Expanding the Organismal Proteostasis Network: Linking Systemic Stress Signaling with the Innate Immune Response.

Stress response pathways regulate proteostasis and mitigate macromolecular damage to promote long-term cellular health. Intercellular signaling is an essential layer of systemic proteostasis in an organism and is facilitated via transcellular signaling molecules that orchestrate the activation of stress responses across tissues and organs. Accumulating evidence indicates that components of the immune response act as signaling factors that regulate the cell-non-autonomous proteostasis network. Here, we review emergent advances in our understanding of cell-non-autonomous regulators of proteostasis networks in multicellular settings, from the model organism, Caenorhabditis elegans, to humans. We further discuss how innate immune responses can be players of the organismal proteostasis network and discuss how both are linked in cancer.

Annular lesions of cutaneous sarcoidosis with granulomatous vasculitis.

Sarcoidosis is known to be involved in diseases with vasculitis as sarcoid vasculitis. However, vasculitis in cutaneous sarcoidal lesions is extremely rare. Here we describe a case of sarcoidosis with multiple annular skin lesions with granulomatous vasculitis. A 62-year-old female was diagnosed with sarcoidosis by chest-abdominal computed tomographic examination and laboratory tests. The skin lesions had appeared on her lower limbs 2 years before. Physical examination showed multiple infiltrated annular eruptions on the lower extremities. A skin biopsy of an area of erythema showed multiple non-caseating epithelioid cell granulomas in the dermis and subcutaneous fat and granulomatous vasculitis with fibrinoid degeneration in the subcutaneous fat. There are two types of vasculitis in sarcoidosis: leukocytoclastic and granulomatous vasculitis. Ulcers and livedo were more common in granulomatous vasculitis than in leukocytoclastic vasculitis. The present case had unique annular skin lesions of sarcoidosis with granulomatous vasculitis.

Histopathology of bilateral lower extremity inflammatory lymphedema in military basic trainees: A leukocytoclastic vasculitis of the deep vascular plexus.

Bilateral lower extremity inflammatory lymphedema (BLEIL) is a recently described condition that presents with exquisite tenderness, erythema and edema of the lower leg, ankle and dorsal foot resembling an acute cellulitis. It was first reported in healthy, young adult military basic trainees with a normal body mass index during the first 72 hours of arrival to basic training. It occurs while standing at attention for many hours, and shows rapid resolution with elevation and rest. We report an additional case of BLEIL and describe the histopathology of this case and 2 of the previously reported cases. All 3 biopsies showed a deep perivascular infiltrate of neutrophils with karyorrhectic debris and prominent red blood cell extravasation. One of the 3 cases was positive for complement by direct immunofluorescence. We postulate this condition represents a deep leukocytoclastic vascultis with secondary reactive lymphedematous changes.

Leukocytoclastic vasculitis in children: clinical characteristics, subtypes, causes and direct immunofluorescence findings of 56 biopsy-confirmed cases.

BACKGROUND: Leukocytoclastic vasculitis (LCV) in children is a complex group of conditions. OBJECTIVES: This study presents the demographics, clinical features, direct immunofluorescence (DIF) results and suspected aetiologies of 56 biopsy-confirmed cases of leukocytoclastic vasculitis in children. METHODS: Retrospective review of 56 children seen at Mayo Clinic in Rochester, Minnesota, from 1993 to 2013 with clinical features and cutaneous biopsy consistent with LCV. RESULTS: Twenty-seven (48%) cases were found to be due to IgA vasculitis (Henoch-Schonlein purpura). The remaining cases were found to be due to cutaneous small-vessel vasculitis (n = 19, 34%), urticarial vasculitis (n = 5, 9%), ANCA-associated vasculitis (n = 4, 7%) and acute haemorrhagic oedema of infancy (n = 1, 2%). IgA vasculitis was found to be associated with abdominal pain (P = 0.008), whereas the non-IgA vasculitis group was associated with headache (P = 0.052). Children with IgA vasculitis had palpable purpura (P = <0.001), petechia (P = 0.057), vesicles (P = 0.009) and involvement of the buttock (P = 0.004) more frequently than the non-IgA vasculitis group. On DIF, perivascular IgA was positive in IgA vasculitis compared to non-IgA vasculitis cases (P = <0.001), the other conjugates were similar between the two groups. CONCLUSION: The most common subtype of biopsy-confirmed LCV in children is IgA vasculitis. Clinical features, exam characteristics and DIF results can be helpful in determining the subtype of cutaneous vasculitis in children.

Acute neutrophilic vasculitis (leukocytoclasia) in 36 COVID-19 autopsy brains.

BACKGROUND: Hypercytokinemia, the renin-angiotensin system, hypoxia, immune dysregulation, and vasculopathy with evidence of immune-related damage are implicated in brain morbidity in COVID-19 along with a wide variety of genomic and environmental influences. There is relatively little evidence of direct SARS-CoV-2 brain infection in COVID-19 patients. METHODS: Brain histopathology of 36 consecutive autopsies of patients who were RT-PCR positive for SARS-CoV-2 was studied along with findings from contemporary and pre-pandemic historical control groups. Immunostaining for serum and blood cell proteins and for complement components was employed. Microcirculatory wall complement deposition in the COVID-19 cohort was compared to historical control cases. Comparisons also included other relevant clinicopathological and microcirculatory findings in the COVID-19 cohort and control groups. RESULTS: The COVID-19 cohort and both the contemporary and historical control groups had the same rate of hypertension, diabetes mellitus, and obesity. The COVID-19 cohort had varying amounts of acute neutrophilic vasculitis with leukocytoclasia in the microcirculation of the brain in all cases. Prominent vascular neutrophilic transmural migration was found in several cases and 25 cases had acute perivasculitis. Paravascular microhemorrhages and petechial hemorrhages (small brain parenchymal hemorrhages) had a slight tendency to be more numerous in cohort cases that displayed less acute neutrophilic vasculitis. Tissue burden of acute neutrophilic vasculitis with leukocytoclasia was the same in control cases as a group, while it was significantly higher in COVID-19 cases. Both the tissue burden of acute neutrophilic vasculitis and the activation of complement components, including membrane attack complex, were significantly higher in microcirculatory channels in COVID-19 cohort brains than in historical controls. CONCLUSIONS: Acute neutrophilic vasculitis with leukocytoclasia, acute perivasculitis, and associated paravascular blood extravasation into brain parenchyma constitute the first phase of an immune-related, acute small-vessel inflammatory condition often termed type 3 hypersensitivity vasculitis or leukocytoclastic vasculitis. There is a higher tissue burden of acute neutrophilic vasculitis and an increased level of activated complement components in microcirculatory walls in COVID-19 cases than in pre-pandemic control cases. These findings are consistent with a more extensive small-vessel immune-related vasculitis in COVID-19 cases than in control cases. The pathway(s) and mechanism for these findings are speculative.

Myelodysplasia and malignancy-associated vasculitis.

While the link between malignancy and vasculitis has been known for some time, the association of vasculitis and myelodysplastic syndrome (MDS) has only recently been reported. This article reviews the most current and landmark publications regarding MDS, as well as malignancy-associated vasculitis. We include theories of paraneoplastic associations, immune pathogenesis including an associated cytokine transcriptional factor (interferon regulatory factor-1 [IFN-1]), and the relationship to treatment. Key clinical features that suggest underlying malignancy in patients with vasculitis are highlighted. Although the association between vasculitis and malignancy is rare, leukocytoclastic vasculitis is the most common vasculitis associated with MDS, hematologic malignancies as well as solid tumors. We review several articles that demonstrate a paraneoplastic association between vasculitis and various malignancies, but overall, the connection is still unclear and not well defined. Certain features that suggest a true paraneoplastic association are outlined. Further studies are needed to advance our understanding of this complex topic.

The Anti-inflammatory Effects of HMGB1 Blockades in a Mouse Model of Cutaneous Vasculitis.

In our previous study, we have found increased serum levels of HMGB1 in patients with Henoch- Schonlein purpura (HSP), allergic vasculitis (AV), and urticarial vasculitis (UV) and altered HMGB1 distribution in lesional skin in patients with HSP. HMGB1 plays a pro-inflammatory role in the pathogenesis of HSP. To further investigate the role of HMGB1 in the pathogenic mechanism of vasculitis, we investigated the anti-inflammatory effects of HMGB1 blockades (including anti-HMGB1 mAb and glycyrrhizin) in a mouse model of a cutaneous reverse passive Arthus (RPA) reaction. A total of 36 balb/c mice were randomly divided into four groups: the control group, IC model group, HMGB1 monoclonal antibody (anti-HMGB1-mAb) group and the glycyrrhizin group, with nine mice in each group. A cutaneous RPA reaction mouse model was established by injections of the OVA antibody and the OVA antigen. Mice of the anti-HMGB1-mAb group and glycyrrhizin group were pre-treated with anti-HMGB1 mAb or glycyrrhizin, respectively, before the RPA reaction. Our results indicated that HMGB1 blockades (anti-HMGB1 mAb and glycyrrhizin) obviously extenuated the severity of vasculitis skin damage and improved the histological evolvement of inflammatory cells infiltration, vascular fibroid necrosis, and vasodilation in a cutaneous RPA reaction mouse model. In addition, HMGB1 blockades reduced the infiltration of neutrophils, DCs, and T cells and decreased the mRNA expression of IL-6 and CCL5 in skin lesions in the cutaneous RPA reaction mouse model. We suggest that HMGB1 blockades may represent a new direction for the treatment of cutaneous vasculitis.

Circulating immune complexes in cutaneous vasculitis. Detection with C1q and monoclonal rheumatoid factor.

To investigate the pathogeneic significance of immune complexes in cutaneous vasculitis, 107 patients with various forms of cutaneous vasculitis, including 59 patients with necrotizing (leukocytoclastic) vasculitis (group 1), and 48 patients with lymphocytic vasculitis, or a predominately lymphocytic perivascular infiltrate (group 2), were studied. Immunoglobulins or complement components in cutaneous blood vessels were detected by direct immunofluorescence in high frequency in both groups (91 and 88%, respectively). Using two radioassays for circulating immune complexes, Clq or monoclonal rheumatoid factor (mRF) reactive material was detected in 68% of the patients with necrotizing vasculitis but only 44% of the patients in the lymphocytic-perivascular group. The mRF radioassay was elevated in 58% of the first group of patients and 41% of the patients in group 2, although Clq binding activity was increased in 54% of the patients with necrotizing vasculitis but only in 9% of the patients with a lymphocytic vasculitis or lymphocytic perivascular infiltrate. By using both sucrose density gradient ultracentrifugation and Sepharose 6B gel filtration, the Clq and mRF reactive material detected in some patients with necrotizing vasculitis eluted in high molecular weight fractions that were also anticomplementary. In one patient with necrotizing vasculitis and hepatitis B antigenemia, these heavy molecular weight Clq and mRF reactive fractions contained a two- to three-fold increase in hepatitis B surface antigen when compared with lighter molecular weight fractions. Heavy and light molecular weight mRF reactive material could be detected in selected patients in the lymphocytic-perivascular group as well as in the necrotizing vasculitis group. These studies suggest that cutaneous vasculitis, including acute necrotizing (leukocytoclastic) vasculitis and some forms of lymphocytic vasculitis, and perhaps some diseases characterized by a lymphocytic perivascular infiltrate, may represent cutaneous expressions of immune complex disease.

ICAM-1 expression on endothelium and systemic cytokine production in cutaneous neutrophilic leukocytoclastic vasculitis in NZBxNZWF1 mice.

The present study has examined relationship between cutaneous microvessel injury and adhesion molecule expression on the endothelium by cytokines in NZBxNZWF1 (B/WF1) mice, a model for human systemic lupus erythematosus. In advanced ages associated with overt clinical manifestation, but not in early ages, neutrophils with a minor proportion of monocytes and lymphocytes mainly adhered to the endothelium of capillary and the venule with fragmentation (leukocytoclasis), leading to the vascular injury (leukocytoclastic vasculitis). This was confirmed by the leak of monstral blue from the blood vessel. At this stage LFA-1+ leukocytes adhered to intensely expressed ICAM-1 on the endothelium, and this was paralleled with a significant rise in IL-1 alpha and TNF-alpha in the circulation. The present study suggests that IL-1 alpha and TNF-alpha may, at least in part, be responsible for the increased ICAM-1 expression on endothelium in cutaneous microvessels, resulting in the vascular injury characterized by neutrophilic leukocytoclasis in B/WF1 mice.

P-selectin glycoprotein ligand-1 is required for the development of cutaneous vasculitis induced by immune complex deposition.

Immune complex (IC)-induced tissue injury is mediated by inflammatory cell infiltration that is highly regulated by various adhesion molecules. To assess the contribution of P-selectin glycoprotein ligand-1 (PSGL-1) and selectins in the pathogenetic process, the cutaneous reverse-passive Arthus reaction was examined in mice treated with monoclonal antibodies (mAb) to PSGL-1 or P- and/or E-selectin. Edema and hemorrhage were significantly reduced in mice treated with anti-P-selectin mAb compared with control mice while they were not inhibited in mice treated with anti-E-selectin mAb. It is remarkable that blocking PSGL-1 by mAb resulted in significant, further reduction in edema and hemorrhage compared with blocking anti-P- or anti-E-selectin. However, blockade of E- and P-selectins exhibited more significant reduction relative to PSGL-1 blockade. The inhibited edema and hemorrhage paralleled reduced infiltration of neutrophils and mast cells. Reduced infiltration of neutrophils and mast cells was observed in the peritoneal Arthus reaction and was associated with the decreased production of tumor necrosis factor alpha and interleukin-6. The results of this study indicate that PSGL-1 contributes to the Arthus reaction mainly as a ligand of P-selectin and partly as a ligand of E- and/or L-selectin by regulating neutrophil and mast-cell recruitment and that PSGL-1 would be a therapeutic target for human IC-mediated diseases.

Isolation of tissue plasminogen activator from skin lesions with allergic vasculitis.

A tissue plasminogen activator was extracted from skin lesions with allergic vasculitis and purified by successive column chromatography on Sephadex G-200, DEAE-cellulose, Hydroxyaptite-cellulose and polyacrylamide gel electrophoresis. By these procedures, 160 micrograms of enzyme with a specific activity of 843.8 international units/mg protein was obtained from 5 g of original skin. The purified material was homogeneous as ascertained by sodium dodecyl sulfate polyacrylamide gel electrophoresis and had an apparent molecular weight of 110,000 as measured by gel filtration on Sephadex G-200. Its identity with human urokinase was investigated and was found to possess the same plasminogen activator activity as that of urokinase. It had high amindolytic activity, but only slight N-alpha-acetyl-glycyl-L-lysine methyl ester esterolytic activity. This tissue plasminogen activator was confirmed to be immunologically identical to human urokinase.

Immune complexes from vasculitis patients bind to endothelial Fc receptors independent of the allelic polymorphism of FcgammaRIIa.

UNLABELLED: Cutaneous leukocytoclastic vasculitis is characterized by the deposition of circulating immune complexes, neutrophil extravasation, and vessel destruction, but mechanisms of circulating immune complexes capture within postcapillary venules are unknown. We demonstrate that circulating immune complexes from sera of vasculitis patients bind to cultured endothelium in an Fc gamma receptor IIa-dependent fashion. In lesional skin, endothelial cells bind immunoglobulin G2 > immunoglobulin G3 and immunoglobulin G4, but not immunoglobulin G1, even before obvious neutrophil transmigration and vessel damage. As the human Fc gamma receptor IIa proteins exist in two allotypes (one with a histidine at position 131, which binds immunoglobulin G1, 2, 3 and the other with an arginine at position 131, which binds immunoglobulin G1, and 3, but is unable to bind immunoglobulin G2), we expected an altered prevalence of histidine 131 forms in vasculitis patients. Sequence analysis, however, revealed an equal distribution of allotypes in patients and controls. In conclusion, circulating immune complex binding to endothelial Fc gamma receptor IIa is among the initial steps in the development of vasculitis. Although immunoglobulin G2 is the predominant subtype precipitated at endothelial surfaces, it is not required for fixing circulating immune complexes to endothelium, because patients homozygote for Fc gamma receptor IIa-arginine 131 equally develop leukocytoclastic vasculitis as those bearing the Fc gamma receptor IIa-histidine 131 allele. As immunoglobulin G1 is virtually absent in leukocytoclastic vasculitis lesions and immunoglobulin G4 does not bind to both Fc gamma receptor IIa alleles, these complexes, in addition to immunoglobulin G2, should contain immunoglobulin G3 in order to fix to vascular Fc gamma receptor IIa, at least in persons homozygous for Fc gamma receptor IIa-arginine 131. KEYWORDS: CD32/immunoglobulin G subtypes/leukocytoclastic vasculitis/microvessels.

Decreased expression of decay-accelerating factor on endothelial cells of immune complex-mediated vasculitic skin lesions.

Endothelial cells may be damaged directly by the membrane attack complex of complement in immune complex vasculitis of the skin. However, for endothelial cell membrane injury to occur, normal regulatory mechanisms must fail. One of the main complement regulatory proteins of endothelial cells is decay-accelerating factor, a surface protein which interferes with either the classical or alternative pathway C3 and C5 convertases. We have investigated the expression of decay-accelerating factor in 4 patients with histologically proven cutaneous immune complex vasculitis, using an immuno-electronmicroscopic technique. We demonstrated that endothelial cells of upper dermal vessels in vasculitic lesions were almost completely devoid of decay-accelerating factor. By contrast, the expression of this protein on endothelial cells in uninvolved skin of the patients was the same as in skin of healthy volunteers. As yet, the mechanism responsible for depletion of decay-accelerating factor is not clear. Absence of decay-accelerating factor may follow enzymatic release from the phosphatidylinositol anchor, proteolytic stripping from the cell membrane or a down-regulation of decay-accelerating factor synthesis. Regardless of mechanism, endothelial cell injury or death could serve a phlogistic function to facilitate complement-mediated destruction of endothelial cells for removal and repair.