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Presepsin (soluble CD14 subtype; sCD14-ST) is a biomarker that detects the existence and severity of sepsis. Previous studies have demonstrated that plasma presepsin levels can consistently distinguish systemic inflammatory response syndrome due to non-sepsis conditions from sepsis. We present a case report of a patient with extensive burns who showed high presepsin levels without sepsis. The 33-year-old man was transferred to the emergency room owing to burns on 33% of his total body surface area and inhalation injuries. He was intubated immediately and admitted to the intensive care unit. The patient’s plasma presepsin level increased to 1984 ρg/mL on day 6. However, repeated blood, wound, and urine cultures did not isolate any pathogenic bacteria. Chest radiographs and enhanced computed tomography did not detect any infectious foci. The patient’s Sequential Organ Failure Assessment score also did not meet the criteria for sepsis. After the patient’s condition stabilized and he was extubated, his presepsin level decreased to 354 ρg/mL on day 13. Debridement and split-thickness mesh skin grafting were performed on day 14. The acceptance of the skin graft was excellent and the patient’s condition improved after the surgery; he was discharged on day 59. Although presepsin has been reported to be a reliable biomarker, certain pathophysiological conditions may affect its levels, as indicated by this case. The reason for our patient’s high presepsin level is unclear; however, the case serves as a reminder that presepsin levels may increase in patients without sepsis. Keywords: Extensive burn, Presepsin, Non-sepsis, C-reactive protein

Publisher Summary This chapter describes the cDNA cloning and expression studies for particulate and soluble guanylyl cyclases that have taken place in several laboratories. The synthesis of cyclic GMP is catalyzed by guanylyl cyclase [GTP pyrophosphate-lyase (cyclizing)] and the enzyme is present in several particulate and soluble isoforms, which are structurally different proteins with different properties. The particulate isoforms can be activated by natriuretic peptides and Escherichia coli heat-stable enterotoxin, whereas the soluble enzyme can be activated by nitric oxide and some porphyrins. Recently, the structures of some particulate and soluble guanylyl cyclases have been described from various sources and an activation mechanism has been proposed. The human particulate guanylyl cyclase cDNA has been used as a probe to isolate a cDNA coding for particulate guanylyl cyclase from a rat brain cDNA library. The deduced sequence of the atrial natriuretic peptide (ANP) receptor/guanylyl cyclase is consistent with the notion that the ANP-binding portion is on the exterior surface and the homologous region to the protein-kinase family and the catalytic site on the cytosolic surface.

Publisher Summary Nitric-oxide synthase (NOS) catalyzes the five-electron oxidation of L-arginine to the nitric oxide radical (.NO) and L-citrulline. Molecular oxygen is the cosubstrate of the enzyme. NO synthase activity has been found in a large variety of cells and tissues. The enzyme exists in several isoforms, three of which have been purified, characterized, and cloned. The activities of all three isoforms are found distributed between the soluble and particulate fractions of cells. Isoform I (from brain) and isoform II (from cytokine-induced macrophages) are mostly soluble proteins. Isoform III from endothelial cells is myristoylated and found predominantly in the particulate fraction. The activities of isoforms I and III are regulated by Ca 2+ in the nanomolar range. The activity of isoform II is Ca 2+ independent. Similar, but not identical procedures are used to purify the different isozymes. All three isoforms are hemoproteins and require the same cofactors, NADPH (6 R )-5,6,7,8-tetrahydrobiopterin, flavin adenine dinucleotide (FAD), and flavin mononucleotide (FMN). Flavins and tetrahydrobiopterin are found bound to the purified enzymes in quantities that are sometimes, but not always, sufficient for full activity. This chapter describes the methods for determining the flavin and biopterin content of NO synthase.

The mechanism by which acetylcholine and other transmitters stimulate the synthesis of cyclic GMP was studied at the cellular and molecular levels using neuroblastoma N1E 115 cells and rat brain. (i) Phosphatidic acid added to the medium stimulated the influx of calcium and elevated intracellular cyclic GMP content in the neuroblastoma cells. Treatment of the cells with phospholipase C increased the 32 Pi incorporation into phosphatidic acid and, in parallel, stimulated calcium influx and cyclic GMP synthesis in the cells. (ii) Guanylate cyclase was readily solubilized from neuroblastoma cells by homogenization with hypotonic buffer. The supernatant also contained an endogenous activator of small molecule for guanylate cyclase. The activator was also detected in the supernatant of rat brain and was purified to a high purity. Calcium was required for the activation of guanylate cyclase by the endogenous activator. (iii) Monoclonal antibody to the soluble guanylate cyclase from rat brain cross-reacted with the soluble enzyme from various tissues of rat, but not with the soluble enzyme of mouse brain and rabbit brain indicating a speciecs difference of soluble guanylate cyclase. Immunochemical titration study revealed that guanylate cyclase in the synaptosomal soluble fraction of rat brain was in a highly activated state.