HemaMax™, a recombinant human interleukin-12, is a potent mitigator of acute radiation injury in mice and non-human primates

HemaMax, a recombinant human interleukin-12 (IL-12), is under development to address an unmet medical need for effective treatments against acute radiation syndrome due to radiological terrorism or accident when administered at least 24 hours after radiation exposure. This study investigated pharmacokinetics, pharmacodynamics, and efficacy of m-HemaMax (recombinant murine IL-12), and HemaMax to increase survival after total body irradiation (TBI) in mice and rhesus monkeys, respectively, with no supportive care. In mice, m-HemaMax at an optimal 20 ng/mouse dose significantly increased percent survival and survival time when administered 24 hours after TBI between 8–9 Gy (p<0.05 Pearson's chi-square test). This survival benefit was accompanied by increases in plasma interferon-γ (IFN-γ) and erythropoietin levels, recovery of femoral bone hematopoiesis characterized with the presence of IL-12 receptor β2 subunit–expressing myeloid progenitors, megakaryocytes, and osteoblasts. Mitigation of jejunal radiation damage was also examined. At allometrically equivalent doses, HemaMax showed similar pharmacokinetics in rhesus monkeys compared to m-HemaMax in mice, but more robustly increased plasma IFN-γ levels. HemaMax also increased plasma erythropoietin, IL-15, IL-18, and neopterin levels. At non-human primate doses pharmacologically equivalent to murine doses, HemaMax (100 ng/Kg and 250 ng/Kg) administered at 24 hours after TBI (6.7 Gy/LD_50/30) significantly increased percent survival of HemaMax groups compared to vehicle (p<0.05 Pearson's chi-square test). This survival benefit was accompanied by a significantly higher leukocyte (neutrophils and lymphocytes), thrombocyte, and reticulocyte counts during nadir (days 12–14) and significantly less weight loss at day 12 compared to vehicle. These findings indicate successful interspecies dose conversion and provide proof of concept that HemaMax increases survival in irradiated rhesus monkeys by promoting hematopoiesis and recovery of immune functions and possibly gastrointestinal functions, likely through a network of interactions involving dendritic cells, osteoblasts, and soluble factors such as IL-12, IFN-γ, and cytoprotectant erythropoietin.

Protease and protease inhibitor secretion by postsurgical macrophages following in vitro exposure to tolmetin

Tolmetin sodium was shown previously to reduce the level of adhesions formed after peritoneal surgery. In addition, when tolmetin was administered to rats at the time of surgery, the level of macrophage activity (phagocytosis, superoxide anion production and tumoricidal activity) was elevated. In this study, the level of neutral protease activity in the culture supernatant of peritoneal macrophages from postsurgical rabbits. after in vitro exposure to tolmetin was examined. The level of collagenase, elastase and plasminogen activator inhibitor activity in the culture supernatant of macrophages was modulated after peritoneal surgery. Collagenase activity in the culture supernatant of macrophages from nonsurgical and postsurgical rabbits up to 48 h was reduced after co-culture with tolmetin. In contrast, elastase secretion was elevated to maximal levels (which plateaued 24 h after surgery in cultures of control macrophages) in cultures of macrophages from nonsurgical and early postsurgical (6 and 12 h) rabbits by in vitro exposure to tolmetin. Alternatively, the level of plasminogen activator inhibitor activity in the culture supernatants of postsurgical macrophages was reduced after in vitro exposure to tolmetin. These data indicate that tolmetin, a nonsteroidal anti-inflammatory agent, modulates the levels of collagenase, elastase and plasminogen activator inhibitor activity in culture supernatants of postsurgical macrophages.

Mechanism of the modulation of murine peritoneal cell function and mast cell degranulation by low doses of malathion

Malathion is a widely used organophosphate pesticide that modulates immune function at noncholinergic doses. Previous studies showed that this alteration in immune function was the result of enhanced macrophage function. In the present study, the effects of low doses of purified malathion (as low as 0.25 mg/kg malathion) administered orally to mice enhanced the respiratory burst of peritoneal cells. Microscopic examination of the peritoneal cells showed that mast cells were degranulated within 4 hr after malathion administration. The amount of beta-hexosaminidase, an enzyme released upon immunologic degranulation of mast cells, in the peritoneal lavage fluid of malathion-treated mice was also significantly elevated with 4 hours after malathion administration. Treatment of RBL-1, a rat basophilic cell line, cells with malathion, parathion or paroxon in vitro also led to the release of beta-hexosaminidase with paraoxon being the most potent. Further examination of the peritoneal cells of malathion-treated mice showed that the percentage of phagocytic peritoneal cells ingesting mast cell granules and the number of granules ingested per cell were elevated. These data suggest that malathion may enhance the respiratory burst of peritoneal cells through degranulation of peritoneal mast cells and the subsequent exposure to peritoneal cells to mast cell mediators.

Kinetics of interleukin-1 and tumor necrosis factor secretion by rabbit macrophages recovered from the peritoneal cavity after surgery

Macrophages play a crucial role in wound healing after surgical injury, both as scavenger cells responsible for wound debridement and as cells that secrete soluble factors such as interleukin-1 (IL-1) and tumor necrosis factor (TNF). IL-1 and TNF alter many of the biological activities of cells that appear in postsurgical wounds. In this study, we determined the kinetics of IL-1 and TNF production by rabbit macrophages harvested from postsurgical peritoneal exudate (postsurgical macrophages) at several time points after peritoneal surgery. To further characterize the level of functional activities of postsurgical macrophages, the IL-1 and TNF levels were determined with or without stimulating the cells with lipopolysaccharide (LPS) and phorbol myristate acetate (PMA). After surgery, the number of macrophages harvested by peritoneal lavage increased, reached peak levels on postsurgical day 3, and then decreased. IL-1 levels secreted by macrophages cultured without stimuli were elevated on postsurgical day 14 compared to the values on day 3 and 7. TNF concentrations peaked on days 1 and 14. In the conditioned culture media from LPS-PMA-stimulated macrophages, the levels of both IL-1 and TNF peaked on postsurgical days 3 and 14. These data suggest that the susceptibility of postsurgical macrophages to stimuli changes during the wound healing process with maximum sensitivity to the stimuli present during the early phase of peritoneal repair (day 3).

The effect of intraperitoneal administration of sodium tolmetin-hyaluronic acid on the postsurgical cell infiltration in vivo

Intraperitoneal administration of sodium tolmetin-hyaluronic acid reduced the formation of adhesions at early postsurgical time points. In addition, at 6, 48, 72, and 96 hr following surgery, there was a significant reduction in the number of red blood cells (RBC) recovered from peritoneal lavage. This effect was not the result of fluid or viscous solution in the peritoneal cavity since intraperitoneal administration of Ringer's lactate or Hyskon (a 32% solution of Dextran 70) did not affect RBC recovery. In contrast, the influx of leukocytes into the peritoneal cavity was elevated at 12 hr after surgery, but suppressed at 96 hr. These data may suggest a mechanism by which sodium tolmetin in hyaluronic acid reduced adhesion formation.

Kinetics of interleukin-1 secretion by murine macrophages recovered from the peritoneal cavity after surgery

Macrophages play a central role in wound healing after surgical injury possibly through the secretion of soluble factors like interleukin-1 (IL-1). IL-1 has many biological activities which regulate most of the cell types that appear in postsurgical wounds. In this study, we determined the levels of IL-1 production by murine macrophages harvested from postsurgical exudate at several time points after standardized peritoneal surgery. To further characterize the level of functional activities of postsurgical macrophages, the IL-1 levels were determined with or without stimulating the cells with lipopolysaccharide (LPS) and phorbol myristate acetate (PMA). After surgery, the number of macrophages harvested by peritoneal lavage increased, reached peak levels on Postsurgical Day 3, and then decreased. IL-1 levels secreted by macrophages cultured without stimuli gradually increased after surgery, reaching peak levels on Day 10. In conditioned media from LPS-PMA-stimulated macrophages, IL-1 levels were significantly greater than in media from unstimulated macrophages and peaked on Postsurgical Day 3. These data suggest that the susceptibility of postsurgical macrophages to stimuli changes during the postsurgical wound healing process. Accordingly, IL-1 may play an important role in the late rather than in the early phase of peritoneal repair.

Effects of tolmetin sodium dihydrate on normal and postsurgical peritoneal cell function

Recent studies utilizing intraperitoneal (i.p.) administration of NSAIDs to rabbits after surgical injury to the parietal peritoneum demonstrated macrophage involvement. NSAIDs are known to inhibit the metabolism of arachidonic acid to prostaglandins, which in turn modulate a variety of macrophage functions. Studies presented here examine the effects of tolmetin administration on peritoneal resident and post-surgical leukocyte functions, such as phagocytosis, the release of superoxide anion and tumoricidal activity. Rats, either non-surgical or following peritoneal surgery, were injected i.p. with tolmetin. At various times after treatment, the rats were sacrificed and peritoneal cells collected by lavage. The phagocytic capability of peritoneal leukocytes was transiently decreased 5-7 days after the administration of tolmetin to normal animals. However, administration of tolmetin during surgery extended the length of time that phagocytic capability was enhanced. In non-surgical controls, there was an elevation in superoxide anion release and tumoricidal activity 24 h after tolmetin administration. Superoxide anion release was suppressed at days 5 and 7 after treatment, but returned to control levels by day 14. Intraoperative administration of tolmetin significantly elevated superoxide anion release at days 3 and 5, phagocytosis at days 7 and 14 and tumoricidal activity at day 3. These studies suggest that compounds which suppress prostaglandin synthesis can modulate the function of resident and post-surgical peritoneal cells.

Influence of H-2 haplotypes on poly IC induction of xanthine oxidase and poly IC induced decreases in P-450 mediated enzyme activities

Polyriboinosinic-polyribocytidylic acid (poly IC), a potent interferon inducer, induced xanthine oxidase 24 hours after treatment with 5 mg/kg ip to different degrees among four H-2 congenic mice (P less than 0.05): B10 (H-2b: 236 +/- 27% of the control value) greater than B10.RIII (H-2r: 171 +/- 29%) = B10.F (H-2n: 161 +/- 12%) greater than B10.BR (H-2k: 136 +/- 15%). Aryl hydrocarbon hydroxylase (AHH) activity showed an inverse correlation with inducibility of xanthine oxidase (r = -0.71, P less than 0.01). However, there were no significant changes in activities of heme pool associated enzymes, such as catalase, tryptophan pyrrolase and d-aminolevulinic acid synthase in these mice. H-2 haplotype seems to have an influence on poly IC induction of xanthine oxidase thereby causing a decrease in AHH.