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Human, rat, and mouse C-reactive protein (CRP) possess distinct expression patterns, but have similar conformations and conserved in vivo functions. We have previously demonstrated that this level-function mismatch is delicately tuned by the hidden activities of unfolded CRP. The cholesterol-binding sequence (CBS; a.a. 35-47) is a major functional motif exposed on monomeric CRP, which is the unfolded and activated conformation of CRP. We replaced the CBS of rat CRP with that of either mouse or human CRP, yielding two grafting mutants with unaffected pentameric assembly. However, these mutants exhibited altered cellular foldability and conformational activation efficiency that matched those of the CRP that provided the grafted CBS. These results indicate that CBS is a critical regulatory motif, whose variation maintains the pentameric assembly of CRP but derives distinct cellular foldabilities and conformational activation efficiencies, therefore helping to ensure that CRPs with various expression patterns exhibit overall conserved functions.

Background and aims C-reactive protein (CRP) is a hepatocyte-produced marker of inflammation yet with undefined function in liver injury. We aimed to examine the role of CRP in acetaminophen-induced liver injury (AILI). Methods The effects of CRP in AILI were investigated using CRP knockout mice and rats combined with human CRP rescue. The mechanisms of CRP action were investigated in vitro and in mice with Fcγ receptor 2B knockout, C3 knockout, or hepatic expression of CRP mutants defective in complement interaction. The therapeutic potential of CRP was investigated by intraperitoneal administration at 2 or 6 hours post–AILI induction in wild-type mice. Results CRP knockout exacerbated AILI in mice and rats, which could be rescued by genetic knock-in, adeno-associated virus–mediated hepatic expression or direct administration of human CRP. Mechanistically, CRP does not act via its cellular receptor Fcγ receptor 2B to inhibit the early phase injury to hepatocytes induced by acetaminophen; instead, CRP acts via factor H to inhibit complement overactivation on already injured hepatocytes, thereby suppressing the late phase amplification of inflammation likely mediated by C3a-dependent actions of neutrophils. Importantly, CRP treatment effectively alleviated AILI with a significantly extended therapeutic time window than that of N-acetyl cysteine. Conclusion Our results thus identify CRP as a crucial checkpoint that limits destructive activation of complement in acute liver injury, and we argue that long-term suppression of CRP expression or function might increase the susceptibility to AILI.

C-reactive protein (CRP) can exist in both pentameric (pCRP) and monomeric conformation (mCRP). Though serum pCRP is an established marker of inflammation, the diagnostic significance of mCRP remains unknown largely due to the lack of a reliable assay. The power and specificity of antibody-based assays are limited by the antibody reagents used and by the degree of cross-reactivity that may exist in detecting each antigen, as mCRP is known to be formed from the pentameric and both conformations usually coexist in clinical samples. Here, we describe an assay that measures both CRP conformations in simple samples in a single assay. This assay depends on the rationale that the intra-molecular disulfide bonds in pCRP resist reduction, while those in mCRP can be readily reduced. The distinct sensitivity of pCRP and mCRP to reduction can be easily detected and separated by electrophoresis. This assay may provide a means to study clinical correlation between pCRP and mCRP in clinical samples in the future and to evaluate their respective significance as disease markers.

Phorbol esters are the main toxins in Jatropha curcas seed and oil. The aim of this study was to assess the acute toxicity of phorbol esters given by intragastric administration and to determine the LD50 for Swiss Hauschka mice. The LD50 and 95% confidence limits for male mice were 27.34 mg/kg body mass and 24.90–29.89 mg/kg body mass; and the LD5 and LD95 were 18.87 and 39.62 mg/kg body mass, respectively. The regression equations between the probits of mortalities (Y) and the log of doses (D) was Y = −9.67 + 10.21 log (D). Histopathological studies on the organs from the dead mice showed: (1) no significant abnormal changes in the organs at the lowest dose (21.26 mg/kg body mass) studied, (2) prominent lesions mainly found in lung and kidney, with diffused haemorrhages in lung, and glomerular sclerosis and atrophy in kidney at doses ⩾32.40 mg/kg body mass, and (3) multiple abruption of cardiac muscle fibres and anachromasis of cortical neurons at the highest dose of 36.00 mg/kg body mass. The results obtained would aid in developing safety measures for the Jatropha based biofuel industry and in exploiting the pharmaceutical and agricultural applications of phorbol esters.

A new strain of laboratory rabbit, produced from Japanese White rabbit but characterized by its black eye and higher antibody titer, was used in a series of nitrogen (N) balance trials to investigate the requirement of crude protein (CP) for maintenance. The N balance was determined for growing (6–12 weeks) and finishing period (13–17 weeks). Thirty rabbits were used in each period. The rabbits in both periods were divided into five equal groups and fed the diets with equal digestible energy but different contents of CP (120, 140, 160, 180 and 200 g/kg DM). The N requirements for maintenance were estimated from the relationship between the N retention and N intake. Following the above series of N balance tests, 20 rabbits of 16 of age weeks were used with a N-free diet. The rabbits were divided into five groups and offered the N-free diet at levels of 55, 45, 35, 25 and 0 g/day, respectively. Net protein utilization ranged from 0.45 to 0.50 and increased with the advancing age of rabbits, but no significant difference was found between different contents of dietary CP. The estimated N requirement for maintenance was, on average, 485 mg/kg BW0.75 per day, equivalent to 3.03 g CP/kg BW0.75. The result from the trial with the N-free diet showed that N requirement for maintenance was 486 mg/kgBW0.75 per day, confirming the results obtained in the series of N balance tests. The lower intake of the N-free diet resulted in more N excretion suggesting that protein catabolism may occur in the body of rabbit to meet maintenance requirements for N when the dietary N intake was very low.