Fibronectin (FN) is a widely distributed glycoprotein which is present in different bodily fluids, on the surface of cells and in the extracellular matrix (ECM). It plays roles in various processes, including cell adhesion, migration, growth, proliferation, and tissue repair. Fibronectin exists in 2 forms: a soluble, inactive molecule, called plasma FN (pFN), which is synthesized by hepatocytes in the liver, and an insoluble cellular form (cFN), which is produced locally by different types of cells and is a key component of the ECM. Fibrinogen fibrils ensure structural support for cell adhesion and promote cell migration, proliferation and apoptosis. Additionally, FN controls the availability of growth factors. The plasma form of FN is a crucial component of the fibrin clot in the early wound-healing response, while the cellular form of FN supports efficient platelet adhesion, activation, aggregation, and procoagulant activity. Alternative splicing of the FN gene results in the generation of protein variants which contain the additional isoforms - extra domain A of FN (EDA) and extra domain A of FN (EDB); these are associated with, e.g., tissue remodeling, fibroblast differentiation, inflammation, and tumor progression. Fibronectin also serves as a target for a large number of bacterial proteins, and as part of a 3-component bridge (FN, integrin and FN-binding proteins - FnBPs) it contributes to bacterial colonization of endothelial and epithelial cells. Fibronectin has been identified in sepsis in humans as a negative acute-phase protein, and a low level of FN seems to be a marker of a poor prognosis for a patient. Here, the role of FN in inflammatory processes and sepsis is presented.

Gastrointestinal (GI) failure can be both a cause of sepsis and a consequence of the systemic pro-inflammatory response in sepsis. Changes in biomarkers of enterocyte damage, citrulline and I-FABP (intestinal fatty acid binding protein), may indicate altered intestinal permeability and damage. The study group consisted of patients with sepsis (N = 28) and septic shock (N = 30); the control group included patients without infection (N = 10). Blood samples were collected for citrulline and I-FABP and a 4-point AGI score (acute GI injury score) was calculated to monitor GI function on days 1, 3, 5, 7, and 10. Citrulline concentrations in the study group were lower than in the control. Lower values were also noted in septic patients with shock when compared to the non-shock group throughout the study period. I-FABP was higher in the septic shock group than in the sepsis group only on days 1 and 3. Citrulline was lower in patients with GI failure (AGI III) when compared to AGI I/II, reaching significance on days 7 (p = 0.034) and 10 (p = 0.015); moreover, a higher AGI score was associated with an increased 28 day mortality (p = 0.038). The results indicate that citrulline measurements, along with the AGI assessment, have clinical potential in monitoring GI function and integrity in sepsis.

Gastrointestinal symptoms are common in critically ill COVID-19 patients. There is currently no generally recognized method of assessing gastrointestinal injury in unconscious or sedated intensive care unit (ICU) patients. I-FABP (intestinal fatty acid binding protein) and citrulline have previously been studied as potential biomarkers of enterocyte damage in various gastrointestinal tract diseases, and changes in the levels of these markers may reflect intestinal wall damage in COVID-19. Patients with critical COVID-19, with diagnosed sepsis, or septic shock requiring ICU treatment were included in the study. Blood samples for citrulline and I-FABP were taken daily from day 1 to 5. I-FABP levels were significantly higher in patients who eventually died from COVID-19 than in survivors, and the optimal I-FABP cut-off point for predicting 28-day mortality was 668.57 pg/mL (sensitivity 0.739, specificity 0.765). Plasma levels of I-FABP, but not citrulline, were associated with significantly higher mortality and appeared to be a predictor of poor outcome in multivariate logistic regression analysis. In conclusion, I-FABP seems to be an effective prognostic marker in critically ill COVID-19 patients. Assessing mortality risk based on intestinal markers may be helpful in making clinical decisions regarding the management of intestinal injury, imaging diagnostics, and potential surgical interventions.

Background:Aberrant angiogenesis and senescence of the cerebrovascular system could initiate neurovascular events leading to neurovascular disorders. Fibronectin (FN) exerts a strong angiogenic influence on endothelial cells in the central nervous system. Methods: In the present study the expression of the plasma fibronectin molecular forms in an Alzheimer patient group, compared with vascular dementia and age-matched control groups was analyzed by immunoblotting. Results: FN in the plasma of the elderly individuals with and without dementia exists as a mixture of heterogeneous molecules with increasing molecular masses. Apart from the wide ∼240-kDa and ∼220-kDa FN bands, normally present in plasma, the high molecular FN forms having ∼280 kDa and ∼320 kDa appeared in the plasma of the Alzheimer dementia group more frequently and at the higher amounts than in the vascular dementia and age-matched nondemented groups. Conclusions: The plasma FN molecular status seems to be a molecular additional biomarker for assessment of dementia risk.

Background. Bladder cancer diagnosis and surveillance includes cystoscopy and cytology. New methods for the detection of bladder cancer are needed, because cystoscopy is invasive and expensive, and because urine cytology is not sensitive enough. Objectives. The aim of the study was to select potential plasma protein markers for bladder cancer which could be useful in developing a specific laboratory test to improve diagnosis and to establish treatment strategies in order to prevent the recurrence of the disease. Material and methods. Plasma proteome maps were prepared based on 2-dimensional sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), combined with image gel analysis and matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry of plasma samples from patients with urothelial bladder cancer, and they were compared to normal samples. Results. The analyses of bladder cancer plasma samples allowed us to distinguish 3 groups of proteins whose relative abundance differed from that in normal samples. The 1st one comprised modified forms of plasma transferrin, fibrinogen gamma and complement C3b, which were absent in normal plasma. The 2nd group comprised haptoglobin, alpha-2-macroglobulin, vitamin D-binding protein, and pigment epithelium-derived factor, which occurred in the cancerous samples in large quantities. The 3rd group consisted of 3 molecular forms of immunoglobulin M (IgM), the relative abundance of which was significantly lower in the cancerous plasma samples. Conclusions. The data indicated potential plasma biomarkers associated with inflammation, immunity and coagulation processes accompanying bladder cancer. They could be used for the development of a laboratory test(s) useful in clinical practice.