Endotoxin-neutralizing effects of histidine-rich peptides

AbstractInflammatory responses of human peripheral blood monocytes to the Gram-negative endotoxin lipopolysaccharide (LPS) are enhanced by structurally diverse substances, such as anionic polysaccharides or cationic polypeptides. Only a few substances are known to effectively blunt LPS-induced monocyte activation. We now show that synthetic poly-L-histidine (Hn) binds to LPS and abrogates the release of the proinflammatory cytokine interleukin-8 (IL-8) in LPS-stimulated human whole blood. LPS-induced stimulation of monocytes was strictly pH-dependent with only minor amounts of IL-8 secreted in acidic blood. Maximum levels of IL-8 secretion occurred at a strongly basic pH. Hn inhibition of the release of IL-8 from LPS-stimulated monocytes was observed under acidic, neutral and physiological conditions. With increasing alkalosis, the effectiveness of Hn was gradually lost, suggesting that protonated, but not deprotonated, Hn was effective in inhibiting LPS-induced monocyte responses. Histidine-rich protein 2 from the malaria parasite, Plasmodium falciparum, inhibited the ability of LPS to evoke an inflammatory response in CD14-transfected THP-1 cells. Further, a short synthetic peptide derived from human histidine- and proline-rich glycoprotein also exhibited LPS-inhibitory effects in CD14 transfectants. Taken together, these observations demonstrate the capacity of histidine-rich peptides, irrespective of their origin, to neutralize LPS-induced proinflammatory host responses

Withdrawal-induced delirium associated with a benzodiazepine switch: a case report

<p>Abstract</p> <p>Introduction</p> <p>Introduced in the early 1960s, diazepam remains among the most frequently prescribed benzodiazepine-type sedatives and hypnotics. Patients with chronic use of short-acting benzodiazepines are frequently switched to diazepam because the accumulating, long-acting metabolite, N-desmethyl-diazepam, prevents benzodiazepine-associated withdrawal symptoms, which can occur during trough plasma levels of short-acting benzodiazepines. Although mild to moderate withdrawal symptoms are frequently observed during benzodiazepine switching to diazepam, severe medical complications associated with this treatment approach have thus far not been reported.</p> <p>Case presentation</p> <p>A 64-year-old female Caucasian with major depression, alcohol dependence and benzodiazepine dependence was successfully treated for depression and, after lorazepam-assisted alcohol detoxification, was switched from lorazepam to diazepam to facilitate benzodiazepine discontinuation. Subsequent to the benzodiazepine switch, our patient unexpectedly developed an acute delirious state, which quickly remitted after re-administration of lorazepam. A newly diagnosed early form of mixed dementia, combining both vascular and Alzheimer-type lesions, was found as a likely contributing factor for the observed vulnerability to benzodiazepine-induced withdrawal symptoms.</p> <p>Conclusion</p> <p>Chronic use of benzodiazepines is common in the elderly and a switch to diazepam often precedes benzodiazepine discontinuation trials. However, contrary to common clinical practice, benzodiazepine switching to diazepam may require cross-titration with slow tapering of the first benzodiazepine to allow for the build-up of N-desmethyl-diazepam, in order to safely prevent severe withdrawal symptoms. Alternatively, long-term treatment with low doses of benzodiazepines may be considered, especially in elderly patients with chronic use of benzodiazepines and proven vulnerability to benzodiazepine-associated withdrawal symptoms.</p

Arginine-Rich Cationic Polypeptides Amplify Lipopolysaccharide-Induced Monocyte Activation

The human neutrophil-derived cationic protein CAP37, also known as azurocidin or heparin-binding protein, enhances the lipopolysaccharide (LPS)-induced release of tumor necrosis factor alpha (TNF-α) in isolated human monocytes. We measured the release of the proinflammatory cytokine interleukin-8 (IL-8) in human whole blood and found that in addition to CAP37, other arginine-rich cationic polypeptides, such as the small structurally related protamines, enhance LPS-induced monocyte activation. As CAP37 and protamines share high levels of arginine content, we tested different synthetic poly-l-amino acids and found that poly-l-arginine, and to a lesser extent poly-l-lysine, increased IL-8 production in LPS-stimulated human whole blood. Protamine-enhanced LPS responses remained unaffected by the presence of free l-arginine or l-lysine, indicating that basic polypeptides but not basic amino acids act synergistically with LPS. In agreement with observations previously reported for CAP37, the LPS-enhancing effect of poly-l-arginine was completely abolished upon antibody blockade of the human LPS receptor, CD14. Protamines, either immobilized or in solution, bound LPS specifically. Poly-l-arginines, protamines, and CAP37 were equally effective in inhibiting binding of LPS to immobilized l-arginines. Taken together, our results suggest a CD14-dependent mechanism by which arginine-rich cationic proteins modulate LPS-induced monocyte activation and support the prediction that other strongly basic proteins could act as amplifiers of LPS responses