Tuftsin: an immunomodulating peptide hormone and its clinical potential as a natural biological response modifier

Tuftsin ameliorates splenic inflammatory injury by promoting neuropilin-1 in severe acute pancreatitis

Severe acute pancreatitis (SAP)-associated spleen injury causing immune disturbances aggravates organs injuries, which contributes to higher mortality rate. However, there are no effective drugs to cure SAP-induced spleen injury. Here, we found that Tuftsin (TN) is effective for ameliorating SAP-induced pathological damage and inflammation of spleen, mainly via alleviating mitochondrial dysfunction, oxidative stress, ATP depletion and the expression of pro-inflammatory factors. We further found that TN promoted anti-inflammatory macrophage phenotype M2 via up-regulating NRP1 on macrophage in spleen during SAP. Meanwhile, EG00229 (an inhibitor of NRP1 bound to TN) weakened TN's therapeutic effect in SAP-associated spleen injury. And EG00229 also inhibited M2 macrophage, leading to increasing inflammasome formation. Additionally, EG00229 reduced the protective efficiency of TN on mitochondrial dysfunction, and inflammation injury via NRP1 in spleen caused by SAP. Similarly, siRNA-Nrp1 into macrophage also prevented TN's inhibition on apoptosis. These findings reveal that TN alleviates SAP-induced spleen injury by promoting NRP1.

Laparoscopic hand-assisted spleen autotransplantation

BACKGROUND

Only recently has the spleen been perceived as an organ with a major immune function. This raised an interest in spleen salvage after spleen trauma and pancreatic tail resection, for the treatment of hematologic disorders and inducement tolerance for allogenic transplants. The purpose of this study was to evaluate the feasibility of a new technique for spleen transplantation: laparoscopic spleen autotransplantation in a large animal model.

METHODS

Ten 35-kg pigs were used for this study. A laparoscopic hand-assisted splenectomy was first performed. The spleen was extracted through the handport to be flushed with a 4 degrees C saline solution and prepared extracorporeally. The graft was then reintroduced into the same animal's abdominal cavity, and a splenic-to-common iliac artery and vein bypass was performed laparoscopically using a 7-0 polytetrafluoroethylene running suture. The animal was killed 1 week postoperatively for histologic examination.

RESULTS

All 10 animals tolerated the procedure well. No conversion to open surgery was required. The mean operative time was 253 +/- 45 min. The mean time needed to create the artery and vein anastomoses was 116 +/- 165 min, and the mean blood loss was 190 +/- 120 ml. There was no intra- or postoperative death. Intraoperative complications included two stenosed vascular anastomoses, which were taken down and revised. Seven of the 10 spleens were histologically viable 1 week after surgery. The nonviable transplantations were attributable to a thrombosis of the common iliac artery (n = 1) or the transplant artery (n = 2).

CONCLUSIONS

Hand-assisted laparoscopic spleen autotransplantation is feasible in an animal model. This procedure could constitute an option when spleen resection is necessary for pancreatic tail resection, or when spleen preservation is important to the maintenance or restoration of an immune function.

Study on the degeneracy of antisense peptides using affinity chromatography

The degeneracy of antisense peptides was studied by high-performance affinity chromatography. A model sense peptide (AAAA) and its antisense peptides (CGGG, GGGG, RGGG, SGGG) were designed and synthesized according to the degeneracy of genetic codes. An affinity column with AAAA as the ligand was prepared. The affinity chromatographic behaviors of antisense peptides on the column were evaluated. The results indicated that model antisense peptides have clear retention on the immobilized AAAA affinity column. RGGG showed the strongest affinity interaction. Similar result was obtained from another experiment that Arg-substituted antisense peptide of fusion peptide (1-11) of influenza virus A was also shown the highest affinity binding to immobilized fusion peptide.

Solution conformation of a potent cyclic analogue of tuftsin: low- temperature nuclear magnetic resonance study in a cryoprotective mixture

Tuftsin, a linear tetrapeptide (Thr-Lys-Pro-Arg), corresponding to the sequence 289-292 of the heavy chain of leukokinin, has been the object of intensive SAR studies during the past 30 years, owing to its numerous biological activities and to the possibility of generating a novel anticancer drug. A cyclic tuftsin analogue, c-[T-K-P-R-G], has biological activity 50 times higher than that of the parent linear peptide. Here we present a conformational study of c-[T-K-P-R-G] based on NMR data in a cryoprotective DMSO/water mixture. The preferred conformation is a type VIa turn centered on the K-P residues. The orientation of the side chains of the two basic residues (K and R) may represent the essential feature of the bioactive conformation of tuftsin. A possible role of tuftsin as a DNA binding motif is suggested by the similarity of the bioactive conformation of c-[T-K-P-R-G] and of the beta-turn conformation proposed by Suzuki for the [T,S]-P-K-R motif.

Enhanced phagocytosis activity of cyclic analogs of tuftsin

Cyclic analogs of the physiological immunostimulating peptide tuftsin (Thr-Lys-Pro-Arg), cyclo(Thr-Lys-Pro-Arg-Gly) (ctuf-G) and cyclo(Thr-Lys-Pro-Arg-Asp) (ctuf-D), were synthesized based on molecular modeling studies, and assayed for the ability to stimulate phagocytosis by human polymorphonuclear leukocytes. As predicted, the synthesis of ctuf-D resulted in two isomers with the correct molecular mass and amino acid composition. In phagocytosis assays, tuftsin, ctuf-G and two isomers of ctuf-D showed the usual bell-shaped activity profiles. The optimum concentration of ctuf-G was 50-fold less than that of tuftsin, whereas the degree of stimulation was similar. One isomer of ctuf-D was almost inactive, and the other ctuf-D exhibited the same degree of phagocytosis as tuftsin but its optimum concentration was 5-fold lower. The enhanced potency of ctuf-G and one isomer of ctuf-D may be due to conformational effects and/or to the possibility that these cyclic peptides are resistant to proteolytic degradation.

A comparative study of [Leu1]Tuftsin and tuftsin, a natural phagocytosis-stimulating peptide

1. [Leu1]tuftsin was reported to have greater phagocytosis-stimulating activity than tuftsin (Thr-Lys-Pro-Arg). 2. However, a study on inactivation of tuftsin by polymorphonuclear leukocytes (PMNs) demonstrated that leucine aminopeptidase, an ecto-enzyme, located on PMN surface was responsible for this mechanism. 3. Since leucine aminopeptidase is known to cleave Leu more easily than Thr at the N-terminal position of peptides, this suggested to us that [Leu1]tuftsin might then be inactivated by PMNs more easily than tuftsin, and thus this analog might be less active than tuftsin. 4. In addition, many tuftsin preparations used in earlier studies were not fully active, as high-performance liquid chromatography was not available to separate out many contaminating diastereomers. 5. In view of this, we have synthesized and purified [Leu1]tuftsin and compared its phagocytosis-stimulating activity with tuftsin. 6. Our results indicate that [Leu1]tuftsin is not as active as tuftsin in stimulating phagocytosis.

Tuftsin-enhanced thymidine incorporation by murine splenic monocytes

Tuftsin (Thr-Lys-Pro-Arg), a natural immunomodulating peptide originally found to stimulate phagocytosis by polymorphonuclear leukocytes (PMN), is now known to bind to both PMN and monocyte-macrophages, affecting many of their functions. Administration of tuftsin induces leukocytosis in vivo. We have recently observed that while tuftsin remains in the cytoplasm upon binding and internalization in human PMNs, it translocates into the human monocyte nucleus, suggesting that tuftsin may directly affect growth of monocytes. We have therefore examined the effect of tuftsin on [3H]thymidine incorporation in fractions of murine splenocytes to identify a cell population responding to tuftsin. Tuftsin showed the greatest effect in [3H]thymidine incorporation of splenocytes over controls at optimum conditions of 2% fetal bovine serum and 1 microgram/ml of tuftsin. Splenocyte fractionation by Lymphocyte Separation Medium indicated that tuftsin primarily affects the mononuclear cell fraction; further fractionation revealed that tuftsin affects mostly the monocytes that adhered to plastic. We subsequently further purified the splenic monocytes by repeated plastic adhesion and Percoll gradient separation, to show that tuftsin increases [3H]thymidine incorporation of these highly purified monocytes.

Human peritoneal macrophage activity is increased by tuftsin

Peritonitis caused by Candida albicans is a major complication of continuous ambulatory peritoneal dialysis (CAPD). Increasing the activity of the peritoneal macrophages--the predominant cell type found in the peritoneal cavity--may be of great importance in the prevention and therapy of peritonitis. Therefore, the activating effect of tuftsin was studied on human peritoneal macrophages from CAPD patients. Tuftsin induced a biphasic effect on macrophage activity within a range of 2 X 10(-9)-2 X 10(-6) M, with a maximal activity of 2 X 10(-7) M. At this concentration, tuftsin enhanced by twofold cell association with radiolabelled candida (from 2 +/- 0.2 to 4 +/- 0.2 candida per macrophage) and superoxide anion production in response to exposure to candida (from 150 +/- 20 to 300 +/- 20 nmoles/mg). These results suggest the potential use of tuftsin as a therapeutic drug.

Regulation of macrophage phagocytosis

The removal of pathogens from the circulation is achieved primarily by cells of the mononuclear phagocyte system, also known as the reticuloendothelial system. The tissue macrophage is the most important component of this system. The phagocytic activity of macrophages is regulated by opsonins on pathogenic materials and by endogenous cytokines. A number of diseases are caused by qualitative or quantitative disorders of phagocytosis by four major mechanisms: a decrease in the flow of blood to organs which contain macrophages (e.g. congestive heart failure and portal hypertension); a decrease in the quantity of tissue which contains macrophages (e.g. hepatic cirrhosis and splenectomy); a decrease in the effective opsonization of pathogens because of a deficiency of complement or IgG; and qualitative dysfunction of macrophages due to a deficiency of regulatory cytokines (e.g. gamma interferon and tuftsin) or a direct inhibitory effect on the macrophage (e.g. viral infections). New approaches for selective regulation of the phagocytic activity of macrophages are emerging.