Effects of hypoxia and hyperoxia on the differential expression of VEGF-A isoforms and receptors in Idiopathic Pulmonary Fibrosis (IPF)

Dysregulation of VEGF-A bioavailability has been implicated in the development of lung injury/fibrosis, exemplified by Idiopathic Pulmonary Fibrosis (IPF). VEGF-A is a target of the hypoxic response via its translational regulation by HIF-1α. The role of hypoxia and hyperoxia in the development and progression of IPF has not been explored. In normal lung (NF) and IPF-derived fibroblasts (FF) VEGF-A_xxxa protein expression was upregulated by hypoxia, mediated through activation of VEGF-A_xxxa gene transcription. VEGF-A receptors and co-receptors were differentially expressed by hypoxia and hyperoxia. Our data supports a potential role for hypoxia, hyperoxia and VEGF-A_xxxa isoforms as drivers of fibrogenesis.

Differential Expression of VEGF-Axxx Isoforms Is Critical for Development of Pulmonary Fibrosis

RATIONALE

Fibrosis after lung injury is related to poor outcome, and idiopathic pulmonary fibrosis (IPF) can be regarded as an exemplar. Vascular endothelial growth factor (VEGF)-A has been implicated in this context, but there are conflicting reports as to whether it is a contributory or protective factor. Differential splicing of the VEGF-A gene produces multiple functional isoforms including VEGF-A₁₆₅a and VEGF-A₁₆₅b, a member of the inhibitory family. To date there is no clear information on the role of VEGF-A in IPF.

OBJECTIVES

To establish VEGF-A isoform expression and functional effects in IPF.

METHODS

We used tissue sections, plasma, and lung fibroblasts from patients with IPF and control subjects. In a bleomycin-induced lung fibrosis model we used wild-type MMTV mice and a triple transgenic mouse SPC-rtTA^+/-TetoCre^+/-LoxP-VEGF-A^+/+ to conditionally induce VEGF-A isoform deletion specifically in the alveolar type II (ATII) cells of adult mice.

MEASUREMENTS AND MAIN RESULTS

IPF and normal lung fibroblasts differentially expressed and responded to VEGF-A₁₆₅a and VEGF-A₁₆₅b in terms of proliferation and matrix expression. Increased VEGF-A₁₆₅b was detected in plasma of progressing patients with IPF. In a mouse model of pulmonary fibrosis, ATII-specific deficiency of VEGF-A or constitutive overexpression of VEGF-A₁₆₅b inhibited the development of pulmonary fibrosis, as did treatment with intraperitoneal delivery of VEGF-A₁₆₅b to wild-type mice.

CONCLUSIONS

These results indicate that changes in the bioavailability of VEGF-A sourced from ATII cells, namely the ratio of VEGF-A_xxxa to VEGF-A_xxxb, are critical in development of pulmonary fibrosis and may be a paradigm for the regulation of tissue repair.

VEGF isoforms have differential effects on permeability of human pulmonary microvascular endothelial cells

BACKGROUND

Alternative splicing of Vascular endothelial growth factor-A mRNA transcripts (commonly referred as VEGF) leads to the generation of functionally differing isoforms, the relative amounts of which have potentially significant physiological outcomes in conditions such as acute respiratory distress syndrome (ARDS). The effect of such isoforms on pulmonary vascular permeability is unknown. We hypothesised that VEGF₁₆₅a and VEGF₁₆₅b isoforms would have differing effects on pulmonary vascular permeability caused by differential activation of intercellular signal transduction pathways.

METHOD

To test this hypothesis we investigated the physiological effect of VEGF₁₆₅a and VEGF₁₆₅b on Human Pulmonary Microvascular Endothelial Cell (HPMEC) permeability using three different methods: trans-endothelial electrical resistance (TEER), Electric cell-substrate impedance sensing (ECIS) and FITC-BSA passage. In addition, potential downstream signalling pathways of the VEGF isoforms were investigated by Western blotting and the use of specific signalling inhibitors.

RESULTS

VEGF₁₆₅a increased HPMEC permeability using all three methods (paracellular and transcellular) and led to associated VE-cadherin and actin stress fibre changes. In contrast, VEGF₁₆₅b decreased paracellular permeability and did not induce changes in VE-cadherin cell distribution. Furthermore, VEGF₁₆₅a and VEGF₁₆₅b had differing effects on both the phosphorylation of VEGF receptors and downstream signalling proteins pMEK, p42/44MAPK, p38 MAPK, pAKT and peNOS. Interestingly specific inhibition of the pMEK, p38 MAPK, PI3 kinase and eNOS pathways blocked the effects of both VEGF₁₆₅a and VEGF₁₆₅b on paracellular permeability and the effect of VEGF₁₆₅a on proliferation/migration, suggesting that this difference in cellular response is mediated by an as yet unidentified signalling pathway(s).

CONCLUSION

This study demonstrates that the novel isoform VEGF₁₆₅a and VEGF₁₆₅b induce differing effects on permeability in pulmonary microvascular endothelial cells.

Insulin Receptor Isoform Variations in Prostate Cancer Cells

Men who develop prostate cancer (PCa) increasingly have one of the co-morbidities associated with a Western lifestyle that are characterized by hyperinsulinemia, hyperglycemia and increased expression of insulin-like growth factors-I (IGF-I) and IGF-II. Each have been associated with poor prognosis and more aggressive cancers that exhibit increased metabolism and increased glucose uptake. The insulin receptor (IR) has two splice isoforms IR-A and IR-B: IR-A has a higher affinity for IGF-II comparable to that for insulin, whereas the IR-B isoform predominantly just binds to insulin. In this study, we assessed alterations in the IR-A and IR-B isoform ratio and associated changes in cell proliferation and migration of PCa cell lines following exposure to altered concentrations of glucose and treatment with IGF-II and insulin. We observed that where IR-B predominated insulin had a greater effect on migration than IGF-II and IGF-II was more effective when IR-A was the main isoform. With regard to proliferation IGF-II was more effective than insulin regardless of which isoform was dominant. We assessed the abundance of the IR isoforms both in vivo and in vitro and observed that the majority of the tissue samples and cell lines expressed more IR-A than IR-B. Alterations in the isoforms in response to changes in their hormonal milieu could have a profound impact on how malignant cells behave and play a role in promoting carcinogenesis. A greater understanding of the mechanisms underlying changes in alternative splicing of the IR may provide additional targets for future cancer therapies.

IGFBP-3 can either inhibit or enhance EGF-mediated growth of breast epithelial cells dependent upon the presence of fibronectin

Progression of breast cancer is associated with remodeling of the extracellular matrix, often involving a switch from estrogen dependence to a dependence on EGF receptor (EGFR)/HER-2 and is accompanied by increased expression of the main binding protein for insulin-like growth factors (IGFBP-3). We have examined the effects of IGFBP-3 on EGF responses of breast epithelial cells in the context of changes in the extracellular matrix. On plastic and laminin with MCF-10A normal breast epithelial cells, EGF and IGFBP-3 each increased cell growth and together produced a synergistic response, whereas with T47D breast cancer cells IGFBP-3 alone had no effect, but the ability of EGF to increase cell proliferation was markedly inhibited in the presence of IGFBP-3. In contrast on fibronectin with MCF-10A cells, IGFBP-3 alone inhibited cell growth and blocked EGF-induced proliferation. With the cancer cells, IGFBP-3 alone had no effect but enhanced the EGF-induced increase in cell growth. The insulin-like growth factor-independent effects of IGFBP-3 alone on cell proliferation were completely abrogated in the presence of an EGFR, tyrosine kinase inhibitor, Iressa. Although IGFBP-3 did not affect EGFR phosphorylation [Tyr(1068)], it was found to modulate receptor internalization and was associated with activation of Rho and subsequent changes in MAPK phosphorylation. The levels of fibronectin and IGFBP-3 within breast tumors may determine their dependence on EGFR and their response to therapies targeting this receptor.

Hyperglycaemia confers resistance to chemotherapy on breast cancer cells: the role of fatty acid synthase

The prognosis for women with breast cancer is adversely affected by the comorbidities of obesity and diabetes mellitus (DM), which are conditions associated with elevated levels of circulating fatty acids, hyperglycaemia and hyperinsulinaemia. We investigated the effects of exposure of non-malignant and malignant human breast epithelial cells to elevated levels of fatty acids and glucose on their growth, survival and response to chemotherapeutic agents. We found that palmitate induced cell death in the non-malignant cells but not in the malignant cells, which was abrogated through the inhibition of ceramide production and by oleate but not by IGF1. Fatty acid synthase (FAS) is responsible for the de novo synthesis of fatty acids from sugars, and is over-expressed in many epithelial cancers. Abundance of FAS was higher in malignant cells than in non-malignant cells, and was up-regulated by IGF1 in both cell types. IGF-induced growth of non-malignant cells was unaffected by suppression of FAS expression, whereas that of malignant cells was blocked as was their resistance to palmitate-induced cell death. Palmitate did not affect cell proliferation, whereas oleate promoted the growth of non-malignant cells but had the opposite effect, that is, inhibition of IGF1-induced growth of malignant cells. However, when the phosphatidylinositol 3-kinase pathway was inhibited, oleate enhanced IGF1-induced growth in both cell types. Hyperglycaemia conferred resistance on malignant cells, but not on non-malignant cells, to chemotherapy-induced cell death. This resistance was overcome by inhibiting FAS or ceramide production. Understanding the mechanisms involved in the associations between obesity, DM and breast cancer may lead to more effective treatment regimens and new therapeutic targets.

Virtual outreach: a randomised controlled trial and economic evaluation of joint teleconferenced medical consultations

OBJECTIVES

To test the hypotheses that virtual outreach would reduce offers of hospital follow-up appointments and reduce numbers of medical interventions and investigations, reduce numbers of contacts with the health care system, have a positive impact on patient satisfaction and enablement, and lead to improvements in patient health status. To perform an economic evaluation of virtual outreach.

DESIGN

A randomised controlled trial comparing joint teleconsultations between GPs, specialists and patients with standard outpatient referral. It was accompanied by an economic evaluation.

SETTING

The trial was centred on the Royal Free Hampstead NHS Trust, London, and the Royal Shrewsbury Hospital Trust in Shropshire. The project teams recruited and trained a total of 134 GPs from 29 practices and 20 consultant specialists.

PARTICIPANTS

In total, 3170 patients were referred, of whom 2094 consented to participate in the study and were eligible for inclusion. In all, 1051 patients were randomised to the virtual outreach group and 1043 to standard outpatient appointments. The patients were followed 6 months after their index consultation.

INTERVENTIONS

Patients randomised to virtual outreach underwent a joint teleconsultation, in which they attended the general practice surgery where they and their GP consulted with a hospital specialist via a videolink between the hospital and the practice.

MAIN OUTCOME MEASURES

Outcome measures included offers of follow-up outpatient appointments, numbers of tests, investigations, procedures, treatments and contacts with primary and secondary care, patient satisfaction (Ware Specific Visit Questionnaire), enablement (Patient Enablement Instrument) and quality of life (Short Form-12 and Child Health Questionnaire). An economic evaluation of the costs and consequences of the intervention was undertaken. Sensitivity analysis was used to test the robustness of the results.

RESULTS

Patients in the virtual outreach group were more likely to be offered a follow-up appointment. Significant differences in effects were observed between the two sites and across different specialities. Virtual outreach increased the offers of follow-up appointments more in Shrewsbury than in London, and more in ENT and orthopaedics than in the other specialities. Fewer tests and investigations were ordered in the virtual outreach group, by an average of 0.79 per patient. In the 6-month period following the index consultation, there were no significant differences overall in number of contacts with general practice, outpatient visits, accident and emergency contacts, inpatient stays, day surgery and inpatient procedures or prescriptions between the randomised groups. Tests of interaction indicated that virtual outreach decreased the number of tests and investigations, particularly in patients referred to gastroenterology, and increased the number of outpatient visits, particularly in those referred to orthopaedics. Patient satisfaction was greater after a virtual outreach consultation than after a standard outpatient consultation, with no heterogeneity between specialities or sites. However, patient enablement after the index consultation, and the physical and psychological scores of the Short Form-12 for adults and the scores on the Child Health Questionnaire for children under 16, did not differ between the randomised groups at 6 months' follow-up. NHS costs over 6 months were greater for the virtual outreach consultations than for conventional outpatients, pound 724 and pound 625 per patient, respectively. The index consultation accounted for this excess. Cost and time savings to patients were found. Estimated productivity losses were also less in the virtual outreach group.

CONCLUSIONS

Virtual outreach consultations result in significantly higher levels of patient satisfaction than standard outpatient appointments and lead to substantial reductions in numbers of tests and investigations, but they are variably associated with increased rates of offer of follow-up according to speciality and site. Changes in costs and technological advances may improve the relative position of virtual consultations in future. The extent to which virtual outreach is implemented will probably be dependent on factors such as patient demand, costs, and the attitudes of staff working in general practice and hospital settings. Further research could involve long-term follow-up of patients in the virtual outreach trial to determine downstream outcomes and costs; further study into the effectiveness and costs of virtual outreach used for follow-up appointments, rather than first-time referrals; and whether the costs of virtual outreach could be substantially reduced without adversely affecting the quality of the consultation if nurses or other members of the primary care team were to undertake the hosting of the joint teleconsultations in place of the GP. Qualitative work into the attitudes of the patients, GPs and hospital specialists would also be valuable.

Client perceptions of the polysomnography experience and compliance with therapy

A grounded theory approach was used to generate theory about clients' perceptions of polysomnography, and the relationships between these perceptions and compliance with therapy. Interviews were conducted with two groups of clients: those who complied with recommended therapy (Continuous Positive Airways Pressure) and those who did not. Compliance with suggested therapy appeared to be related to the degree of benefit derived by the client. In addition, there were problems with the process of diagnosis and follow-up that impacted on client satisfaction and may have influenced their compliance. These findings have highlighted issues which have been used to generate theories that will be tested in future research.

Education and training of practice nurses

Seventeen nurses in eight rural general practices participated in a distance education project. Low-cost videoconferencing equipment was assessed for its suitability in two training sessions, concerning asthma and travel immunization. The intended learning outcomes were reached and although initially apprehensive, the nurses quickly became accustomed to the medium. Videoconferencing has now become an accepted part of in-service training. Technical reliability remains the most important problem.

Associations between oncogenic human papillomaviruses and local invasive patterns in cervical cancer

The polymerase chain reaction (PCR) was used to detect human papillomavirus (HPV) DNA in Formalin-acetic acid alcohol (FAA)-fixed paraffin-embedded tissue from 40 patients whose primary cervical cancers showed a tentacular pattern of invasion at their advancing edges, and 40 patients (matched by age, International Federation of Obstetrics and Gynecology (FIGO) stage and histology type) whose tumors showed broad front invasion. The rate of HPV DNA positivity was the same in both the tentacular and the broad front tumors (83%), but the ratios of HPV 16 to HPV 18 in the two groups were markedly different (20:10 versus 27:4, respectively). HPV type 18 was detected more frequently in tentacular than broad front tumors (P = 0.03). The overall rates of recurrence and mortality were 15 and 9%, respectively (18 and 10% in the tentacular group compared with 13 and 8% in the broad front group). Univariate analysis showed statistically significant associations between HPV 18 and tumor recurrence (P = 0.04), but not between a tentacular pattern of invasion and tumor recurrence (P < 0.05). The findings to emerge from this survey indicate that the presence of particular HPV types may, in part, mediate the histological and clinical behavior of cervical cancers.

Induction of feline immunodeficiency virus-specific cytotoxic T cells in vivo with carrier-free synthetic peptide

The role of cellular immunity in the establishment and progression of immunosuppressive lentivirus infection remains equivocal. To develop a model system with which these aspects of the host immune response can be studied experimentally, we examined the response of cats to a hybrid peptide containing predicted T-and B-cell epitopes from the gag and env genes of feline immunodeficiency virus (FIV). Cats were immunized with an unmodified 17-residue peptide incorporating residues 196 to 208 (from gag capsid protein p24) and 395 to 398 (from env glycoprotein gp120) of the FIV Glasgow-8 strain by using Quil A as an adjuvant. Virus-specific lymphocytotoxicity was measured by chromium-51 release assays. The target cells were autologous or allogeneic skin fibroblasts either infected with recombinant FIV gag vaccinia virus or pulsed with FIV peptides. Effector cells were either fresh peripheral blood mononuclear cells or T-cell lines stimulated with FIV peptides in vitro. Cytotoxic effector cells from immunized cats lysed autologous, but not allogeneic, target cells when they were either infected with recombinant FIV gag vaccinia virus or pulsed with synthetic peptides comprising residues 196 to 205 or 200 to 208 plus 395. Depletion of CD8+ T cells, from the effector cell population abrogated the lymphocytotoxicity. Immunized cats developed an antibody response to the 17-residue peptide immunogen and to recombinant p24. However, no antibodies which recognized smaller constituent peptides could be detected. This response correlated with peptide-induced T-cell proliferation in vitro. This study demonstrates that cytotoxic T lymphocytes specific for FIV can be induced following immunization with an unmodified short synthetic peptide and defines a system in which the protective or pathological role of such responses can be examined.