Interferon-alpha, unlike interferon-gamma, does not cause bone loss in the rat

Differential Gene Expression Profiles and Pathways Highlight the Role of Osteoimmunology in Neurofibromatosis Type 1-Related Dystrophic Scoliosis With Osteopenia

STUDY DESIGN

Microarray approach and integrated gene network analysis.

OBJECTIVE

To explore the differential genetic expression profile, Gene Ontology terms, and Kyoto Encyclopedia of Genes and Genomes pathways in human trabecular bone (HTB)-derived cells of dystrophic scoliosis secondary to neurofibromatosis type 1 (DS-NF1) and compare these to normal controls.

SUMMARY OF BACKGROUND DATA

The pathogenesis of DS-NF1 and the accompanying generalized osteopenia remain unclear. We hypothesized that HTBs may play a significant role in the etiology and pathogenesis of DS-NF1.

MATERIALS AND METHODS

Microarray analysis was used to identify differentially expressed genes of HTBs from patients with DS-NF1 compared with those from healthy individuals. Functional and pathway enrichment analysis were implemented through Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway database. Then, the "search tool for the retrieval of interacting genes/proteins" database, Cytoscape, and "Molecular Complex Detection" were applied to construct the protein-protein interaction (PPI) network and screen hub genes. Pathway enrichment analysis was further performed for hub genes and gene clusters identified through module analysis. Six potential crucial genes were selected for validation by reverse transcription polymerase chain reaction.

RESULTS

Bioinformatic analysis revealed that there are 401 previously unrecognized differentially expressed genes (238 up and 163 downregulated genes) in HTBs from patients with DS-NF1, and they were mainly enriched in terms of immune response, type-I interferon (IFN) signaling, TNF signaling pathway and etinoic acid inducible gene I-like receptor signaling pathway. Five hub genes, including signal transducer and activator of transcription 1, 2'-5'-oligoadenylate synthetase-like, IFN induced with helicase C domain 1, IFN regulatory factor 7, and MX dynamin-like GTPase 1 were identified through PPI network, which were mainly enriched in terms of Jak-STAT and etinoic acid inducible gene I-like receptor signaling pathway. An independently dysregulated protein cluster containing CCL2, CXCL1, CXCL3, CX3CL1, TLR1 , and CXCL12 was also identified through the PPI network. This indicated that the upper abnormally expressed genes may play essential roles in DS-NF1 pathogenesis and accompanied osteopenia.

CONCLUSION

Six key genes were identified in the progression of DS-NF1-related osteopenia. Immune response might play a key role in the progression of osteopenia, whereas a CXCL12 -mediated osteogenic effect might play a protective role.

Cytokines and Bone: Osteoimmunology

Cytokines and hematopoietic growth factors have traditionally been thought of as regulators of the development and function of immune and blood cells. However, an ever-expanding number of these factors have been discovered to have major effects on bone cells and the development of the skeleton in health and disease (Table 1). In addition, several cytokines have been directly linked to the development of osteoporosis in both animal models and in patients. In order to understand the mechanisms regulating bone cells and how this may be dysregulated in disease states, it is necessary to appreciate the diverse effects that cytokines and inflammation have on osteoblasts, osteoclasts, and bone mass. This chapter provides a broad overview of this topic with extensive references so that, if desired, readers can access specific references to delve into individual topics in greater detail.

Pegylated interferon α/ribavirin therapy enhances bone mineral density in children with chronic genotype 4 HCV infection

BACKGROUND

The impact of chronic hepatitis C (CHC) on bone mineral density (BMD) has been well studied in adults with a relative paucity of data in children, especially concerning effect of treatment with pegylated interferon (PEG-IFN) plus ribavirin (RV). In the current work, we assessed prospectively changes in BMD in children with CHC before, during, and after treatment.

METHODS

Forty-six consecutive children with noncirrhotic genotype 4 CHC were subjected to dual-energy X-ray absorptiometry at baseline, 24 weeks, 48 weeks of therapy and 24 weeks after treatment. BMD, bone mineral content (BMC), and Z score of lumbar spine (L2-L4) were reported. Tanner pubertal stage, viral load, liver function tests, serum calcium, phosphorus, alkaline phosphatase, parathyroid hormone, and liver histopathology were assessed in all included children.

RESULTS

Thirty (65.2%) patients had normal BMD, 10 (21.7%) were at risk for low BMD, and 6 (13.1%) had low BMD for chronological age. Patients with low BMD were significantly older (P=0.001), with higher frequency of delayed puberty than other groups (P=0.002). Baseline densitometric parameters (BMD & BMC) were significantly positively correlated with patients' age, weight, height, body mass index and hemoglobin level; while they were insignificantly correlated with basal viral load, histopathology activity index and fibrosis score. Densitometric parameters improved significantly on PEG-IFN plus RV treatment, this improvement was found to be sustainable 24 weeks after therapy.

CONCLUSIONS

Low BMD is detectable in a proportion of CHC children. Antiviral therapy leads to a sustainable increase in BMD.

Cells of the immune system orchestrate changes in bone cell function

There is a complex interplay between the cells of the immune system and bone. Immune cells, such as T and NK cells, are able to enhance osteoclast formation via the production of RANKL. Yet there is increasing evidence to show that during the resolution of inflammation or as a consequence of increased osteoclastogenesis there is an anabolic response via the formation of more osteoblasts. Furthermore, osteoblasts themselves are involved in the control of immune cell function, thus promoting the resolution of inflammation. Hence, the concept of "coupling"-how bone formation is linked to resorption-needs to be more inclusive rather than restricting our focus to osteoblast-osteoclast interactions as in a whole organism these cells are never in isolation. This review will investigate the role of immune cells in normal bone homeostasis and in inflammatory diseases where the balance between resorption and formation is lost.

Osteoimmunology and the influence of pro-inflammatory cytokines on osteoclasts

Bone and immune system are functionally interconnected. Immune and bone cells derive from same progenitors in the bone marrow, they share a common microenvironment and are being influenced by similar mediators. The evidence on increased bone resorption associated with inappropriate activation of T cells such as during inflammation, is well established. However, the molecular mechanisms beyond this clinical observation have begun to be intensively studied with the advancement of osteoimmunology. Now days, we have firm evidence on the influence of numerous proinflammatory cytokines on bone cells, with the majority of data focused on osteoclasts, the bone resorbing cells. It has been shown that some proinflammatory cytokines could possess osteoclastogenic and/or anti-osteoclastogenic properties and can target osteoclasts directly or via receptor activator of nuclear factor κB (RANK)/RANK ligand(RANKL)/osteoprotegerin (OPG) system. Several studies have reported opposing data regarding (anti)osteoclastogenic properties of these cytokines.

Therefore, the first part of this review is summarizing current evidence on the influence of pro-inflammatory cytokines on osteoclasts and thus on bone resorption. In the second part, the evidence on the role of pro-inflammatory cytokines in osteoporosis and osteoarthritis is reviewed to show that unravelling the mechanisms beyond such complex bone diseases, is almost impossible without considering skeletal and immune systems as an indivisible integrated system.

Skeletal sequelae of cancer and cancer treatment

INTRODUCTION

Survivors of cancer may experience lingering adverse skeletal effects such as osteoporosis and osteomalacia. Skeletal disorders are often associated with advancing age, but these effects can be exacerbated by exposure to cancer and its treatment. This review will explore the cancer and cancer treatment-related causes of skeletal disorders.

METHODS

We performed a comprehensive search, using various Internet-based medical search engines such as PubMed, Medline Plus, Scopus, and Google Scholar, for published articles on the skeletal effects of cancer and cancer therapies.

RESULTS

One-hundred-forty-two publications, including journal articles, books, and book chapters, met the inclusion criteria. They included case reports, literature reviews, systematic analyses, and cohort reports. Skeletal effects resulting from cancer and cancer therapies, including hypogonadism, androgen deprivation therapy, estrogen suppression, glucocorticoids/corticosteroids, methotrexate, megestrol acetate, platinum compounds, cyclophosphamide, doxorubicin, interferon-alpha, valproic acid, cyclosporine, vitamin A, NSAIDS, estramustine, ifosfamide, radiotherapy, and combined chemotherapeutic regimens, were identified and described. Skeletal effects of hyperparathyroidism, vitamin D deficiency, gastrectomy, hypophosphatemia, and hyperprolactinemia resulting from cancer therapies were also described.

DISCUSSION/CONCLUSIONS

The publications researched during this review both highlight and emphasize the association between cancer therapies, including chemotherapy and radiotherapy, and skeletal dysfunction.

IMPLICATIONS FOR CANCER SURVIVORS

These studies confirm that cancer survivors experience a more rapid acceleration of bone loss than their age-matched peers who were never diagnosed with cancer. Further studies are needed to better address the skeletal needs of cancer survivors.

Prospective study of bone mineral density and metabolism in patients with chronic hepatitis C during pegylated interferon alpha and ribavirin therapy

The importance of osteoporosis as a complication of end-stage liver disease is well known. However, significant osteopenia may occur in earlier stages of chronic hepatitis C (CHC). Furthermore, antiviral therapy may influence bone metabolism. Thirty patients with CHC genotype 1 infection and without established cirrhosis were treated with peginterferon-alfa and ribavirin. Dual-energy x-ray absorptiometry was performed at baseline, after 48 weeks of therapy, and by the end of a 24-week follow-up period. Bone mineral density (BMD), T-scores, and Z-scores were assessed. Serum C-terminal propeptide of type I collagen (CICP) and osteocalcin levels were measured. Thirteen patients had osteopenia (43%) and osteoporosis was present in four patients (13%). Antiviral therapy led to significant on-treatment increases of lumbar spine and hip BMD (P < or = 0.05) as well as T-scores (P < or = 0.05) and Z-scores (P < or = 0.01) irrespective of subsequent treatment response. Further analyses showed that in patients with sustained virological response (n = 19) most parameters remained highly above baseline values by the end of the 24-week follow-up period, while patients with virological relapse (n = 11) had decreases of BMD, T-scores and Z-scores thereafter that did not differ from baseline. Serum CICP and osteocalcin levels decreased during therapy. Osteocalcin levels remained below baseline in sustained responder, but showed an increase in relapsers by the end of the 24-week follow-up (P < or = 0.05). Osteopenia is detectable in a substantial proportion of CHC patients without established cirrhosis. Antiviral therapy leads to an on-treatment increase of BMD, which may last in those patients who achieve a sustained virological response.

Osteoimmunology: cytokines and the skeletal system

It has become clear that complex interactions underlie the relationship between the skeletal and immune systems. This is particularly true for the development of immune cells in the bone marrow as well as the functions of bone cells in skeletal homeostasis and pathologies. Because these two disciplines developed independently, investigators with an interest in either often do not fully appreciate the influence of the other system on the functions of the tissue that they are studying. With these issues in mind, this review will focus on several key areas that are mediated by crosstalk between the bone and immune systems. A more complete appreciation of the interactions between immune and bone cells should lead to better therapeutic strategies for diseases that affect either or both systems.

Osteoimmunology: interactions of the bone and immune system

Bone and the immune system are both complex tissues that respectively regulate the skeleton and the body's response to invading pathogens. It has now become clear that these organ systems often interact in their function. This is particularly true for the development of immune cells in the bone marrow and for the function of bone cells in health and disease. Because these two disciplines developed independently, investigators in each don't always fully appreciate the significance that the other system has on the function of the tissue they are studying. This review is meant to provide a broad overview of the many ways that bone and immune cells interact so that a better understanding of the role that each plays in the development and function of the other can develop. It is hoped that an appreciation of the interactions of these two organ systems will lead to better therapeutics for diseases that affect either or both.

IFN-gamma stimulates osteoclast formation and bone loss in vivo via antigen-driven T cell activation

T cell-produced cytokines play a pivotal role in the bone loss caused by inflammation, infection, and estrogen deficiency. IFN-gamma is a major product of activated T helper cells that can function as a pro- or antiresorptive cytokine, but the reason why IFN-gamma has variable effects in bone is unknown. Here we show that IFN-gamma blunts osteoclast formation through direct targeting of osteoclast precursors but indirectly stimulates osteoclast formation and promotes bone resorption by stimulating antigen-dependent T cell activation and T cell secretion of the osteoclastogenic factors RANKL and TNF-alpha. Analysis of the in vivo effects of IFN-gamma in 3 mouse models of bone loss - ovariectomy, LPS injection, and inflammation via silencing of TGF-beta signaling in T cells - reveals that the net effect of IFN-gamma in these conditions is that of stimulating bone resorption and bone loss. In summary, IFN-gamma has both direct anti-osteoclastogenic and indirect pro-osteoclastogenic properties in vivo. Under conditions of estrogen deficiency, infection, and inflammation, the net balance of these 2 opposing forces is biased toward bone resorption. Inhibition of IFN-gamma signaling may thus represent a novel strategy to simultaneously reduce inflammation and bone loss in common forms of osteoporosis.

Local immunomodulation with CD4 and CD8 antibodies, but not cyclosporine A, improves osteogenesis induced by ADhBMP9 gene therapy

This study was designed to see if immunosuppression achieved using local application of cyclosporine A (Cs. A) or CD4 and CD8 antibodies would improve bone formation following intramuscular injections of human BMP-4 and BMP-9 adenoviral vectors (ADhBMP4 and ADhBMP9) in Sprague-Dawley rats. Cs. A was injected into the thigh muscle. After 2 days, ADhBMP4, ADhBMP9, and the antibodies were separately injected into the left and right rear legs. At this time, the number of CD4+/CD3+ cells was significantly lower and the number of CD8+/CD3+ cells higher in the Cs. A group than in the control group (P < 0.01). The total number of white blood cells 3 days following injection of CD4 and CD8 antibodies was significantly lower than that before the injection (P < 0.01). At 4 weeks after the viral and antibody injections, mean bone volumes at the ADhBMP9 treatment sites were 0.29 +/- 0.01 cm3 in the viral control group, 0.17 +/- 0.03 cm3 in the Cs. A-ADhBMPs group, and 0.59 +/- 0.07 cm3 in the antibodies-ADhBMPs group. ADhBMP4 did not induce new bone formation in any group. This study demonstrates that local immunomodulation may improve the osteogenic potential of bone morphogenetic protein gene therapy in the clinical setting.

Bone mineral density and cytokine levels during interferon therapy in children with chronic hepatitis B: does interferon therapy prevent from osteoporosis?

BACKGROUND

Our aim was to determinate bone mineral density (BMD), levels of biochemical markers and cytokines in children with chronic hepatitis B treated with interferon (IFN)-alpha and to investigate effect of IFN-alpha therapy on these variables. To the best of our knowledge, this is first study carried out about BMD and cytokine levels in pediatric patients with chronic hepatitis B treated with IFN-alpha.

METHODS

BMD, levels of parathyroid hormone (PTH), osteocalcin, C-terminal cross-linking telopeptide of type I collagen (CTX), calcium, alkaline phosphates (ALP), cytokines as TNF-alpha, interleukin (IL)-1beta, IL-2r, IL-6, and IL-8 were studied in 54 children with chronic hepatitis B (4-15 years old) treated with interferon alone (n = 19) or in combination with lamivudine (n = 35) for six months and as controls in 50 age-matched healthy children.

RESULTS

There was no significant difference in respect to serum IL-1beta, TNF-alpha and osteocalcin levels while serum IL-2r (p = 0.002), IL-6 (p = 0.001), IL-8 (p = 0.013), PTH (p = 0.029), and CTX (p = 0.021) levels were higher in children with chronic hepatitis B than in healthy controls. BMD of femur neck (p = 0.012) and trochanter (p = 0.046) in patients were higher than in healthy controls. There was a statistically significant correlation between serum IL-1beta and osteocalcin (r = -0.355, p < 0.01); between serum IL-8 and CTX levels (r = 0.372, p = 0.01), and ALP (r = 0.361, p = 0.01); between serum ALP and femur neck BMD (r = 0.303, p = 0.05), and trochanter BMD (r = 0.365, p = 0.01); between spine BMD and IL-2R (r = -0.330, p < 0.05).

CONCLUSION

In conclusion, our study suggest that BMD of femur, serum IL-2r, IL-6, IL-8, PTH, and CTX levels were higher in children with chronic hepatitis B treated with IFN-alpha alone or combination with lamivudine than in healthy children. High femur BMD measurements found in patients may suggest that IFN-alpha therapy in children with chronic hepatitis B could contribute indirectly to prevent from hip osteoporosis. Additionally, further investigations on effects of IFN-alpha for bone structure in children should be performed in the future.

Ribavirin, but not interferon alpha-2b, is associated with impaired osteoblast proliferation and differentiation in vitro

Hepatitis C treatment with interferon alpha-2b (IFN-alpha) and ribavirin has been related to decreased bone mineral density. The aim of this study was to investigate the in vitro effects of different concentrations of ribavirin and IFN-alpha on osteoblast-like cells. Human osteoblast-like cells obtained by the outgrowth of cells from bone chips were exposed to ribavirin (0.1-10 microg/mL) or IFN-alpha (0.1-1000 UI/mL). At regular time-points, cultures were harvested for posterior analysis. Alkaline phosphatase (ALP) activity was determined on days 7 and 14, and cell growth was accessed by C3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) and cell count on days 1, 3, 5, and 7. Flow cytometry analysis was used for investigating cell death on days 1, 3, 5, and 7. IFN-alpha affected ALP expression only at the higher concentration (1000 UI/mL) after 7 days (P < 0.05). No effects were detected in cell growth. In ribavirin treated cultures, concentrations higher than 2.5 microg/mL were associated with a decrease in ALP activity within 7 and 14 days (P < 0.01 and P < 0.001, respectively). Furthermore, the reduction in cell growth was dose-dependent and was detected after the fifth day. This decrease can be explained by an increase in the number of dead cells and a decrease in cell proliferation. In conclusion, our experiments demonstrated that ribavirin reduced, in a time- and dose-dependent manner, the number of metabolically active cells through a decrease in proliferation and an increase in cell death, and induced an impairment in osteoblast differentiation. These negative effects of ribavirin on osteblast-like cells might contribute to the bone loss reported in vivo.

Hypocalcemia and Azotemia Associated with Zoledronic Acid and Interferon Alfa

OBJECTIVE

To describe severe hypocalcemia and acute renal failure associated with zoledronic acid and interferon alfa in a patient with metastatic carcinoid tumors.

CASE SUMMARY

A 39-year-old white man with metastatic carcinoid tumor tolerated treatment with subcutaneous long-acting octreotide monthly and interferon alfa 6 million units 3 times weekly for 6 months. Due to multiple bony metastases, zoledronic acid was prescribed as a monthly 4-mg intravenous infusion over 30 minutes to prevent skeletal-related events. Although the first infusion went well, the patient developed severe hypocalcemia and acute renal failure after the second zoledronic infusion.

DISCUSSION

Bisphosphonates may infrequently cause symptomatic hypocalcemia, especially among patients who have vitamin D deficiency or hypoparathyroidism or receive treatment with an aminoglycoside. Our literature review suggests that zoledronic acid and interferon alfa may exert additive effects on the inhibition of osteoclasts, thus potentially precipitating hypocalcemia. Renal dysfunction may not be a direct consequence of interferon alfa. However, altered mental function due to hypocalcemia may lead to dehydration and further exacerbate renal dysfunction, a known adverse effect of zoledronic acid. Since therapeutic indications of both interferon alfa and zoledronic acid continue to expand, clinicians should be aware of these serious adverse reactions and potential interaction. Supportive treatment with hydration, calcium supplement, and oral calcitriol resulted in resolution of hypocalcemia, but only partial improvement of azotemia.

CONCLUSIONS

In our patient with metastatic carcinoid tumor, treatment with zoledronic acid and interferon alfa was associated with symptomatic hypocalcemia and acute renal failure.

Bone metabolism during interferon-alpha treatment of essential thrombocythemia

In-vitro studies have demonstrated that interferon (IFN) has an inhibitory effect on bone formation. Changes in bone metabolism were investigated in 19 patients treated for essential thrombocythemia with IFN-alpha. Serum biochemical parameters of bone remodeling [total alkaline phosphatase, osteocalcin, type-I procollagen carboxy-terminal propeptide (PICP), cross-linked telopeptide type-I collagen (ICTP)] and mineral metabolism (total calcium, inorganic phosphate, parathyroid hormone, 25-hydroxyvitamin D) were measured before and after long-term IFN-alpha treatment. The effects of the cumulative IFN-alpha dose and duration of therapy on biochemical markers of bone metabolism were analyzed. No uniform trend or pattern was observed in the measured biochemical parameters except for ICTP, which decreased after treatment. Correlations indicated modulation of bone metabolism, i.e. remodeling with suppression of resorption, as a consequence of therapy with IFN-alpha.

Pamidronate is superior to ibandronate in decreasing bone resorption, interleukin-6 and beta 2-microglobulin in multiple myeloma

OBJECTIVES

Bisphosphonates have been found to reduce skeletal events in patients with multiple myeloma (MM). This is the first randomised trial to compare the efficacy of pamidronate and ibandronate, a third-generation aminobisphosphonate, in bone turnover and disease activity in MM patients.

METHODS

Patients with MM, stage II or III, were randomly assigned to receive either pamidronate 90 mg (group I: 23 patients) or ibandronate 4 mg (group II: 21 patients) as a monthly intravenous infusion in addition to conventional chemotherapy. Skeletal events, such as pathologic fractures, hypercalcaemia, and bone radiotherapy were analysed. Bone resorption markers [N-terminal cross-linking telopeptide of type-I collagen (NTX) and tartrate-resistant acid phosphatase type 5b (TRACP-5b)], bone formation markers (bone alkaline phosphatase and osteocalcin), markers of disease activity (paraprotein, CRP, beta 2-microglobulin), and interleukin-6 (IL-6) were also studied.

RESULTS

In both groups, the combination of chemotherapy with either pamidronate or ibandronate produced a reduction in bone resorption and tumour burden as measured by NTX, IL-6, paraprotein, CRP, and beta 2-microglobulin from the second month of treatment, having no effect on bone formation. TRACP-5b also had a significant reduction in the pamidronate group from the second month of treatment and in the ibandronate group from the sixth month. However, there was a greater reduction of NTX, IL-6, and beta 2-microglobulin in group I than in group II, starting at the second month of treatment (P = 0.002, 0.001, and 0.004, respectively) and of TRACP-5b, starting at the fourth month (P = 0.014), that being continued throughout the 10-month follow-up of this study. There was no difference in skeletal events during this period. A significant correlation was observed between changes of NTX and changes of TRACP-5b, IL-6, and beta 2-microglobulin from the second month for patients of both groups.

CONCLUSIONS

These results suggest that a monthly dose of 90 mg of pamidronate is more effective than 4 mg of ibandronate in reducing osteoclast activity, bone resorption, IL-6, and possibly tumour burden in MM. TRACP-5b has also proved to be a useful new marker for monitoring bisphosphonates treatment in MM.

Pamidronate increases markers of bone formation in patients with multiple myeloma in plateau phase under interferon-alpha treatment

Bisphosphonates are potent inhibitors of osteoclastic activity and reduce the disease-related skeletal complications when they are used in combination with chemotherapy in patients with multiple myeloma (MM). Pamidronate also inhibits apoptosis of primary osteoblastic cells and probably induces apoptosis on human MM cells and osteoclasts. It has been reported that interferon-alpha (IFN-alpha) decreases bone resorption and that low doses of IFN-alpha result in a significant increase in serum osteocalcin (OSC). The aim of this study was to determine the effects of pamidronate treatment on biochemical markers of bone resorption [cross-linked N-telopeptides of type I collagen (NTx)], bone formation [bone alkaline phosphatase (BAP) and OSC], disease activity [beta2-microglobulin, CRP, paraprotein], and interleukin-6 (IL-6) in patients with MM in plateau phase under IFN-alpha maintenance. The above parameters were evaluated in 28 patients (13 M, 15 F, median age 70 years) during maintenance treatment, before the addition of pamidronate and after 1, 3, 6, 9, 12, and 14 months of the combined therapy. The addition of pamidronate to maintenance treatment resulted in a significant reduction of NTx, IL-6, beta2-microglobulin, CRP from the 3rd month and paraprotein from the 6th month of treatment, whereas BAP and OSC were significantly increased from the 6th month. These changes continued during the 14-month follow-up of the combined treatment. Multivariate analysis showed a significant negative correlation between changes of BAP and OSC and the patients' age. The greater increase of the bone formation markers was observed in younger patients. These results suggest that, in addition to the inhibition of osteoclastic activity, pamidronate in combination with IFN-alpha was shown to induce bone formation in patients with MM in the plateau phase.