition, energy expenditure, feeding behavior, and locomotor activity in female C57BL/6J mice. Mice were subjected to a 5% reduction of food intake relative to baseline intake of ad libitum (AL) mice for 3 or 4 weeks. In experiment 1, body weight was monitored weekly and body composition (fat and lean mass) was determined at weeks 0, 2, and 4 by dual energy X-ray absorptiometry. In experiment 2, body weight was measured every 3 days and body composition was determined by quantitative magnetic resonance weekly, and energy expenditure, feeding behavior, and locomotor activity were determined over 3 weeks in a metabolic chamber. At the end of both experiments, CR mice had greater fat mass (P < 0.01) and less lean mass (P < 0.01) compared with AL mice. Total energy expenditure (P < 0.05) and resting energy expenditure (P < 0.05) were significantly decreased in CR mice compared with AL mice over 3 weeks. CR mice ate significantly more food than AL mice immediately following daily food provisioning at 1600 hours (P < 0.01). These findings showed that mild CR caused increased fat mass, decreased lean mass and energy expenditure, and altered feeding behavior in female C57BL/6J mice. Locomotor activity or brown adipose tissue (BAT) thermogenic capacity did not appear to contribute to the decrease in energy expenditure. The increase in fat mass and decrease in lean mass may be a stress response to the uncertainty of food availability.

Variation in the upstream region of P-Selectin (SELP) is a risk factor for SLE

Systemic lupus erythematosus (SLE) is a complex autoimmune disease. Genome-wide linkage studies implicated a region containing the adhesion molecule P-Selectin. This family-based study revealed two regions of association within P-Selectin. The strongest signal, from a 21.4-kb risk haplotype, stretched from the promoter into the first two consensus repeat (CR) regions (P=8 × 10⁻⁴), with a second association from a 14.6-kb protective haplotype covering CR 2–9 (P=0.0198). The risk haplotype is tagged by the rare C allele of rs3753306, which disrupts the binding site of the trans-activating transcription factor HNF-1. One other variant (rs3917687) on the risk haplotype was significant after permutation (P₁₀₀₀₀<1 × 10⁻⁵), replicated in independent pseudo case-control analysis and was significant by meta-analysis (P=4.37 × 10⁻⁶). A third associated variant on the risk haplotype (rs3917657) replicated in 306 US SLE families and was significant in a joint UK-SLE data set after permutation. The protective haplotype is tagged by rs6133 (a non-synonymous variant in CR8 (P=9.00 × 10⁻⁴), which also shows association in the pseudo case-control analysis (P=1.09 × 10⁻³) and may contribute to another signal in P-Selectin. We propose that polymorphism in the upstream region may reduce expression of P-Selectin, the mechanism by which this promotes autoimmunity is unknown, although it may reduce the production of regulatory T cells.

ICOS controls effector function but not trafficking receptor expression of kidney-infiltrating effector T cells in murine lupus

Renal pathology in systemic lupus erythematosus involves both autoantibody deposition and a cellular inflammatory response, both of which are mediated by effector CD4 T cells. MRL(lpr) mice spontaneously develop massive perivascular infiltrates, but the pathways that regulate the development, trafficking, and effector functions of kidney-infiltrating T cells are poorly defined. To address these questions, we first surveyed inflammatory chemokine protein levels in nephritic kidneys from lupus-prone MRL(lpr) mice. After identifying highly elevated levels of the CXCR3 ligand CXCL9, we found that kidney-infiltrating effectors are enriched for expression of CXCR3, as well as P-selectin ligand and ICOS. Using genetic ablation, we demonstrate that ICOS plays an essential role in the establishment of renal perivascular infiltrates, although a small number of infiltrating cells remain around the blood vessels. Interestingly, though IgG autoantibody production is substantially reduced in Icos(-/-) MRL(lpr) mice, the progression of immune complex glomerulonephritis is only modestly diminished and the production of inflammatory chemokines, such as CXCL9, remains high in the kidney. We find that Icos(-/-) effector cell numbers are only slightly reduced and these have normal expression of CXCR3 and P-selectin ligand with intact migration to CXCL9. However, they have impaired production of inflammatory cytokines and fail to show evidence of efficient proliferation in the kidney. Thus, while dispensable for acquisition of renal trafficking receptor expression, ICOS is strictly required for local inflammatory functions of autoreactive CD4 T cells in murine lupus.

Risperidone alters food intake, core body temperature, and locomotor activity in mice

Risperidone induces significant weight gain in female mice; however, the underlying mechanisms related to this effect are unknown. We investigated the effects of risperidone on locomotor activity, core body temperature, and uncoupling protein (UCP) and hypothalamic orexin mRNA expression. Female C57BL/6J mice were acclimated to individual housing and randomly assigned to either risperidone (4 mg/kg BW day) or placebo (PLA). Activity and body temperature were measured over 48-hour periods twice a week for 3 weeks. Food intake and body weights were measured weekly. UCP1 (BAT), UCP3 (gastrocnemius), and orexin (hypothalamus) mRNA expressions were measured using RT-PCR. Risperidone-treated mice consumed more food (p=0.050) and gained more weight (p=0.0001) than PLA-treated mice after 3 weeks. During the initial 2 days of treatment, there was an acute effect of treatment on activity (p=0.046), but not body temperature (p=0.290). During 3 weeks of treatment, average core body temperatures were higher in risperidone-treated mice compared to controls during the light phase (p=0.0001), and tended to be higher during the dark phase (p=0.057). Risperidone-treated mice exhibited lower activity levels than controls during the dark phase (p=0.006); there were no differences in activity during the light phase (p=0.47). UCP1 (p<0.01) and UCP3 (p<0.05) mRNA expressions were greater in risperidone-treated mice compared to controls, whereas, orexin mRNA expression was lower in risperidone-treated mice (p<0.01). These results suggest that risperidone-induced weight gain in mice is a consequence of increased energy intake and reduced activity, while the elevation in body temperature may be a result of thermogenic effect of food intake and elevated UCP1, UCP3, and a reduced hypothalamic orexin expression.

Altered balance of inhibitory and active Fc gamma receptors in murine autoimmune glomerulonephritis

Mag is an MRL-derived glomerulonephritis susceptibility locus that includes the Fcgr2b and Fcgr3 genes encoding the inhibitory Fc gamma receptor IIB (FcgammaRIIB) and active FcgammaRIII, respectively. We measured changes in gene balance in three B6.MRLc1 congenic mouse strains containing the 82-86, 92-100 and 100 cM regions of the MRL chromosome 1. We found that only the strain that has 92-100 (which includes Fcgr loci) developed glomerulonephritis. These congenic mice had splenomegaly, elevated blood urea nitrogen, anti-dsDNA antibodies and higher urinary albumin excretion compared to the parental strain C57BL/6(B6). Prior to the development of glomerulonephritis, large CD3- (T cell) and B220- (B cell) positive areas were identified in the spleens of B6.MRLc1(92-100) mice. Both Fc receptors were found in mesangial and dendritic cells; important sites of immune-complex clearance and antigen presentation. The FcgammaRIII-positive areas were more prominent in the congenic strain. Fcgr2b mRNA was lower in the B6.MRLc1(92-100) kidney and spleen than in those organs of the B6 mice while Fcgr3 expression and the Fcgr3 to Fcgr2b mRNA ratio was higher in the congenic strain kidneys, spleen and thymus than in those of the B6 prior to and at an early stage of glomerulonephritis. We conclude that the imbalance of inhibitory and active Fc gamma receptors influences the pathogenesis of glomerulonephritis.

Differential roles of ICAM-1 and VCAM-1 in leukocyte-endothelial cell interactions in skin and brain of MRL/faslpr mice

MRL/fas(lpr) mice, which undergo a systemic autoimmune disease with similarities to systemic lupus erythematosus (SLE), display reduced pathology and prolonged survival if rendered deficient in ICAM-1. However, it remains unclear whether this is a result of the ability of ICAM-1 to promote the immune response or mediate leukocyte recruitment. Therefore, the aim of these studies was to compare the role of ICAM-1 in the elevated leukocyte-endothelial interactions, which affect MRL/fas(lpr) mice. Intravital microscopy was used to compare leukocyte rolling and adhesion in postcapillary venules in the dermal and cerebral (pial) microcirculations of wild-type (ICAM+/+) and ICAM-1-deficient (ICAM-1-/-) MRL/fas(lpr) mice. In the dermal microcirculation of 16-week MRL/fas(lpr) mice, leukocyte adhesion was increased relative to nondiseased MRL+/+ mice. However, this increase was abolished in ICAM-1-/- MRL/fas(lpr) mice. ICAM-1 deficiency was also associated with reduced dermal pathology. In contrast, in the pial microcirculation, the elevation in leukocyte adhesion observed in ICAM+/+ MRL/fas(lpr) mice also occurred in ICAM-1-/- MRL/fas(lpr) mice. VCAM-1 expression was detectable in both vascular beds, but higher levels were detected in the pial vasculature. Furthermore, VCAM-1 blockade significantly reduced leukocyte adhesion and rolling in the cerebral microcirculation of ICAM-1-/- MRL/fas(lpr) mice. Therefore, ICAM-1 was critical for leukocyte adhesion in the skin but not the brain, where VCAM-1 assumed the major function. Given the ongoing development of anti-adhesion molecule therapies and their potential in inflammatory diseases such as SLE, these data indicate that implementation of these therapies in SLE should take into account the potential for tissue-specific functions of adhesion molecules.

Experimental anti-GBM disease as a tool for studying spontaneous lupus nephritis

Lupus nephritis is an immune-mediated disease, where antibodies and T cells both play pathogenic roles. Since spontaneous lupus nephritis in mouse models takes 6-12 months to manifest, there is an urgent need for a mouse model that can be used to delineate the pathogenic processes that lead to immune nephritis, over a quicker time frame. We propose that the experimental anti-glomerular basement membrane (GBM) disease model might be a suitable tool for uncovering some of the molecular steps underlying lupus nephritis. This article reviews the current evidence that supports the use of the experimental anti-GBM nephritis model for studying spontaneous lupus nephritis. Importantly, out of about 25 different molecules that have been specifically examined in the experimental anti-GBM model and also spontaneous lupus nephritis, all influence both diseases concordantly, suggesting that the experimental model might be a useful tool for unraveling the molecular basis of spontaneous lupus nephritis. This has important clinical implications, both from the perspective of genetic susceptibility as well as clinical therapeutics.

Detection of early changes in renal function using 99mTc-MAG3 imaging in a murine model of ischemia-reperfusion injury

Accurate determination of renal function in mice is a major impediment to the use of murine models in acute kidney injury. The purpose of this study was to determine whether early changes in renal function could be detected using dynamic gamma camera imaging in a mouse model of ischemia-reperfusion (I/R) injury. C57BL/6 mice (n = 5/group) underwent a right nephrectomy, followed by either 30 min of I/R injury or sham surgery of the remaining kidney. Dynamic renal studies (21 min, 10 s/frame) were conducted before surgery (baseline) and at 5, 24, and 48 h by injection of (99m)Tc-mercaptoacetyltriglycine (MAG3; approximately 1.0 mCi/mouse) via the tail vein. The percentage of injected dose (%ID) in the kidney was calculated for each 10-s interval after MAG3 injection, using standard region of interest analyses. A defect in renal function in I/R-treated mice was detected as early as 5 h after surgery compared with sham-treated mice, identified by the increased %ID (at peak) in the I/R-treated kidneys at 100 s (P < 0.01) that remained significantly higher than sham-treated mice for the duration of the scan until 600 s (P < 0.05). At 48 h, the renal scan demonstrated functional renal recovery of the I/R mice and was comparable to sham-treated mice. Our study shows that using dynamic imaging, renal dysfunction can be detected and quantified reliably as early as 5 h after I/R insult, allowing for evaluation of early treatment interventions.