Chaperone insufficiency links TLR4 protein signaling to endoplasmic reticulum stress

Inflammation plays an important pathogenic role in a number of metabolic diseases such as obesity, type 2 diabetes, and atherosclerosis. The activation of inflammation in these diseases depends at least in part on the combined actions of TLR4 signaling and endoplasmic reticulum stress, which by acting in concert can boost the inflammatory response. Defining the mechanisms involved in this phenomenon may unveil potential targets for the treatment of metabolic/inflammatory diseases. Here we used LPS to induce endoplasmic reticulum stress in the human monocyte cell-line, THP-1. The unfolded protein response, produced after LPS, was dependent on CD14 activity but not on RNA-dependent protein kinase and could be inhibited by an exogenous chemical chaperone. The induction of the endoplasmic reticulum resident chaperones, GRP94 and GRP78, by LPS was of a much lower magnitude than the effect of LPS on TLR4 and MD-2 expression. In face of this apparent insufficiency of chaperone expression, we induced the expression of GRP94 and GRP78 by glucose deprivation. This approach completely reverted endoplasmic reticulum stress. The inhibition of either GRP94 or GRP78 with siRNA was sufficient to rescue the protective effect of glucose deprivation on LPS-induced endoplasmic reticulum stress. Thus, insufficient LPS-induced chaperone expression links TLR4 signaling to endoplasmic reticulum stress.     

Effect of antibiotics on the bacterial population of the rabbit caecum

The effect feeding antibiotics has on the bacterial population of the rabbit caecum was investigated. No changes in total volatile fatty acid production or total bacterial counts were observed compared with nonantibiotic treated controls. However, treatment with chlortetracycline resulted in an increase of propionate at the apparent cost of butyrate (P<0.05). Denaturing gradient gel electrophoresis analysis indicated that the two antibiotics that inhibit protein synthesis (chlortetracycline and tiamulin) exerted the most similar changes on the bacterial population structure, decreasing the diversity of the profiles. Sequence analysis of DNA from excised denaturing gradient gel electrophoresis bands was carried out. The majority of the sequences observed were most similar to bacterial sequences previously described in other gut environments, with 11% being most similar to those previously reported from the rabbit, and 95% of the sequences having 95% or greater identity to sequences already in GenBank.     

Taste memory formation: role of nucleus accumbens

When a novel taste has been associated with postingestive malaise, animals recognize this taste as aversive. This associative learning is known as conditioned taste aversion. However, when an animal consumes a novel taste and no aversive consequences follow, it becomes recognized as a safe signal, leading to an increase in its consumption in subsequent presentations. In this review, we will discuss the results related to the taste memory formation focusing particularly on the nucleus accumbens (NAcc). The NAcc keeps projections with amygdala, insular cortex, parabrachial nucleus, and nucleus of the solitary tract areas important for taste memory formation. We will review the evidence relating to how the NAcc could be involved in taste memory formation, due to its role in the taste memory trace formation and its role in the association of the conditioned stimulus-unconditioned stimulus, and finally the retrieval of taste memory. In this context, we will review the participation of the cholinergic, dopaminergic, and glutamatergic systems in the NAcc during taste memory formation.     

Overexpression of Gremlin-1 in Patients with Loeys-Dietz Syndrome: Implications on Pathophysiology and Early Disease Detection

Backgrounds

The Loeys-Dietz syndrome (LDS) is an inherited connective tissue disorder caused by mutations in the transforming growth factor β (TGF-β) receptors TGFBR1 or TGFBR2. Most patients with LDS develop severe aortic aneurysms resulting in early need of surgical intervention. In order to gain further insight into the pathophysiology of the disorder, we investigated circulating outgrowth endothelial cells (OEC) from the peripheral blood of LDS patients from a cohort of 23 patients including 6 patients with novel TGF-β receptor mutations.

Methods and Results

We performed gene expression profiling of OECs using microarray analysis followed by quantitative PCR for verification of gene expression. Compared to OECs of age- and sex-matched healthy controls, OECs isolated from three LDS patients displayed altered expression of several genes belonging to the TGF-β pathway, especially those affecting bone morphogenic protein (BMP) signalling including BMP2, BMP4 and BMPR1A. Gene expression of BMP antagonist Gremlin-1 (GREM1) showed the most prominent up-regulation. This increase was confirmed at the protein level by immunoblotting of LDS-OECs. In immunohistochemistry, abundant Gremlin-1 protein expression could be verified in endothelial cells as well as smooth muscle cells within the arterial media. Furthermore, Gremlin-1 plasma levels of LDS patients were significantly elevated compared to healthy control subjects.

Conclusions

These findings open new avenues in the understanding of the pathogenesis of Loeys-Dietz syndrome and the development of new diagnostic serological methods for early disease detection.     

Increased Na+/Ca2+ Exchanger Expression/Activity Constitutes a Point of Inflection in the Progression to Heart Failure of Hypertensive Rats

Spontaneously hypertensive rat (SHR) constitutes a genetic model widely used to study the natural evolution of hypertensive heart disease. Ca²⁺-handling alterations are known to occur in SHR. However, the putative modifications of Ca²⁺-handling proteins during the progression to heart failure (HF) are not well established. Moreover, the role of apoptosis in SHR is controversial. We investigated intracellular Ca²⁺, Ca²⁺-handling proteins and apoptosis in SHR vs. control Wistar rats (W) from 3 to 15 months (mo). Changes associated with the transition to HF (i.e. lung edema and decrease in midwall fractional shortening), occurred at 15 mo in 38% of SHR (SHRF). In SHRF, twitch and caffeine-induced Ca²⁺ transients, significantly decreased relative to 6/9 mo and 15 mo without HF signs. This decrease occurred in association with a decrease in the time constant of caffeine-Ca²⁺ transient decay and an increase in Na⁺/Ca²⁺ exchanger (NCX) abundance (p<0.05) with no changes in SERCA2a expression/activity. An increased Ca²⁺-calmodulin-kinase II activity, associated with an enhancement of apoptosis (TUNEL and Bax/Bcl2) was observed in SHR relative to W from 3 to 15 mo. Conclusions: 1. Apoptosis is an early and persistent event that may contribute to hypertrophic remodeling but would not participate in the contractile impairment of SHRF. 2. The increase in NCX expression/activity, associated with an increase in Ca²⁺ efflux from the cell, constitutes a primary alteration of Ca²⁺-handling proteins in the evolution to HF. 3. No changes in SERCA2a expression/activity are observed when HF signs become evident.     

Climatic effects and phenological mismatch in cuckoo–host interactions: a role for host phenotypic plasticity in laying date?

Climatic effects on breeding phenology vary across organisms and therefore might promote a phenological mismatch in ecologically interacting species, including those engaged in coevolutionary interactions such as brood parasites and their hosts. Recent studies suggest that climatic induced changes in migration phenology may have mismatched cuckoos and their hosts in Europe. However, it is currently unknown whether cuckoo–host phenological mismatch results from different degrees of phenotypic plasticity or to different speeds of microevolutionary processes affecting hosts and parasites. Here we performed 1) cross‐sectional correlations between climate conditions and population level of phenological mismatch between the migratory brood parasite great spotted cuckoo Clamator glandarius and its main resident host in Europe, the magpie Pica pica; and 2) a longitudinal analysis to study within‐individual variation in breeding phenology for individual hosts experiencing different climate conditions over a period of nine years (2005–2013). Cross‐sectional analyses revealed independent and contrary effects of winter and spring temperature on magpie phenology: magpie hosts tend to breed earlier those years with lower February temperatures, however, high temperature in the first half of April spur individuals to lay eggs. Breeding phenology of cuckoos was tuned to that of their magpie host in time and duration. However, annual phenological mismatch between cuckoos and magpie hosts increased with NAO index and January temperature. Longitudinal analyses revealed high individual consistency in magpie host phenology, but a low influence of climate, suggesting that the climatic‐driven phenological mismatch between cuckoos and magpies at the population‐level cannot be explained by a host plastic response to climatic conditions.     

Dark nests and egg colour in birds: a possible functional role of ultraviolet reflectance in egg detectability

Owing to the conspicuousness of ultraviolet (UV) colour in dark environments, natural selection might have selected UV egg coloration because it would enhance egg detectability by parents in murky nests. Here, we tested this hypothesis by using comparative and experimental approaches. First, we studied variation in egg coloration of 98 species of European passerines measured using UV-visible reflectance spectrometry (300-700nm) in relation to nesting habits. Analyses based on raw data and controlling for phylogenetic distances both at the species and the family levels revealed that hole-nester species produced eggs with higher UV reflectance than those nesting in open habitats. The experimental approach consisted of the manipulation of UV reflectance of the experimental eggs introduced outside the nest-cup of the hole-nester spotless starling Sturnus unicolor and the study of the retrieval of these eggs. Ultraviolet-reflecting eggs (controls) were more frequently retrieved to the nest-cup than non-reflecting (-UV) eggs. These results were not due to '-UV' eggs being recognized by starlings as parasitic because when a parasitic egg is detected, starlings removed it from the nest-box. Therefore, these results are consistent with the hypothesis that UV egg colours are designed to provide highly detectable targets for parent birds in dark nest environments.