Lessons from comparative physiology: could uric acid represent a physiologic alarm signal gone awry in western society?

Uric acid has historically been viewed as a purine metabolic waste product excreted by the kidney and gut that is relatively unimportant other than its penchant to crystallize in joints to cause the disease gout. In recent years, however, there has been the realization that uric acid is not biologically inert but may have a wide range of actions, including being both a pro- and anti-oxidant, a neurostimulant, and an inducer of inflammation and activator of the innate immune response. In this paper, we present the hypothesis that uric acid has a key role in the foraging response associated with starvation and fasting. We further suggest that there is a complex interplay between fructose, uric acid and vitamin C, with fructose and uric acid stimulating the foraging response and vitamin C countering this response. Finally, we suggest that the mutations in ascorbate synthesis and uricase that characterized early primate evolution were likely in response to the need to stimulate the foraging “survival” response and might have inadvertently had a role in accelerating the development of bipedal locomotion and intellectual development. Unfortunately, due to marked changes in the diet, resulting in dramatic increases in fructose- and purine-rich foods, these identical genotypic changes may be largely responsible for the epidemic of obesity, diabetes and cardiovascular disease in today’s society. Disclaimers  Dr Johnson is listed as an inventor on several patent applications related to the role of uric acid in hypertension and metabolic syndrome; Dr Johnson is also an author for a book on fructose and uric acid (The Sugar Fix) that was published by Rodale in 2008.     

Antiproliferative activity of guava leaf extract via inhibition of prostaglandin endoperoxide H synthase isoforms

Prostaglandin endoperoxide H synthase (PGHS) is a key enzyme for the synthesis of prostaglandins (PGs) which play important roles in inflammation and carcinogenesis. Because the extract from Psidium guajava is known to have a variety of beneficial effects on our body including the anti-inflammatory, antioxidative and antiproliferative activities, we investigated whether the extract inhibited the catalytic activity of the two PGHS isoforms using linoleic acid as an alternative substrate. The guava leaf extract inhibited the cyclooxygenase reaction of recombinant human PGHS-1 and PGHS-2 as assessed by conversion of linoleic acid to 9- and 13-hydroxyoctadecadienoic acids (HODEs). The guava leaf extract also inhibited the PG hydroperoxidase activity of PGHS-1, which was not affected by nonsteroidal anti-inflammatory drugs (NSAIDs). Quercetin which was one of the major components not only inhibited the cyclooxygenase activity of both isoforms but also partially inhibited the PG hydroperoxidase activity. Overexpression of human PGHS-1 and PGHS-2 in the human colon carcinoma cells increased the DNA synthesis rate as compared with mock-transfected cells which did not express any isoforms. The guava leaf extract not only inhibited the PGE₂ synthesis but also suppressed the DNA synthesis rate in the PGHS-1- and PGHS-2-expressing cells to the same level as mock-transfected cells. These results demonstrate the antiproliferative activity of the guava leaf extract which is at least in part caused by inhibition of the catalytic activity of PGHS isoforms.     

SLPI prevents cytokine release in mite protease-exposed conjunctival epithelial cells

House dust mites are a major source of allergens associated with allergic diseases including allergic conjunctivitis. Here, we demonstrate that mite-derived serine protease activity induces the release of cytokines from human ocular conjunctival epithelial cells in vitro and innate antiproteases, secretory leukocyte protease inhibitor (SLPI) and α1-antitrypsin, can inhibit the response. An extract prepared from a whole-mite culture induced the release of IL-6 and IL-8 and upregulated their gene expression in the human conjunctival epithelial cell line Chang, responses which were inhibited not only by a synthetic serine protease-specific inhibitor, AEBSF, but also by SLPI and α1-antitrypsin at a physiologically relevant concentration. The findings suggest a homeostatic role for SLPI and α1-antitrypsin against the proteases contained in allergen sources in the ocular conjunctiva and that exposure to house dust particles containing mite-derived serine protease activity could be involved in the initiation of sensitization through the ocular conjunctival epithelium and/or exacerbation of allergic conjunctivitis.     

TRIM44 interacts with and stabilizes terf, a TRIM ubiquitin E3 ligase

Terf/TRIM17 is a member of the TRIM family of proteins, which is characterized by the RING finger, B-box, and coiled-coil domains. In the present study, we found that terf interacts with TRIM44. Terf underwent ubiquitination in vitro in the presence of the E2 enzyme UbcH6; this suggests that terf exhibits E3 ubiquitin ligase activity. It was also found that terf was conjugated with polyubiquitin chains and stabilized by the proteasome inhibitor in mammalian cells; this suggested that terf rendered itself susceptible to proteasomal degradation through polyubiquitination. We also found that TRIM44 inhibited ubiquitination of terf, and thus stabilized the protein. The N-terminal region of TRIM44 contains a zinc-finger domain found in ubiquitin hydrolases (ZF UBP) and ubiquitin specific proteases (USPs). Thus, we proposed that TRIM44 may function as a new class of the “USP-like-TRIM” which regulates the activity of associated TRIM proteins.     

Polycystic Kidney Disease in the Medaka (Oryzias latipes) pc Mutant Caused by a Mutation in the Gli-Similar3 (glis3) Gene

Polycystic kidney disease (PKD) is a common hereditary disease in humans. Recent studies have shown an increasing number of ciliary genes that are involved in the pathogenesis of PKD. In this study, the Gli-similar3 (glis3) gene was identified as the causal gene of the medaka pc mutant, a model of PKD. In the pc mutant, a transposon was found to be inserted into the fourth intron of the pc/glis3 gene, causing aberrant splicing of the pc/glis3 mRNA and thus a putatively truncated protein with a defective zinc finger domain. pc/glis3 mRNA is expressed in the epithelial cells of the renal tubules and ducts of the pronephros and mesonephros, and also in the pancreas. Antisense oligonucleotide-mediated knockdown of pc/glis3 resulted in cyst formation in the pronephric tubules of medaka fry. Although three other glis family members, glis1a, glis1b and glis2, were found in the medaka genome, none were expressed in the embryonic or larval kidney. In the pc mutant, the urine flow rate in the pronephros was significantly reduced, which was considered to be a direct cause of renal cyst formation. The cilia on the surface of the renal tubular epithelium were significantly shorter in the pc mutant than in wild-type, suggesting that shortened cilia resulted in a decrease in driving force and, in turn, a reduction in urine flow rate. Most importantly, EGFP-tagged pc/glis3 protein localized in primary cilia as well as in the nucleus when expressed in mouse renal epithelial cells, indicating a strong connection between pc/glis3 and ciliary function. Unlike human patients with GLIS3 mutations, the medaka pc mutant shows none of the symptoms of a pancreatic phenotype, such as impaired insulin expression and/or diabetes, suggesting that the pc mutant may be suitable for use as a kidney-specific model for human GLIS3 patients.     

TRAF6 Establishes Innate Immune Responses by Activating NF-κB and IRF7 upon Sensing Cytosolic Viral RNA and DNA

Background

In response to viral infection, the innate immune system recognizes viral nucleic acids and then induces production of proinflammatory cytokines and type I interferons (IFNs). Toll-like receptor 7 (TLR7) and TLR9 detect viral RNA and DNA, respectively, in endosomal compartments, leading to the activation of nuclear factor κB (NF-κB) and IFN regulatory factors (IRFs) in plasmacytoid dendritic cells. During such TLR signaling, TNF receptor-associated factor 6 (TRAF6) is essential for the activation of NF-κB and the production of type I IFN. In contrast, RIG-like helicases (RLHs), cytosolic RNA sensors, are indispensable for antiviral responses in conventional dendritic cells, macrophages, and fibroblasts. However, the contribution of TRAF6 to the detection of cytosolic viral nucleic acids has been controversial, and the involvement of TRAF6 in IRF activation has not been adequately addressed.

Principal Findings

Here we first show that TRAF6 plays a critical role in RLH signaling. The absence of TRAF6 resulted in enhanced viral replication and a significant reduction in the production of IL-6 and type I IFNs after infection with RNA virus. Activation of NF-κB and IRF7, but not that of IRF3, was significantly impaired during RLH signaling in the absence of TRAF6. TGFβ-activated kinase 1 (TAK1) and MEKK3, whose activation by TRAF6 during TLR signaling is involved in NF-κB activation, were not essential for RLH-mediated NF-κB activation. We also demonstrate that TRAF6-deficiency impaired cytosolic DNA-induced antiviral responses, and this impairment was due to defective activation of NF-κB and IRF7.

Conclusions/Significance

Thus, TRAF6 mediates antiviral responses triggered by cytosolic viral DNA and RNA in a way that differs from that associated with TLR signaling. Given its essential role in signaling by various receptors involved in the acquired immune system, TRAF6 represents a key molecule in innate and antigen-specific immune responses against viral infection.     

Determination of pyrrole–imidazole polyamide in rat plasma by liquid chromatography–tandem mass spectrometry

Pyrrole (Py)–imidazole (Im) polyamides synthesized by combining N-methylpyrrole and N-methylimidazole amino acids have been identified as novel candidates for gene therapy. In this study, a sensitive method using liquid chromatography–tandem mass spectrometry (LC–MS/MS) with an electrospray ionization (ESI) source was developed and validated for the determination and quantification of Py–Im polyamide in rat plasma. Py–Im polyamide was extracted from rat plasma by solid-phase extraction (SPE) using a Waters Oasis^® HLB cartridge. Separation was achieved on an ACQUITY UPLC HSS T3 (1.8 μm, 2.1 × 50 mm) column by gradient elution using acetonitrile:distilled water:acetic acid (5:95:0.1, v/v/v) and acetonitrile:distilled water:acetic acid (95:5:0.1, v/v/v). The method was validated over the range of 10–1000 ng/mL and the lower limit of quantification (LLOQ) was 10 ng/mL. This method was successfully applied to the investigation of the pharmacokinetics of Py–Im polyamide after intravenous administration.     

Zoonotic filariasis caused by Onchocerca dewittei japonica in a resident of Hiroshima Prefecture,Honshu, Japan

A female of Onchocerca sp. was found to be the probable causative agent of a subcutaneous nodule in the left knee of a 70-year-old man in a rural area of Hiroshima Prefecture, Honshu, the main island of Japan. We compared the characteristics of the agent with the features of the four previously suspected species found in cattle and horses in various parts of the world, as well as O. lupi and O. jakutensis that were suspected or proved, respectively, in zoonotic cases in Europe. In addition, the morphologic characteristics of this parasite were compared with those of the four Onchocerca species found in wild animals in Japan. Based on such characteristics as the large triangle ridges, the considerable distance between any two adjacent ridges, and the absence of inner cuticular striae in the longitudinal sections, we found the causative agent in the present case to be identical to the female of Onchocerca dewittei japonica. All five previous cases of zoonotic onchocerciasis in Japan had been found in Oita, Kyushu, the main southern island. This human case caused by O. dewittei japonica suggests that zoonotic onchocerciasis is liable to occur in rural areas in Japan where wild boar, Simulium vectors, and humans overlap.     

New filarial nematode from Japanese serows (Naemorhedus crispus: Bovidae) close to parasites from elephants

A new onchocercid species, Loxodontofilaria caprini n. sp. (Filarioidea: Nematoda), found in subcutaneous tissues of 37 (33%) of 112 serows (Noemorhedus crispus) examined in Japan, is described. The female worm had the characteristics of Loxodontofilaria, e.g., the large body size, well-developed esophagus with a shallow buccal cavity, and the long tail with three caudal lappets. The male worm of the new species, which was first described in the genus, had unequal length of spicules, 10 pairs of pre- and post-caudal papillae, and three terminal caudal lappets. Deirids were present in both sexes. Among four species of the genus loxodontofiloria: one from the hippopotamus and three from the Elepantidae, L. caprini n. sp. appears close to L. asiatica Bain, Baker & Chabaud, 1982, a subcutaneous parasite of Elephas indicus in Myanmar (Burma). However, L. caprini n. sp. is distinct from L. asiatica in that the Japanese female worm has an esophagus half as long and the microfilariae also half as long with a coiled posterior. The microfilariae were found in the skin of serows. The new parasite appears to clearly illustrate a major event in the evolution of onchocercids: the host-switching. This might have occurred on the Eurasian continent, where elephantids and the lineage of rupicaprines diversified during the Pliocene-Pleistocene, or in Japan, into which some of these hosts migrated.