Immunoneutralization of the aminoprocalcitonin peptide of procalcitonin protects rats from lethal endotoxaemia: neuroendocrine and systemic studies

Abstract

Severe sepsis and septic shock are an important cause of mortality and morbidity. These illnesses can be triggered by the bacterial endotoxin LPS (lipopolysaccharide) and pro-inflammatory cytokines, particularly TNF-α (tumour necrosis factor-α) and IL (interleukin)-1β. Severity and mortality of sepsis have also been associated with high concentrations of N-PCT (aminoprocalcitonin), a 57-amino-acid neuroendocrine peptide derived from ProCT (procalcitonin). Previous studies in a lethal model of porcine polymicrobial sepsis have revealed that immunoneutralization with IgG that is reactive to porcine N-PCT significantly improves short-term survival. To explore further the pathophysiological role of N-PCT in sepsis, we developed an antibody raised against a highly conserved amino acid sequence of human N-PCT [N-PCT-(44-57)]. This sequence differs by only one amino acid from rat N-PCT. First, we demonstrated the specificity of this antibody in a well-proven model of anorexia induced in rats by central administration of human N-PCT-(1-57). Next we explored further the therapeutic potential of anti-N-PCT-(44-57) in a rat model of lethal endotoxaemia and determined how this immunoneutralization affected LPS-induced lethality and cytokine production. We show that this specific antibody inhibited the LPS-induced early release of TNF-α and IL-1β and increased survival, even if treatment began after the cytokine response had occurred. In addition, anti-N-PCT-(44-57) may increase long-term survival in LPS-treated rats by up-regulating the late production of counter-regulatory anti-inflammatory mediators such as ACTH (adrenocorticotropic hormone) and IL-10. In conclusion, these results support N-PCT as a pro-inflammatory factor in both the early and the late stages of lethal endotoxaemia, and suggest anti-N-PCT as a candidate for septic shock therapy.

Deletion of the Gene Encoding Calcitonin and Calcitonin Gene–Related Peptide α Does Not Affect the Outcome of Severe Infection in Mice

“…In animal models, both gain-of-function and loss-of-function studies support a causal role of PCT in worsening outcomes. In a hamster model of sepsis, the administration of human PCT worsened mortality (6), whereas, in hamster, rat, and pig models of sepsis, the immunoneutralization of PCT reduced the severity of hypotension and rate of mortality (6)(7)(8)(9). These findings are surprising, because patients with thyroidal and other tumors may have very elevated PCT levels without apparent adverse effects, although it is possible that elevated PCT levels exert an adverse effect only in septic conditions or when they rise rapidly.…”

“…Therapeutic administration of Igs 3 hours after challenge in the same model reduced mortality from 100 to 20% (7). In a rat model of sepsis induced by intraperitoneal injection of bacterial LPS, prophylactic intraperitoneal injection of rabbit antibodies or a mouse monoclonal antibody against human PCT reduced mortality from 100% to 15% and 30%, respectively, and therapeutic injection 2 hours after LPS reduced mortality to 45% (8). Taken together, these results, in a variety of animal models, challenged with a variety of infectious and inflammatory insults, suggest that PCT or its metabolic products play an important role in the pathogenesis of mortality from sepsis.…”

“…However, the gainof-function experimental approach was subject to artifact in that endogenous PCT may not naturally achieve the level or rate of rise reached by exogenous administration, and the exogenous PCT polypeptide was from a different species, and so could trigger an immune recognition response (6). The immunoneutralization loss-of-function approach was subject to artifact in that PCT-antibody complexes might have immunomodulatory roles, and the antibodies were from different species, and so could themselves trigger an immune recognition response (6)(7)(8)(9). To test further the role of PCT in the outcome of sepsis with a genetic loss-of-function approach that is free from these possible artifacts, we used gene-targeted mice that lack expression of PCT and proCGRPa.…”

Intraosseous Versus Intravenous Infusion of Hydroxocobalamin for the Treatment Of Acute Severe Cyanide Toxicity in a Swine Model

“…Nitric oxide is a welldocumented modulator of the immune system that has been implicated in in vitro as well as in vivo inductions of multiple cytokines, and its effects may be concentration dependent. 30 Another intriguing observation of the present study was the release of IL-10, which may represent a compensatory response to downregulate the activity of cyanide-induced proinflammatory cytokines, a situation that has also been documented for inflammatory conditions such as sepsis, 31 delayed type hyperreactivity, or trauma. [32][33][34] Based on the results of our study, hydroxocobalamin infused by IO may be effective for severe cyanide toxicity.…”

“…However, the swine model has been used in previous studies of cyanide toxicity and of resuscitation and cardiac arrest. 15,31,32 The swine cardiovascular system is also analogous to humans. 5,32,33 Although the pig appears to be an acceptable model for IO needle placement, differences in physiology may make extrapolations to humans problematic.…”