Anti-inflammatory and antimicrobial effect of lectin from Lonchocarpus sericeus seeds in an experimental rat model of infectious peritonitis

We have investigated the anti-inflammatory and antimicrobial effect of the lectin from Lonchocarpus sericeus seeds (LSL) in a model of infectious peritonitis in adult Wistar rats. Animals were treated with saline or LSL (10 mg kg(-1), i.v) immediately and 6 h after the induction of peritonitis via cecal ligation and single puncture. Twelve hours after surgery, animals were killed and the infectious process was monitored by total and differential count of cells from blood and peritoneal washing liquid, adenosine deaminase activity, antibiogram and the number of viable bacteria of the peritoneal cavity. LSL treatment decreased the inflammatory response evoked by the induction of peritonitis, as seen by the inhibition of neutrophil migration into peritoneal cavities, leucocytosis and reduction of adenosine deaminase activity in the peritoneal fluid. All these effects were reversed by the lectin association to N-acetyl-glucosamine. LSL in-vitro did not show any antimicrobial action, but promoted a marked decrease of the viable bacterial population in peritoneal cavities. In conclusion, LSL inhibited the inflammatory response and the bacterial colonization of infectious peritonitis in rats.

Purification, chemical, and immunochemical properties of a new lectin from Mimosoideae (Parkia discolor)

A glucose/mannose-binding lectin was isolated from seeds of Parkia discolor (Mimosoideae) using affinity chromatography on Sephadex G-100 gel. The protein presented a unique component in SDS-PAGE corresponding to a molecular mass of 58,000 Da, which is very similar to that of a closely related lectin from Parkia platycephala. Among the simple sugars tested, mannose was the best inhibitor, but biantennary glycans, containing the trimannoside core, present in N-glycoproteins, also seem to be powerful inhibitors of the haemagglutinating activity induced by the purified lectin. The protein was characterised by high content of glycine and proline and absence of cysteine. Rabbit antibodies, anti-P. platycephala seed lectin, recognised the P. discolor lectin. However, no cross-reaction was observed when a set of other legume lectins from sub-family Papilionoideae and others from families Moraceae and Euphorbiaceae were assayed with the Parkia lectins. This suggests that Parkia lectins comprise a new group of legume lectins exhibiting distinct characteristics.