Human growth hormone-releasing factor (hGRF)1-29-albumin bioconjugates activate the GRF receptor on the anterior pituitary in rats: identification of CJC-1295 as a long-lasting GRF analog

In vivo bioconjugation to the free thiol on Cys34 of serum albumin by a strategically placed reactive group on a bioactive peptide is a useful tool to extend plasma half-life. Three maleimido derivates of human GH-releasing factor (hGRF)(1-29) were synthesized and bioconjugated to human serum albumin ex vivo. All three human serum albumin conjugates showed enhanced in vitro stability against dipeptidylpeptidase-IV and were bioactive in a GH secretion assay in cultured rat anterior pituitary cells. When the maleimido derivatives were individually administered sc to normal male Sprague Dawley rats, an acute secretion of GH was measured in plasma. The best compound, CJC-1295, showed a 4-fold increase in GH area under the curve over a 2-h period compared with hGRF(1-29). CJC-1295, a tetrasubstituted form of hGRF(1-29) with an added N epsilon-3-maleimidopropionamide derivative of lysine at the C terminus, was selected for further pharmacokinetic evaluation, where it was found to be present in plasma beyond 72 h. A Western blot analysis of the plasma of a rat injected with CJC-1295 showed the presence of a CJC-1295 immunoreactive species on the band corresponding to serum albumin, appearing after 15 min and remaining in circulation beyond 24 h. These results led to the identification of CJC-1295 as a stable and active hGRF(1-29) analog with an extended plasma half-life.

Kringle 5 peptide–albumin conjugates with anti-migratory activity

Three peptide fragments of the kringle 5 region of plasminogen and their respective N- and C-terminus maleimido derivatives conjugated to Cys34 of human serum albumin were evaluated in vitro using a human umbilical vein endothelial cell (HUVEC) migration assay and a human plasma stability assay. The N-terminus maleimido derivative of the 64 to 74 segment of kringle 5 conjugated to human serum albumin possessed remarkable anti-migratory activity.

Synthesis and in vitro analysis of atrial natriuretic peptide–albumin conjugates

Atrial natriuretic peptide (ANP) is a clinically useful anti-hypertensive hormone. Maleimide derivatives of ANP have been synthesized and conjugated to cysteine-34 of human serum albumin. The conjugates were analyzed to assess their stability, receptor binding affinity and ability to stimulate guanylyl-cyclase activity in rat lung fibroblasts.

Development and characterization of a glucagon-like peptide 1-albumin conjugate: the ability to activate the glucagon-like peptide 1 receptor in vivo

The rapid degradation of native glucagon-like peptide 1 (GLP-1) by dipeptidyl peptidase-IV (DPP-IV) has fostered new approaches for generation of degradation-resistant GLP-1 analogues. We examined the biological activity of CJC-1131, a DPP-IV-resistant drug affinity complex (DAC) GLP-1 compound that conjugates to albumin in vivo. The CJC-1131 albumin conjugate bound to the GLP-1 receptor (GLP-1R) and activated cAMP formation in heterologous fibroblasts expressing a GLP-1R. CJC-1131 lowered glucose in wild-type mice, but not in GLP-1R-/- mice. Basal glucose and glycemic excursion following glucose challenge remained significantly reduced 10-12 h following a single injection of CJC-1131. Twice daily administration of CJC-1131 to db/db mice significantly reduced glycemic excursion following oral and IP glucose challenge (P < 0.01 to 0.05) but did not significantly lower body weight during the 4-week study period. Levels of random fed glucose were significantly lower in CJC-1131-treated +/+ and db/db mice and remained significantly lower even 1 week following discontinuation of CJC-1131 administration. CJC-1131 increased levels of pancreatic proinsulin mRNA transcripts, percent islet area, and the number of bromodeoxyuridine-positive islet cells. These findings demonstrate that an albumin-conjugated DAC:GLP-1 mimics the action of native GLP-1 and represents a new approach for prolonged activation of GLP-1R signaling.

Increased apoptosis, changes in intracellular Ca2+, and functional alterations in lymphocytes and macrophages after in vitro exposure to static magnetic field

Electromagnetic-related alteration of cellular functions is well documented for extremely low-frequency low-energy pulsing electromagnetic fields (ELF-EMF). In this study we examined the in vitro effects of static magnetic fields (SMF) on the cellular immune parameters of the C57BI/6 murine macrophages, spleen lymphocytes, and thymic cells. The cells were exposed in vitro for 24 h at 37 degrees C, 5% CO2, to 250-1500 G SMF. Exposure to the SMF resulted in the decreased phagocytic uptake of fluorescent latex microspheres, which was accompanied by an increased intracellular Ca2+ level in macrophages. Exposure to SMF decreased mitogenic responses in lymphocytes, as determined by incorporation of [3H]thymidine into the cells. This was associated with the increased Ca2+ influx in concanavalin A-stimulated lymphocytes. Furthermore, exposure to SMF produced markedly increased apoptosis of thymic cells, as determined by flow cytometry. Overall, in vitro exposure of immunocompetent cells to 250-1500 G SMF altered several functional parameters of C57BI/6 murine macrophages, thymocytes, and spleen lymphocytes.

In vivo indomethacin reverse exercise-induced immunosuppression in rats

The effect of oral indomethacin on the immunosuppressive effect of exercise was examined in exercised untrained female Wistar rats immunized with sheep red blood cell (SRBC) antigens. Intensity of the 1 h exercise was controlled by 0-50 kPa air pressure, generated by a compressor located at the bottom of a water tank, during continuous swimming of the rats, previously immunized with SRBC. After 48-72 h, depending on the ip (intraperitoneal) or iv (intravenous) route of SRBC immunization, the exercise suppressed humoral PFC response and augmented phagocytosis of peritoneum macrophages. These effects occurred only when exercise was performed at 48 h after antigen injection. Animals receiving indomethacin, however, did not show any exercise-related suppression of the PFC response. The data suggest a relationship between exercise-induced immunosuppression and possible increased in vivo prostaglandin synthesis during the intense exercise. Overall, exercise-related suppression of humoral PFC response was dependent on the intensity of the exercise, was time specific, and was reversible by pharmacological blockade of the cyclooxygenase pathway of prostaglandin synthesis.

Modulation of exercise-induced immunosuppression by dietary polyunsaturated fatty acids in mice

The possible interaction between intense exercise, known to suppress the immune response, and nutritive factors, such as polyunsaturated fatty acids (PUFA), was examined in inbred female C57Bl/6 mice. The animals received for 8 wk either a natural ingredient diet or a diet supplemented with 10 g/100 g linseed oil containing over 50% of 18:3 (n-3) alpha-linoleic acid. Other groups received PUFA containing only traces of 18:3 (n-3) fatty acid; beef tallow, containing mostly 18:1 (n-9) saturated fat, safflower oil, an 18:2 (n-6) PUFA, and fish oil, containing longer chain (n-3) PUFA. Each dietary group was divided into two subgroups: sedentary diet controls and exercised animals. Exercise consisted of continuous swimming at high intensity until exhaustion. It was shown in three separate experiments that (1) the primary humoral response to sheep red blood cells, determined by the plaque-forming cell (PFC) assay, was affected by PUFA diet in sedentary animals in the order beef tallow > control diet > safflower oil > fish oil > linseed oil, and (2) the PFC response was suppressed by the exhaustive exercise, as compared to sedentary controls, except for animals fed 18:3 (n-3) linseed oil, where the normal response was noted. Phagocytosis of fluorescent microspheres by peritoneal macrophages, determined by flow cytometry, was significantly lower in exercised animals receiving the linseed oil diet, whereas other diets either increased or did not significantly change the macrophage phagocytic activity, compared to the sedentary diet controls. Spleen lymphocyte subsets were unchanged in exercised animals except for a marked shift from the lymphoid peak toward the erythroid peak. Generally, our data showed a marked immunomodulatory effect of 18-3 (n-3) alpha-linoleic acid on the exhaustive exercise-related immunosuppression, as compared to the effects of other selected PUFA.