Pathophysiology of photoaging of human skin: focus on neutrophils.

UV-induced skin damage is the result of a complex cascade of events. Many studies have focused on the skin effects induced by UV-B or UV-A separately. Recently a UV-source that emits UV-B and UV-A together in a ratio comparable to daily sunlight has been introduced: i.e. solar simulated radiation (SSR). By exposing human skin type I-III to erythematogenic doses of UV (> or =1 MED) emitted by a SSR source we have noticed that: (a) neutrophils are initially the main infiltrating cell type in the dermis and (b) these infiltrating cells are the a key source of in vivo enzymatically [corrected] active enzymes such as elastase, [corrected] matrix metallo proteinases-1 and -9 (MMPs-1 and -9). These enzymes are relevant to the process of photoaging, as they break down the extracellular matrix. Keratinocytes and fibroblasts also produce matrix degrading enzymes, but to a lesser extent. Our results indicate a primary role for infiltrating neutrophils in the initial steps of photoaging. This is further supported by the observation that after exposure of skin type VI to physical doses of SSR, equivalent to those used for skin types I-III, no neutrophils and neutrophil-derived enzymatic activity were observed, explaining why skin type VI is [corrected] less susceptible to photoaging than skin types [corrected] I-III. Statement: Although most of the data, referred to, have been published, the current perspective in which they are put together is completely novel and has not been published elsewhere.     

Selective induction of IL-6 by aluminum-induced oxidative stress can be prevented by selenium

In this study the acute toxic effects of aluminum (Al) on mice have been investigated, including the interactions of Al and selenium (Se). Focus was put on the systemic effects of (co)exposure to Al and Se as a reflection of the redox status in the liver, kidney and brain.Short-term exposure (16 h) to Al resulted in an increase in the systemic inflammation parameters IL-6 and PAI-1, whereas serum levels of TNF-α remained unaffected. The different response pattern of IL-6 and TNF-α probably indicates an increased intracellular oxidative stress and altered redox status in the liver, because the selective increase in IL-6 serves as a protective intrahepatocellular process driven by oxidative stress. The intracellular glutathione concentration GSH_tot decreased significantly upon Al exposure. Both the increase in IL-6 and decrease in glutathione status could be prevented by co-exposure to Se, but not the increase in PAI-1. The redox status of the kidney and brain was not markedly affected.Therefore it was concluded that short-term exposure to Al causes adverse effects on the intracellular oxidative stress processes in the liver, as reflected by the selective increase in the IL-6 concentration. This process can be restored by co-administration of the trace element Se as a part of the glutathione redox system.     

Sexual agglutination in Chlamydomonas eugametos is mediated by a single pair of hydroxyproline-rich glycoproteins

Abstract The sexual mating reaction between gametes of the green alga Chlamydomonas eugametos starts by cell-cell contacts involving sex-specific cell-adhesion molecules (agglutinins) at the flagellar membrane. An in vitro adhesion assay is described using glutaraldehyde-fixed gametes. In vitro adhesion was fully comparable to in vivo adhesion, making it a reliable assay to study the initial recognition step of sexual adhesion in vivo. It was shown that both agglutinins are capable of inhibiting sexual adhesion at similar concentrations (1−2×10⁻¹⁰ M), indicating that mt⁺ and mt⁻ agglutinins interact with each other during binding. This was confirmed by demonstrating that charcoal particles adsorbed with purified agglutinins of the opposite mating type aggregate with each other.     

THE COST OF BEING COMMON: EVIDENCE FROM NATURAL DAPHNIA POPULATIONS

The Red Queen coevolutionary hypothesis predicts that parasites drive oscillations in host genotype frequencies due to frequency-dependent selection where common hosts are at disadvantage. However, examples of this phenomenon in natural populations are scarce. To examine if the Red Queen theory operates in the wild, we studied the genetic structure of populations of the crustacean waterflea ( Daphnia ), in relation to their infection levels, for which we collected multiple samples from a variety of lakes. The most common clone in a given population was often underinfected. This advantage, however, did not remain stable over time. Instead, the most common clone decreased in frequency over subsequent generations, indicating that parasites can track common clones. Such decreases were not observed in uninfected populations. Moreover, host clonal evenness was higher across the set of infected lakes compared to uninfected lakes; suggesting that any common clone is selected against when parasites are present. These results strongly suggest that Red Queen dynamics do operate in the wild.     

Abscisic acid promotes lectin biosynthesis in developing and germinating rice embryos

Immature rice (Oryza sativa, L) embryos isolated about 12 days post anthesis are fully able to develop into young seedlings when cultured in vitro. Concomitantly, they rapidly loose their lectin synthesis activity. Abscisic acid added to the nutrient medium prevents precocious germination of the immature embryos and simultaneously strongly promotes lectin biosynthesis activity. Similarly, abscisic acid keeps mature embryos grown in a nutrient medium in a dormant state and maintains their lectin synthesis activity, whereas control embryos rapidly germinate but also quickly loose their lectin synthesis activity. It appears, therefore, that rice lectin is typically synthesized in embryos which are kept in a dornant state.Abbreviations ABA abscisic acid - GA₃ gibberellic acid - WGA wheat germ agglutinin - DPA days post anthesis