Indole carboxamides inhibit bovine testes hyaluronidase at pH 7.0 and indole acetamides activate the enzyme at pH 3.5 by different mechanisms

Abstract

Hyaluronidases are enzymes controlling many crucial physiological processes. Imbalanced enzymatic activity is connected with severe diseases. Because there is limited availability of drugs modulating hyaluronidase activity, the search for hyaluronidase interacting compounds is getting more and more important. A series of fifteen indole carboxamides and acetamides were synthesized and tested on inhibition of bovine testes hyaluronidase. In vitro assays were performed using stains-all at pH 7 and the Morgan-Elson reaction at pH 3.5. At neutral pH, the most active inhibitory compound was N-(Pyridin-4yl)-[5-bromo-1-(4-fluorobenzyl)indole-3-yl]carboxamide (20) with an IC 50 value of 46 mM. Surprisingly, inhibition of all compounds was completely abolished by a decrease in pH. At pH 3.5 the activity of the enzyme was increased up to 134% by compound N-(4,6-Dimethylpyridin-2yl)-(1-ethylindole-3-yl)acetamide (24) at a concentration of 100 mM. The known activating effect of bovine serum albumine (BSA) on hyaluronidase activity was verified in the assay and compared to the effect of compound 24. Structure-activity relationships are discussed and a model is proposed, which explains the increase in activity at pH 3.5 by bonding of the protonated form of N-(4,6-Dimethylpyridin-2yl)-(1-ethylindole-3-yl)-acetamide (24) to hyaluronic acid. The bonding results in an elongated form of the substrate with easier enzymatic access.

Hyaluronidase Inhibitors: A Biological and Therapeutic Perspective

“…Thus the authors concluded that indole derivatives are potent HAase inhibitors than the benzimidazole and benzothiazole derivatives. Recently, Kaessler et al [174] tested a series of fifteen indole carboxamides and acetamides on the bovine testicular HAase. Among the compounds tested, N-(Pyridin-4yl)-[5-bromo-1-(4-fluorobenzyl)indole-3-yl] carboxamide exhibited maximum inhibition at neutral pH.…”

Honey shows potent inhibitory activity against the bovine testes hyaluronidase

“…HA inhibitors have also led to new therapeutic concepts in pathophysiological conditions, such as laryngeal or breast cancer treatment, that are associated with the hyaluronanhyaluronidase system 3,4,7 . Since the partial control of hyaluronidases possesses several important physiological functions, they have recently attracted considerable scientific interest as synthetic and natural inhibitors 4,[8][9][10][11][12] . Honey and bee products are natural materials whose antioxidant, anti-inflammatory and anti-tumoral efficacies vary depending on the flora from which they are produced.…”

In vitro effects of 2, 4-Dichlorophenoxy acetic acid dimethylamine salt and enrofloxacin on BTH

“…Same kind of effect was mentioned by Kaessler et al (2008). Therefore, these effects increase or decrease enzyme inhibition activity.…”