Effector function of human tumor-specific CD8 T cells in melanoma lesions: a state of local functional tolerance.

Although tumor-specific CD8 T-cell responses often develop in cancer patients, they rarely result in tumor eradication. We aimed at studying directly the functional efficacy of tumor-specific CD8 T cells at the site of immune attack. Tumor lesions in lymphoid and nonlymphoid tissues (metastatic lymph nodes and soft tissue/visceral metastases, respectively) were collected from stage III/IV melanoma patients and investigated for the presence and function of CD8 T cells specific for the tumor differentiation antigen Melan-A/MART-1. Comparative analysis was conducted with peripheral blood T cells. We provide evidence that in vivo-priming selects, within the available naive Melan-A/MART-1-specific CD8 T-cell repertoire, cells with high T-cell receptor avidity that can efficiently kill melanoma cells in vitro. In vivo, primed Melan-A/MART-1-specific CD8 T cells accumulate at high frequency in both lymphoid and nonlymphoid tumor lesions. Unexpectedly, however, whereas primed Melan-A/MART-1-specific CD8 T cells that circulate in the blood display robust inflammatory and cytotoxic functions, those that reside in tumor lesions (particularly in metastatic lymph nodes) are functionally tolerant. We show that both the lymph node and the tumor environments blunt T-cell effector functions and offer a rationale for the failure of tumor-specific responses to effectively counter tumor progression.

Effective exposure to solar UV in building workers: influence of local and individual factors.

Excessive exposure to solar UV light is the main cause of skin cancers in humans. UV exposure depends on environmental as well as individual factors related to activity. Although outdoor occupational activities contribute significantly to the individual dose received, data on effective exposure are scarce and limited to a few occupations. A study was undertaken in order to assess effective short-term exposure among building workers and characterize the influence of individual and local factors on exposure. The effective exposure of construction workers in a mountainous area in the southern part of Switzerland was investigated through short-term dosimetry (97 dosimeters). Three altitudes, of about 500, 1500 and 2500 m were considered. Individual measurements over 20 working periods were performed using Spore film dosimeters on five body locations. The postural activity of workers was concomitantly recorded and static UV measurements were also performed. Effective exposure among building workers was high and exceeded occupational recommendations, for all individuals for at least one body location. The mean daily UV dose in plain was 11.9 SED (0.0-31.3 SED), in middle mountain 21.4 SED (6.6-46.8 SED) and in high mountain 28.6 SED (0.0-91.1 SED). Measured doses between workers and anatomical locations exhibited a high variability, stressing the role of local exposure conditions and individual factors. Short-term effective exposure ranged between 0 and 200% of ambient irradiation, indicating the occurrence of intense, subacute exposures. A predictive irradiation model was developed to investigate the role of individual factors. Posture and orientation were found to account for at least 38% of the total variance of relative individual exposure, and were also found to account more than altitude on the total variance of effective daily exposures. Targeted sensitization actions through professional information channels and specific prevention messages are recommended. Altitude outdoor workers should also benefit from preventive medical examination.

Local delivery of glial cell line-derived neurotrophic factor improves facial nerve regeneration after late repair.

OBJECTIVES/HYPOTHESIS: Facial nerve regeneration is limited in some clinical situations: in long grafts, by aged patients, and when the delay between nerve lesion and repair is prolonged. This deficient regeneration is due to the limited number of regenerating nerve fibers, their immaturity and the unresponsiveness of Schwann cells after a long period of denervation. This study proposes to apply glial cell line-derived neurotrophic factor (GDNF) on facial nerve grafts via nerve guidance channels to improve the regeneration. METHODS: Two situations were evaluated: immediate and delayed grafts (repair 7 months after the lesion). Each group contained three subgroups: a) graft without channel, b) graft with a channel without neurotrophic factor; and c) graft with a GDNF-releasing channel. A functional analysis was performed with clinical observation of facial nerve function, and nerve conduction study at 6 weeks. Histological analysis was performed with the count of number of myelinated fibers within the graft, and distally to the graft. Central evaluation was assessed with Fluoro-Ruby retrograde labeling and Nissl staining. RESULTS: This study showed that GDNF allowed an increase in the number and the maturation of nerve fibers, as well as the number of retrogradely labeled neurons in delayed anastomoses. On the contrary, after immediate repair, the regenerated nerves in the presence of GDNF showed inferior results compared to the other groups. CONCLUSIONS: GDNF is a potent neurotrophic factor to improve facial nerve regeneration in grafts performed several months after the nerve lesion. However, GDNF should not be used for immediate repair, as it possibly inhibits the nerve regeneration.

Skin hyperemia induced by local heating : why is it blunted on repeat stimulations ?

Background: In human skin, local heating produces local vasodilatation, a response termed thermal hyperemia. Thermal hyperemia is largely mediated by nitric oxide (NO). It is blunted on repeat stimulations applied to the same skin spot, a phenomenon termed desensitization. As this phenomenon could reflect a desensitization in the vasodilator effects of NO, we investigated whether a prior exposure to exogenous NO would result in an attenuated vasodilatory response to a subsequent thermal challenge. Methods: Thirteen healthy young men were studied. Skin blood flow (SkBF) was mesured on forearm skin with laser Doppler imaging. Exposure to exogenous NO was carried out by iontophoresis of sodium nitroprusside (SNP), a donor of NO. A local thermal stimulus (temperature step from 34 to 41°C maintained for 30 minutes) was applied with temperature-controlled chambers. We tested the influence of a previous transient exposure to exogenous NO on : 1) thermal hyperemia and 2) the response to a second identical exposure to exogeneous NO. Results: Thermal hyperemia (plateau SkBF at 30 minutes minus SkBF at 34°C) obtained on a site preexposed to exogenous NO two hours before was lower than obtained on a site preexposed to iontophoretic current only (mean±SD 395±139 perfusion units [PU] vs 540±79 PU ; p<0.01). When repeated on the same skin site two hours after the first one, exposure to exogenous NO led to a blunted vasodilatory response (298±121 PU vs 394±92 PU), although this difference was not statistically significant (p≈0.09). Conclusion: In forearm human skin, prior exposure to exogenous NO partially inhibits thermal hyperemia. These data support that desensitization of thermal hyperemia depends on a downregulation of the NO-cGMP pathway, possibly downstream from the endogenous production of NO.

Trans-scleral local resection of toxic choroidal melanoma after proton beam radiotherapy.

AIM: To report on trans-scleral local resection of choroidal melanoma for exudative retinal detachment and neovascular glaucoma (toxic tumour syndrome) after proton beam radiotherapy (PBR). METHODS: A non-randomised, prospective study of secondary trans-scleral local resection of choroidal melanoma for exudative retinal detachment with or without neovascular glaucoma after PBR. The patients were treated at the Liverpool Ocular Oncology Centre between February 2000 and April 2008. The trans-scleral local resection was performed with a lamellar-scleral flap, using systemic hypotension to reduce haemorrhage. RESULTS: 12 patients (six women, six men) with a mean age of 51 years (range 20-75) were included in this study. The tumour margins extended anterior to ora serrata in six patients. On ultrasonography, the largest basal tumour dimension averaged 12.4 mm (range 6.8-18.1) and the tumour height averaged 7.1 mm (range 4.2-10.7). The retinal detachment was total in seven patients. Neovascular glaucoma was present in four patients. The time between PBR and local resection had a mean of 17.4 months (range 1-84). The ophthalmic follow-up time after the local resection had a mean of 46.2 months (range 14-99). At the latest known status, the eye was conserved in 10 patients, with a flat retina in all these patients and visual acuity equal or better than 6/30 in four patients. The reasons for enucleation were: patient request for enucleation when rhegmatogenous retinal detachment complicated the resection (one patient) and phthisis (one patient). CONCLUSIONS: Exudative retinal detachment, rubeosis and neovascular glaucoma after PBR of a choroidal melanoma can resolve after trans-scleral local resection of the tumour. Our findings suggest that these complications are caused by the persistence of the irradiated tumour within the eye ('toxic tumour syndrome').

BDNF overexpression in mouse hippocampal astrocytes promotes local neurogenesis and elicits anxiolytic-like activities.

The therapeutic activity of selective serotonin (5-HT) reuptake inhibitors (SSRIs) relies on long-term adaptation at pre- and post-synaptic levels. The sustained administration of SSRIs increases the serotonergic neurotransmission in response to a functional desensitization of the inhibitory 5-HT1A autoreceptor in the dorsal raphe. At nerve terminal such as the hippocampus, the enhancement of 5-HT availability increases brain-derived neurotrophic factor (BDNF) synthesis and signaling, a major event in the stimulation of adult neurogenesis. In physiological conditions, BDNF would be expressed at functionally relevant levels in neurons. However, the recent observation that SSRIs upregulate BDNF mRNA in primary cultures of astrocytes strongly suggest that the therapeutic activity of antidepressant drugs might result from an increase in BDNF synthesis in this cell type. In this study, by overexpressing BDNF in astrocytes, we balanced the ratio between astrocytic and neuronal BDNF raising the possibility that such manipulation could positively reverberate on anxiolytic-/antidepressant-like activities in transfected mice. Our results indicate that BDNF overexpression in hippocampal astrocytes produced anxiolytic-/antidepressant-like activity in the novelty suppressed feeding in relation with the stimulation of hippocampal neurogenesis whereas it did not potentiate the effects of the SSRI fluoxetine on these parameters. Moreover, overexpressing BDNF revealed the anxiolytic-like activity of fluoxetine in the elevated plus maze while attenuating 5-HT neurotransmission in response to a blunted downregulation of the 5-HT1A autoreceptor. These results emphasize an original role of hippocampal astrocytes in the synthesis of BDNF, which can act through neurogenesis-dependent and -independent mechanisms to regulate different facets of anxiolytic-like responses.

No major impact of skin aging on the response of skin blood flow to a submaximal local thermal stimulus

La peau est sujette à un vieillissement intrinsèque (processus naturel et chronologique) et extrinsèque (processus induit par l'environnement et notamment les rayons UV). Plusieurs études ont montré que le vieillissement cutané s'accompagne d'une réduction de la densité capillaire au sein du derme et d'une dégradation de plusieurs protéines de la matrice extracellulaire. Cette atteinte morphologique est associée à une diminution de la capacité vasodilatatrice maximale de la microcirculation dermique et en particulier, de la réponse maximale du flux sanguin cutané à un échauffement local de la surface cutanée à des températures avoisinant les 43-44°C. Cette réponse, appelée hyperémie locale induite par la chaleur (local thermal hyperemia), est facilement mesurable par des investigations non invasives, telles que le laser Doppler. Nous avons entrepris cette étude afin d'investiguer les effets de l'âge sur la réactivité de la microcirculation dermique dans des zones cutanées exposées différemment aux rayons UV. Pour ce faire, nous avons étudié, chez des patients jeunes (18 à 30 ans, n=13) et des patients âgés (> 60 ans, n=13), la vasodilatation cutanée induite par réchauffement local de la peau, au niveau de 3 sites anatomiques différents (la cuisse, l'avant- bras et le front). Les mesures ont été effectuées au moyen d'un laser Doppler. Pour chaque sujet et chaque site, la température cutanée fut tout d'abord amenée à 34°C par 2 corps de chauffe (A et B), disposés de manière adjacente sur la peau. La température fut ensuite augmentée à 39°C (corps de chauffe A) et à 41°C (corps de chauffe B) pour une durée de 30 minutes, dans l'optique d'induire une vasodilatation sous- maximale. Ensuite, la température fut augmentée à 43 °C (corps de chauffe A et B) pour 15 minutes supplémentaires. Enfin, la vasodilatation maximale a été induite par un échauffement local à 44°C pour 15 minutes supplémentaires (corps de chauffe A et B). L'enregistrement séquentiel du flux sanguin cutané, effectué chaque minute par laser Doppler imager, donne des images sur lesquelles peut être calculé le flux sanguin cutané (unités de perfusion, PU). Par la suite, nous avons calculé les conductances vasculaires cutanées (CVC), en divisant le flux sanguin (PU) par la tension artérielle moyenne (mmHg), afin de permettre une normalisation entre les différents sujets. Les CVC, évaluées au temps de départ (température 34°C) et après vasodilatation maximale (température 44°C), étaient plus hautes au niveau du front qu'au niveau des 2 autres sites anatomiques. Sur les 3 sites, la CVC maximale (température 44°C) diminuait avec l'âge mais de façon moins importante au niveau du front, en comparaison avec les 2 autres sites. La réponse aux températures sous-maximales (température 39 et 41°C), exprimée en pourcentage de la CVC maximale, ne variait pas avec l'âge ni en fonction du site anatomique étudié. En conclusion, cette étude est la première à étudier simultanément l'hyperémie locale induite par la chaleur sur 3 sites ayant une exposition différente aux rayons UV. Le processus utilisé (laser Doppler imager) est également unique dans la littérature concernant les altérations de la microcirculation cutanée en lien avec l'âge. Cette étude confirme ainsi que le vieillissement cutané intrinsèque et/ou extrinsèque réduit la capacité vasodilatatrice maximale de la microcirculation dermique. Par contre, la réactivité à réchauffement local à des températures moindres ne semble pas être affectée.