Serum amyloid P (female protein) of the Syrian hamster. Gene structure and expression

Different response of Acipenser gueldenstaedtii CRP/SAP and SAA to bacterial challenge and chronic thermal stress sheds light on the innate immune system of sturgeons

Sturgeons are chondrostean fish critically endangered due to anthropogenic loss and degradation of natural habitat and overfishing for meat and caviar production. Consequently, sturgeon aquaculture has extensively developed lately, being Russian sturgeon (Acipenser gueldenstaedtii) the second most important species reared for caviar production. However, Russian sturgeon aquaculture in subtropical countries, such as Uruguay, confronts difficulties because fish have to endure excessive summertime warm temperatures, which weaken their innate defences facilitating opportunistic infections. To address this problem, we look for identifying putative acute phase proteins (APPs), which might be robust serum biomarkers of both infection and chronic thermal stress, applied to monitoring Russian sturgeon health status in farms. We focused on the C-Reactive Protein/Serum Amyloid P (CRP/SAP) pentraxin since the pentraxin family includes well-known APPs, better characterised in mammals than fish. We identified A.gueldenstaedtii CRP/SAP (AgCRP/SAP), as a member of the universal CRP/SAP pentraxin sub-family, and studied AgCRP/SAP involvement in sturgeon response to bacterial challenge and chronic thermal stress, in comparison with A. gueldenstaedtii Serum Amyloid A (AgSAA), a previously described positive APP. Results showed that AgCRP/SAP is a constitutive serum component that remained constant upon Aeromonas hydrophila challenge and chronic thermal stress. Contrastingly, serum AgSAA was subjected to regulation by bacterial and thermal stress challenges, showing a 50-fold increase and 3-fold decline in serum levels, respectively. Overall, results highlight the potential value of AgSAA, but not of AgCRP/SAP, as a biomarker of bacterial infection and the need to continue searching for robust chronic thermal stress biomarkers in sturgeons.

Zebrafish C-reactive protein isoforms inhibit SVCV replication by blocking autophagy through interactions with cell membrane cholesterol

In the present work, the mechanisms involved in the recently reported antiviral activity of zebrafish C-reactive protein-like protein (CRP1-7) against the spring viraemia of carp rhabdovirus (SVCV) in fish are explored. The results neither indicate blocking of the attachment or the binding step of the viral replication cycle nor suggest the direct inhibition of G protein fusion activity or the stimulation of the host’s interferon system. However, an antiviral state in the host is induced. Further results showed that the antiviral protection conferred by CRP1-7 was mainly due to the inhibition of autophagic processes. Thus, given the high affinity of CRPs for cholesterol and the recently described influence of the cholesterol balance in lipid rafts on autophagy, both methyl-β-cyclodextrin (a cholesterol-complexing agent) and 25-hydroxycholesterol (a cholesterol molecule with antiviral properties) were used to further describe CRP activity. All the tested compounds exerted antiviral activity by affecting autophagy in a similar manner. Further assays indicate that CRP reduces autophagy activity by initially disturbing the cholesterol ratios in the host cellular membranes, which in turn negatively affects the intracellular regulation of reactive oxygen species (ROS) and increases lysosomal pH as a consequence. Ultimately, here we propose that such pH changes exert an inhibitory direct effect on SVCV replication by disrupting the pH-dependent membrane-fusogenic ability of the viral glycoprotein G, which allows the release of the virus from endosomes into cytoplasm during its entry phase.

Sex differences impact the lung-bone inflammatory response to repetitive inhalant lipopolysaccharide exposures in mice

Skeletal health consequences associated with inflammatory diseases of the airways significantly contribute to morbidity. Sex differences have been described independently for lung and bone diseases. Repetitive inhalant exposure to lipopolysaccharide (LPS) induces bone loss and deterioration in male mice, but comparison effects in females are unknown. Using an intranasal inhalation exposure model, 8-week-old C57BL/6 male and female mice were treated daily with LPS (100 ng) or saline for 3 weeks. Bronchoalveolar lavage fluids, lung tissues, tibias, bone marrow cells, and blood were collected. LPS-induced airway neutrophil influx, interleukin (IL)-6 and neutrophil chemoattractant levels, and bronchiolar inflammation were exaggerated in male animals as compared to female mice. Trabecular bone micro-CT imaging and analysis of the proximal tibia were conducted. Inhalant LPS exposures lead to deterioration of bone quality only in male mice (not females) marked by decreased bone mineral density, bone volume/tissue volume ratio, trabecular thickness and number, and increased bone surface-to-bone volume ratio. Serum pentraxin-2 levels were modulated by sex differences and LPS exposure. In proof-of-concept studies, ovarectomized female mice demonstrated LPS-induced bone deterioration, and estradiol supplementation of ovarectomized female mice and control male mice protected against LPS-induced bone deterioration findings. Collectively, sex-specific differences exist in LPS-induced airway inflammatory consequences with significant differences found in bone quantity and quality parameters. Male mice demonstrated susceptibility to bone loss and female animals were protected, which was modulated by estrogen. Therefore, sex differences influence the biologic response in the lung-bone inflammatory axis in response to inhalant LPS exposures.

Evolution of the pentraxin family: the new entry PTX4

Pentraxins (PTXs) are a superfamily of multifunctional conserved proteins, some of which are components of the humoral arm of innate immunity and behave as functional ancestors of Abs. They are divided into short (C-reactive protein and serum amyloid P component) and long pentraxins (PTX3 and neuronal pentraxins). Based on a search for pentraxin domain-containing sequences in databases, a phylogenetic analysis of the pentraxin family from mammals to arthropods was conducted. This effort resulted in the identification of a new long pentraxin (PTX4) conserved from mammals to lower vertebrates, which clusters alone in phylogenetic analysis. The results indicated that the pentraxins consist of five clusters: short pentraxins, which can be found in chordate and arthropods; neuronal pentraxins; the prototypic long pentraxin PTX3, which originated very early at the divergence of the vertebrates; the Drosophila pentraxin-like protein B6; and the long pentraxin PTX4 discovered in this study. Conservation of flanking genes in mammalian evolution indicates maintenance of synteny. Analysis of PTX4, in silico and by transcript expression, shows that the gene is well conserved from mammals to lower vertebrates and has a unique pattern of mRNA expression. Thus, PTX4 is a new unique member of the pentraxin superfamily, conserved in evolution.

Isolation of two C-reactive protein homologues from cod (Gadus morhua L.) serum

Pentraxins are important molecules in innate defence and play a role in the acute phase response of both mammals and fish. Isolation of cod pentraxins by affinity chromatography using phosphorylcholine agarose revealed two pentraxin-like proteins, referred to as PI and PII proteins. These varied in their overall charge, pentameric and subunit molecular size, glycosylation and N-terminal amino acid sequences. The PI protein was homologous with the CRP-like pentraxin previously described in cod whereas the PII protein was a new CRP homologue, which was characterized by substantial individual heterogeneity with regard to subunit size and relative density. The results indicate considerable genetic variations in the cod pentraxins.

A female-specific pentraxin, CrOctin, bridges pattern recognition receptors to bacterial phosphoethanolamine

Pathogen recognition and binding are crucial functions of innate immunity. It has been observed that the short pentraxin superfamily including C-reactive protein (CRP) and serum amyloid P component are pathogen pattern recognition receptors (PRR) in the plasma. We isolated and characterized a novel and distinctive pentraxin from the plasma of horseshoe crab, Carcinoscorpius rotundicauda, henceforth named CrOctin, which binds to bacteria via phosphoethanolamine (PE), a chemical component present on lipid A and core polysaccharide moieties of bacterial lipopolysaccharide (LPS). Infection enhances the formation of the PRR interactome constituting CrOctin, CRP and galactose-binding protein. In particular, infection increases the affinity of CRP to CrOctin by 1000-fold. Furthermore, we observed that by binding to PE, CrOctin acts as a linker that bridges the PRR interactome to the inner core of LPS. On the other hand, under normal physiological conditions, binding of CrOctin to PE appears to obscure other PRR from interacting directly with PE. Interestingly, the cluster of "CrOctin-interactive PRR" is sex specific. We report, for the first time, the change in PRR protein profiles with a distinctive gender difference during Pseudomonas infection.

Hormonal effects on hamster lacrimal gland female-specific major 20 kDa secretory protein and its immunological similarity with submandibular gland major male-specific proteins

Hormonal regulation of a major 20 kDa protein of hamster exorbital lacrimal gland (LG) was studied by SDS-PAGE profile analysis and the purified protein's antisera was used to screen tissues of hamster and other species for crossreacting proteins. This protein was seen in female LG but not in males and late-pregnant or hCG-treated females. Low estrogen state in females after gonadectomy, prolonged light-deprivation, prolonged starvation or lactation increased its level several folds to approximately 20% of LG soluble proteins and similar levels were induced in males after gonadectomy (low androgen state). However, light-deprivation or melatonin treatment-induced low androgen state in males had no effect. In gonadectomized hamsters, this LG protein was obliterated on treatment with androgens, estrogens or thyroid hormones. Only estrogen inhibition of LG 20 kDa was prevented by simultaneous tamoxifen administration. Simultaneous treatment of gonadectomized hamsters with gonadotrophins and estrogen/androgen did not prevent the LG 20 kDa protein's inhibition. Relative potencies of estrogens (3.6 microg daily dose) were: estradiol-17beta approximately diethylstilbestrol > estrone > estradiol-17alpha, while estriol and chlorotrianisene had no effect. Dexamethasone, progesterone, prolactin, hypothyroid state or adrenalectomy had no effect on LG 20 kDa expression. Western blot studies confirmed the marked repression of LG 20 kDa by estrogen androgen and thyroid hormone and detected the protein in tears of females and gonadectomized hamsters but not in males. Interestingly, among other tissues tested, crossreaction was only seen with the estrogen-repressed 24 and 20.5 kDa major male-specific secretory proteins of hamster submandibular glands (SMG) which were previously reported by us. This strongly indicated that the LG and SMG proteins are products of the same or closely related genes. A possible role for these hamster sex-specific LG and SMG major secretory proteins in olfactory communication is suggested.

Cloning and sequencing of cDNA encoding haptoglobin, an acute phase protein in Syrian hamster, Mesacricetus auratus

One of the most prominent acute phase proteins in Syrian hamster (Mesacricetus auratus) was identified as haptoglobin and cDNA encoding this protein was sequenced. The deduced amino acid sequence of the mature protein is 83.6, 80.5, 79.6, and 76.1% identical to those of mouse, rat, human (1 s isoform), and dog homologues, respectively. As compared with six known members of this family, including human haptoglobin-related protein, hamster haptoglobin had 11 unique substitutions and one unique codon deletion, that is, the corresponding residues have been conserved in all other members. This indicates that hamster haptoglobin gene has accumulated these unique mutations after the time of cricetid-murid split while the ancestral sequence has been conserved in all other species examined. Hamster haptoglobin, however, contains nine cysteine residues, all of which are found in conserved positions in primate and rodent homologues. Molecular phylogenetic trees of alpha- and beta-chains show that the alpha-chain is more divergent than the beta-chain and that the difference in genetic distance between canine and hamster alpha-chains is much greater than that of corresponding beta-chains.

Effects of hormone replacement therapy on serum amyloid P component in postmenopausal women

The pentraxin serum amyloid P component (SAP) is a 9.5Sz1-glycoprotein and it has recently been found to be deposited in atherosclerotic lesions or neurofibrillary tangles, which are related to the aging process and Alzheimer's disease. The level of SAP was measured by micro single radial-immunodiffusion. Sample sera were obtained from 420 healthy humans, from newborn to 86 years old. The changes in SAP during the menstrual cycle were investigated in 6 women that were 20-21 years. Fifty of the postmenopausal women, suffering from climacteric symptoms, were administered either conjugated estrogen (E), or dehydroepiandrosterone (DHEA). The SAP levels increased with age, being 1.12 +/- 0.82 mg/dl (means +/- S.D.) in neonates, and 6.15 +/- 0.92 mg/dl in persons over 80 years. The SAP level in the females between 15 and 49 years (3.32 +/- 0.95 mg/dl) was significantly (P < 0.001) lower than that in the males in the same age group (5.19 +/- 1.25 mg/dl). The SAP level in the follicular phase was significantly (P < 0.01) lower than that in menstrual phase (menstrual: 4.36 +/- 0.90 mg/dl versus follicular: 2.61 +/- 0.99 mg/dl). In the post-menopausal women that were administered E (1.25 mg/day), the SAP decreased significantly (P < 0.001) from the prelevel of 5.64 +/- 1.40 mg/dl to 4.26 +/- 0.98 mg/dl on the 14th day. In the postmenopausal women that were administered DHEA (60 mg/day), the SAP increased rapidly from the prelevel of 4.97 +/- 0.76 mg/dl to 6.17 +/- 1.20 mg/dl on the 21st day. SAP seems to be a marker that can monitor the effect of hormone replacement therapy.

Acute phase proteins and transformed cells

Acute phase proteins (APP) are plasma proteins whose concentration and glycosylation alters in response to tissue injury, inflammation, or tumor growth. Significant interspecies and sex differences in APP response exist. APP are produced mainly by hepatocytes, and their synthesis and glycosylation are controlled by a network consisting of cytokines, their soluble receptors, and glucocorticoids. The major cytokines involved in these processes belong to a group of interleukin-6-type cytokines that act through the hematopoietin receptor complex on hepatocytes and JAK-STAT signal transduction pathway. Transformed cells (hepatoma) display significant differences in synthesis of APP, cytokine responsiveness, expression of cytokine-receptor subunits and signal-transduction machinery. The most striking variability relates to the glycosylation alterations induced by cytokines. However, transformed cells (hepatoma) form a basic model for studying and understanding mechanisms controlling the synthesis and glycosylation of APP. Furthermore, APP may be secreted by transformed (tumor) cells of various origins and may display a growth factor-like function in certain cancer types.

Structure and function of the pentraxins

Over the past two years, the three-dimensional structure of the serum amyloid P component was defined by X-ray diffraction, the first such visualization of a pentraxin. Binding sites for calcium, ligands and complement were identified. New fusion proteins with amino acid sequence homology to the pentraxins were described, and new insights were gained into pentraxin phylogeny, biosynthesis, ligands, complement activation, leukocyte reactivity and biological functions in vivo.

Serum amyloid-P component of the Armenian hamster: gene structure and comparison with structure and expression of the SAP gene from Syrian hamster

Serum amyloid P (SAP), a phylogenetically conserved pentraxin, is an integral component of all amyloid deposits. Regulation of expression of SAP gene expression is quite different in two related hamster species. In Syrian hamsters, the resting serum levels of SAP are determined by gender, and the direction of alteration following inflammation is divergent. In Armenian hamsters, SAP is not a prominent acute-phase reactant and there is no gender dimorphism of expression. The structure and expression of the SAP gene of the Armenian hamsters was investigated by isolation of genomic clones, nucleotide sequence analysis, and RNA studies. The gene structure of Armenian hamster SAP is similar to the genes of all other pentraxins studied. While the upstream regions of the SAP genes of Syrian and Armenian hamsters are quite similar, important differences in potential enhancer sites have been recognized by comparing the corresponding sequences of SAP genes from both species. Little alteration in hepatic levels of transcripts encoding SAP or CRP, the other pentraxin, were noted following administration of lipopolysaccharide to Armenian hamsters. This relative lack of response occurred despite a marked acute phase reaction documented for serum amyloid A mRNA levels.