Dionysios J. Papachristou

FSH Directly Regulates Bone Mass

Postmenopausal osteoporosis, a global public health problem, has for decades been attributed solely to declining estrogen levels. Although FSH levels rise sharply in parallel, a direct effect of FSH on the skeleton has never been explored. We show that FSH is required for hypogonadal bone loss. Neither FSHbeta nor FSH receptor (FSHR) null mice have bone loss despite severe hypogonadism. Bone mass is increased and osteoclastic resorption is decreased in haploinsufficient FSHbeta+/- mice with normal ovarian function, suggesting that the skeletal action of FSH is estrogen independent. Osteoclasts and their precursors possess G(i2alpha)-coupled FSHRs that activate MEK/Erk, NF-kappaB, and Akt to result in enhanced osteoclast formation and function. We suggest that high circulating FSH causes hypogonadal bone loss.

Obesity increases the severity of acute pancreatitis: performance of APACHE-O score and correlation with the inflammatory response.

Background: Obese patients appear to be at risk for complications of acute pancreatitis (AP). APACHE-O score has been suggested to improve APACHE-II accuracy in predicting severe outcome in AP. Aims: To determine if APACHE-O adds any predictive value to APACHE-II score and to test the hypothesis that obese patients are at increased risk of severe AP (SAP) because of a more intense inflammatory response to pancreatic injury. Methods: 102 AP patients were prospectively studied. Using a body mass index (BMI) >30, 28% of the subjects were obese. Nineteen patients developed organ dysfunction and were classified as SAP. Receiver-operating curves for prediction of SAP were calculated using admission APACHE-II and APACHE-O scores. Binary logistic regression was performed to assess if obesity is a risk for SAP and to determine the clinical factors associated with severe disease. Serum levels of IL-6, MCP-1 and CRP as well as Ranson’s scores were compared between obese and non-obese patients. Results: Admission APACHE-O (area under the curve AUC 0.895) and APACHE-II (AUC 0.893) showed similar accuracy in predicting severe outcome. BMI was identified as a significant risk for SAP (OR 2.8, p = 0.048) and mortality (OR 11.2, p = 0.022). CRP levels were significantly higher in obese AP patients (p = 0.0001) as well as Ranson’s score (p = 0.021). IL-6 and MCP-1 levels were higher in obese patients but did not reach statistical significance. Conclusions: Obesity is an independent risk for SAP. Admission APACHE-O score is not more accurate than APACHE-II. Our study results suggest that obesity increases the severity of AP by amplifying the immune response to injury.

Activation of the JNK-AP-1 signal transduction pathway is associated with pathogenesis and progression of human osteosarcomas.

Osteosarcomas represent the most common primary malignant bone tumors; however, comprehension of the molecular mechanisms underlying their pathogenesis is far from thorough. Studies in cultured cells have demonstrated that the c-Jun N-terminal kinase (JNK) signal transduction pathway participates in the proliferation, differentiation, and apoptosis of osteoblasts. Phosphorylated JNKs activate the oncoprotein c-Jun, which is known to form the activator protein-1 (AP-1) transcription factor as a homo- or heterodimer. c-Juns principal dimerization partner is c-Fos, which participates in the differentiation and function of osteoblasts and in the pathogenesis of osteosarcomas. A similar role for the JNK cascade in the malignant transformation of human osteoblasts and in the generation of osteosarcomas has not been documented. Our study addressed the possibility that a functional upregulation of the JNK pathway is implicated in the pathogenesis of osteosarcomas. To this end, we employed immunohistochemistry to examine normal bone and osteosarcoma cells in paraffin-embedded sections from 56 patients with high-grade tumors and 15 patients with low-grade tumors. We assessed the protein levels of the two major JNK isoforms (JNK1 and JNK2); their phosphorylated-hence activated-species, p-JNK; their substrate, c- Jun; its phosphorylated (activated) form, pc-Jun; and c-Juns heterodimeric partner, c-Fos. We also examined the immunohistochemical profile of the alpha chain of the nascent polypeptide-associated complex (alpha-NAC), an osteoblast-specific AP-1 coactivator that potentiates the transcriptional activity of the c-Jun/c-Jun homodimer. Positive immunostaining for JNK1, JNK2, p-JNK, c-Jun, pc-Jun, c-Fos, and alpha-NAC was observed in 86, 93, 94, 99, 97, 99, and 97.5% of the samples, respectively, whereas normal bone was devoid of these immunoreactivities. The cellular levels of all proteins were significantly correlated to each other (P < 0.001 for each correlation). Moreover, significantly higher expression levels of all proteins were detected in high-grade tumors compared to levels in low-grade ones. The observed expression profile of alpha-NAC implies that the active AP-1 in human osteosarcomas most likely comprises c-Jun/c-Jun homodimers. When cellular levels of the JNK pathway components and c-Fos were evaluated as possible biological markers of tumor grade, high expression of c-Jun and abundant pc-Jun predicted a high-grade tumor. Our findings provide novel evidence that the JNK signaling pathway is functionally operative in the malignant transformation of osteoblasts and the subsequent development and progression of human osteosarcomas. Evaluation of c-Jun expression and JNK-dependent activation may facilitate an improved prediction of the tumors clinical behavior and potentially be exploited in designing patient-tailored treatment regimens.

Signaling networks and transcription factors regulating mechanotransduction in bone

Mechanical stimulation has a critical role in the development and maintenance of the skeleton. This function requires the perception of extracellular stimuli as well as their conversion into intracellular biochemical responses. This process is called mechanotransduction and is mediated by a plethora of molecular events that regulate bone metabolism. Indeed, mechanoreceptors, such as integrins, G protein‐coupled receptors, receptor protein tyrosine kinases, and stretch‐activated Ca2+ channels, together with their downstream effectors coordinate the transmission of load‐induced signals to the nucleus and the expression of bone‐related genes. During the past decade, scientists have gained increasing insight into the molecular networks implicated in bone mechanotransduction. In the present paper, we consider the major signaling cascades and transcription factors that control bone and cartilage mechanobiology and discuss the influence of the mechanical microenvironment on the determination of skeletal morphology.

Chronic Alcohol Consumption Is a Major Risk Factor for Pancreatic Necrosis in Acute Pancreatitis

BACKGROUND:Much of the late morbidity and mortality of acute pancreatitis (AP) is attributed to complications of pancreatic necrosis (PNEC). Early diagnosis of PNEC in high-risk patients is critical to management. Hemoconcentration is one risk factor for PNEC, but additional risk factors are likely implicated.AIMS:(1) To evaluate a series of preselected clinical factors in a prospectively collected cohort with AP to identify risk factors for PNEC and (2) to verify the relative risk of any newly identified factor(s) by retrospective analysis of a large patient cohort.METHODS:Phase I: 102 AP patients were prospectively ascertained, of which 77 (mean age 49 yr; 35 women, 42 men) underwent contrast-enhanced computerized tomography (CECT) and were studied. Eleven subjects developed PNEC (14%). Binary logistic regression was performed to identify any clinical factors associated with PNEC. Phase II: 1,474 anonymized patients admitted to the hospital with a diagnosis of AP were electronically reviewed to identify 359 subjects (mean age 54 yr; 157 women, 202 men) with AP and CECT. Seventy-six of these patients (21%) exhibited CECT evidence of PNEC. The associations found in the Phase I group were compared with Phase II by logistic regression analysis.RESULTS:In Phase I, only chronic alcohol consumption was identified as a significant new risk factor for the development of PNEC (6/19 vs 5/58, p = 0.02, OR 4.8, CI 1.27–18.2). In Phase II, it was verified that excessive alcohol consumption was a significant risk factor for PNEC (18/52 vs 58/307, p = 0.012, OR 2.27, CI 1.19–4.30).CONCLUSION:Chronic alcohol consumption seems to constitute a strong risk factor for PNEC.

Expression of the ribonucleases Drosha, Dicer, and Ago2 in colorectal carcinomas

The pathogenesis of colorectal carcinoma (CRC) is a complex process that involves the recruitment of both genetic and epigenetic mechanisms. Recent studies underline the cardinal role of small, noncoding RNA molecules, called microRNAs (miRs), in the pathobiology of numerous physiological and pathological processes, including oncogenesis. MiR biogenesis and maturation is mainly regulated by the nuclear ribonuclease Drosha and the cytoplasmic ribonucleases Dicer and Ago2. In the present study, we investigated the expression and distribution of these molecules in three colon cancer cell lines and in human CRC samples. Drosha, Dicer, and Ago2 mRNA and protein expression was assessed with real-time PCR, western blotting, and immunofluorescence. Our experiments showed that Drosha, Dicer, and Ago2 were expressed in all the cell lines and in the majority of the CRC samples examined. The mRNA levels of Dicer were significantly augmented in stage III compared to stage II tumors. Our results suggest that Drosha, Dicer, and Ago2 are possibly implicated in CRC pathobiology and that Dicer might have a role in the progression of these tumors to advanced stages.

Bone Metastases: Molecular Mechanisms and Novel Therapeutic Interventions

It has been long recognized that skeleton represents one of the most favored metastatic sites for common cancers like breast and prostate. During the last decade the molecular mechanisms that are responsible for the development of bone metastasis have been gradually illuminated. It appears that the bone microenvironment has a pivotal role in this process. Metastatic tumor cells interact with bone triggering a cascade of molecular events that produce osteolytic and/or osteoblastic phenomena. In this review, we summarize and discuss the most significant factors and signaling pathways implicated in bone colonization. Moreover, based on the recent literature and data, we foresee the need for designing novel agents that will efficiently disrupt these interactions among cancer cells and bone microenvironment, bringing hope for more effective treatments.

Perturbations in the HDL metabolic pathway predispose to the development of osteoarthritis in mice following long-term exposure to western-type diet

OBJECTIVE Recent data suggest that obesity and related metabolic aberrations are associated with osteoarthritis (OA) development, a phenomenon that is attributed at least in part to the consumption of lipid-rich diets. To date, the molecular mechanisms that govern the lipid-OA connection remain largely unknown. Given the important role of high-density lipoprotein (HDL) in plasma and tissue lipid metabolism, the main purpose of the present study was to investigate the role of HDL metabolism in the pathobiology of OA. METHODS We used apolipoprotein A-I (apoA-I)(-/-) mice that lack classical apoA-I containing HDL, LCAT(-/-) mice that have only immature HDL and relatively reduced HDL-cholesterol levels and control C57BL/6 mice. Mice were placed on chow or western-type (WTD) and monitored for 24 weeks. Knee joints were removed and articular cartilage was isolated for further analyses. RESULTS The LCAT(-/-) mice were significantly more sensitive to the development of diet-induced obesity compared to the C57BL/6 and apoA-I(-/-) mice. Morphological, biochemical and molecular analyses revealed that the LCAT(-/-) obese mice developed OA, while the C57BL/6 mice that were fed WTD did not. Notably, apoA-I(-/-) mice that received WTD also developed OA although their body-weight gain was similar to their wild-type counterparts. Interestingly, bone marrow from LCAT(-/-) and apoA-I(-/-) mice contained significantly increased number of adipocytes, compared to the other groups. CONCLUSIONS Our findings suggest that perturbations in HDL metabolism predispose to OA following chronic insult with WTD and raise the challenging possibility that HDL has a causative relation to OA in patients with metabolic syndrome.

The MAPK–AP-1/–Runx2 signalling axes are implicated in chondrosarcoma pathobiology either independently or via up-regulation of VEGF

Aims : To investigate whether and how the JNK/ERK–AP‐1/–Runx2 signalling pathways and vascular endothelial growth factor (VEGF) are engaged in the pathogenesis of cartilaginous tumours. Chondrosarcoma is the third most common primary skeletal malignancy. Nevertheless, the molecular events underlying its pathogenesis remain elusive. JNK/ERK MAPKs and their downstream effectors, c‐Jun and c‐Fos (AP‐1), are involved in chondroblastic differention/proliferation. These proteins interact with the Runx2 transcription factor, which is also implicated in chondroblast biology. VEGF, a key angiogenic factor, is up‐regulated in human chondrosarcomas.

Immunohistochemical Expression of Vascular Endothelial Growth Factor (VEGF) and C-KIT in Cutaneous Melanocytic Lesions

Vascular endothelial growth factor (VEGF) and C-KIT are involved in tumor progression in several human neoplasms. The aim of the present study has been to investigate their immunohistochemical expression in melanocytic lesions. We examined 11 compound nevi, 12 dysplastic nevi, and 18 melanomas. Immunostaining for VEGF was observed only in melanomas; c-kit expression was detected in melanomas (higher in radial than in vertical growth phase) and in nevi (predominantly in the junctional component). Our data indicate that assessment of VEGF expression might aid in the differential diagnosis between dysplastic nevi and melanomas. Moreover, VEGF might be a candidate for targeted therapy. The loss of c-kit expression might contribute to melanoma progression.