No abstract

Sepsis is a systemic inflammatory state caused by infection. Complications of this infection with multiple organ failure lead to more lethal conditions, such as severe sepsis and septic shock. Sepsis is one of the leading causes of US deaths. Novel biomarkers with high sensitivity and specificity may be helpful for early diagnosis of sepsis and for improvement of patient outcomes through the development of new therapies. Mass spectrometry-based proteomics offers powerful tools to identify such biomarkers and furthermore to give insight to fundamental mechanisms of this clinical condition. In this review, we summarize findings from proteomics studies of sepsis and how their applications have provided more understanding into the pathogenesis of septic infection. Literatures related to "proteomics", "sepsis", "systemic inflammatory response syndrome", "severe sepsis", "septic infection", and "multiple organ dysfunction syndrome" were searched using PubMed. Findings about neonatal and adult sepsis are discussed separately. Within the adult sepsis studies, results are grouped based on the models (e.g., human or animal). Across investigations in clinical populations and in rodent and mammalian animal models, biological pathways, such as inflammatory and acute phase response, coagulation, complement, mitochondrial energy metabolism, chaperones, and oxidative stress, are altered at the protein level. These proteomics studies have discovered many novel biomarker candidates of septic infection. Validation the clinical use of these biomarker candidates may significantly impact the diagnosis and prognosis of sepsis. In addition, the molecular mechanisms revealed by these studies may also guide the development of more effective treatments.

The role of ␣␥ and ␤␥ dimers as intermediates in the assembly of fibrinogen was examined in cell fusion experiments using stably transfected baby hamster kidney cell lines expressing one or combinations of fibrinogen chains. Fibrinogen was readily formed and secreted into the culture media when cells co-expressing ␤ and ␥ chains and generating ␤␥ complexes were fused with cells expressing only the ␣ chain. Likewise, when cells co-expressing ␣ and ␥ chains and generating ␣␥ complexes were fused with cells expressing only the ␤ chain, fibrinogen was also formed and secreted. The relative amounts of ␣␥ or ␤␥ intermediates observed during fibrinogen biosynthesis were determined by the levels of the component chains; i.e. when the ␤ chain was limiting, the ␣␥ dimer was the predominant intermediate; likewise, when the ␣ chain was limiting, the ␤␥ complex was the predominant intermediate. The incorporation of preformed ␣␥ and ␤␥ complexes into secreted fibrinogen did not require concurrent protein synthesis, as shown by experiments employing cycloheximide. These data strongly support the role of ␣␥ and ␤␥ complexes as functional intermediates in the assembly of fibrinogen.Human fibrinogen is a large soluble plasma protein that plays a critical role in protecting the vascular network against the loss of blood following tissue injury (Hantgan, 1987). Fibrinogen (M r 340,000) is composed of two sets of three polypeptide chains including the ␣ (M r 66,000), ␤ (M r 52,000), and ␥ (M r 46,500) chains (McKee et al., 1966). The six chains, (a␤␥) 2 , contain 29 disulfide bonds and form a complex trinodular structure (Hall and Slayter, 1959;Erickson and Fowler, 1983) linked by two coiled-coil regions (Doolittle et al., 1978). The ␣, ␤, and ␥ chains are encoded by three independent genes clustered on chromosome 4 at 4q23-32 (Chung et al., 1990; Forman and Barnhardt, 1964). During the synthesis of fibrinogen, the individual chains are translated, processed, assembled, and eventually secreted into plasma as a mature fibrinogen molecule. The assembly of fibrinogen appears to follow a single sequential chain-addition pathway (Huang et al., 1993a), although other pathways have also been proposed (Hartwig and Danishefsky, 1991;Roy et al., 1991). Data from our laboratory suggest that the initial steps in fibrinogen assembly involve the formation of the ␣␥ and ␤␥ dimers linked by disulfide bonds. A third chain is then added to the each dimer to form ␣␤␥ halfmolecules. Finally, two half-molecules dimerize and become linked by five disulfide bonds to form the intact fibrinogen molecule (Huang et al., 1993b). It has not been clearly established, however, whether both ␤␥ and ␣␥ are functional intermediates in fibrinogen assembly, since no precursor-to-product relationship has been demonstrated.Imbalances in the intracellular levels of the ␣, ␤, and ␥ chains have been observed in hepatocytes and hepatoma cells from several species. A common feature is an excess amount of ␥ chain, but limited levels of either the ␤ chain, as in human hepatocy...

Sepsis is commonly caused by community-acquired pneumonia (CAP) and may develop into severe sepsis, characterized by multiple organ failure. The risk of severe sepsis among CAP patients and subsequent mortality increases sharply after the age of 65. The molecular mechanisms associated with this age-related risk are not fully understood. To better understand factors involved with increased incidence and mortality of severe sepsis in the elderly, we used a nested case-control study of patients enrolled in a multicenter observational cohort of 2,320 participants with CAP. We identified a total of 39 CAP patients 50-65 and 70-85 years old who did or did not develop severe sepsis. Plasma samples were obtained on presentation to the emergency department and prior to therapeutic interventions. A semi-quantitative plasma proteomics workflow was applied which incorporated tandem immunoaffinity depletion, iTRAQ labeling, strong cation exchange fractionation, and nanoflow-liquid chromatography coupled to high resolution mass spectrometry. In total, 772 proteins were identified, of which, 58 proteins exhibit statistically significant differences in expression levels amongst patients with severe sepsis as a function of age. Differentially-expressed proteins are involved in pathways such as acute phase response, coagulation signaling, atherosclerosis signaling, lipid metabolism, and production of nitric oxide and reactive oxygen species. This study provides insight into factors that may explain age-related differences in incidence of severe sepsis in the elderly.

Low-dose 5-fluorouracil (5-FU), a widely used chemotherapeutic, has been reported to have immunomodulatory effects. This study aimed to evaluate the optimal dose of 5-FU that produces antitumor and immunomodulatory effects. In a hepatoma 22 tumor-bearing mouse model, 0, 10, 20 and 40 mg/kg 5-FU (i.p.) was administered for 10 days. Tumor weight and volume were measured, thymus index (TI) and spleen index (SI) were calculated, and the number of white blood cells (WBCs) and lymphocytes (LYs) were counted following treatment. The percentages of CD3+, CD4+, CD8+ and natural killer (NK) cells were measured by flow cytometry. In addition, the body weights of the mice were measured and the average diet consumption was calculated. Administration of 5-FU produced a potent antitumor effect in a dose-dependent manner (P<0.01). At 20 and 40 mg/kg, a significant reduction of body weight and food consumption was observed. TI and SI decreased in the 20- and 40-mg/kg groups (P<0.01) for 10 days. The number of WBCs significantly decreased in each group (P<0.01); however, the number of LYs only decreased in the 40-mg/kg group (P<0.01). Percentages of CD3+ and CD4+ cells were increased in the 10- and 20-mg/kg groups (P<0.01). Thus, 5-FU at 10 mg/kg inhibits tumor growth while maintaining the immune function of the mice. 5-FU may exert its antitumor effect at a low dose with low toxicity and stimulate the host immune system. Future clinical trials taking into account the immunostimulatory capacity of chemotherapeutic agents are desirable for certain patients.