A Naphthoquinone from Sinningia canescens Inhibits Inflammation and Fever in Mice.

We previously showed that plants from the genus Sinningia are a source of antiinflammatory and analgesic compounds with different mechanisms of action. The present study evaluated the antiinflammatory, antinociceptive, and antipyretic effects of a crude extract (CE) from Sinningia canescens, its fractions, and 6-methoxy-7-hydroxy-α-dunnione (MHD) in mice. These effects were evaluated using carrageenan (Cg)-induced paw edema, acetic acid- and formalin-induced nociception, mechanical hyperalgesia, lipopolysaccharide (LPS)-induced fever, and plasma cytokine levels. The CE and dichloromethane and hexane fractions reduced Cg-induced paw edema and hyperalgesia, LPS-induced fever, and plasma tumor necrosis factor-α (TNF-α) levels. The CE also reduced acetic acid-induced writhing and the second phase of formalin-induced nociception but did not alter thermal nociception or motor performance. Partition with solvents showed that the antiinflammatory, antihyperalgesic, and antipyretic activities were present in dichoromethane and hexane fractions, and the major compound isolated from these fractions was MHD. Oral and intraplantar MHD administration reduced paw edema. Oral MHD administration also reduced prostaglandin E2-induced hyperalgesia but did not alter hyperalgesia that was induced by dopamine and dibutyryl cyclic adenosine monophosphate. Treatment with glibenclamide, a KATP channel blocker, did not alter the analgesic effect of MHD. Lipopolysaccharide-induced fever and TNF-α, interleukin-1ß, and interleukin-6 levels were inhibited by MHD. Altogether, these data suggest that the CE has antiinflammatory, analgesic, and antipyretic activity, and these actions are at least partially related to MHD. These results also suggest that MHD acts by blocking cytokine synthesis and/or blocking prostaglandin activity.

In vitro interaction between the ammonium transport protein AmtB and partially uridylylated forms of the P(II) protein GlnZ.

The ammonium transport family Amt/Rh comprises ubiquitous integral membrane proteins that facilitate ammonium movement across biological membranes. Besides their role in transport, Amt proteins also play a role in sensing the levels of ammonium in the environment, a process that depends on complex formation with cytosolic proteins of the P(II) family. Trimeric P(II) proteins from a variety of organisms undergo a cycle of reversible posttranslational modification according to the prevailing nitrogen supply. In proteobacteria, P(II) proteins are subjected to reversible uridylylation of each monomer. In this study we used the purified proteins from Azospirillum brasilense to analyze the effect of P(II) uridylylation on the protein's ability to engage complex formation with AmtB in vitro. Our results show that partially uridylylated P(II) trimers can interact with AmtB in vitro, the implication of this finding in the regulation of nitrogen metabolism is discussed. We also report an improved expression and purification protocol for the A. brasilense AmtB protein that might be applicable to AmtB proteins from other organisms.