Eliana M. Cela

Lipoteichoic acid from Lactobacillus rhamnosus GG as an oral photoprotective agent against UV-induced carcinogenesis

Probiotics are live micro-organisms that when administered in adequate amounts confer a health benefit on the host. Cell surface molecules of these micro-organisms are being studied in relation to their ability to interact with the host. The cell wall of lactobacilli possesses lipoteichoic acids (LTA) which are molecules with immunomodulatory properties. UV radiation (UVR) has been proposed as the main cause of skin cancer because of its mutagenic and immunosuppressive effects. Photoprotection with some nutrition interventions including probiotics has recently been shown. The aim of the present study was to investigate whether the oral administration of purified LTA from Lactobacillus rhamnosus GG can modulate the immune-suppressive effect of UVR and skin tumour development in female Crl:SKH-1-hrBR mice. For this purpose, two irradiation models were studied: (1) a chronic irradiation scheme consisting of daily irradiations during twenty consecutive days and (2) a long-term irradiation schedule, irradiating the animals three times per week, during 34 weeks for tumour development. The results showed that T-cells in the inguinal lymph node of LTA-treated mice produced higher levels of (1) interferon-γ and (2) a number of total, helper and cytotoxic T-cells compared with non-treated mice. Moreover, a significant delay in tumour appearance was found in LTA-treated mice. An increased IgA⁺ cell number was found in the small intestine together with a higher number of activated dendritic cells in the mesenteric lymph nodes. The latter results might be indicative of a direct effect of LTA in the gut, affecting the cutaneous immune system and restoring homeostasis through the gut-skin axis.

Time–course study of different innate immune mediators produced by UV-irradiated skin: comparative effects of short and daily versus a single harmful UV exposure

The modulatory effects of solar UV radiation on the immune system have been widely studied. As the skin is the main target of UV radiation, our purpose was to compare the impact on skin innate immunity of two contrasting ways to be exposed to sunlight. Hairless mice were UV irradiated with a single high UV dose simulating a harmful exposure, or with repetitive low UV doses simulating short occasional daily exposures. Skin samples were taken at different times after UV irradiation to evaluate skin histology, inflammatory cell recruitment, epidermal T‐cell population and the mitochondrial function of epidermal cells. The transcriptional profiles of pro‐inflammatory cytokines, chemokines, antimicrobial peptides and Toll‐like receptors were evaluated by RT‐PCR and ELISA in tissue homogenates. Finally, a lymphangiography was performed to assess modification in the lymphatic vessel system. A single high UV dose produces a deep inflammatory state characterized by the production of pro‐inflammatory cytokines and chemokines that, in turn, induces the recruitment of neutrophils and macrophages into the irradiated area. On the other hand, repetitive low UV doses drive the skin to a photo‐induced alert state in which there is no sign of inflammation, but the epithelium undergoes changes in thickness, the lymphatic circulation increases, and the transcription of antimicrobial peptides is induced.

Skin Exposure to Chronic But Not Acute UV Radiation Affects Peripheral T-Cell Function

Ultraviolet (UV) radiation (UVR) produces deleterious effects that may finally lead to carcinogenesis. These adverse effects include tissue inflammation, free radical formation with consequent oxidation of proteins and lipids, DNA damage, and immune function suppression. The aim of this study was to evaluate the effects of UVR at the local and systemic levels following acute (4 consecutive days with 0.5 minimal erythema dose [MED]) or chronic (20 consecutive days with 0.25 MED) exposure. Locally, histological alterations and epidermal T-cell populations were studied. Systemically, inguinal lymph-node and spleen T cells were analyzed with respect to proliferative response and cytokine production against a nonspecific mitogen. Lymph-node T-cell populations were also characterized. Our results indicated that while both acute and chronic UVR produced epidermal hyperplasia and a decrease in epidermal T-cell density, acute UVR increased T-cell proliferative response, while chronic UVR produced the opposite effect, shifting the cytokine production toward a Th2/Treg profile. Therefore, even though acute irradiation produced a direct effect on skin, it did not correlate with a marked modification of overall T-cell response, which is in contrast to marked effects in chronically irradiated animals. These findings may contribute to understanding the clinical relevance of occupational UVR exposure, typically related to outdoor activities, which is associated with nonmelanoma skin carcinogenesis.

Mitochondrial function evaluation in epidermal cells ex vivo after ultraviolet irradiation.

Abstract:  Ultraviolet radiation (UVR) effects on skin have been extensively studied. However, mitochondrial dysfunction and superoxide () production have only been studied using cell cultures, which are useful models, but do not consider the crosstalk between tissues or cellular differentiation. We aimed to evaluate the usefulness of fluorescent dyes to study skin ex vivo. Mitochondrial alterations were evaluated in epidermal cells isolated from UVR‐exposed mice. Furthermore, a combination of dyes and antibodies was tested to analyse specific skin cell types. UVR caused a decrease in the percentage of total cells with polarized mitochondria, but did not change the mitochondrial production. However, this production was increased significantly in cells. Furthermore, it was possible to evaluate the cellular damage produced to basal keratinocytes and Langerhans cells. The results show that fluorescent dyes – alone or in combination with antibodies – are useful to analyse cellular events that take place in whole organs.

Daily very low UV dose exposure enhances adaptive immunity, compared with a single high-dose exposure. Consequences for the control of a skin infection

Ultraviolet radiation (UVr) promotes several well‐known molecular changes, which may ultimately impact on health. Some of these effects are detrimental, like inflammation, carcinogenesis and immunosuppression. On the other hand, UVr also promotes vitamin D synthesis and other beneficial effects. We recently demonstrated that exposure to very low doses of UVr on four consecutive days [repetitive low UVd (rlUVd)] does not promote an inflammatory state, nor the recruitment of neutrophils or lymphocytes, as the exposure to a single high UV dose (shUVd) does. Moreover, rlUVd reinforce the epithelium by increasing antimicrobial peptides transcription and epidermal thickness. The aim of this study was to evaluate the adaptive immune response after shUVd and rlUVd, determining T‐cell and B‐cell responses. Finally, we challenged animals exposed to both irradiation procedures with Staphylococcus aureus to study the overall effects of both innate and adaptive immunity during a cutaneous infection. We observed, as expected, a marked suppression of T‐cell and B‐cell responses after exposure to an shUVd but a novel and significant increase in both specific responses after exposure to rlUVd. However, the control of the cutaneous S. aureus infection was defective in this last group, suggesting that responses against pathogens cannot be ruled out from isolated stimuli.

Mitochondrial Dysfunction and Tissue Alterations of Ultraviolet-Irradiated Skin in Five Different Mice Strains

Ultraviolet radiation (UVR) effects on skin have been extensively studied. Several mice strains have been used worldwide in photobiology and photoimmunology studies. Recently, we have developed a method based on flow cytometry in order to analyze mitochondrial dysfunction and superoxide (O 2 • - ) production ex vivo in keratinocytes isolated from irradiated-mice. This method can be helpful to evaluate mitochondrial alterations in different mice models. In this work, we aimed to compare epidermal response to UVR in five mice strains, both pigmented and albino as well as hairy and hairless strains (SKH:1, Balb/c, C57/BL, DBA/2N and Swiss). Keratinocytes mitochondrial alterations, epidermal hyperplasia and inflammatory mediators’ production (epidermis and serum) were determined 72 hours after a 400 mJ/cm 2 UV dose. All strains showed epidermal hyperplasia and loss of mitochondrial polarization after irradiation, differing in the magnitude of the response. However, there were significant differences in the basal mitochondrial polarization between strains, showing that the metabolic state of keratinocytes may vary between them. Moreover, mitochondrial O 2 • - production was induced in SKH:1 and Balb/c after irradiation, whereas in DBA/2N, Swiss and C57/BL it was at the same level or even lower than in the non-irradiated control. Finally, an increase in inflammatory mediators was only detected in the serum of C57/BL and Swiss mice and in the epidermis of DBA/2N and C57/BL. Results show that each mice strain has particular characteristics related to cellular metabolism, which may lead to particular responses to UVR exposure. Therefore, the use of a particular mice strain in photobiology models should be carefully considered.

Activity modulation of microbial enzymes by llama (Lama glama) heavy-chain polyclonal antibodies during in vivo immune responses.

Since they were first described in 1993, it was found that recombinant variable fragments (rVHHs) of heavy-chain antibodies (HCAbs) from Camelidae have unusual biophysical properties, as well as a special ability to interact with epitopes that are cryptic for conventional Abs. It has been assumed that in vivo raised polyclonal HCAbs (pHCAbs) should behave in a similar manner than rVHHs; however, this assumption has not been tested sufficiently. Furthermore, our own preliminary work on a single serum sample from a llama immunized with a β-lactamase, has suggested that pHCAbs have no special ability to down-modulate catalytic activity. In this work, we further explored the interaction of pHCAbs from four llamas raised against two microbial enzymes and analyzed it within a short and a long immunization plan. The relative contribution of pHCAbs to serum titer was found to be low compared with that of the most abundant conventional subisotype (IgG(1)), during the whole immunization schedule. Furthermore, pHCAbs not only failed to inhibit the enzymes, but also activated one of them. Altogether, these results suggest that raising high titer inhibitory HCAbs is not a straightforward strategy - neither as a biotechnological strategy nor in the biological context of an immune response against infection - as raising inhibitory rVHHs.

Comment on “A Role for Immature Myeloid Cells in Immune Senescence”

We recently read an article published in The Journal of Immunology by Enioutina et al. ([1][1]) and found an experimental procedure we believe should be discussed. In this article, as well as in many others by the same authors—also in The Journal of Immunology and other renowned journals ([2][2