Zebrafish Collagen Type I: Molecular and Biochemical Characterization of the Major Structural Protein in Bone and Skin

Over the last years the zebrafish imposed itself as a powerful model to study skeletal diseases, but a limit to its use is the poor characterization of collagen type I, the most abundant protein in bone and skin. In tetrapods collagen type I is a trimer mainly composed of two α1 chains and one α2 chain, encoded by COL1A1 and COL1A2 genes, respectively. In contrast, in zebrafish three type I collagen genes exist, col1a1a, col1a1b and col1a2 coding for α1(I), α3(I) and α2(I) chains. During embryonic and larval development the three collagen type I genes showed a similar spatio-temporal expression pattern, indicating their co-regulation and interdependence at these stages. In both embryonic and adult tissues, the presence of the three α(I) chains was demonstrated, although in embryos α1(I) was present in two distinct glycosylated states, suggesting a developmental-specific collagen composition. Even though in adult bone, skin and scales equal amounts of α1(I), α3(I) and α2(I) chains are present, the presented data suggest a tissue-specific stoichiometry and/or post-translational modification status for collagen type I. In conclusion, this data will be useful to properly interpret results and insights gained from zebrafish models of skeletal diseases.

Phosphoproteomics reveals that Parkinson's disease kinase LRRK2 regulates a subset of Rab GTPases

Mutations in Park8, encoding for the multidomain Leucine-rich repeat kinase 2 (LRRK2) protein, comprise the predominant genetic cause of Parkinson's disease (PD). G2019S, the most common amino acid substitution activates the kinase two- to threefold. This has motivated the development of LRRK2 kinase inhibitors; however, poor consensus on physiological LRRK2 substrates has hampered clinical development of such therapeutics. We employ a combination of phosphoproteomics, genetics, and pharmacology to unambiguously identify a subset of Rab GTPases as key LRRK2 substrates. LRRK2 directly phosphorylates these both in vivo and in vitro on an evolutionary conserved residue in the switch II domain. Pathogenic LRRK2 variants mapping to different functional domains increase phosphorylation of Rabs and this strongly decreases their affinity to regulatory proteins including Rab GDP dissociation inhibitors (GDIs). Our findings uncover a key class of bona-fide LRRK2 substrates and a novel regulatory mechanism of Rabs that connects them to PD.

The sphingosine kinase inhibitor 2-(p-hyroxyanilino)-4-(p-chlorophenyl)thiazole reduces androgen receptor expression via an oxidative stress-dependent mechanism

BACKGROUND AND PURPOSE

Sphingosine kinase catalyses the formation of sphingosine 1-phosphate and is linked with androgen receptor signalling in prostate cancer cells. Therefore, we investigated the effect of sphingosine kinase inhibitors on androgen receptor expression.

EXPERIMENTAL APPROACH

Androgen-sensitive LNCaP cells were treated with SKi (2-(p-hydroxyanilino)-4-(p-chlorophenyl)thiazole), which inhibits sphingosine kinases 1 and 2 activity, and the effect on androgen receptor expression was measured.

KEY RESULTS

Treatment of cells with SK1 inhibitors reduced the expression of the androgen receptor and prostate-specific antigen, while (R)-FTY720 methyl ether (a sphingosine-kinase-2-selective inhibitor), at a concentration that eliminates sphingosine kinase 2 from cells, had no significant effect on androgen receptor expression. The effect of SKi on androgen receptor expression was independent of the SKi-induced proteasomal degradation of SK1 and was post translational, although androgen receptor mRNA transcript was reduced. Fumonisin B1 (a ceramide synthase inhibitor) also failed to reverse the effect of SKi on androgen receptor expression, thereby excluding a role for ceramide derived from the salvage pathway. The effect of SKi on androgen receptor expression was reversed by N-acetylcysteine, which was used to scavenge reactive oxygen species.

CONCLUSION AND IMPLICATIONS

Inhibition of sphingosine kinase 1 activity abrogates androgen receptor signalling via an oxidative stress-induced, p53-independent mechanism in prostate cancer cells. Therefore, SK1 inhibitors may offer therapeutic potential in promoting the removal of AR receptors from prostate cancer cells, resulting in an increased efficacy, which is likely to be superior to inhibitors that simply reversibly inhibit AR signalling.

TGFβ1 evokes myoblast apoptotic response via a novel signaling pathway involving S1P4 transactivation upstream of Rho-kinase-2 activation

In view of its multiple detrimental effects, transforming growth factor β1 (TGFβ1) is recognized as critical negative regulator of skeletal muscle repair. Apoptosis of skeletal muscle precursor cells driven by TGFβ1 contributes to the negative role exerted by the cytokine in tissue repair, although the underlying molecular mechanisms are still elusive. Herein we report the identification of a new signaling pathway, relying on Rho kinase-2 stimulation, subsequent to SMAD-dependent S1P4 up-regulation and transactivation via sphingosine kinase (SK)-2, that accounts for TGFβ1-induced apoptosis in cultured myoblasts. S1P4-specific gene silencing reduced by almost 50% activation of caspase-3 and poly-ADP ribosyl transferase cleavage elicited by TGFβ1. Moreover, the selective S1P4 antagonist CYM50358 also reduced the TGFβ1 proapoptotic effects. By employing pharmacological and molecular biological approaches, the involvement of SK2 and ROCK2 in the transmission of the TGFβ1 apoptotic action was also demonstrated. These results reinforce the notion that the SK/S1P axis plays a fundamental role in TGFβ1 mode of action in skeletal muscle cells and, by disclosing a novel mechanism by which TGFβ1 exerts its harmful action, pinpoint new molecular targets that in principle could be beneficial in the treatment of several skeletal muscle disorders or aging-dependent muscle atrophy.

The roles of sphingosine kinases 1 and 2 in regulating the Warburg effect in prostate cancer cells

Two isoforms of sphingosine kinase, SK1 and SK2, catalyze the formation of the bioactive lipid sphingosine 1-phosphate (S1P) in mammalian cells. We have previously shown that treatment of androgen-sensitive LNCaP prostate cancer cells with a non-selective SK isoform inhibitor, 2-(p-hydroxyanilino)-4-(p-chlorophenyl)thiazole (SKi), induces the proteasomal degradation of SK1. This is concomitant with a significant increase in C22:0-ceramide and sphingosine levels and a reduction in S1P levels, resulting in the apoptosis of LNCaP cells. In contrast, we show here that a SK2-selective inhibitor, (R)-FTY720 methyl ether (ROME), increases sphingosine and decreases S1P levels but has no effect on ceramide levels and does not induce apoptosis in LNCaP cells. We also show that several glycolytic metabolites and (R)-S-lactoylglutathione are increased upon treatment of LNCaP cells with SKi, which induces the proteasomal degradation of c-Myc. These changes reflect an indirect antagonism of the Warburg effect. LNCaP cells also respond to SKi by diverting glucose 6-phosphate into the pentose phosphate pathway to provide NADPH, which serves as an antioxidant to counter an oxidative stress response. SKi also promotes the formation of a novel pro-apoptotic molecule called diadenosine 5',5'''-P(1),P(3)-triphosphate (Ap3A), which binds to the tumor suppressor fragile histidine triad protein (FHIT). In contrast, the SK2-selective inhibitor, ROME, induces a reduction in some glycolytic metabolites and does not affect oxidative stress. We conclude that SK1 functions to increase the stability of c-Myc and suppresses Ap3A formation, which might maintain the Warburg effect and cell survival, while SK2 exhibits a non-overlapping function.

Inhibition kinetics and regulation of sphingosine kinase 1 expression in prostate cancer cells: functional differences between sphingosine kinase 1a and 1b

Sphingosine kinase 1 catalyses the formation of the bioactive lipid, sphingosine 1-phosphate and is a target for anti-cancer agents. We demonstrate here that 2-(p-hydroxyanilino)-4-(p-chlorophenyl)thiazole (SKi, also referred to as SKI-II), FTY720 (Fingolimod), and (S)-FTY720 vinylphosphonate inhibit sphingosine kinase 1 activity with distinct kinetics, indicating that these compounds exhibit different binding modalities with sphingosine kinase 1. Thus, SKi is a mixed inhibitor of sphingosine and ATP binding, whereas FTY720 is competitive with sphingosine and uncompetitive with ATP, and (S)-FTY720 vinylphosphonate is uncompetitive with sphingosine and is a mixed inhibitor with respect to ATP. A novel 'see-saw' model is proposed for the binding of inhibitor to catalytic and allosteric sites, the latter dependent on substrate binding, that provides an explanation for the different inhibitor kinetics. In addition, we demonstrate that the expression level and properties unique to an N-terminal 86 amino-acid isoform variant of sphingosine kinase 1 (SK1b) in prostate cancer cells reduce its sensitivity to SKi-induced proteasomal degradation in comparison to SK1a, i.e. these two N-terminal variants of sphingosine kinase 1 (SK1a and SK1b) have different properties. The reduced sensitivity of SK1b to proteasomal degradation in response to SKi is translated into specific changes in ceramide and S1P levels that leads to apoptosis of androgen-sensitive but not androgen-independent LNCaP prostate cancer cells. Therefore, our proposed 'see-saw' model might be usefully employed in the design of sphingosine kinase inhibitors to promote apoptosis of chemotherapeutic resistant cancer cells.

FTY720 analogues as sphingosine kinase 1 inhibitors: enzyme inhibition kinetics, allosterism, proteasomal degradation, and actin rearrangement in MCF-7 breast cancer cells

Sphingosine kinase 1 (SK1) catalyzes the conversion of sphingosine to the bioactive lipid sphingosine 1-phosphate. We have previously demonstrated that FTY720 and (S)-FTY720 vinylphosphonate are novel inhibitors of SK1 activity. Here, we show that (S)-FTY720 vinylphosphonate binds to a putative allosteric site in SK1 contingent on formation of the enzyme-sphingosine complex. We report that SK1 is an oligomeric protein (minimally a dimer) containing noncooperative catalytic sites and that the allosteric site exerts an autoinhibition of the catalytic site. A model is proposed in which (S)-FTY720 vinylphosphonate binding to and stabilization of the allosteric site might enhance the autoinhibitory effect on SK1 activity. Further evidence for the existence of allosteric site(s) in SK1 was demonstrated by data showing that two new FTY720 analogues (a conjugate of sphingosine with a fluorophore and (S)-FTY720 regioisomer) increased SK1 activity, suggesting relief of autoinhibition of SK1 activity. Comparisons with the SK1 inhibitor, SKi or siRNA knockdown of SK1 indicated that (S)-FTY720 vinylphosphonate and FTY720 behave as typical SK1 inhibitors in preventing sphingosine 1-phosphate-stimulated rearrangement of actin in MCF-7 cells. These findings are discussed in relation to the anticancer properties of SK1 inhibitors.

Prognostic factors in primary and iterative surgery of colorectal liver metastases

The aim of this study was to evaluate the results of surgery of colorectal liver metastases and assess prognostic factors influencing the outcome. A total of 135 hepatic resections performed in 107 patients was reviewed. The following prognostic factors were analyzed: primary tumor localization, Dukes stage, number and presence of metastases in one or two lobes, synchronous or metachronous occurrence, type of resection, use and modality of chemotherapy. The perioperative morbidity rate was 6.5% and mortality was 1.9%. Overall survival was 41.2% and disease-free survival 31.5% at 5 years. Survival at 5 years was better for patients with metachronous than for those with synchronous lesions (60.9% vs 28.1%; p<0.05). There were no significant differences in terms of long-term survival between patients with synchronous metastases that were excised simultaneously or with a delay of 3-6 months (p=n.s.). Site of the primary tumor, Dukes stage, number of metastases and type of resection did not influence survival. A favorable survival trend was observed in those patients who underwent both neoadjuvant and adjuvant chemotherapy. The overall survival rate at 5 years was 45.3% for patients undergoing a second hepatic resection and 50% for those with a third or a fourth hepatic resection. Liver resection remains the "gold standard" for the treatment of patients with colorectal liver metastases, with metachronous type having a better outcome than synchronous. Simultaneous or delayed surgery for synchronous metastases does not influence prognosis. Iterative resection is very encouraging and justifies an aggressive surgical approach.

The sphingosine kinase 1 inhibitor 2-(p-hydroxyanilino)-4-(p-chlorophenyl)thiazole induces proteasomal degradation of sphingosine kinase 1 in mammalian cells

Sphingosine kinase 1 (SK1) is an enzyme that catalyzes the phosphorylation of sphingosine to produce the bioactive lipid sphingosine 1-phosphate (S1P). We demonstrate here that the SK1 inhibitor, SKi (2-(p-hydroxyanilino)-4-(p-chlorophenyl)thiazole) induces the proteasomal degradation of SK1 in human pulmonary artery smooth muscle cells, androgen-sensitive LNCaP prostate cancer cells, MCF-7 and MCF-7 HER2 breast cancer cells and that this is likely mediated by ceramide as a consequence of catalytic inhibition of SK1 by SKi. Moreover, SK1 is polyubiquitinated under basal conditions, and SKi appears to increase the degradation of SK1 by activating the proteasome. In addition, the proteasomal degradation of SK1a and SK1b in androgen-sensitive LNCaP cells is associated with the induction of apoptosis. However, SK1b in LNCaP-AI cells (androgen-independent) is less sensitive to SKi-induced proteasomal degradation and these cells are resistant to SKi-induced apoptosis, thereby implicating the ubiquitin-proteasomal degradation of SK1 as an important mechanism controlling cell survival.

FTY720 and (S)-FTY720 vinylphosphonate inhibit sphingosine kinase 1 and promote its proteasomal degradation in human pulmonary artery smooth muscle, breast cancer and androgen-independent prostate cancer cells

Sphingosine kinase 1 (SK1) is an enzyme that catalyses the phosphorylation of sphingosine to produce the bioactive lipid sphingosine 1-phosphate (S1P). We demonstrate here that FTY720 (Fingolimod) and (S)-FTY720 vinylphosphonate are novel inhibitors of SK1 catalytic activity and induce the proteasomal degradation of this enzyme in human pulmonary artery smooth muscle cells, MCF-7 breast cancer cells and androgen-independent LNCaP-AI prostate cancer cells. Proteasomal degradation of SK1 in response to FTY720 and (S)-FTY720 vinylphosphonate is associated with the down-regulation of the androgen receptor in LNCaP-AI cells. (S)-FTY720 vinylphosphonate also induces the apoptosis of these cells. These findings indicate that SK1 is involved in protecting LNCaP-AI from apoptosis. This protection might be mediated by so-called 'inside-out' signalling by S1P, as LNCaP-AI cells exhibit increased expression of S1P(2/3) receptors and reduced lipid phosphate phosphatase expression (compared with androgen-sensitive LNCaP cells) thereby potentially increasing the bioavailability of S1P at S1P(2/3) receptors.

[Tuberculosis. Focus on risk assessment and health surveillance in health workers: results and perspectives of a multicenter working group]

INTRODUCTION

Tuberculosis (TB) is still a threat for healthcare workers (HCW), due to the non decreasing incidence, the spread of drug-resistance, the introduction of new tests for the screening, the relevant costs of surveillance of exposed subjects. These issues implicate a revision of activities to prevent TB in health-care settings.

METHODS

A multidisciplinary working group, led by occupational physicians, examined the activities to prevent TB performed in 9 Italian hospitals and reviewed the literature, with the aim to formulate evidence-based procedures.

RESULTS

In the considered hospitals, 23.000 HCW are classified as exposed to TB, out of 32.000 HCW exposed to biological risks; yearly, about 6000 subjects are screened for preventive, periodical or post-exposure surveillance and 110-130 chemoprophylaxis are prescribed. A high proportion of HCW (54-75%) refused or interrupt to assume the drugs. In the period 2004-2008, 14 occupational TB were diagnosed (9/100.000 HCW exposed to biological risks).

DISCUSSION

Critical issues are the availability of a specific, written TB control plan, including risk assessment, protocols for identifying, evaluating, managing infectious TB patients, health surveillance, education programs, specifically addressed to increase Standard Precaution adoption and compliance to the screening and to adequate risk perception. Risk assessment identify HCW to be included in TB testing (characterized by low positive predictive value), unrecognized TB and environmental control needed; TB risk classification should include no more than 3 or 4 classes and performed by assessing the issues suggested in the Italian guideline. Tubercolin skin test should be used for HCW screening, adding in vitro test in specific circumstances (for example, skin test positivity in BCG vaccinated HCW); the frequency of the screening should not exceed 2 years. Periodical revision of preventive activities should follow up to date scientific literature and need appropriate data computing.

[Focus on risk assessment in health environments: results and perspectives of a multicenter working group]

The hospital risk assessment (VdR) is certainly a relevant issue concerning the activities of prevention for the health of healthcare workers in relation to biological risk. The aim of this paper is to provide an up-date of the issue, based on the suggestions of recent literature about the rules ratified by the new legislative decree and data supplied by the Group of 10 Hospitals participated in this multicenter study. From the analysis of data on healthcare settings (HCS) participating in the project the following considerations can be formulated: i) All HCS considered VdR from biological agents. The method recommended in the Guidelines SIMLII 2005 is the most followed ii) To grading the risk, the use of invasive procedures for carrying out the analysis results is a necessary element iii) the operators classified as exposed to biological risk, and therefore subject to health surveillance, represent almost all of workforce in 7 out of 10 HCS. The subgroup believes that VdR must be conducted in close collaboration with the occupational physician and should represent a worthwhile investment with spin-off character on prevention, decision making, empowering. The presence of environmental requirements and organizational procedures should be considered, so that HCS is enabled for an effective risk management, without which risk assessments cannot be performed. The method of VdR mentioned in the guidelines MLIS 2005, besides being the most widely used by the company participating in the study, still has practical reasons and opportunities to justify its use. The HCS group felt the need to propose an implementation of the definition of invasive procedures and EPP, together with individual assessment. Flexibility was suggested in identifying different levels of risk with the involvement of occupational physicians, especially in the presence of EPP, also in order to plan content and frequency of health surveillance.

[Focus on coverage and promotion of anti influenza vaccine in health workers: results and perspectives of a multicenter working group]

INTRODUCTION

The influenza illness is a concern for health care workers (HCW) due to the potential nosocomial transmission and sickness absenteeism. Immunization and Isolation Precautions might be effective preventive measures.

AIMS

To formulate recommendations on vaccination in healthcare settings.

METHODS

A multidisciplinary working group, led by occupational physicians (OP), examined the information on seasonal influenza immunisation campaign in 9 Italian hospitals in the period 2005-2009 and reviewed scientific evidence.

RESULTS

Many health organizations recommend vaccination of HCW. The literature shows that seasonal influenza vaccination of healthy adult have a modest effect in reducing work day lost; there is no evidence that it affects transmission or it prevents the disease in elderly residents. These observations might be conditioned by methodological limitations. Further studies are required to avoid the risk of bias and in pediatric settings. The rate of flu vaccination among HCW is widely variable and it depends on individual risk perception and information about efficacy and side effects. In the considered hospitals, in the five-years period the vaccination rate ranged between 0 and 29%: the median value was 16-17% in 2005, 2008 and 2009 (only against H1N1 influence), 11% and 13% in 2007 and 2006 respectively. OP participation in the vaccination campaign seems to increase the immunization rate.

DISCUSSION

Seasonal influenza immunization of HCW might be effective. We recommend to formalize written procedures in health care settings, to perform data computing and to periodically revise immunization activities and promotion and scientific literature, with the aim to appropriately address resources.