The uremic solute p-cresol decreases leukocyte transendothelial migration in vitro

Chronic renal failure (CRF) patients display an immunodeficiency state, and uremic solutes that accumulate during CRF may be involved in this immunodeficiency. In this study, we examined whether the uremic solute para-cresol (p-cresol), at concentrations similar to those found in patients, alters leukocyte transmigration in vitro. We found that p-cresol significantly inhibited monocyte THP-1 cell line and PBMCs transmigration across IL-1beta-stimulated human umbilical vein endothelial cell (HUVEC) in a static two-compartment model. This inhibitory effect of p-cresol persisted in the presence of a physiologic concentration of human serum albumin. In order to investigate the mechanism involved, expression of endothelial chemokines, fractalkine, monocyte chemoattractant protein 1 (MCP-1) and IL-8 and membrane expression of junctional adhesion molecule A (JAM-A or JAM-1) were studied. We found that p-cresol decreased mRNA expression of the chemokine fractalkine in IL-1beta-stimulated HUVEC, without modifying mRNA expression of MCP-1 and IL-8. In addition, p-cresol decreased IL-1beta-induced expression of membrane-bound and soluble forms of fractalkine and impaired the membrane expression of JAM-A. Taken together, these results suggest that p-cresol, by impairing leukocyte transendothelial migration, plays a role in the immune dysfunction of uremic patients.

The requirement of ammonium or other cations linked with p-cresol sulfate for cross-reactivity with a peptide of myelin basic protein

Urinary myelin basic protein-like material (MBPLM), so designated because of its immunoreactivity with a polyclonal antibody directed against a cryptic epitope located in residues 83-89 of myelin basic protein (MBP), exists in humans normally but increases in concentration in patients with multiple sclerosis who have progressive disease. Given its possible role in reflecting events of neural tissue destruction occurring in multiple sclerosis, urinary MBPLM is a candidate surrogate marker for this phase of the disease. Previously, it has been demonstrated that p-cresol sulfate (PCS) is the dominant component of MBPLM; however, another component(s) was essential in enabling p-cresol sulfate to have molecular mimicry with MBP peptide 83-89 detected by immunoreactivity. In the present investigation, this remaining component(s) was characterized by a combination of high performance size exclusion chromatography followed by nuclear magnetic resonance spectroscopy and shown to be ammonium. The monovalent cation ammonium could be substituted in vitro by several different monovalent and divalent cations, most notably zinc, in restoring to deprotonated p-cresol sulfate its immunoreactivity as MBPLM. These findings indicate the basis for the unexpected molecular mimicry between an epitope of an encephalitogenic protein and a complex containing a small organic molecule, p-cresol sulfate. Furthermore, the reaction of either ammonium or other cations with p-cresol sulfate may represent an in vivo process directly related to damage of axonal membranes.

Allergenicity evaluation of p-chloro-m-cresol and p-chloro-m-xylenol by non-radioactive murine local lymph-node assay and multiple-dose guinea pig maximization test

p-Chloro-m-cresol (PCMC) and p-chloro-m-xylenol (PCMX) are known to cause allergic contact dermatitis. For risk assessment of skin sensitizers, information on dose-response profiles in the induction and elicitation phases and cross-reactivity with analogous chemicals are important. In the non-radioactive local lymph-node assay (LLNA) using 5-bromo-2'-deoxyuridine instead of 3H-methyl thymidine, significant effect on lymph node cell proliferation was detected at 10% PCMC and 25% PCMX, while in the multiple-dose guinea pig maximization test (GPMT) at least one animal tested in the group was sensitized at a 5 ppm induction dose of either chemical. When mean skin reaction score in an animal group maximally sensitized with each allergen with the GPMT was plotted against log challenge concentration, linear regression lines with high correlations were obtained in both cases. The calculated elicitation threshold was lower for PCMC than PCMX. The area under the linear regression line between the threshold point and 1% of the elicitation concentration, another index of relative elicitation potency, was also greater for PCMC. Bidirectional cross-reactivity between PCMX and PCMC was detected in the GPMT. PCMC was thus identified in both LLNA and GPMT as a stronger sensitizer than PCMX in both the induction and elicitation phases. These results suggest that the non-radioactive LLNA is a simple and useful method for evaluating allergenicity in the induction phase, while the GPMT using a maximally sensitized animal group is more suitable for assessing the dose-response profile and cross-reactivity in the elicitation phase.

p-Cresol sulfate is the dominant component of urinary myelin basic protein like material

Multiple sclerosis (MS) is clinically heterogeneous and has an uncertain natural history. A high priority for more effective treatment of MS is an objective and feasible laboratory test for predicting the disease's course and response to treatments. Urinary myelin basic protein (MBP)-like material (MBPLM), so designated because it is immunoreactive as a cryptic epitope in peptide 83-89 of the human MBP molecule of 170 amino acids, is present in normal adults, remains normal in relapsing-remitting, but increases in progressive MS. In the present investigation, MBPLM was purified from urine and characterized. p-Cresol sulfate is the major component of urinary MBPLM. This conclusion is based on the following: (1) MBPLM and p-cresol sulfate both have a mass of 187 on negative scans by electrospray ionization mass spectrometry, the same fragments on tandem mass spectrometry of 80 (SO(-)(3)) and 107 (methylphenol), and similar profiles on multiple reaction monitoring; (2) (1)H and (13)C nuclear magnetic resonance spectroscopy revealed identical spectra for MBPLM and p-cresol sulfate; (3) purified p-cresol sulfate reacted in parallel with MBP peptide 83-89 in the same radioimmunoassay for MBPLM; and (4) p-cresol sulfate has the same behavior on preparative HPLC columns as urinary MBPLM. The unexpected immunochemical degeneracy permitting a cross-reaction between p-cresol sulfate and a peptide of an encephalitogenic myelin protein is postulated to be based on shared conformational features. The mechanisms by which urinary p-cresol sulfate, possibly derived from tyrosine-SO(4), reflects progressive worsening that is disabling in MS are unknown.