Cellular Functions of Optineurin in Health and Disease.

Optineurin (OPTN) was initially identified as a regulator of NF-κB and interferon signaling, but attracted most attention because of its association with various human disorders such as glaucoma, Paget disease of bone, and amyotrophic lateral sclerosis. Importantly, OPTN has recently been identified as an autophagy receptor important for the autophagic removal of pathogens, damaged mitochondria, and protein aggregates. This activity is most likely compromised in patients carrying OPTN mutations, and contributes to the observed phenotypes. In this review we summarize recent studies describing the molecular mechanisms by which OPTN controls immunity and autophagy, and discuss these findings in the context of several diseases that have been associated with OPTN (mal)function.

Antibody Response to Paramyxoviruses in Paget's Disease of Bone.

Paget's disease of bone (PDB) is a common skeletal disorder characterised by focal abnormalities of increased and disorganised bone turnover. Genetic factors play a central role in the pathogenesis of PDB but environmental factors also contribute. Measles virus (MV), respiratory syncytial virus (RSV) and canine distemper virus (CDV) have all been implicated as potential disease triggers but the data are conflicting. Since chronic paramyxovirus infection with measles is known to be accompanied by increased production of antiviral antibodies, we have analysed circulating concentrations of antibodies to MV, CDV, and RSV as well as mumps, rubella and varicella zoster virus (VZV) in 463 patients with PDB and 220 aged and gender-matched controls. We also studied the relation between viral antibody concentrations and various markers of disease severity and extent in 460 PDB patients. A high proportion of cases and controls tested positive for antiviral antibodies but there was no significant difference in circulating antibody concentrations between PDB cases and controls for MV, CDV, RSV, rubella or VZV. However, mumps virus antibody levels were significantly higher in the PDB cases (mean ± SD = 3.1 ± 0.84 vs. 2.62 ± 0.86. p < 0.001). There was no association between disease severity and circulating antibody concentrations to any of the viruses. In conclusion, we found no evidence to suggest that PDB is associated with abnormalities of immune response to measles or other paramyxoviruses, although there was evidence of a greater antibody response to mumps. The results do not support that hypothesis that PDB is associated with a persistent infection with measles or other paramyxoviruses.

Calcitonin resistance: clinical and immunologic studies in subjects with Paget's disease of bone treated with porcine and salmon calcitonins.

15 patients with Paget's bone disease were treated with varying schedules of porcine (3.8-157.5 MRCU/kg per wk) and/or salmon (1.5-210 MRCU/kg per wk) calcitonins over periods ranging from 4 to 24 months. All of the subjects experienced a striking decrease in serum alkaline phosphatase during the first 4 months of treatment. In six patients, however, resistance to these peptides was suggested by a subsequent elevation of alkaline phosphatase activity in spite of continued and augmented hormone administration. These rebounds in alkaline phosphatase levels correlated with the appearance of calcitonin-binding substances and neutralizing material in serum. Incubations of calcitonins-(125)I and sera from these six subjects resulted in the association of radioactivity with material whose behavior on chromatoelectrophoresis (6/6), sucrose density ultracentrifugation and immunoelectrophoresis (one subject) was identical with that of 7S immunoglobulin. Specific, reversible in vitro binding of salmon calcitonins-(125)I was observed in sera obtained from these patients 5 to 12 months after initiation of salmon calcitonin therapy. All six of these subjects' sera acquired the capacity to neutralize salmon calcitonin's hypocalcemic effect in rat bioassay. Neutralization titers correlated with maximal binding capacities, which ranged from 0.042 to 6.6 mg/liter of serum. Competitive displacement of calcitonins-(125)I from the sera of one patient treated with both porcine and salmon calcitonin indicated separate populations of antibodies to these hormones. In spite of return of disease activity comparable to baseline levels, 3/5 resistant subjects treated with salmon calcitonin failed to develop hypocalcemia after injection of 300-1000 MRCU of salmon calcitonin, but two of these patients developed hypocalcemia in response to the porcine hormone. The disappearance of total radioactivity from the circulation after intravenous administration of salmon calcitonin-(125)I was retarded and the amount of serum radioactivity precipitable in 50% (NH(4))(2)SO(4) greater in 3/3 resistant patients compared to control subjects. These observations on the incidence of significant titers of neutralizing antibodies to salmon (40%) and porcine (66%) calcitonins during their chronic (> 4 months) administration to man clearly indicate that an appraisal of this possibility be included in studies involving protracted use of these hormones.

An evaluation of antibodies and clinical resistance to salmon calcitonin.

21 patients with Paget's disease of bone and one with osteoporosis were studied to detect development of antibodies to salmon calcitonin during chronic therapy. Antibody titers ranged from 1:40 to 1:30,000 in plasma obtained after treatment of 11 patients. Radio-immunoelectrophoresis revealed that the antibodies were restricted to the gammaG class. One patient, W. O., with Paget's disease initially responded to treatment with a decrease in bone turnover, but later became resistant to the hormone in association with the appearance of a very high titer (1:30,000) of antibody against salmon calcitonin. A 1:10 dilution of his plasma was shown to completely inactivate 20 mMRC units/ml of salmon calcitonin as detected by bioassay in rats; slight inactivation was detected at a 1:200 dilution. All other patients continued to respond to salmon calcitonin despite the development of antibody to the hormone in ten cases. No evidence of systemic allergic reactions or other toxicity was found in any patient. The data suggest that although antibody formation may occur in as many as 50% of patients treated with salmon calcitonin, this antibody response is unlikely to be of clinical significance in most patients. However, in an occasional patient, a marked antibody response may occur which interferes with the therapeutic use of the hormone.

Regulation of TBK1 activity by Optineurin contributes to cell cycle-dependent expression of the interferon pathway.

The innate immune system has evolved to detect and neutralize viral invasions. Triggering of this defense mechanism relies on the production and secretion of soluble factors that stimulate intracellular antiviral defense mechanisms. The Tank Binding Kinase 1 (TBK1) is a serine/threonine kinase in the innate immune signaling pathways including the antiviral response and the host defense against cytosolic infection by bacteries. Given the critical roles of TBK1, important regulatory mechanisms are required to regulate its activity. Among these, Optineurin (Optn) was shown to negatively regulate the interferon response, in addition to its important role in membrane trafficking, protein secretion, autophagy and cell division. As Optn does not carry any enzymatic activity, its functions depend on its precise subcellular localization and its interaction with other proteins, especially with components of the innate immune pathway. This review highlights advances in our understanding of Optn mechanisms of action with focus on the relationships between Optn and TBK1 and their implication in host defense against pathogens. Specifically, how the antiviral immune system is controlled during the cell cycle by the Optn/TBK1 axis and the physiological consequences of this regulatory mechanism are described. This review may serve to a better understanding of the relationships between the different functions of Optn, including those related to immune responses and its associated pathologies such as primary open-angle glaucoma, amyotrophic lateral sclerosis and Paget's disease of bone.

Paget's disease of bone: an osteoimmunological disorder?

Osteoimmunology represents a large area of research resulting from the cross talk between bone and immune systems. Many cytokines and signaling cascades are involved in the field of osteoimmunology, originating from various cell types. The RANK/receptor activator of nuclear factor Kappa-B ligand (RANKL)/osteoprotegerin (OPG) signaling has a pivotal role in osteoimmunology, in addition to proinflammatory cytokines such as tumor necrosis factor-α, interleukin (IL)-1, IL-6, and IL-17. Clinically, osteoimmunological disorders, such as rheumatoid arthritis, osteoporosis, and periodontitis, should be classified according to their pattern of osteoimmunological serum biomarkers. Paget's disease of bone is a common metabolic bone disorder, resulting from an excessively increased bone resorption coupled with aberrant bone formation. With the exception of the cellular responses to measles virus nucleocapsid protein and the interferon-gamma signature, the exact role of the immune system in Paget's disease of bone is not well understood. The cytokine profiles, such as the increased levels of IL-6 and the interferon-gamma signature observed in this disease, are also very similar to those observed in other osteoimmunological disorders. As a potential osteoimmunological disorder, the treatment of Paget's disease of bone may also benefit from progress made in targeted therapies, in particular for receptor activator of nuclear factor Kappa-B ligand and IL-6 signaling inhibition.

Interleukin-6 and the acute phase response during treatment of patients with Paget's disease with the nitrogen-containing bisphosphonate dimethylaminohydroxypropylidene bisphosphonate.

Bisphosphonates suppress bone resorption and are used in the management of bone diseases with increasing frequency. In some patients treated for the first time with potent nitrogen-containing bisphosphonates, there is a transient febrile reaction and transient hematological changes suggestive of an acute phase response. Because IL-6 is considered to be an important mediator of the acute phase response, we examined the changes in circulating IL-6 bioactivity in 38 patients with Paget's disease treated with the nitrogen-containing bisphosphonate (3-dimethyl-amino-1-hydroxypropylidene)-1,1-bisphosphonate (dimethyl-APD). 16 patients who had never received such bisphosphonate were treated with oral dimethyl-APD (100-400 mg/day) and 22 (9 for the first time) with intravenous dimethyl-APD 4 mg/day. Treatment was given for 10 days. Eleven of 38 patients, all first treatments, showed an increase in body temperature of more than 0.5 degrees C exceeding 37 degrees C associated with a significant decrease in lymphocyte count and an increase in serum CRP values. These changes were transient and did not occur in the patients with no febrile response. In patients with a febrile reaction circulating IL-6 bioactivity increased significantly and this increase generally preceeded the rise in temperature. Moreover, patients with an acute phase response had significantly higher peak IL-6 values than those without (128 +/- 30 vs. 31 +/- 4 U/ml, p < 0.001). The peaks in plasma IL-6 were further correlated with the peaks in temperature and in serum CRP values (r = 0.49, p < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Formation of neutralizing antibodies during intranasal synthetic salmon calcitonin treatment of Paget's disease.

Nine patients with Paget's disease were treated with 200 U (15 nmol) synthetic salmon calcitonin (sCT) intranasally (in)/day for 12 months. Five of them had received im or in sCT therapy for 1-4 yr up to 0.5-5 yr before this study. Low titer antibodies to sCT were detected in the serum of three of these five patients, but not in the four patients who had not received prior sCT therapy. After 2 months of in sCT administration, four of the former group, but none of the latter group, had antibodies to sCT. After 12 months of treatment, antibodies to sCT were found in all patients who had received sCT earlier and in three of the four patients who had not. The half-maximal inhibition of [125I]sCT binding ranged from 44-284 pmol/L sCT. In a cultured human breast cancer cell line (T47D) cAMP production was stimulated by sCT (EC50, 70 pmol/L). cAMP production stimulated by sCT (5 pmol/L) was reduced to 6-20% of the control value in the presence of serum from patients which inhibited [125I]sCT binding by more than 50% in a dilution of 1:50 or greater. In patients with lower titer antibodies cAMP production was not inhibited. Serum alkaline phosphatase activity was transiently lowered to 79 +/- 6% (+/- SE) of basal levels in the patients who had earlier received sCT (P greater than 0.1), while sustained reduction to between 66 +/- 2% and 84 +/- 6% of basal levels (P less than 0.05) occurred in the patients who had not been treated with sCT previously. In conclusion, reexposure to sCT of five patients with Paget's disease caused secondary antibody responses and clinical resistance.

Paget's disease of the bone: observations after cessation of long-term synthetic salmon calcitonin treatment.

Thirteen patients with Paget's disease of the bone were treated with subcutaneous injections of synthetic salmon calcitonin (SCT) for a mean period of 22 months at doses of 50-100 MCR units daily or 3 times a week. They manifested symptomatic improvement and significant reductions in serum alkaline phosphatase and urinary hydroxyproline excretion during SCT administration. Following discontinuation of SCT, symptomatic improvement was maintained in 10 patients for up to one year, whereas a recurrence of symptoms was seen in only 3 patients. The serum alkaline phosphatase generally showed a return toward pretreatment values 6 months after discontinuation of SCT, whereas urinary hydroxyproline remained depressed for up to a year.

A viral antigen-bearing cell line derived from culture of Paget's bone cells.

This study documents the characteristics of a viral antigen-bearing cell line derived from co-culture of the bone from a 71-year-old woman with Paget's disease of bone and HEp-2 cells. The cell line has survived in continuous culture for 3 1/2 years and 185 subcultures. The cells are epithelioid in appearance, produce alkaline and acid phosphatase, increase alkaline phosphatase activity in response to 1,25-(OH)2-D3 and contain receptors for 1,25-(OH)2-D3. Immunofluorescent studies utilizing antisera to respiratory syncytial virus and measles virus reveal antigens of both viruses in the cells. These cells do not produce bone in culture and the adenylate cyclase activity found in their plasma membrane does not increase significantly in response to parathyroid hormone or calcitonin. The cells are not contact inhibited and form spherical colonies in agarose. They are aneuploid and have a modal number of 62-74 as well as HeLa markers. When injected into athymic mice, osteosarcomas are produced. These tumors continue to bear viral antigens. The availability of this cell line should aid in further studies of the viral antigens associated with Paget's disease of bone.

Paget's disease of bone.

Nuclear medicine techniques are currently playing an important complementary role in the evaluation, management, and follow-up of the patient who is suspected of having Paget's disease of bone. The earlier diagnoses made possible by some of the described techniques should lead to a better understanding of the basic pathophysiology and, in addition, result in improved therapeutic modalities.

Serum levels of CA-125 in patients with endometriosis: a preliminary report.

Seven out of 8 patients with endometriosis demonstrated levels of CA-125 antigen above 35 U/ml. None of 15 patients with other benign gynecologic diagnoses demonstrated elevated levels. This antigen has been proposed as a tumor marker for epithelial carcinoma and other gynecologic neoplasms. However, it cannot be used to differentiate clinically between cancer and endometriosis.

Clinical significance of antibodies against calcitonin.

Calcitonin (CT) inhibits osteoclast-mediated bone resorption and is being used to treat Paget's disease of bone, hypercalcemia of malignancy and postmenopausal osteoporosis. The formation of antibodies against heterologuous calcitonins like salmon calcitonin (sCT) is common and occurs in 40-70% of the patients treated for more than 4 months. Not all of these patients, however, develop a secondary resistance to sCT, therefore the clinical significance of sCT antibodies is discussed controversially. In vivo and in vitro approaches demonstrate a neutralizing effect in 35 to 60% of the patient sera with antibodies against sCT. These neutralizing antibodies appear to explain most cases of clinically relevant secondary resistance to sCT treatment, which occurs in 25-45% of the patients after treatment periods of 6 months and longer. A positive treatment response to human CT after development of secondary resistance to sCT proves the diagnosis of antibody related resistance. Few cases develop secondary resistance in the absence of sCT binding antibodies, the mechanism of this phenomenon is unclear. Antibody related resistance is a significant problem in long term treatment with sCT. Especially in conditions like postmenopausal osteoporosis, where no readily accessable marker of treatment response is available, the development of sCT antibodies and their possible neutralizing effect has to be considered.

Coexisting Paget's disease of bone and hyperparathyroidism.

A patient with Paget's disease of bone and primary hyperparathyroidism is described. It has been suggested that a metabolite from pagetic tissue might stimulate parathyroid cell function. To test this, serum parathyroid hormone (iPTH) levels were measured by radio immunometric assay in 106 patients with Paget's disease of bone and 139 control subjects. There was no significant difference between the mean levels of the two groups. Of five sera with elevated PTH levels QUOSO extraction revealed an interfering substance in 3/5 from control patients tested and extractable iPTH in 2/2 from Paget's patients. One of the latter had renal failure. The results suggest that increased parathyroid function is unlikely to be a primary event in the genesis of Paget's disease of bone.

An atypical presentation of Paget's disease in an immunocompromised individual. A case report.

Paget's disease of bone is a localized disorder of bony resorption. The mechanism underlying the development of the disease remains controversial. There is substantial evidence suggesting a genetic basis for Paget's disease in some patients. A viral etiology of Paget's disease has been advocated. A further hypothesis implicating an immunological mechanism for this disease is based on growing evidence reviewed in the text. The presented case showed clinical and X-ray features typical of a very aggressive form of Paget's disease. We hypothesize that the extreme local aggressiveness of this case was secondary to the patient's concomitant immunosuppression due to an extended therapy following renal transplant.