Uncoupling proteins: a role in protection against reactive oxygen species--or not?

A physiological function of the original uncoupling protein, UCP1, is well established: UCP1 is the molecular background for nonshivering thermogenesis. The functions of the "novel" UCPs, UCP2 and UCP3, are still not established. Recent discussions imply that all UCPs may play a role in protection against reactive oxygen species (ROS). Here we examine critically the evidence that UCP1, UCP2 and UCP3 are stimulated by ROS (superoxide) or ROS products (4-hydroxy-2-nonenal), and that the UCPs actually diminish oxidative damage. We conclude that, concerning UCP1, it is unlikely that it has such a role; concerning UCP2/UCP3, most evidence for physiologically significant roles in this respect is still circumstantial.     

Signal transduction induced by activated protein C: no role in protection against sepsis?

The anticoagulant activated protein C (APC) is historically known as a risk factor for venous thrombosis. However, after the positive results of the protein C worldwide evaluation in severe sepsis (PROWESS) trial, which showed that APC was the first drug that considerably reduced sepsis-related mortality, APC is considered a pleiotropic protein with both anticoagulant and anti-inflammatory properties. In addition, in vitro studies have suggested that APC-induced intracellular signal transduction is a potential mechanism by which APC might be protective against sepsis. Recently, however, the efficacy of APC in sepsis has been argued, and also the extent to which the signal transduction capacity of APC contributes to its pro-survival effects is debated. Here, we review the role of APC in the body natural defense against sepsis and discuss the mechanism by which APC might act at a cellular level.     

Uncoupling proteins: A role in protection against reactive oxygen species—or not?

A physiological function of the original uncoupling protein, UCP1, is well established: UCP1 is the molecular background for nonshivering thermogenesis. The functions of the “novel” UCPs, UCP2 and UCP3, are still not established. Recent discussions imply that all UCPs may play a role in protection against reactive oxygen species (ROS). Here we examine critically the evidence that UCP1, UCP2 and UCP3 are stimulated by ROS (superoxide) or ROS products (4-hydroxy-2-nonenal), and that the UCPs actually diminish oxidative damage. We conclude that, concerning UCP1, it is unlikely that it has such a role; concerning UCP2/UCP3, most evidence for physiologically significant roles in this respect is still circumstantial.     

High level expression of functional human IgMs in human PER.C6? cells

Natural IgM antibodies play an important role in the body''s defense mechanisms against transformed cells in the human body and are currently being exploited both in prognoses of malignant lesions and in the therapy of cancer patients. However, despite growing interest and clinical promise, thus far the IgM class of antibodies has failed to gain widespread commercial interest as these are considered to be difficult to produce recombinantly. IgMs are polymeric and have a relatively large mass. In addition, IgM molecules are heavily glycosylated and, when produced in non-human cell lines, they may contain non-human glycan structures which may be potentially immunogenic. Clearly, production systems capable of expressing human recombinant IgM antibodies are needed. We have successfully used PER.C6® cells—a human cell line—to generate three separate human recombinant monoclonal IgMs in suspension cultures in protein-free medium. All three of the IgMs were constructed with joining (J) chain and were expressed in the pentameric form. One of the IgMs was also expressed as a hexamer without J chain. Clones with cell specific productivities greater than 20 pg/cell/day were generated, which led to yields of 0.5 g/L to 2g/L in fed-batch production. All the IgMs expressed were biologically active as shown in binding and cytotoxicity assays. These studies demonstrate the potential of PER.C6® cells for the production of high levels of functional recombinant IgM and other polymeric molecules, using a straightforward and rapid stable cell line generation method.Key words: PER.C6®, IgM, expression, hexamer, pentamer, J chain     

Facilitation of tree saplings by nurse plants: Microhabitat amelioration or protection against herbivores?

Question: Positive interactions are predicted to be common in communities developing under high physical stress or high herbivory pressure due to neighbour amelioration of limiting physical and consumer stresses, respectively. However, when both stress sources meet in the same community, the relative importance of the two facilitation mechanisms is poorly understood. We ask: What is the relative importance of abiotic vs. biotic mechanisms of facilitation of tree saplings by shrubs in Mediterranean mountain forests? Location: Sierra Nevada, SE Spain (1800–1850 m a.s.l.) Methods: Saplings of four tree taxa (Acer opalus ssp. grana‐tense, Quercus ilex, Pinus nigra ssp. salzmanii and P. sylvestris var. nevadensis) were planted following a 2 × 2 factorial design: two levels of herbivory (control and ungulate exclusion) and two microhabitats (under shrubs and in open areas). Sapling survival and growth were monitored for five years. Results: Shrubs had positive effects on sapling survival both in control and ungulate excluded plots. This effect was species‐specific, with shrubs increasing the survival of Acer opalus and Quercus ilex three and twofold, respectively, but having a minor effect on the Pinus species. Herbivory damage was also species‐specific, being much higher for Acer opalus than for any other species. Shrubs did not protect saplings of any species against ungulates. Thus, all Acer saplings (the most damaged species) suffered herbivory outside the exclosures, which largely reduced sapling height. Conclusions: Protection from abiotic stress (summer drought and winter frost) was much more relevant than protection from biotic stress (herbivory). However, we propose that the final balance between the two mechanisms can be expected to vary strongly between sites, depending on the relative magnitude of the different sources of stress and the intrinsic traits (e.g. palatability) of the species interacting.     

Is activation of the intra-S checkpoint in human fibroblasts an important factor in protection against UV-induced mutagenesis?

The ATR/CHK1-dependent intra-S checkpoint inhibits replicon initiation and replication fork progression in response to DNA damage caused by UV (UV) radiation. It has been proposed that this signaling cascade protects against UV-induced mutations by reducing the probability that damaged DNA will be replicated before it can be repaired. Normal human fibroblasts (NHF) were depleted of ATR or CHK1, or treated with the CHK1 kinase inhibitor TCS2312, and the UV-induced mutation frequency at the HPRT locus was measured. Despite clear evidence of S-phase checkpoint abrogation, neither ATR/CHK1 depletion nor CHK1 inhibition caused an increase in the UV-induced HPRT mutation frequency. These results question the premise that the UV-induced intra-S checkpoint plays a prominent role in protecting against UV-induced mutagenesis.     

The role of melanocytes in protection against photooxidative stress Krystyna Stepień

Excessive exposure to solar ultraviolet radiation is an essential etiological factor for skin cancer. UV radiation, directly or indirectly through the generation of reactive oxygen species (ROS), causes damage to DNA, proteins and lipids, and induces inflammation and immunosuppression. Cutaneous pigmentation afforded by melanocytes is the main photoprotective mechanism in human skin. In response to UV, melanocytes produce melanin pigments and transfer them to adjacent keratinocytes. This review describes: (i) the photoprotective action of melanin; (ii) the regulation of UV-induced melanogenesis and the role of p53 in this process; (iii) the relation between melanogenic and antioxidant activities in melanocytes. The possible involvement of UV-induced ROS in the stimulation of melanin synthesis is also discussed.     

Tumor necrosis factor-alpha induces the phosphorylation of 28kDa stress proteins in endothelial cells: possible role in protection against cytotoxicity?

Tumor necrosis factor-alpha has been shown to rapidly increase the phosphorylation of three 28 kDa proteins in bovine aortic endothelial cells but not in L929 cells. Tumor necrosis factor-alpha induces the necrosis of the latter cells but not of the former. Arsenite enhanced the phosphorylation of the same 28kDa proteins as tumor necrosis factor-alpha in the endothelial cells. As stress proteins often play a protective role, we suggest that the phosphorylation of these proteins in endothelial cells may be responsible for the resistance of these cells to tumor necrosis factor-alpha.     

Symbiont‐conferred protection against Hymenopteran parasitoids in aphids: how general is it?

1. Hosts are often targeted by multiple species of parasites, leading to a confluence of selective pressures on them. In response, hosts may either evolve defences that act very generally, or specific defences against particular parasites. Aphids are attacked by multiple species of endoparasitoid wasps, and there is clear evidence that heritable endosymbionts can confer resistance against some of these wasps. Less clear is how symbiont‐conferred resistance in a single host acts against multiple parasitoid species. 2. This question was addressed in the black bean aphid, Aphis fabae (Scopoli). Unprotected aphids and aphids protected by three different strains of the defensive endosymbiont Hamiltonella defensa were exposed to four species of parasitic wasps: the parthenogenetic species Lysiphlebus fabarum (Marshall), which was represented by three different asexual lines, and the sexual species Aphidius colemani (Viereck), Binodoxys angelicae (Halliday), and Aphelinus chaonia (Walker). 3. Hamiltonella defensa provided strong protection against L. fabarum and Aphidius colemani, but there was no evidence that H. defensa‐infected aphids were more resistant to the other parasitoid species. While Aphidius colemani was virtually unable to parasitise any aphids harbouring H. defensa, there was variation among the three asexual lines of L. fabarum in how susceptible they were to the defence provided by the different symbiont strains, resulting in a significant genotype‐by‐genotype interaction. 4. The present results suggest that symbiosis with H. defensa does not provide aphids with a general defence against parasitoid wasps, possibly because some species have evolved specific counter adaptations or because biological differences preclude the symbiont's effectiveness against these species.     

Excess of malignancies in grandparents of children with malformations? Short communication

In a prospective study, the occurrence of malignancies in children referred to genetic counseling for congenital malformations, in their sibs, parents and grandparents was registered in 120 families by means of personal interviews. One hundred-and-twenty age matched subjects, admitted for acute respiratory infections or trauma, served as controls. No difference in the occurrence of tumors or leukemias between the two groups was found when the values of patients, sibs, and parents were compared. At the same time, the grandparents of probands with malformations had had significantly more malignancies than the grandparents of the controls. This may be explained by the fact that grandparents lived beyond the age of the usual onset of common cancers and leukemias.     

Coumarin derivatives protection against ROS production in cellular models of Aβ toxicities

The role of oxidative stress and free radicals in the development of Alzheimer's disease (AD) has been the focus of many recent studies. The role of hydrogen peroxide (H₂O₂) in AD is thought to be associated with Aβ (amyloid – β) damage in cells. A number of coumarin derivatives were previously found to be potent anti-inflammatory and antioxidant agents. Herein, these coumarin derivatives were tested as H₂O₂ scavengers with the DCF assay using two types of neuronal cells: (a) wild type (N2a) neuroblastoma cells and (b) APP/PS1 transgenic cell line expressing Aβ. Their scavenging activity was varied between the types of cell cultures and it was found to be concentration and time dependent in the mutant cells. Their protective role against cell death further supports this notion. These results suggest that these compounds could be used as a template in the design of new molecules with a possible role in AD.     

Peripheral organ doses from radiotherapy for heterotopic ossification of non-hip joints: Is there a risk for radiation-induced malignancies?

Radiotherapy, used for heterotopic ossification (HO) management, may increase radiation risk to patients. This study aimed to determine the peripheral dose to radiosensitive organs and the associated cancer risks due to radiotherapy of HO in common non-hip joints. A Monte Carlo model of a medical linear accelerator combined with a mathematical phantom representing an average adult patient were employed to simulate radiotherapy for HO with standard AP and PA fields in the regions of shoulder, elbow and knee. Radiation dose to all out-of-field radiosensitive organs defined by the International Commission on Radiological Protection was calculated. Cancer induction risk was estimated using organ-specific risk coefficients. Organ dose change with increased field dimensions was also evaluated. Radiation therapy for HO with a 7 Gy target dose in the sites of shoulder, elbow and knee, resulted in the following equivalent organ dose ranges of 0.85–62 mSv, 0.28–1.6 mSv and 0.04–1.6 mSv, respectively. Respective ranges for cancer risk were 0–5.1, 0–0.6 and 0–1.3 cases per 10⁴ persons. Increasing the field size caused an average increase of peripheral doses by 15–20%. Individual organ dose increase depends upon the primary treatment site and the distance between organ of interest and treatment volume. Relatively increased risks of more than 1 case per 10,000 patients were found for skin, breast and thyroid malignancies after treatment in the region of shoulder and for skin cancer following elbow irradiation. The estimated risk for inducing any other malignant disease ranges from negligible to low.     

Moralization as protection against exploitation: do individuals without allies moralize more?

Over the course of human evolutionary history, individuals have required protection from other individuals who sought to exploit them. Moralization – broadcasting relevant behaviors as immoral – is proposed as a strategy whereby individuals attempt to engage third parties in the protection against exploitation. Whereas previous accounts of strategic morality have focused on the effect of individual differences in mating strategies, we here argue for the importance of another factor: differences in the availability of alternative sources of protection. Given the potential costs of moralization, it is predicted that it is primarily used among individuals lacking protection in the form of social allies. Consistent with this, a large cross-national set of surveys is used to reveal how individuals without friends moralize more. In contrast, however, support from other social sources such as family or religious individuals increases moralization.     

The secretory ependymal cells of the subcommissural organ: Which role in hydrocephalus?

Ependyma in the central nervous system gives rise to several specialized cell types, including the secretory ependymal cells located in the subcommissural organ. These elongated cells show large cisternae in their cytoplasm, which are filled with material secreted into the cerebrospinal fluid and toward the leptomeningeal spaces. A specific secretion of the subcommissural organ was named SCO-spondin, regarding its marked homology with developmental proteins of the thrombospondin superfamily (presence of thrombospondin type 1 repeats). The ependymal cells of the subcommissural organ and SCO-spondin secretion are suspected to play a crucial role in cerebrospinal fluid flow and/or homeostasis. There is a close correlation between absence of the subcommissural organ and hydrocephalus in rat and mouse strains exhibiting congenital hydrocephalus, and in a number of mice transgenic for developmental genes. The ependymal cells of the subcommissural organ are under research as a key factor in several developmental processes of the central nervous system.     

Polyethylene glycols interact with membrane glycerophospholipids: is this part of their mechanism for hypothermic graft protection?

Polyethylene glycol (PEG), a high-molecular-weight colloid present in new organ preservation solutions, protects against cold ischemia injuries leading to better graft function of transplanted organs. This protective effect cannot be totally explained by immuno-camouflaging property or signaling-pathway modifications. Therefore, we sought for an alternative mechanism dependent on membrane fluidity. Using the Langmuir–Pockles technique, we show here that PEGs interacted with lipid monolayers of defined composition or constituted by a renal cell lipid extract. High-molecular-weight PEGs stabilized the lipid monolayer at low surface pressure. Paradoxically, at high surface pressure, PEGs destabilized the monolayers. Hypothermia reduced the destabilization of saturated monolayer whereas unsaturated monolayer remained unaffected. Modification of ionic strength and pH induced a stronger stabilizing effect of PEG 35,000 Da which could explain its reported higher effectiveness on cold-induced injuries during organ transplantation. This study sheds a new light on PEG protective effects during organ preservation different from all classical hypotheses.