Asociación de valores elevados de péptido natriurético auricular y copeptina con riesgo de mortalidad / High levels of atrial natriuretic peptide and copeptin and mortality risk

OBJETIVO: Determinar si los niveles plasmáticos de región media del péptido natriurético proauricular (RM-proPNA), copeptina y procalcitonina (PCT) se asocian con aumento del riesgo de mortalidad. MÉTODOS: Estudio prospectivo observacional que incluyó a 254 niños críticamente enfermos. Se compararon los niveles de RM-proPNA, copeptina y PCT entre niños con alto (grupo A; n=33) y bajo (grupo B; n=221) riesgo de mortalidad y entre pacientes con un número de órganos en fallo mayor de 1 (grupo 1; n=71) y menor de 2 (grupo 2; n=183). RESULTADOS: Las medianas (rangos) de RM-proPNA, copeptina y PCT en grupo A vs. grupo B fueron, respectivamente: 209,4 (30,5-1.415,8) vs. 75,0 (14,6-867,2) pmol/l (p < 0,001); 104,4 (7,4-460,9) vs. 26,6 (0,00-613,1) pmol/l (p < 0,001) y 7,8 (0,3-552,0) vs. 0,3 (0,02-107,0) ng/ml (p < 0,001). El área bajo la curva (AUC) para diferenciar grupo A y B fue (intervalo de confianza del 95%): 0,764 (0,674-0,854) para RM-proPNA; 0,735 (0,642-0,827) para copeptina y 0,842 (0,744-0,941) para PCT, sin diferencias significativas. Las AUC para diferenciar los grupos 1 y 2 fueron: 0,837 (0,784-0,891) para RM-proPNA, 0,735 (0,666-0,804) para copeptina y 0,804 (0,715-0,892) para PCT, con diferencias significativas entre RM-proPNA y copeptina, p = 0,01. CONCLUSIONES: Los niveles elevados de RM-proPNA, copeptina y PCT se asocian con aumento de las puntuaciones de riesgo de mortalidad. RM-proPNA mostró mayor asociación que la copeptina con el número de órganos en fallo

OBJECTIVE: To determine whether high levels of mid-regional pro-atrial natriuretic peptide (MR-proANP), copeptin, and procalcitonin (PCT) plasma concentrations are associated with increased mortality risk. METHODS: Prospective observational study including 254 critically ill children. MR-proANP, copeptin and PCT were compared between children with high (Group A; n=33) and low (Group B; n=221) mortality risk, and between patients with failure of more than 1 organ (Group 1; n=71) and less than 2 (Group 2; n=183). RESULTS: Median (range) of MR-proANP, copeptin, and PCT levels in group A vs B were, respectively: 209.4 (30.5-1415.8) vs. 75.0 (14.6-867.2) pmol/L (P<.001); 104.4 (7.4-460.9) vs. 26.6 (0.00-613.1) pmol/L (P<.001), and 7.8 (0.3-552.0) vs. 0.3 (0.02-107.0) ng/mL (P<.001). The area under the curve (AUC) for the differentiation of group A and B was 0.764 (95% CI: 0.674-0.854) for MR-proANP; 0.735 (0.642-0.827) for copeptin, and 0.842 (0.744-0.941) for PCT, with no statistical differences. The AUCs for the differentiation of group 1 and 2 were: 0.837 (0.784-0.891) for MR-proANP, 0.735 (0.666-0.804) for copeptin, and 0.804 (0.715-0.892) for PCT, with statistical differences between MR-proANP and copeptin, P=.01. CONCLUSIONS: High levels of MR-proANP, copeptin and PCT were associated with increased mortality risk scores. MR-proANP showed a higher association than copeptin with number of organs in failure

Isolation, homology modeling and renal effects of a C-type natriuretic peptide from the venom of the Brazilian yellow scorpion (Tityus serrulatus).

Mammalian natriuretic peptides (NPs) have been extensively investigated for use as therapeutic agents in the treatment of cardiovascular diseases. Here, we describe the isolation, sequencing and tridimensional homology modeling of the first C-type natriuretic peptide isolated from scorpion venom. In addition, its effects on the renal function of rats and on the mRNA expression of natriuretic peptide receptors in the kidneys are delineated. Fractionation of Tityus serrulatus venom using chromatographic techniques yielded a peptide with a molecular mass of 2190.64 Da, which exhibited the pattern of disulfide bridges that is characteristic of a C-type NP (TsNP, T. serrulatus Natriuretic Peptide). In the isolated perfused rat kidney assay, treatment with two concentrations of TsNP (0.03 and 0.1 µg/mL) increased the perfusion pressure, glomerular filtration rate and urinary flow. After 60 min of treatment at both concentrations, the percentages of sodium, potassium and chloride transport were decreased, and the urinary cGMP concentration was elevated. Natriuretic peptide receptor-A (NPR-A) mRNA expression was down regulated in the kidneys treated with both concentrations of TsNP, whereas NPR-B, NPR-C and CG-C mRNAs were up regulated at the 0.1 µg/mL concentration. In conclusion, this work describes the isolation and modeling of the first natriuretic peptide isolated from scorpion venom. In addition, examinations of the renal actions of TsNP indicate that its effects may be related to the activation of NPR-B, NPR-C and GC-C.

A novel method for the large-scale production of PG-CNP37, a C-type natriuretic peptide analogue.

Achondroplasia is the most common form of human dwarfism caused by a mutation in the fibroblast growth factor receptor 3 (FGFR3), resulting in abnormal endochondral bone formation. C-type natriuretic peptide (CNP) is a potent stimulator of endochondral bone growth and represents a potential therapy for achondroplasia. We have developed a novel, simple and cost effective method to produce a CNP analogue, PG-CNP37, at a large scale from Escherichia coli. A PG-CNP37 fusion protein was over-expressed as inclusion bodies in E. coli, which were purified then cleaved by formic acid to release the PG-CNP37 peptide. Approximately 0.5g of 95% pure, soluble and active PG-CNP37 peptide was produced from 1L of culture using this method and may represent a viable means for large-scale production of other therapeutic peptides.

An SRLLR motif downstream of the scissile bond enhances enterokinase cleavage efficiency.

In a previous paper, we reported more efficient enterokinase cleavage at a C-terminal non-target LKGDR(201) site compared with an internally sited canonical recognition site, DDDDK(156). When this non-target site was placed internally to replace DDDDK(156) between the thioredoxin moiety and mouse NT-proCNP(1-50), this site was poorly processed leading us to conclude that efficient processing at LKGDR(201) in the first instance was due to its accessibility at the C-terminus of the fusion protein. Subsequently, we reasoned that treatment of thioredoxin-fused NT-proCNP(1-81) would allow us to retrieve full-length NT-proCNP(1-81) without undue processing at the LKGDR(201) site since this non-target site would now be located internally about 36 residues away from the C-terminus and hence not be hydrolyzed efficiently. Surprisingly, ESI-MS data showed that the LKGDR site in thioredoxin-fused human NT-proCNP(1-81) was still very efficiently cleaved and revealed a new but slow hydrolysis site with the sequence RVDTK/SRAAW to yield a peptide consistent with NT-proCNP(58-81). The evidence obtained from these experiments led us to postulate that efficient cleavage at the non-target LKGDR(201) site was not merely influenced by steric constraints but also by the sequence context downstream of the scissile bond. Hence, we constructed variants of thioredoxin-mouse NT-proCNP(1-50) where SRLLR residues (i.e. those immediately downstream from the LKGDR(201) site in NT-proCNP(1-50)) were systematically added one at a time downstream of the internal DDDDK(156) site. To evaluate the relative effects of site accessibility and downstream sequence context on the efficiency of enterokinase cleavage, we have also replaced the native LKGDR(201) sequence with DDDDK(201). Our results showed that incremental addition of SRLLR residues led to a steady increase in the rate of hydrolysis at DDDDK(156). Further variants comprising DDDDK(156)SS, DDDDK(156)SD and DDDDK(156)RR showed that the minimal critical determinants for enhanced enterokinase cleavage are serine in the P1' position followed by a serine or a basic residue, lysine or arginine, in the P2' position. Our data provided conclusive evidence that the influence of downstream sequences on recombinant light chain enterokinase activity was greater than accessibility of the target site at the terminus region of the protein. We further showed that the catalytic efficiency of the native holoenzyme was influenced primarily by residues on the N-terminal side of the scissile bond while being neutral to residues on the C-terminal side. Finally, we found that cleavage of all nine fusion proteins reflects accurate hydrolysis at the DDDDK(156) and DDDDK(201) sites when recombinant light chain enterokinase was used while non-specific processing at secondary sites were observed when these fusion proteins were treated with the native holoenzyme.

A C-type natriuretic peptide from the venom of the platypus (Ornithorhynchus anatinus): structure and pharmacology.

A peptide which relaxes rat uterine smooth muscle and exhibits homology with the mammalian C-type natriuretic peptide (CNP) has previously been identified in platypus (Ornithorhynchus anatinus) venom from its partial N-terminal amino acid sequence. In this study we describe the purification, detailed structure, synthesis and pharmacological characteristics of this peptide, which has been designated ovCNP-39 (Ornithorhynchus venom C-type natriuretic peptide). Elucidation of the 39-residue amino acid sequence confirms the homology with mammalian CNPs. These peptides produce hypotension in vivo and relax smooth muscle in vitro, but are poorly characterised in terms of physiological function. ovCNP-39 is equipotent with human/rat/porcine CNP-22 in eliciting cyclic guanosine 5'-monophosphate (cGMP) elevation in cultured vascular smooth muscle cells, suggesting that, like CNP, it acts through the ANPB natriuretic peptide receptor subtype. The direct elevation of cGMP in vascular smooth muscle by ovCNP-39 may underlie the vasodilatory effects of platypus envenomation.