Breast cancer screening adhesion among migrants: a matter of communication strategy?

Background

Migrants’ engagement to cancer screening programs is a relevant issue for universalistic health systems. To increase breast cancer screening coverage among migrant women, a public-private partnership involving a multidisciplinary team of Primary Care, Public Health, Hospital and private social workers has been built up in a district in Italy. The team worked in two steps, planning health promotion (HP) meetings addressing women in refugees’ reception programs and a web-based workshop involving intercultural mediators (IMs) and community health promoters.

Objectives

The workshop, involving 10 professionals among IMs and community health promoters, realized in 3 online meetings during March ‘22, aimed at identifying communication tools to enable migrants’ participation to breast cancer screening and increasing health literacy (HL) and cultural competence (CC) among the team. A participatory approach, supported by learning methods, such as storytelling and role-play, has been adopted to identify the major barriers to access to screening and public health messages. Participants worked on critical words and concepts, highlighted during HP meetings, accounting for HL, literacy, language skills, communication techniques and different perspectives about health and prevention.

Results

Several barriers, such as lack of knowledge on preventive initiatives and different approaches to health, decrease the perception of cancer risk. Others, like family and work duties, influence the adhesion. Fear or shame about the exam and linguistic issues are further hampering factors. Participants pointed out text, audio and video messages, in Italian and native plain language, as useful tools to explain the screening procedure and give relevant and practical information supported by simple and clear illustrations to diffuse via WhatsApp.

Conclusions

The intervention enabled the team to improve HL and CC defining suitable communication strategies for cancer screening programs.

Key messages

Proteostasis unbalance in prion diseases: Mechanisms of neurodegeneration and therapeutic targets

Transmissible spongiform encephalopathies (TSEs), or prion diseases, are progressive neurodegenerative disorders of the central nervous system that affect humans and animals as sporadic, inherited, and infectious forms. Similarly to Alzheimer's disease and other neurodegenerative disorders, any attempt to reduce TSEs' lethality or increase the life expectancy of affected individuals has been unsuccessful. Typically, the onset of symptoms anticipates the fatal outcome of less than 1 year, although it is believed to be the consequence of a decades-long process of neuronal death. The duration of the symptoms-free period represents by itself a major obstacle to carry out effective neuroprotective therapies. Prions, the infectious entities of TSEs, are composed of a protease-resistant protein named prion protein scrapie (PrP^Sc) from the prototypical TSE form that afflicts ovines. PrP^Sc misfolding from its physiological counterpart, cellular prion protein (PrP^C), is the unifying pathogenic trait of all TSEs. PrP^Sc is resistant to intracellular turnover and undergoes amyloid-like fibrillation passing through the formation of soluble dimers and oligomers, which are likely the effective neurotoxic entities. The failure of PrP^Sc removal is a key pathogenic event that defines TSEs as proteopathies, likewise other neurodegenerative disorders, including Alzheimer's, Parkinson's, and Huntington's disease, characterized by alteration of proteostasis. Under physiological conditions, protein quality control, led by the ubiquitin-proteasome system, and macroautophagy clears cytoplasm from improperly folded, redundant, or aggregation-prone proteins. There is evidence that both of these crucial homeostatic pathways are impaired during the development of TSEs, although it is still unclear whether proteostasis alteration facilitates prion protein misfolding or, rather, PrP^Sc protease resistance hampers cytoplasmic protein quality control. This review is aimed to critically analyze the most recent advancements in the cause-effect correlation between PrP^C misfolding and proteostasis alterations and to discuss the possibility that pharmacological restoring of ubiquitin-proteasomal competence and stimulation of autophagy could reduce the intracellular burden of PrP^Sc and ameliorate the severity of prion-associated neurodegeneration.

N6-Isopentenyladenosine Hinders the Vasculogenic Mimicry in Human Glioblastoma Cells through Src-120 Catenin Pathway Modulation and RhoA Activity Inhibition

BACKGROUND

Vasculogenic mimicry (VM) is a functional microcirculation pattern formed by aggressive tumor cells. Thus far, no effective drugs have been developed to target VM. Glioblastoma (GBM) is the most malignant form of brain cancer and is a highly vascularized tumor. Vasculogenic mimicry represents a means whereby GBM can escape anti-angiogenic therapies.

METHODS

Here, using an in vitro tube formation assay on Matrigel, we evaluated the ability of N6-isopentenyladenosine (iPA) to interfere with vasculogenic mimicry (VM). RhoA activity was assessed using a pull-down assay, while the modulation of the adherens junctions proteins was analyzed by Western blot analysis.

RESULTS

We found that iPA at sublethal doses inhibited the formation of capillary-like structures suppressing cell migration and invasion of U87MG, U343MG, and U251MG cells, of patient-derived human GBM cells and GBM stem cells. iPA reduces the vascular endothelial cadherin (VE-cadherin) expression levels in a dose-dependent manner, impairs the vasculogenic mimicry network by modulation of the Src/p120-catenin pathway and inhibition of RhoA-GTPase activity.

CONCLUSIONS

Taken together, our results revealed iPA as a promising novel anti-VM drug in GBM clinical therapeutics.

Global health challenges: Are future physicians prepared? The results of a 4 years training experience

Background

Current health challenges are highlighting as Global Health (GH) is a discipline of growing importance for future physicians. Although its training is globally recommended, it has not universally entered the curricula of degree courses in Medicine and Surgery. A cycle of 6 seminars in global health has been promoted by researchers and public health residents of the Center for Research and Studies in GH of the Università Cattolica del Sacro Cuore (UCSC) in Rome, and offered for 4 consecutive years to medical students attending the UCSC.

Objectives and Methods

Main goal was increasing students knowledge and awareness in global health issues exploring their needs and perceptions about the impact of the topic on their future career. Two-hours frontal lessons held by experts and practical sessions (PBL) facilitated by promoters were planned on topics as determinants and inequalities in health, UHC, fragile and vulnerable population as migrants and victims of violence, SDGs, AIDS and emerging infectious diseases,international cooperation, maternal-child health. A pre-course, single event and post-course questionnaire was administered to participants.

Results

A mean of 48 students (± 15.7SD), 66.7% females, attending mainly the second(40.4%) and the third year (39%), joined each event. The analysis of the pre-course questionnaire has highlighted students' interest in healthcare inequalities, pandemics, migration, health in developing countries, healthcare systems. At the end, 92% of participants has considered the course interesting, 87% stated that the topic should be part of the degree course and 78% that it will influence their career. The methodology was considered adequate in 94% of cases underlining its strong incentive to work in team.

Conclusions

The strong interest of medical students in acquiring skills in global health seems to firmly encourage its inclusion and strengthening in study plans to prepare them properly to face the future challenges in health.

Key messages

Medical students consider the global health training relevant for their career encouraging its inclusion in the Medicine and Surgery curriculum. Practical sessions and team work could be useful tools to adequately train the future health workforce.

Experimental Evidence and Clinical Implications of Pituitary Adenoma Stem Cells

Pituitary adenomas, accounting for 15% of diagnosed intracranial neoplasms, are usually benign and pharmacologically and surgically treatable; however, the critical location, mass effects and hormone hypersecretion sustain their significant morbidity. Approximately 35% of pituitary tumors show a less benign course since they are highly proliferative and invasive, poorly resectable, and likely recurring. The latest WHO classification of pituitary tumors includes pituitary transcription factor assessment to determine adenohypophysis cell lineages and accurate designation of adenomas, nevertheless little is known about molecular and cellular pathways which contribute to pituitary tumorigenesis. In malignant tumors the identification of cancer stem cells radically changed the concepts of both tumorigenesis and pharmacological approaches. Cancer stem cells are defined as a subset of undifferentiated transformed cells from which the bulk of cancer cells populating a tumor mass is generated. These cells are able to self-renew, promoting tumor progression and recurrence of malignant tumors, also conferring cytotoxic drug resistance. On the other hand, the existence of stem cells within benign tumors is still debated. The presence of adult stem cells in human and murine pituitaries where they sustain the high plasticity of hormone-producing cells, allowed the hypothesis that putative tumor stem cells might exist in pituitary adenomas, reinforcing the concept that the cancer stem cell model could also be applied to pituitary tumorigenesis. In the last few years, the isolation and phenotypic characterization of putative pituitary adenoma stem-like cells was performed using a wide and heterogeneous variety of experimental models and techniques, although the role of these cells in adenoma initiation and progression is still not completely definite. The assessment of possible pituitary adenoma-initiating cell population would be of extreme relevance to better understand pituitary tumor biology and to identify novel potential diagnostic markers and pharmacological targets. In this review, we summarize the most updated studies focused on the definition of pituitary adenoma stem cell phenotype and functional features, highlighting the biological processes and intracellular pathways potentially involved in driving tumor growth, relapse, and therapy resistance.

Emerging Role of Cellular Prion Protein in the Maintenance and Expansion of Glioma Stem Cells

Cellular prion protein (PrP^C) is a membrane-anchored glycoprotein representing the physiological counterpart of PrP scrapie (PrP^Sc), which plays a pathogenetic role in prion diseases. Relatively little information is however available about physiological role of PrP^C. Although PrP^C ablation in mice does not induce lethal phenotypes, impairment of neuronal and bone marrow plasticity was reported in embryos and adult animals. In neurons, PrP^C stimulates neurite growth, prevents oxidative stress-dependent cell death, and favors antiapoptotic signaling. However, PrP^C activity is not restricted to post-mitotic neurons, but promotes cell proliferation and migration during embryogenesis and tissue regeneration in adult. PrP^C acts as scaffold to stabilize the binding between different membrane receptors, growth factors, and basement proteins, contributing to tumorigenesis. Indeed, ablation of PrP^C expression reduces cancer cell proliferation and migration and restores cell sensitivity to chemotherapy. Conversely, PrP^C overexpression in cancer stem cells (CSCs) from different tumors, including gliomas—the most malignant brain tumors—is predictive for poor prognosis, and correlates with relapses. The mechanisms of the PrP^C role in tumorigenesis and its molecular partners in this activity are the topic of the present review, with a particular focus on PrP^C contribution to glioma CSCs multipotency, invasiveness, and tumorigenicity.

Mobile clinic approach towards hard-to-reach populations’ health in Roman suburban settings

Key messages

Mobile clinics can close the gap between health services and disadvantaged children and hard-to-reach populations. Outreach can be a mean of promotion, prevention and health services inclusion.

Asylum seekers’ healthcare in Italy: policies and practices among different regions

Background

The Italian law provides for international protection and universal health-care coverage for asylum seekers (AS). Indeed, they are entitled to be regularly registered at the National Healthcare Service. Before submitting the application for refugee status, medical assistance to migrants is up to local administration. Our aim was to describe and compare policies and protocols regulating AS healthcare from their arrival to their application for refugee status, at national and regional level. Moreover, we investigated the daily healthcare practice addressing potential gaps between policies and practice.

Methods

The research team is a subgroup of the Inequality working group of the Italian hygiene society and it is composed of public health residents. The research involved also local health workers and other professionals belonging to regional groups of Italian migrant medicine society (SIMM). We collected national, regional and local policies and protocols and we compared them using a specific framework. Furthermore, we achieved a mapping of daily practice implementation at local health organization (LHO) level using a checklist.

Results

The most relevant findings were that regional policies themselves vary notably from each other and, as regard practices, LHO implement differently the same regional legislation. Furthermore, we found some critical issues: the delayed inclusion in primary care assistance and lack of continuity of care and of a computerized system of recording information.

Conclusions

The lack of uniformity concerning policies and practices of AS healthcare might also result in unawareness and uncertainty about how to access to healthcare services by migrants. An enhanced cooperation between groups dealing with migrants’ issues may lead to avoid variability at the implementation. Finally, a computerized system for data collection might facilitate the continuity of care and the assessment of the real health needs of the AS population.

Key messages

It is a priority challenge for health systems to strengthen the interventions aimed at overcoming the linguistic, economic, cultural and administrative barriers to the health services access. It is crucial to improve the recording information system to detect the real health needs of AS, their change and the inequalities in access and to improve collaboration between groups and university.

An Italian pilot study of a psycho-social intervention to support family caregivers' engagement in taking care of patients with complex care needs: the Engage-in-Caring project

BACKGROUND

The raising of disability and chronic illness burden among European population is calling for a new paradigm of care, focused on primary health care interventions. Engage-In-Caring is a novel multicomponent intervention clearly dedicated to improve family caregiver engagement in the care of patients with complex care needs, by supporting them to develop a stronger consciousness of their role, needs and skills.

METHOD

Engage-In-Caring intervention's efficacy and feasibility have been evaluated through a single arm pre-post observational pilot study settled in Rome. A qualitative phase, consisting of literature analysis of caregivers' unmet needs and a final revision from an experts' group, led to the structuration of the intervention, following the Caregiver Health Engagement Model (CHE-Model). Afterwards, a quantitative phase allowed understanding the feasibility of the intervention through Kruskal-Wallis test on a sample of 47 caregivers.

RESULTS

Results showed a reduction of the physical burden (Chi Squared = 6,483; p = .01) perceived by the caregivers and increase of the health literacy (Chi Squared = 3,560; p = .059) after the intervention.

CONCLUSIONS

Feasibility tests on caregivers of patients with complex care needs are promising: this pilot study suggests a first effectiveness evidence, particularly concerning aspects related to burden perception and improvements in health literacy. Randomised controlled trials on larger samples are needed.

Autophagy Activator Drugs: A New Opportunity in Neuroprotection from Misfolded Protein Toxicity

The aim of this review is to critically analyze promises and limitations of pharmacological inducers of autophagy against protein misfolding-associated neurodegeneration. Effective therapies against neurodegenerative disorders can be developed by regulating the “self-defense” equipment of neurons, such as autophagy. Through the degradation and recycling of the intracellular content, autophagy promotes neuron survival in conditions of trophic factor deprivation, oxidative stress, mitochondrial and lysosomal damage, or accumulation of misfolded proteins. Autophagy involves the activation of self-digestive pathways, which is different for dynamics (macro, micro and chaperone-mediated autophagy), or degraded material (mitophagy, lysophagy, aggrephagy). All neurodegenerative disorders share common pathogenic mechanisms, including the impairment of autophagic flux, which causes the inability to remove the neurotoxic oligomers of misfolded proteins. Pharmacological activation of autophagy is typically achieved by blocking the kinase activity of mammalian target of rapamycin (mTOR) enzymatic complex 1 (mTORC1), removing its autophagy suppressor activity observed under physiological conditions; acting in this way, rapamycin provided the first proof of principle that pharmacological autophagy enhancement can induce neuroprotection through the facilitation of oligomers’ clearance. The demand for effective disease-modifying strategies against neurodegenerative disorders is currently stimulating the development of a wide number of novel molecules, as well as the re-evaluation of old drugs for their pro-autophagic potential.

Effects of Prion Protein on Aβ42 and Pyroglutamate-Modified AβpΕ3-42 Oligomerization and Toxicity

Soluble Aβ oligomers are widely recognized as the toxic forms responsible for triggering AD, and Aβ receptors are hypothesized to represent the first step in a neuronal cascade leading to dementia. Cellular prion protein (PrP) has been reported as a high-affinity binder of Aβ oligomers. The interactions of PrP with both Aβ42 and the highly toxic N-truncated pyroglutamylated species (AβpE3-42) are here investigated, at a molecular level, by means of ThT fluorescence, NMR and TEM. We demonstrate that soluble PrP binds both Aβ42 and AβpE3-42, preferentially interacting with oligomeric species and delaying fibril formation. Residue level analysis of Aβ42 oligomerization process reveals, for the first time, that PrP is able to differently interact with the forming oligomers, depending on the aggregation state of the starting Aβ42 sample. A distinct behavior is observed for Aβ42 1-30 region and C-terminal residues, suggesting that PrP protects Aβ42 N-tail from entangling on the mature NMR-invisible fibril, consistent with the hypothesis that Aβ42 N-tail is the locus of interaction with PrP. PrP/AβpE3-42 interactions are here reported for the first time. All interaction data are validated and complemented by cellular tests performed on Wt and PrP-silenced neuronal cell lines, clearly showing PrP dependent Aβ oligomer cell internalization and toxicity. The ability of soluble PrP to compete with membrane-anchored PrP for binding to Aβ oligomers bears relevance for studies of druggable pathways.

Pharmacological activation of autophagy favors the clearing of intracellular aggregates of misfolded prion protein peptide to prevent neuronal death

According to the “gain-of-toxicity mechanism”, neuronal loss during cerebral proteinopathies is caused by accumulation of aggregation-prone conformers of misfolded cellular proteins, although it is still debated which aggregation state actually corresponds to the neurotoxic entity. Autophagy, originally described as a variant of programmed cell death, is now emerging as a crucial mechanism for cell survival in response to a variety of cell stressors, including nutrient deprivation, damage of cytoplasmic organelles, or accumulation of misfolded proteins. Impairment of autophagic flux in neurons often associates with neurodegeneration during cerebral amyloidosis, suggesting a role in clearing neurons from aggregation-prone misfolded proteins. Thus, autophagy may represent a target for innovative therapies. In this work, we show that alterations of autophagy progression occur in neurons following in vitro exposure to the amyloidogenic and neurotoxic prion protein-derived peptide PrP90-231. We report that the increase of autophagic flux represents a strategy adopted by neurons to survive the intracellular accumulation of misfolded PrP90-231. In particular, PrP90-231 internalization in A1 murine mesencephalic neurons occurs in acidic structures, showing electron microscopy hallmarks of autophagosomes and autophagolysosomes. However, these structures do not undergo resolution and accumulate in cytosol, suggesting that, in the presence of PrP90-231, autophagy is activated but its progression is impaired; the inability to clear PrP90-231 via autophagy induces cytotoxicity, causing impairment of lysosomal integrity and cytosolic diffusion of hydrolytic enzymes. Conversely, the induction of autophagy by pharmacological  blockade of mTOR kinase or trophic factor deprivation restored autophagy resolution, reducing intracellular PrP90-231 accumulation and neuronal death. Taken together, these data indicate that PrP90-231 internalization induces an autophagic defensive response in A1 neurons, although incomplete and insufficient to grant survival; the pharmacological enhancement of this process exerts neuroprotection favoring the clearing of the internalized peptide and could represents a promising neuroprotective tool for neurodegenerative proteinopathies.

In vitro and in vivo characterization of stem-like cells from canine osteosarcoma and assessment of drug sensitivity

Cancer stem cell (CSC) self-renewing and drug resistance cause treatment failure and tumor recurrence. Osteosarcoma is an aggressive bone tumor characterized by biological and molecular heterogeneity, possibly dependent on CSCs. CSC identification in osteosarcoma and their efficient targeting are still open questions. Spontaneous canine osteosarcoma shares clinical and biological features with the human tumors, representing a model for translational studies. We characterized three CSC-enriched canine osteosarcoma cultures. In serum-free conditions, these CSC cultures grow as anchorage-independent spheroids, show mesenchymal-like properties and in vivo tumorigenicity, recapitulating the heterogeneity of the original osteosarcoma. Osteosarcoma CSCs express stem-related factors (Sox2, Oct4, CD133) and chemokine receptors and ligands (CXCR4, CXCL12) involved in tumor proliferation and self-renewal. Standard drugs for osteosarcoma treatment (doxorubicin and cisplatin) affected CSC-enriched and parental primary cultures, showing different efficacy within tumors. Moreover, metformin, a type-2 diabetes drug, significantly inhibits osteosarcoma CSC viability, migration and self-renewal and, in co-treatment with doxorubicin and cisplatin, enhances drug cytotoxicity. Collectively, we demonstrate that canine osteosarcoma primary cultures contain CSCs exhibiting distinctive sensitivity to anticancer agents, as a reliable experimental model to assay drug efficacy. We also provide proof-of-principle of metformin efficacy, alone or in combination, as pharmacological strategy to target osteosarcoma CSCs.

Different Effects of Human Umbilical Cord Mesenchymal Stem Cells on Glioblastoma Stem Cells by Direct Cell Interaction or Via Released Soluble Factors

Glioblastoma (GBM), the most common primary brain tumor in adults, is an aggressive, fast-growing and highly vascularized tumor, characterized by extensive invasiveness and local recurrence. In GBM and other malignancies, cancer stem cells (CSCs) are believed to drive invasive tumor growth and recurrence, being responsible for radio- and chemo-therapy resistance. Mesenchymal stem cells (MSCs) are multipotent progenitors that exhibit tropism for tumor microenvironment mediated by cytokines, chemokines and growth factors. Initial studies proposed that MSCs might exert inhibitory effects on tumor development, although, to date, contrasting evidence has been provided. Different studies reported either MSC anti-tumor activity or their support to tumor growth. Here, we examined the effects of umbilical cord (UC)-MSCs on in vitro GBM-derived CSC growth, by direct cell-to-cell interaction or indirect modulation, via the release of soluble factors. We demonstrate that UC-MSCs and CSCs exhibit reciprocal tropism when co-cultured as 3D spheroids and their direct cell interaction reduces the proliferation of both cell types. Contrasting effects were obtained by UC-MSC released factors: CSCs, cultured in the presence of conditioned medium (CM) collected from UC-MSCs, increased proliferation rate through transient ERK1/2 and Akt phosphorylation/activation. Analysis of the profile of the cytokines released by UC-MSCs in the CM revealed a strong production of molecules involved in inflammation, angiogenesis, cell migration and proliferation, such as IL-8, GRO, ENA-78 and IL-6. Since CXC chemokine receptor 2 (CXCR2), a receptor shared by several of these ligands, is expressed in GBM CSCs, we evaluated its involvement in CSC proliferation induced by UC-MSC-CM. Using the CXCR2 antagonist SB225002, we observed a partial but statistically significant inhibition of CSC proliferation and migration induced by the UC-MSC-released cytokines. Conversely, CXCR2 blockade did not reduce the reciprocal tropism between CSCs and UC-MSCs grown as spheroids. In conclusion, we show that direct (cell-to-cell contact) or indirect (via the release of soluble factors) interactions between GBM CSCs and UC-MSCs in co-culture produce divergent effects on cell growth, invasion and migration, with the former mainly causing an inhibitory response and the latter a stimulatory one, involving a paracrine activation of CXCR2.

A critical concentration of N-terminal pyroglutamylated amyloid beta drives the misfolding of Ab1-42 into more toxic aggregates

A wide consensus based on robust experimental evidence indicates pyroglutamylated amyloid-β isoform (AβpE3-42) as one of the most neurotoxic peptides involved in the onset of Alzheimer's disease. Furthermore, AβpE3-42 co-oligomerized with excess of Aβ1-42, produces oligomers and aggregates that are structurally distinct and far more cytotoxic than those made from Aβ1-42 alone. Here, we investigate quantitatively the influence of AβpE3-42 on biophysical properties and biological activity of Aβ1-42. We tested different ratios of AβpE3-42/Aβ1-42 mixtures finding a correlation between the biological activity and the structural conformation and morphology of the analyzed mixtures. We find that a mixture containing 5% AβpE3-42, induces the highest disruption of intracellular calcium homeostasis and the highest neuronal toxicity. These data correlate to an high content of relaxed antiparallel β-sheet structure and the coexistence of a population of big spheroidal aggregates together with short fibrils. Our experiments provide also evidence that AβpE3-42 causes template-induced misfolding of Aβ1-42 at ratios below 33%. This means that there exists a critical concentration required to have seeding on Aβ1-42 aggregation, above this threshold, the seed effect is not possible anymore and AβpE3-42 controls the total aggregation kinetics.

Canine osteosarcoma cell lines contain stem-like cancer cells: biological and pharmacological characterization

Cancer stem cells (CSCs) represent a small subpopulation of cells responsible for tumor formation and progression, drug resistance, tumor recurrence and metastasization. CSCs have been identified in many human tumors including osteosarcoma (OSA). CSC distinctive properties are the expression of stem cell markers, sustained growth, self-renewal and tumorigenicity. Here we report the isolation of stem-like cells from two canine OSA cultures, characterized by self-renewal, evaluated by sphere formation ability, differential marker expression, and in vitro proliferation when cultured in a medium containing EGF and bFGF. Current therapies for OSA increased survival time, but prognosis remains poor, due to the development of drug resistance and metastases. Chemotherapy shrinks the tumor mass but CSCs remain unaffected, leading to tumor recurrence. Metformin, a drug for type 2 diabetes, has been shown to possess antitumor properties affecting CSC survival in different human and animal cancers. Here we show that metformin has a significant antiproliferative effect on canine OSA stem-like cells, validating this in vitro model for further pre-clinical drug evaluations. In conclusion, our results demonstrate the feasibility of obtaining CSC-enriched cultures from primary canine OSA cells as a promising model for biological and pharmacological studies of canine and human OSAs.

Combined microwave thermal ablation and liver resection for single step treatment of otherwise unresectable colorectal liver metastases; a monoistitutional experiences

OBJECTIVE

Over half of colorectal cancer patients will develop liver metastases.

BACKGROUND

Thermal ablation with or without associated liver resection for colorectal hepatic metastasis has been suggested as an alternative method to improve survival if radical surgical resection is not achievable. A retrospective case series of patients treated with microwave ablation(MWA) associated with hepatic resection in one step procedure, was reviewed to analyze the clinical outcome.

MATERIALS AND METHODS

In a group of 40 patients surgically cured for liver tumors in our Department, 5 patients with technically unresectable disease underwent combined treatment LR-MWA.

RESULTS

Four patients were treated with multiple segmentectomies and MWA and one patient received a left lobectomy (S2-S3) and MWA. Only 1 patient (20%) developed post surgical complication which was a liver abscess (grade II of Dindo classification).

CONCLUSIONS

Hepatic resection combined with MWA expanded indications for operative treatment of multiple bilobar liver metastasis. This procedure promise to have good long-term outcomes.

Emerging Targets in Pituitary Adenomas: Role of the CXCL12/CXCR4-R7 System

Chemokines are chemotactic regulators of immune surveillance in physiological and pathological conditions such as inflammation, infection, and cancer. Several chemokines and cognate receptors are constitutively expressed in the central nervous system, not only in glial and endothelial cells but also in neurons, controlling neurogenesis, neurite outgrowth, and axonal guidance during development. In particular, the chemokine CXCL12 and its receptors, CXCR4 and CXCR7, form a functional network that controls plasticity in different brain areas, influencing neurotransmission, neuromodulation, and cell migration, and the dysregulation of this chemokinergic axis is involved in several neurodegenerative, neuroinflammatory, and malignant diseases. CXCR4 primarily mediates the transduction of proliferative signals, while CXCR7 seems to be mainly responsible for scavenging CXCL12. Importantly, the multiple intracellular signalling generated by CXCL12 interaction with its receptors influences hypothalamic modulation of neuroendocrine functions, although a direct modulation of pituitary functioning via autocrine/paracrine mechanisms was also reported. Both CXCL12 and CXCR4 are constitutively overexpressed in pituitary adenomas and their signalling induces cell survival and proliferation, as well as hormonal hypersecretion. In this review we focus on the physiological and pathological functions of immune-related cyto- and chemokines, mainly focusing on the CXCL12/CXCR4-7 axis, and their role in pituitary tumorigenesis. Accordingly, we discuss the potential targeting of CXCR4 as novel pharmacological approach for pituitary adenomas.

Metformin selectively affects human glioblastoma tumor-initiating cell viability: A role for metformin-induced inhibition of Akt

Cancer stem cell theory postulates that a small population of tumor-initiating cells is responsible for the development, progression and recurrence of several malignancies, including glioblastoma. In this perspective, tumor-initiating cells represent the most relevant target to obtain effective cancer treatment. Metformin, a first-line drug for type II diabetes, was reported to possess anticancer properties affecting the survival of cancer stem cells in breast cancer models. We report that metformin treatment reduced the proliferation rate of tumor-initiating cell-enriched cultures isolated from four human glioblastomas. Metformin also impairs tumor-initiating cell spherogenesis, indicating a direct effect on self-renewal mechanisms. Interestingly, analyzing by FACS the antiproliferative effects of metformin on CD133-expressing subpopulation, a component of glioblastoma cancer stem cells, a higher reduction of proliferation was observed as compared with CD133-negative cells, suggesting a certain degree of cancer stem cell selectivity in its effects. In fact, glioblastoma cell differentiation strongly reduced sensitivity to metformin treatment. Metformin effects in tumor-initiating cell-enriched cultures were associated with a powerful inhibition of Akt-dependent cell survival pathway, while this pathway was not affected in differentiated cells. The specificity of metformin antiproliferative effects toward glioblastoma tumor-initiating cells was confirmed by the lack of significant inhibition of normal human stem cells (umbilical cord-derived mesenchymal stem cells) in vitro proliferation after metformin exposure. Altogether, these data clearly suggest that metformin exerts antiproliferative activity on glioblastoma cells, showing a higher specificity toward tumor-initiating cells, and that the inhibition of Akt pathway may represent a possible intracellular target of this effect.

Differential toxicity, conformation and morphology of typical initial aggregation states of Aβ1-42 and Aβpy3-42 beta-amyloids

Among the different species of water-soluble β-peptides (Aβ1-42, Aβ1-40 and N-terminal truncated Aβ-peptides), Aβpy3-42 is thought to play a relevant role in Alzheimer's pathogenesis due to its abundance, resistance to proteolysis, fast aggregation kinetics, dynamic structure and high neurotoxicity. To evaluate the specific structural characteristics and neurotoxicity of Aβpy3-42, we separated different aggregation states of Aβ1-42 and Aβpy3-42 using fast protein liquid chromatography, isolating in both cases three peaks that corresponded to sa (small), ma (medium) and la (large) aggregates. Conformational analysis, by circular dichroism showed a prevailing random coil conformation for sa and ma, and typical β-sheet conformation for la. AFM and TEM show differential structural features between the three aggregates of a given β-peptide and among the aggregate of the two β-peptides. The potential toxic effects of the different aggregates were evaluated using human neuroblastoma SH-SY5Y cells in the MTT reduction, in the xCELLigence System, and in the Annexin V binding experiments. In the case of Aβ1-42 the most toxic aggregate is la, while in the case of Aβpy3-42 both sa and la are equally toxic. Aβ aggregates were found to be internalized in the cells, as estimated by confocal immunofluorescence microscopy, with a higher effect observed for Aβpy3-42, showing a good correlation with the toxic effects. Together these experiments allowed the discrimination of the intermediate states more responsible of oligomer toxicity, providing new insights on the correlation between the aggregation process and the toxicity and confirming the peculiar role in the pathogenesis of Alzheimer disease of Aβpy3-42 peptide.

Excitotoxicity through NMDA receptors mediates cerebellar granule neuron apoptosis induced by prion protein 90-231 fragment

Prion diseases recognize, as a unique molecular trait, the misfolding of CNS-enriched prion protein (PrP(C)) into an aberrant isoform (PrP(Sc)). In this work, we characterize the in vitro toxicity of amino-terminally truncated recombinant PrP fragment (amino acids 90-231, PrP90-231), on rat cerebellar granule neurons (CGN), focusing on glutamatergic receptor activation and Ca(2+) homeostasis impairment. This recombinant fragment assumes a toxic conformation (PrP90-231(TOX)) after controlled thermal denaturation (1 h at 53 °C) acquiring structural characteristics identified in PrP(Sc) (enrichment in β-structures, increased hydrophobicity, partial resistance to proteinase K, and aggregation in amyloid fibrils). By annexin-V binding assay, and evaluation of the percentage of fragmented and condensed nuclei, we show that treatment with PrP90-231(TOX), used in pre-fibrillar aggregation state, induces CGN apoptosis. This effect was associated with a delayed, but sustained elevation of [Ca(2+)]i. Both CGN apoptosis and [Ca(2+)]i increase were not observed using PrP90-231 in PrP(C)-like conformation. PrP90-231(TOX) effects were significantly reduced in the presence of ionotropic glutamate receptor antagonists. In particular, CGN apoptosis and [Ca(2+)]i increase were largely reduced, although not fully abolished, by pre-treatment with the NMDA antagonists APV and memantine, while the AMPA antagonist CNQX produced a lower, although still significant, effect. In conclusion, we report that CGN apoptosis induced by PrP90-231(TOX) correlates with a sustained elevation of [Ca(2+)]i mediated by the activation of NMDA and AMPA receptors.

Calcium binding promotes prion protein fragment 90-231 conformational change toward a membrane destabilizing and cytotoxic structure

The pathological form of prion protein (PrP(Sc)), as other amyloidogenic proteins, causes a marked increase of membrane permeability. PrP(Sc) extracted from infected Syrian hamster brains induces a considerable change in membrane ionic conductance, although the contribution of this interaction to the molecular mechanism of neurodegeneration process is still controversial. We previously showed that the human PrP fragment 90-231 (hPrP₉₀₋₂₃₁) increases ionic conductance across artificial lipid bilayer, in a calcium-dependent manner, producing an alteration similar to that observed for PrP(Sc). In the present study we demonstrate that hPrP₉₀₋₂₃₁, pre-incubated with 10 mM Ca⁺⁺ and then re-suspended in physiological external solution increases not only membrane conductance but neurotoxicity as well. Furthermore we show the existence of a direct link between these two effects as demonstrated by a highly statistically significant correlation in several experimental conditions. A similar correlation between increased membrane conductance and cell degeneration has been observed assaying hPrP₉₀₋₂₃₁ bearing pathogenic mutations (D202N and E200K). We also report that Ca⁺⁺ binding to hPrP₉₀₋₂₃₁ induces a conformational change based on an alteration of secondary structure characterized by loss of alpha-helix content causing hydrophobic amino acid exposure and proteinase K resistance. These features, either acquired after controlled thermal denaturation or induced by D202N and E200K mutations were previously identified as responsible for hPrP₉₀₋₂₃₁ cytotoxicity. Finally, by in silico structural analysis, we propose that Ca⁺⁺ binding to hPrP₉₀₋₂₃₁ modifies amino acid orientation, in the same way induced by E200K mutation, thus suggesting a pathway for the structural alterations responsible of PrP neurotoxicity.

Recombinant human prion protein fragment 90-231, a useful model to study prion neurotoxicity

Transmissible spongiform encephalopathies (TSE), or prion diseases, are a group of fatal neurodegenerative disorders of animals and humans. Human diseases include Creutzfeldt-Jakob (CJD) and Gerstmann-Straussler-Scheinker (GSSD) diseases, fatal familial insomnia, and Kuru. Human and animal TSEs share a common histopathology with a pathognomonic triad: spongiform vacuolation of the grey matter, neuronal death, glial proliferation, and, more inconstantly, amyloid deposition. According to the "protein only" hypothesis, TSEs are caused by a unique post-translational conversion of normal, host-encoded, protease-sensitive prion protein (PrP(sen) or PrP(C)) to an abnormal disease-associated isoform (PrP(res) or PrP(Sc)). To investigate the molecular mechanism of neurotoxicity induced by PrP(Sc) we developed a protocol to obtain millimolar amounts of soluble recombinant polypeptide encompassing the amino acid sequence 90-231 of human PrP (hPrP90-231). This protein corresponds to the protease-resistant prion protein fragment that originates after amino-terminal truncation. Importantly, hPrP90-231 has a flexible backbone that, similar to PrP(C), can undergo to structural rearrangement. This peptide, structurally resembling PrP(C), can be converted in a PrP(Sc)-like conformation, and thus represents a valuable model to study prion neurotoxicity. In this article we summarized our experimental evidence on the molecular and structural mechanisms responsible of hPrP90-231 neurotoxicity on neuroectodermal cell line SHSY5Y and the effects of some PrP pathogen mutations identified in familial TSE.

Neurotoxic properties of the anabolic androgenic steroids nandrolone and methandrostenolone in primary neuronal cultures

Anabolic-androgenic steroid (AAS) abuse is associated with multiple neurobehavioral disturbances. The sites of action and the neurobiological sequels of AAS abuse are unclear at present. We investigated whether two different AASs, nandrolone and methandrostenolone, could affect neuronal survival in culture. The endogenous androgenic steroid testosterone was used for comparison. Both testosterone and nandrolone were neurotoxic at micromolar concentrations, and their effects were prevented by blockade of androgen receptors (ARs) with flutamide. Neuronal toxicity developed only over a 48-hr exposure to the steroids. The cell-impermeable analogues testosterone-BSA and nandrolone-BSA, which preferentially target membrane-associated ARs, were also neurotoxic in a time-dependent and flutamide-sensitive manner. Testosterone-BSA and nandrolone-BSA were more potent than their parent compounds, suggesting that membrane-associated ARs were the relevant sites for the neurotoxic actions of the steroids. Unlike testosterone and nandrolone, toxicity by methandrostenolone and methandrostenolone-BSA was insensitive to flutamide, but it was prevented by the glucocorticoid receptor (GR) antagonist RU-486. Methandrostenolone-BSA was more potent than the parent compound, suggesting that its toxicity relied on the preferential activation of putative membrane-associated GRs. Consistently with the evidence that membrane-associated GRs can mediate rapid effects, a brief challenge with methandrostenolone-BSA was able to promote neuronal toxicity. Activation of putative membrane steroid receptors by nontoxic (nanomolar) concentrations of either nandrolone-BSA or methandrostenolone-BSA became sufficient to increase neuronal susceptibility to the apoptotic stimulus provided by β-amyloid (the main culprit of AD). We speculate that AAS abuse might facilitate the onset or progression of neurodegenerative diseases not usually linked to drug abuse.

High hydrophobic amino acid exposure is responsible of the neurotoxic effects induced by E200K or D202N disease-related mutations of the human prion protein

Mutations in prion protein are thought to be causative of inherited prion diseases favoring the spontaneous conversion of the normal prion protein into the scrapie-like pathological prion protein. We previously reported that, by controlled thermal denaturation, human prion protein fragment 90-231 acquires neurotoxic properties when transformed in a β-rich conformation, resembling the scrapie-like conformation. In this study we generated prion protein fragment 90-231 bearing mutations identified in familial prion diseases (D202N and E200K), to analyze their role in the induction of a neurotoxic conformation. Prion protein fragment 90-231(wild type) and the D202N mutant were not toxic in native conformation but induced cell death only after thermal denaturation. Conversely, prion protein fragment 90-231(E200K) was highly toxic in its native structure, suggesting that E200K mutation per se favors the acquisition of a peptide neurotoxic conformation. To identify the structural determinants of prion protein fragment 90-231 toxicity, we show that while the wild type peptide is structured in α-helix, hPrP90-231 E200K is spontaneously refolded in a β-structured conformer characterized by increased proteinase K resistance and propensity to generate fibrils. However, the most significant difference induced by E200K mutation in prion protein fragment 90-231 structure in native conformation we observed, was an increase in the exposure of hydrophobic amino-acids on protein surface that was detected in wild type and D202N proteins only after thermal denaturation. In conclusion, we propose that increased hydrophobicity is one of the main determinants of toxicity induced by different mutations in prion protein-derived peptides.

The interaction of humic substances with the human prion protein fragment 90-231 affects its protease K resistance and cell internalization

In this paper we analyzed the determinants and the structural effects of the interaction of human prion protein fragment 90-231 (HuPrP) with humic substances, (HS) including humic (HA) and fulvic (FA) acids, natural refractory organic polyanions widely diffused in soils and waters. We show that this interaction is mainly driven by non-specific electrostatic attraction involving regions situated within alpha-helix A and beta-sheet S1 of human PrP. FA binding to HuPrP altered its ability to acquire some PrPSc-like characteristics induced by the mild thermal denaturation of the peptide (1 h at 53 degrees C). In particular, in the presence of FA, HuPrP shows a reduced amount of beta-sheet content (as demonstrated by the reduced binding of thioflavin T), an increased sensitivity to protease K and an inhibition of the entering in the fibrillogenic pathway. FA/HuPrP interaction caused the aggregation of the peptide in unstructured macrocomplexes, as demonstrated by the altered electrophoretic migration in semi-denaturing detergent-agarose gel assay. Importantly, in the presence of FA the rate of internalization of HuPrP in human neuroblastoma cells was significantly reduced as compared to that of the beta-structured peptide. Therefore, HS inhibited the acquisition of PrP(Sc)-like structural properties that, in turn, are responsible for HuPrP intracellular accumulation and lead to neuronal death. Important implications of these data are that HuPrP-HS complexes, being unable to be internalized in living cells may represent a molecular mechanism for the reduced transmission of prion transmission from HS-rich soil also in the presence of contamination from infected animals.

Dual modulation of ERK1/2 and p38 MAP kinase activities induced by minocycline reverses the neurotoxic effects of the prion protein fragment 90-231

Several in vitro and in vivo studies addressed the identification of molecular determinants of the neuronal death induced by PrP(Sc) or related peptides. We developed an experimental model to assess PrP(Sc) neurotoxicity using a recombinant polypeptide encompassing amino acids 90-231 of human PrP (hPrP90-231) that corresponds to the protease-resistant core of PrP(Sc) identified in prion-infected brains. By means of mild thermal denaturation, we can convert hPrP90-231 from a PrP(C)-like conformation into a PrP(Sc)-like structure. In virtue of these structural changes, hPrP90-231 powerfully affected the survival of SH-SY5Y cells, inducing caspase 3 and p38-dependent apoptosis, while in the native alpha-helix-rich conformation, hPrP90-231 did not induce cell toxicity. The aim of this study was to identify drugs able to block hPrP90-231 neurotoxic effects, focusing on minocycline, a tetracycline with known neuroprotective activity. hPrP90-231 caused a caspase 3-dependent apoptosis via the blockade of ERK1/2 activation and the subsequent activation of p38 MAP kinase. We propose that hPrP90-231-induced apoptosis is dependent on the inhibition of ERK1/2 responsiveness to neurotrophic factors, removing a tonic inhibition of p38 activity and resulting in caspase 3 activation. Minocycline prevented hPrP90-231-induced toxicity interfering with this mechanism: the pretreatment with this tetracycline restored ERK1/2 activity and reverted p38 and caspase 3 activities. The effects of minocycline were not mediated by the prevention of hPrP90-231 structural changes or cell internalization (differently from Congo Red). In conclusion, minocycline elicits anti-apoptotic effects against the neurotoxic activity of hPrP90-231 and these effects are mediated by opposite modulation of ERK1/2 and p38 MAP kinase activities.

ERK1/2 and p38 MAP kinases control prion protein fragment 90-231-induced astrocyte proliferation and microglia activation

Astrogliosis and microglial activation are a common feature during prion diseases, causing the release of chemoattractant and proinflammatory factors as well as reactive free radicals, involved in neuronal degeneration. The recombinant protease-resistant domain of the prion protein (PrP90-231) displays in vitro neurotoxic properties when refolded in a beta-sheet-rich conformer. Here, we report that PrP90-231 induces the secretion of several cytokines, chemokines, and nitric oxide (NO) release, in both type I astrocytes and microglial cells. PrP90-231 elicited in both cell types the activation of ERK1/2 MAP kinase that displays, in astrocytes, a rapid kinetics and a proliferative response. Conversely, in microglia, PrP90-231-dependent MAP kinase activation was delayed and long lasting, inducing functional activation and growth arrest. In microglial cells, NO release, dependent on the expression of the inducible NO synthase (iNOS), and the secretion of the chemokine CCL5 were Ca(2+) dependent and under the control of the MAP kinases ERK1/2 and p38: ERK1/2 inhibition, using PD98059, reduced iNOS expression, while p38 blockade by PD169316 inhibited CCL5 release. In summary, we demonstrate that glial cells are activated by extracellular misfolded PrP90-231 resulting in a proliferative/secretive response of astrocytes and functional activation of microglia, both dependent on MAP kinase activation. In particular, in microglia, PrP90-231 activated a complex signalling cascade involved in the regulation of NO and chemokine release. These data argue in favor of a causal role for misfolded prion protein in sustaining glial activation and, possibly, glia-mediated neuronal death.

Intracellular accumulation of a mild-denatured monomer of the human PrP fragment 90-231, as possible mechanism of its neurotoxic effects

Because of high tendency of the prion protein (PrP) to aggregate, the exact PrP isoform responsible for prion diseases as well as the pathological mechanism that it activates remains still controversial. In this study, we show that a pre-fibrillar, monomeric or small oligomeric conformation of the human PrP fragment 90-231 (hPrP90-231), rather than soluble or fibrillar large aggregates, represents the neurotoxic species. In particular, we demonstrate that monomeric mild-denatured hPrP90-231 (incubated for 1 h at 53 degrees C) induces SH-SY5Y neuroblastoma cell death, while, when structured in large aggregates, it is ineffective. Using spectroscopic and cellular techniques we demonstrate that this toxic conformer is characterized by a high exposure of hydrophobic regions that favors the intracellular accumulation of the protein. Inside the cells hPrP90-231 is mainly compartmentalized into the lysosomes where it may trigger pro-apoptotic 'cell death' signals. The PrP toxic conformation, which we have obtained inducing a controlled in vitro conformational change of the protein, might mimic mild-unfolding events occurring in vivo, in the presence of specific mutations, oxidative reactions or proteolysis. Thus, in light of this model, we propose that novel therapeutic strategies, designed to inhibit the interaction of the toxic PrP with the plasmamembrane, could be beneficial to prevent the formation of intracellular neurotoxic aggregates and ultimately the neuronal death.

Amyloid precursor protein and presenilin involvement in cell signaling

To date the most relevant role for the amyloid precursor protein (APP) and for the presenilins (PSs) on Alzheimer's disease (AD) genesis is linked to the 'amyloid hypothesis', which considers an aberrant formation of amyloid-beta peptides the cause of neurodegeneration. In this view, APP is merely a substrate, cleaved by the gamma-secretase complex to form toxic amyloid peptides, PSs are key players in gamma-secretase complex, and corollary or secondary events are Tau-linked pathology and gliosis. A second theory, complementary to the amyloid hypothesis, proposes that APP and PSs may modulate a yet unclear cell signal, the disruption of which may induce cell-cycle abnormalities, neuronal death, eventually amyloid formation and finally dementia. This hypothesis is supported by the presence of a complex network of proteins, with a clear relevance for signal transduction mechanisms, which interact with APP or PSs. In this scenario, the C-terminal domain of APP has a pivotal role due to the presence of the 682YENPTY687 motif that represents the docking site for multiple interacting proteins involved in cell signaling. In this review we discuss the significance of novel findings related to cell signaling events modulated by APP and PSs for AD development.

Different structural stability and toxicity of PrP(ARR) and PrP(ARQ) sheep prion protein variants

The polymorphisms at amino acid residues 136, 154, and 171 in ovine prion protein (PrP) have been associated with different susceptibility to scrapie: animals expressing PrP(ARQ) [PrP(Ala136/Arg154/Gln171)] show vulnerability, whereas those that express PrP(ARR) [PrP(Ala136/Arg154/Arg171)] are resistant to scrapie. The aim of this study was to evaluate the in vitro toxic effects of PrP(ARR) and PrP(ARQ) variants in relation with their structural characteristics. We show that both peptides cause cell death inducing apoptosis but, unexpectedly, the scrapie resistant PrP(ARR) form was more toxic than the scrapie susceptible PrP(ARQ) variant. Moreover, the alpha-helical conformation of PrP(ARR) was less stable than that of PrP(ARQ) and the structural determinants responsible of these different conformational stabilities were characterized by spectroscopic analysis. We observed that PrP toxicity was inversely related to protein structural stability, being the unfolded conformation more toxic than the native one. However, the PrP(ARQ) variant displays a higher propensity to form large aggregates than PrP(ARR). Interestingly, in the presence of small amounts of PrP(ARR), PrP(ARQ) aggregability was reduced to levels similar to that of PrP(ARR). Thus, in contrast to PrP(ARR) toxicity, scrapie transmissibility seems to reside in the more stable conformation of PrP(ARQ) that allows the formation of large amyloid fibrils.

Amyloid precursor protein modulates ERK-1 and -2 signaling

The amyloid precursor protein (APP) is a transmembrane protein with a short cytoplasmic tail whose physiological function is unclear, although it is well documented that the proteolytic processing of APP could influence the development of Alzheimer's disease (AD) through the formation of membrane-bound C-terminal fragments (CTFs) and of beta-amyloid peptides (Abeta). We have recently shown that tyrosine-phosphorylated APP and CTFs may interact with Grb2 and ShcA adaptor proteins and that this coupling occurs at a higher extent in AD subjects only. To study the interaction between APP or CTFs and ShcA/Grb2 and to investigate their molecular target we have used as experimental model two different cell lines: H4 human neuroglioma cells and APP/APLP null mouse embryonic fibroblast cells (MEFs). Here we show that in H4 cells APP interacts with Grb2; conversely in APP/APLP-null MEF cells this interaction is possible only after the reintroduction of human APP by transfection. We have also shown that in MEF cells the transfection of a plasmid encoding for human APP wild-type enhances the phosphorylation of ERK-1 and -2 as revealed by Western blotting and immunofluorescence experiments. Finally, also in H4 cells the overexpression of APP upregulates the levels of phospho-ERK-1 and -2. In summary our data suggest that APP may influence phospho-ERK-1 and -2 signaling through its binding with Grb2 and ShcA adaptors. The meaning of this event is not clear, but APP interaction with these adaptors could be relevant to regulate mitogenic pathway.

Characterization of the proapoptotic intracellular mechanisms induced by a toxic conformer of the recombinant human prion protein fragment 90-231

Prion diseases comprise a group of fatal neurodegenerative disorders that affect both animals and humans. The transition of the prion protein (PrP) from a mainly alpha-structured isoform (PrPC) to a prevalent beta-sheet-containing protein (PrPSc) is believed to represent a major pathogenetic mechanism in prion diseases. To investigate the linkage between PrP neurotoxicity and its conformation, we used a recombinant prion protein fragment corresponding to the amino acidic sequence 90-231 of human prion protein (hPrP90-231). Using thermal denaturation, we set up an experimental model to induce the process of conversion from PrPC to PrPSc. We report that partial thermal denaturation converts hPrP90-231 into a beta-sheet-rich isoform, displaying a temperature- and time-dependent conversion into oligomeric structures that share some physico-chemical characteristics with brain PrPSc. SH-SY5Y cells were chosen to characterize the potential neurotoxic effect of hPrP90-231 in its different structural conformations. We demonstrated that hPrP90-231 in beta-conformation, but not when alpha-structured, powerfully affected the survival of these cells. hPrP90-231 beta-structured caused DNA fragmentation and a significant increase in caspase-3 proteolytic activity (maximal effects+170%), suggesting the occurrence of apoptotic cell death. Finally, we investigated the involvement of MAP kinases in the regulation of beta-hPrP90-231-dependent apoptosis. We observed that the p38 MAP kinase blocker SB203580 prevented the apoptotic cell death evoked by hPrP90-231, and Western blot analysis revealed that the exposure of the cells to the peptide induced p38 phosphorylation. In conclusion, we demonstrate that the hPrP90-231 elicits proapoptotic activity when in beta-sheet-rich conformation and that this effect is mediated by p38 and caspase-3 activation.

Amino-terminally truncated prion protein PrP90-231 induces microglial activation in vitro

The conversion of the prion protein (PrP) into a protease-resistant isoform (PrP(Res)) is considered the pathogenic event responsible for prion encephalopathies. Microglia activation accompanies PrP(Res) deposition representing an early event in the progression of these diseases. It is now believed that microglial cells play a worsening, if not causative, role in prion-induced neuronal death, through the release of proinflammatory and neurotoxic molecules. Indeed, in vitro observations have demonstrated that PrP(Res) and the synthetic prion fragment PrP106-126 induce neuronal death by activating microglial to migrate in the lesion area and secrete cytokines. Recently, we and others have demonstrated that the recombinant peptide, corresponding to the protease-resistant portion of PrP encompassing the amino acids 90-231 (PrP90-231), when beta-structured, is toxic for neuronal cells, in vitro. Here we report that PrP90-231 induces activation of N9 microglial cells, characterized by cell proliferation arrest and increased secretion of different cytokines (RANTES, GCSF, and IL-12). Moreover, the treatment of N9 cells with PrP90-231 elicited inducible nitric oxide synthase (i-NOS) expression, nitric oxide release, and a delayed (15 min to 1 h of treatment) extracellular signal-regulated kinases 1/2 (ERK1/2) phosphorylation/activation. Although ERK1/2 is known to regulate proliferative and differentiative events, we show that its blockade, using the specific MEK inhibitor PD98059, did not prevent PrP90-231-induced inhibition of N9 cell proliferation. To our knowledge, this is the first evidence that a recombinant PrP(Res)-like peptide elicits microglial activation in vitro, thus representing a potentially important tool to develop possible therapeutic strategies to target prion-induced brain inflammation.

Amyloid precursor protein and Presenilin 1 interaction studied by FRET in human H4 cells

The mayor pathologic hallmarks of Alzheimer's disease (AD) are senile plaque and neurofibrillary tangles. Senile plaque are primarily made up of deposits of amyloid-beta protein, a proteolytic product derived from the amyloid precursor protein (APP). APP is a transmembrane protein detected into the endoplasmic reticulum, in the Golgi apparatus, at the cell surface, recycled by endocytosis to endosomes, whose physiological function is unclear. Presenilins (PS), are a component of gamma-secretase complex that cleave alpha-CTFs (carboxy-terminal fragment), or beta-CTFs, leaving 40 or 42 amino acids amyloid-beta peptides and 58 or 56 amino acids intracellular domains (AICD). Where the amyloid-beta peptides is generated is not clear. The study of APP-PS interaction in specific cell compartments provides a good opportunity to light upon the molecular mechanisms regulating the activity of the "gamma-secretase complex," and where beta-amyloid is generated. In our study we used a biophysical assay of protein proximity: fluorescence resonance energy transfer (FRET), that can provide information about molecular interactions when two proteins are in the close proximity (<10 nm), to examine the subcellular localization and interaction between APP and PS1 in human neuroglioma cells (H4). Confocal microscopic analysis reveals extensive colocalization in different cells' compartment, and centrosomal or microtubule organizing center (MTOC) localization of APP and PS1, but not necessarily a close molecular interaction. We used FRET to determine if APP and PS1 interact at the cell centrosome. FRET data suggest a close interaction between APP and PS1 in subcellular compartments and at the centrosome of H4 cells. Using this approach we show that APP and PS1 are closely associated in the centrosomes of the H4 cell.

SDF-1 Controls Pituitary Cell Proliferation through the Activation of ERK1/2 and the Ca2+-Dependent, Cytosolic Tyrosine Kinase Pyk2

Stromal cell-derived factor-1 (SDF-1) is a chemokine of the CXC subfamily that exerts its effects via CXCR4, a G-protein-coupled receptor. CXCR4 is often expressed by tumor cells, and its activation causes tumor cell proliferation. Using GH4C1 cells, here we show that SDF-1 induced cell proliferation in a dose-dependent manner. Thus, we evaluated the intracellular signaling involved in this effect. SDF-1 increased cytosolic [Ca2+] and activated Pyk2, ERK1/2, and BKCa channels. To correlate these intracellular effectors with the proliferative activity of SDF-1, we inhibited their activity using BAPTA-AM (Ca2+ chelator), PD98059 (MEK inhibitor), salicylate (Pyk2 inhibitor), and TEA (K+ channel blocker). All these compounds reverted SDF-1-induced proliferation, suggesting the involvement of multiple intracellular pathways. To identify a possible crosstalk and a molecular ordering among these pathways, we tested these antagonists on SDF-1-dependent activation of ERK1/2, Pyk2, and BKCa channels. We report that the inhibition of [Ca2+]i increase or the blockade of BKCa channel activity did not affect ERK1/2 activation by SDF-1; Pyk2 activation was purely Ca2+-dependent, not involving ERK1/2 or BKCa channels; and BKCa channel activity was antagonized by Pyk2 but not by ERK1/2 inhibitors. These data suggest that SDF-1-dependent increase of [Ca2+]i activates Pyk2, which, in turn, regulates BKCa channel activity. Conversely, ERK1/2 activation is an independent phenomenon. In conclusion, we demonstrate that SDF-1 induces proliferation of GH4C1 cells, suggesting that the activation of CXCR4 may represent a novel regulatory mechanism for pituitary cell proliferation which may contribute to pituitary adenoma development.

Conformation dependent pro-apoptotic activity of the recombinant human prion protein fragment 90-231

The transition of prion protein from a mainly alpha-structured isoform (PrPC) to a beta sheet-containing protein (PrPSc) represents a major pathogenetic mechanism in prion diseases. To study the role of PrP structural conformation in prion-dependent neurodegeneration, we analysed the neurotoxicity of PrP in alpha and beta conformations, using a recombinant protein encompassing amino acids 90-231 of the human PrP (hPrP90-231). Using controlled thermal denaturation (53 degrees C, 1h) we converted hPrP90-231 in a structural isoform displaying PrPSc-related characteristics: high beta sheet content, increased aggregability and a slight increase in the resistance to protease K. In virtue of these structural changes, hPrP90-231 powerfully affected the survival of SH-SY5Y cells, inducing a caspase-3 and p38- dependent apoptosis. Conversely, in the native alpha-helix-rich conformation, hPrP90-231 did not show significant cell toxicity. The relationship between the structural state of hPrP90-231 and its neurotoxicity was demonstrated, inducing the thermal denaturation of the peptide in the presence of Congo red that prevented both the transition of hPrP90-231 into a beta-rich isoform and the acquisition of toxic properties. In conclusion, we report that the toxicity of hPrP90-231 is dependent on its three-dimensional structure, as is supposed to occur for the pathogen PrP during TSE.

Chemokine Stromal Cell-Derived Factor 1α Induces Proliferation and Growth Hormone Release in GH4C1 Rat Pituitary Adenoma Cell Line through Multiple Intracellular Signals

We used GH4C1 cells as a model to study the effects of the chemokine stromal cell-derived factor 1 (SDF1) in pituitary functions. In these cells, SDF1alpha induced proliferation and growth hormone secretion, suggesting a possible regulatory role for this chemokine at pituitary level. We evaluated the intracellular signaling involved in these effects: SDF1alpha increased cytosolic [Ca(2+)] and activated Pyk2, extracellular signal-regulated kinases 1 and 2 (ERK1/2), and large-conductance Ca(2+)-activated K(+) channels (BK(Ca)) channels. To correlate these intracellular effectors with the proliferative and secretory effects, we inhibited their activity using BAPTA-AM (Ca(2+) chelator), 2'-amino-3'-methoxyflavone (PD98059; a mitogen-activated protein kinase kinase inhibitor), salicylate (Pyk2 inhibitor), and tetraethyl ammonium (K(+) channel blocker). All of these compounds reverted SDF1alpha-induced proliferation, suggesting the involvement of multiple intracellular pathways. Conversely, only BAPTA-AM reverted growth hormone secretion. To identify a possible cross-talk and a molecular ordering among these pathways, we tested these antagonists on SDF1alpha-dependent activation of ERK1/2, Pyk2, and BK(Ca) channels. From these experiments, we observed that the inhibition of [Ca(2+)](i) increase or BK(Ca) channel activity did not affect ERK1/2 activation by SDF1alpha; Pyk2 activation was purely Ca(2+)-dependent, not involving ERK1/2 or BK(Ca) channels; and BK(Ca) channel activity was antagonized by Pyk2 but not by ERK1/2 inhibitors. These data suggest that an SDF1alpha-dependent increase of [Ca(2+)](i) activates Pyk2, which in turn regulates BK(Ca) channel activity. Conversely, ERK1/2 activation is an independent phenomenon. In conclusion, we demonstrate that SDF1alpha causes both proliferation and growth hormone release from pituitary adenoma cells, suggesting that the activation of CXCR4 may represent a novel regulatory mechanism for growth hormone secretion and pituitary cell proliferation, which may contribute to pituitary adenoma development.

Identification of a conserved N-capping box important for the structural autonomy of the prion alpha 3-helix: the disease associated D202N mutation destabilizes the helical conformation

Peptides corresponding to three alpha helices present in the C-terminal region of the human prion protein have been synthesized and their structural autonomy analyzed by circular dichroism (CD) and NMR spectroscopy. The results obtained indicate that the protein fragment corresponding to the alpha 3-helix, in contrast to alpha 1 and alpha 2 peptides, shows a complete structural autonomy. The chemical shifts values found for NH and CHalpha resonance of the isolated alpha 3 peptide, formed by 30 aminoacid residues, were markedly and surprisingly similar to the corresponding values of the alpha 3-helix in the protein. The structural autonomy of the alpha 3-helix is profoundly determined by the presence of the conserved capping box and, in part, by the ionic bond formed between Glu200 and Lys204. On the basis of these observations a novel PrP consensus pattern, centered on the alpha 3-helix region, has been defined. The data indicate that this autonomous and highly conserved region of the PrPc likely plays a critical role in folding and stability. This gives an explanation of why many of pathogenic mutations occur in this part of the molecule, sharing relevant effects on the overall protein conformation. In particular the D202N capping mutation almost completely destabilizes the isolated alpha 3 peptide. While it is well known that the D202N substitution is associated with a GSS disease, the possible structural basis of this fatal pathology has never been investigated. We propose that a lower alpha 3-helical propensity leading to a major destabilization of the PrPc molecule initiates the pathogenic process associated with D202N capping mutation.