Systemic Involvement in Immunoglobulin G4-Related Ophthalmic Disease

BACKGROUND

Immunoglobulin G4-related ophthalmic disease (IgG4-ROD) poses clinical challenges due to its heterogeneous ocular and systemic manifestations. We aim to report the systemic involvement and the clinical, serological and radiological associations of a cohort of Chinese patients.

METHODS

A territory-wide, biopsy-proven, Chinese cohort. A retrospective, masked chart review of medical records, orbital images, and histopathology reports.

RESULTS

A total of 122 (65 male) patients with a follow-up of 81 ± 49 (24 to 84) months were reviewed. Ninety (74%) patients presented bilaterally. Subacute upper eyelid swelling was the commonest presentation (82/122, 67%). During follow-up, 91/122 patients (75%) underwent extra-orbital imaging including computer tomography (692 films), ultrasonography (182 films), magnetic resonance imaging (76 films) and whole body FDG-PET scan (33 films). Eighty-six (95%) of these 91 patients had extra-orbital involvement radiologically (2.7 ± 1.6 regions, range: 0 to 9). Lymph node was the most prevalent (N = 60,66%), followed by salivary gland (N = 51,56%), lung (N = 49,54%), kidney (N = 22, 24%), hepatobiliary tree (N = 18, 20%) and pancreas (N = 17, 19%). Other organs include thyroid, aorta, meninges/brain and skin. Twenty-eight (23%) patients had allergic diseases (19 asthma, 16 allergic rhinitis, and 6 eczemas). Fifty-seven (48%) patients had paranasal sinusitis. Serum eosinophilia was associated with a higher number (3.24 versus 2.52, P = 0.0304) of organ involvement. Patients with deep organ involvement was associated with a higher age of IgG4-ROD onset (70 ± 12 versus 56 ± 13, P < 0.0001).

CONCLUSIONS

95% of the patients who underwent systemic imaging in our cohort had systemic organ involvement. An early physicians' assessment and radiological imaging are recommended after the diagnosis of IgG4-ROD.

Ocular Surface Evaluation in Immunoglobulin G4-Related Ophthalmic Disease

PURPOSE

To evaluate the functional and structural changes of the meibomian glands and ocular surface in immunoglobulin G4-related ophthalmic disease (IgG4-ROD) patients.

DESIGN

Cross-sectional, matched case-control comparison study.

METHODS

This study included 64 patients with biopsy-proven IgG4-ROD (aged 63.4 ± 12.2 years, 39 male) and 64 sex- and age-matched healthy controls. Patients were managed by hospitals covering the publicly funded ophthalmology service in Hong Kong. Outcome measures included anterior segment examination and keratographic and meibographic imagings.

RESULTS

A total of 64 worst-affected eyes of the 64 IgG4-ROD patients were analyzed. Corneal fluorescein staining (P = .0187), lid margin telangiectasia (P = .0360), lid-parallel conjunctival folds (P = .0112), papillae (P = .0393), meibomian gland plugging (P = .0001), meibomian gland expressibility (P = .0001), and meibum quality (P = .0001) were more significant in IgG4-ROD patients compared with healthy controls. Both upper and lower meibomian gland dropouts (P = .001 and .0003), and tear meniscus height (P = .0001) were higher in IgG4-ROD patients. Non-invasive tear break-up time (NITBUT) (P = .0166) and Schirmer test results (P = .0243) were lower in IgG4-ROD patients. Upper (r = 0.336, P = .0140) meibomian gland dropouts and NITBUT (r = -0.293, P = .0497) were positively and negatively correlated with the IgG4-ROD onset age, respectively. The number of extraocular organ involvement was negatively correlated with the Schirmer test(r = -0.341, P = .0167). Lower NITBUT was found in IgG4-ROD eyes with lacrimal gland enlargement than in IgG4-ROD eyes without lacrimal gland enlargement radiologically (P < .0001).

CONCLUSIONS

IgG4-ROD patients showed features of both aqueous tear deficiency and evaporative dry eye disease. We recommend ocular surface evaluation to all patients newly diagnosed with IgG4-ROD. Further studies are warranted to clarify the mechanism of IgG4-related dry eye disease.

Characterization of the effector-specifying domain of Rac involved in NADPH oxidase activation

Production of microbicidal oxidants by phagocytic leukocytes requires activation of a latent NADPH oxidase by the coordinated assembly of a membrane-associated flavocytochrome b558, with three cytosolic components, p47phox, p67phox, and the low molecular weight GTP-binding protein Rac. Rac1 and Rac2 have 92% sequence identity and are both active in supporting the oxidase, while CDC42Hs, the closest relative to Rac with 70% sequence identity, only weakly supports oxidase activation in vitro. We have used CDC42Hs as a foil to identify residues in Rac that are critical for oxidase activation. Most of the divergent sequences of CDC42Hs could be incorporated into Rac-CDC42Hs chimeric proteins without affecting cell-free NADPH oxidase activity. However, incorporation of the amino-terminal segment of CDC42Hs (residues 1-40), which differs from Rac1 by only four residues (positions 3, 27, 30, and 33), resulted in a marked loss of oxidase activation capacity. Point mutagenesis studies showed that this was due to changes at residues 27 and 30, but not residues 3 and 33. Conversely, incorporation of the amino terminus of Rac1 (residues 1-40) into CDC42Hs increased its activity to that of Rac1, indicating that this terminus contains the effector-specifying domain of Rac. Taken together, these studies show that the difference in the activity between CDC42Hs and Rac1 is due entirely to differences in amino acids at position 27 and 30.

Regulation of the human neutrophil NADPH oxidase by rho-related G-proteins

Superoxide production by phagocytic white blood cells requires the assembly of an NADPH oxidase from membrane and cytosolic proteins. Recombinant cytosolic proteins p47phox and p67phox and neutrophil membranes were used to purify a third cytosolic component that is necessary and sufficient for cell-free reconstitution of NADPH oxidase. The component was isolated as a complex of rho-GDP dissociation inhibitor (rho-GDI) and two members of the rho subfamily of ras-related guanine nucleotide binding proteins, rac2 and CDC42Hs. Oxidase reconstitution with these pure cytosolic proteins was unaffected by GTP gamma S but was inhibited by GDP beta S, suggesting that the active complex contained endogenous bound GTP. Direct binding of rho-GDI to the GTP gamma S-bound forms of these G-proteins was demonstrated by gel filtration following exchange with radiolabeled guanine nucleotide. rho-GDI was shown to be nonessential for cell-free oxidase reconstitution in experiments that compared the activities of pure recombinant forms of these G-proteins. Recombinant rac augmented superoxide production, while recombinant CDC42Hs, which shares 70% amino acid sequence identity with rac, did not. Three highly conserved regions of rac1 and rac2 were noted as markedly divergent in CDC42Hs. It is proposed that one or more of these regions of rac may be involved in the specific interaction of rac with the other NADPH oxidase protein(s).

Cytochrome b558: the flavin-binding component of the phagocyte NADPH oxidase

The phagocyte respiratory burst oxidase is a flavin-adenine dinucleotide (FAD)-dependent dehydrogenase and an electron transferase that reduces molecular oxygen to superoxide anion, a precursor of microbicidal oxidants. Several proteins required for assembly of the oxidase have been characterized, but the identity of its flavin-binding component has been unclear. Oxidase activity was reconstituted in vitro with only the purified oxidase proteins p47phox, p67phox, Rac-related guanine nucleotide (GTP)-binding proteins, and membrane-bound cytochrome b558. The reconstituted oxidase required added FAD, and FAD binding was localized to cytochrome b558. Alignment of the amino acid sequence of the beta subunit of cytochrome b558 (gp91phox) with other flavoproteins revealed similarities to the nicotinamide adenine dinucleotide phosphate (reduced) (NADPH)-binding domains. Thus flavocytochrome b558 is the only obligate electron transporting component of the NADPH oxidase.

Delineation of the phagocyte NADPH oxidase through studies of chronic granulomatous diseases of childhood

The phagocyte NADPH oxidase is a complex system consisting of membrane and cytosolic components that must assemble at the membrane for proper activation. Studies of patients with chronic granulomatous diseases of childhood have enabled the molecular characterization of these components, which has led to studies defining their interaction during NADPH complex assembly. Understanding NADPH oxidase assembly provides an opportunity to develop therapeutics for the regulation of this important reaction of inflammation.

Solubilization of hydroxyapatite crystals by murine bone cells, macrophages and fibroblasts

Calcium phosphate ceramic is widely used as implant material. It is made up of hydroxyapatite, beta-tricalcium phosphate or various combinations of both. In the present study, we use an in vitro model to examine the role of cell-mediated resorption of calcium phosphate ceramic implant material. We compare the abilities of two sequential enzymatic released populations of bone cells from murine calvaria (Population II and Population V), macrophages and dermal fibroblasts to solubilize 45Ca-labelled hydroxyapatite crystals. These crystals were incubated with each of the cell types for 24 h in the presence or absence of parathyroid hormone, prostaglandin E2, calcitonin, and 1,25-dihydroxyvitamin D3. The amount of cell-mediated hydroxyapatite solubilization was determined by measuring the radioactivity in an aliquot of the supernatant after centrifugation. Using dermal fibroblasts as a baseline, relative abilities of macrophages, Population II and Population V to degrade crystals were 10.5, 5 and 2 times that of fibroblasts. Crystal-cell contact was required. While none of the bone resorption agents tested had any effect on this process, crystal dissolution by bone cells was inhibited by two lysosomotropic agents, NH4Cl and chloroquine.

Influence of tumor-promoting phorbol esters on the phosphorylation of membrane proteins in lymphocytes

Treatment of bovine lymphocytes with 12-O-tetradecanoyl-phorbol-13-acetate (TPA) (10(-8) M) for as little as 5 min significantly alters the ability of membrane-particulate fractions to phosphorylate proteins using in situ protein kinases and exogenous [gamma-32P]ATP. After 20 min of treatment, the phosphorylation of two proteins with mol. wts. of 65K and 74K in the isolated membrane-particulate fraction is increased approximately 30-35%, whereas the phosphorylation of a 130K protein is almost completely suppressed. The ability of different phorbol esters to alter membrane protein phosphorylation correlates well with their potency as tumor promoters in mouse epidermis and as comitogens in phytohemagglutinin-treated lymphocytes. This phorbol ester response appears to have a low temperature coefficient since cells treated with TPA at 4 degrees C also responded, although at a slower rate. This action of TPA is neither mimicked nor antagonized by dibutyryl cAMP (1 mM); moreover, it is not affected by retinoic acid, an agent which blocks several other phorbol ester effects in these cells. Inhibition of protein synthesis with cycloheximide also fails to influence this response. In contrast, trifluoperazine, an inhibitor of calmodulin function and certain lipid-dependent protein kinases, depressed the phosphorylation of the 65K and 74K proteins to below the control level.

Antagonism of concanavalin A capping in phorbol ester-activated lymphocytes by calmodulin inhibitors and certain amino acid esters

12-O-Tetradecanoylphorbol-13-acetate (TPA), an effective tumor promoter in mouse skin and comitogen in bovine lymphocytes, rapidly stimulates concanavalin A-mediated cap formation in the latter cells. The ability of different phorbol derivatives to facilitate the capping reaction correlates well with their potencies as lymphocyte comitogens and as tumor-promoting agents. This effect of TPA on capping in bovine lymphocytes, which is apparent within min, is neither mimicked nor altered by dibutyryl cyclic adenosine 3':5'-monophosphate or cyclic guanosine 3':5'-monophosphate. Cytochalasin D, a microfilament-disrupting agent, inhibits cap formation, thereby suggesting the participation of microfilaments in the response. Benzoyl tyrosine ethyl ester selectively inhibits the TPA-stimulated cap formation, whereas benzoyl tyrosinamide is inactive. A comparison of related amino acid derivatives reveals that their activities are dependent on the nature of both the amino acid side chain and the carboxyl end blocking group. Trifluoperazine and N-(6-aminohexyl)-5-chloronaphthalenesulfonamide, known inhibitors of the calmodulin-dependent processes, also selectively block the TPA-stimulated cap formation, whereas trifluoperazine sulfoxide, a less effective calmodulin antagonist, is relatively inactive. These data suggest that the stimulation of capping by TPA involves the activation of a calmodulin-dependent process which may also be regulated by the function of an esterase.

Effects of hexachlorocyclohexane isomers on concanavalin A 'capping' in bovine lymphocytes

The effects of alpha, beta, gamma, and delta isomers of hexachlorocyclohexane on concanavalin A 'capping' in bovine lymphocytes were evaluated, gamma and delta hexochlorocyclohexane inhibited 'capping' whereas the alpha and beta isomers were without effect. In addition, gamma-hexachlorocyclohexane has been shown to antagonize the maintenance of preformed 'caps' and cause the rapid dispersal of the concanavalin A-receptor complexes over the surface of cells by a temperature-dependent mechanism. The possible role of a gamma-hexachlorocyclohexane-sensitive process in the organization of microflow patterns in the lectin-activated lymphocyte membrane is discussed.