Sample preparation, high-performance liquid chromatographic separation and determination of substance P-related peptides

Novel method for determination of substance P levels in unextracted human plasma by using acidification

Substance P (SP) is a member of the tachykinin family and has an important role in immune responses. SP is detectable in plasma in a free and bound state. Simple modification of a commercially available SP enzyme-linked immunosorbent assay allows the dissociation and capture of plasma SP without solid-phase extraction.

Evidence that the etiology of the syndrome containing type 2 diabetes mellitus results from abnormal magnesium metabolism

Evidence is reviewed supporting the presence of an inherited structural defect in the plasma membranes of somatic cells of humans who have type 2 diabetes mellitus and sodium-sensitive essential hypertension. This magnesium-binding defect (MgBD) consists of a decreased content of tightly bound Mg2+ ion in the cell membrane and limits the amount of Mg2+ that enters the cell, some of which combines with ATP4-, produced by the cell, to form MgATP2-, the currency of metabolic energy. Consequently, in both prediabetes and overt diabetes, the intracellular concentration of the interdependent Mg2+ and MgATP2- ions is significantly less than normal. These 2 ions are required as cofactors and (or) substrates for some 300 enzyme systems in human metabolism, many of which are involved with insulin. Thus the decreased activities of particular ones of these enzyme systems due to the decreased intracellular [Mg2+] and its dependent [MgATP2-] are responsible for (i) insulin resistance and (ii) decreased insulin secretion and (or) production, the 2 pathophysiological processes required for the occurrence of type 2 diabetes mellitus. These 2 processes can account for all of the morbid symptoms associated with this disease. Thus, the decreased intracellular concentration of the interdependent Mg2+ and MgATP2- ions constitutes the etiology of genetic predisposition to type 2 diabetes mellitus and can be corrected by 2 identified peptide Mg2+-binding promoters that are derived from the carboxyl terminal of the tachykinin substance P and occur in normal blood plasma. Decreased intracellular [Mg2+] and [MgATP2-] can also result from a dietary deficiency of magnesium or from an abnormal accumulation of saturated fatty acids in cell membranes, which inhibits the entrance of Mg2+ into the cell; thus it is also the etiology not only of diabetes caused by magnesium deficiency, but also of the "lipotoxic" type 2 diabetes mellitus. Although these pathologies cannot be corrected by the Mg2+-binding promoters, they can be corrected, respectively, by dietary magnesium supplementation or by exercise plus dietary caloric and lipid restriction. Theoretically, the disease syndrome containing type 2 diabetes mellitus may involve approximately 30% of the population.

Measurement of plasma-derived substance P: biological, methodological, and statistical considerations

The undecapeptide substance P (SP) is a member of the tachykinin family of neurotransmitters, which has a pivotal role in the regulation of inflammatory and immune responses. One of the major barriers to the study of the in vivo role of SP in a number of immune disorders is the accurate measurement of SP in fluids. This is reflected in the variability of reported SP levels in serum and plasma of humans in both healthy and diseased states. This study was initiated in order to identify sources of variability by the comparative evaluation of the influences of sample preparation and analytical detection methods on the measurement of SP in plasma. The results indicate that sample preparation (peptide extraction versus no extraction) and the choice of analytical method for SP quantitation may yield significantly different values and may contribute to the variability in SP values reported in the literature. These results further emphasize the need for careful consideration in the selection of methods for SP quantitation, as well as caution in the interpretation and comparison of data reported in the literature.

A surface plasmon resonance sensor for substance P using gold-modified calmodulin and melittin

A surface plasmon resonance (SPR) biosensor for the quantification of a neuropeptide substance P (SP) is described based on an inhibition assay using Au colloid-modified calmodulin (Au-CaM) and a target peptide melittin immobilized on carboxymethylated dextran. The modification of CaM with streptavidin Au colloids was achieved in a sample solution by the amine coupling method. The SPR signal sharply increased, corresponding to the formation of a Ca2+-Au-CaM-melittin complex on the sensor surface, and approached a steady state within 5 min. When SP was added to a sample solution, the SPR signal was decreased, due to the formation of a Ca2+-Au-CaM-SP complex in the sample solution. The modification of CaM with streptavidin Au colloids was effective for enhancing the SPR signal for SP. A decrease in the SPR signal was observed for SP in the concentration range from 0.10 to 5.0 microM, whose lower limit was ten-times superior to that (1.0 microM) with unmodified CaM. The response was highly selective to SP and the selectivity was in the order of SP >> neurokinin A > neurokinin B > neurotransmitters (glycine, GABA, L-glutamate, acetylcholine, norepinephrine, 5HT) - substance P fragment (1 - 7). The potential use of the present sensor for the quantification of SP in mouse brain extracts is demonstrated.

Quantification of hemokinin-1 peptide production and secretion from mouse B cells

Hemokinin-1 is a recent addition to the family of mammalian tachykinins and is thought to play an important role in B cell and T cell lymphopoiesis. The mRNA coding for this peptide was expressed in some B lymphocyte cell lines including 70Z/3.12, ABE-8.1/2, and RAW8.1 cells, suggesting the possibility that hemokinin-1 may function in an autocrine or paracrine manner in these cells. Therefore, we quantified secretion of this peptide from the 70Z/3.12 cell line expressing hemokinin-1 mRNA. Despite a sensitive radioimmunoassay, we were surprised to find that hemokinin-1 secretion from confluent cells was below the level of detection of this assay. Furthermore, cell lysates routinely demonstrated a low or undetectable immunoreactive peptide. Collectively these studies show a limited production of hemokinin-1 peptide by transformed B cells.

Substance P in Human Tears

PURPOSE

To determine the levels and biochemical characteristics of substance P-like immunoreactivity (SPLI) in human tears and ascertain whether substance P (SP) concentrations in tears reflect the condition of the ocular surface.

METHODS

Unstimulated tears were collected with a micropipette. Tear samples were partially purified using C-18 cartridges. Levels of SPLI in purified samples were measured using an enzyme immunoassay (EIA). For biochemical characterization of SPLI, tear extracts were fractionated using high-performance liquid chromatography (HPLC); each fraction was then subjected to EIA. To determine the catabolism of SP in tears, synthetic SP was incubated in medium containing pooled tears and then analyzed using HPLC.

RESULTS

The concentration of SPLI in normal human tears was 306.0 +/- 96.5 pg/mL (mean +/- SD, range 148-555 pg/mL). Levels of SPLI did not vary significantly by age or gender. Concentrations of SPLI in tears from eyes with unilateral corneal hypesthesia were lower than those in tears from contralateral healthy eyes. Diclofenac sodium eye drops reduced concentrations of prostaglandin E2 and SPLI in tears. Analysis using HPLC indicated that five different substances contributed to SPLI in tears and that SP was broken down into several fragments, including SP(8-11), by enzymes present in tears.

CONCLUSIONS

Substance P is a normal component of human tears. Levels of SPLI in tears might reflect the denervated status of the ocular surface. Substance P is catabolized by degradative enzymes in tears to maintain the ocular surface by exerting the trophic effects of SP while avoiding undesirable effects.

Possibilities to improve automation, speed and precision of proteome analysis: a comparison of two-dimensional electrophoresis and alternatives

Proteome analysis requires fast methods with high separation efficiencies in order to screen the various cell and tissue types for their proteome expression and monitor the effect of environmental conditions and time on this expression. The established two-dimensional gel electrophoresis (2-DE) is by far too slow for a consequential screening. Moreover, it is not precise enough to observe changes in protein concentrations. There are various approaches that promise faster, automated proteome analysis. This article concentrates on capillary (CT isoelectric focusing coupled to mass spectrometry (CIEF-MSn) and preparative IEF followed by size-exclusion chromatography, hyphenated with MS (PIEF-SEC-MS). These two approaches provide a similar separation pattern as the established 2-DE technique and therefore allow for the continued use of data based on this traditional approach. Their performances have been discussed and compared to 2-DE, evaluating 169 recent articles. Data on analysis time, automation, the detection limit, quantitation, peak capacity, mass and pI accuracy, as well as on the required sample amount are compared in a table.

Investigation of the metabolism of substance P at the blood-brain barrier using capillary electrophoresis with laser-induced fluorescence detection

Substance P (SP) metabolism was investigated upon exposure to a monolayer of bovine brain microvessel endothelial cells (BBMECs), a cell culture model of the blood-brain barrier. SP was incubated with the BBMECs and its metabolism was followed as a function of time over a 5-h period. The resulting samples were derivatized with naphthalene-2,3-dicarboxaldehyde (NDA)/cyanide, separated, and detected using cyclodextrin-modified electrokinetic chromatography with laser-induced fluorescence detection (CDMEKC-LIF). Upon exposure to the BBMEC monolayer, SP rapidly degraded to produce the N-terminal (1-9), (1-4) and (1-7) and C-terminal (2-11) and (3-11) fragments. These results were compared with those in an earlier report from our laboratory, where SP metabolism was investigated in vivo by microdialysis sampling in rat striatum.

Investigation of the metabolism of substance P in rat striatum by microdialysis sampling and capillary electrophoresis with laser-induced fluorescence detection

The metabolism of substance P (SP) was investigated in rat striatum using in vivo microdialysis. Substance P was perfused for 5 h at 0.2 microl/min, and its metabolism was followed for over 13 h. The resulting samples were derivatized precolumn with naphthalene-2,3-dicarboxaldehyde (NDA)/cyanide, separated and detected by cyclodextrin-modified electrokinetic chromatography with laser-induced fluorescence detection (CDMEKC-LIF). Substance P rapidly degraded to form the fragments (3-11), (1-9), (1-4) and, to a lesser extent, (1-7). The metabolites reached steady-state levels 2-3 h after addition of SP.

Identification of substance P metabolites using a combination of reversed-phase high-performance liquid chromatography and capillary electrophoresis

Gradient elution reversed-phase high-performance liquid chromatographic and capillary electrophoretic separations were optimised to separate substance P (SP) and twelve of its fragments. The methods were applied to a study of the in vivo metabolism of substance P in the rat after intrastriatal injection of the peptide (10 nmol). SP and significant amounts of its N-terminal fragments, SP(1-7) and SP(1-4), were detected but no major C-terminal fragments could be identified. At the concentration studied, the metabolism of SP was shown to follow zero order elimination kinetics with a rate of decay of 0.2 nmol/min. As we have shown that SP(1-4) and SP(1-7) can be produced in vivo in the striatum in relatively large amounts, it is conceivable that these fragments contribute to the overall pharmacological pattern of activity of the parent peptide.

Development and evaluation of a chromatographic procedure for partial purification of substance P with quantitation by an enzyme immunoassay

We have developed a simple chromatographic procedure for the partial purification of substance P (SP) from acidified plasma and serum samples. We have evaluated a sensitive antigen competition enzyme immunoassay (EIA) for the quantitation of SP. The chromatographic procedure has recovery efficiencies ranging from 94.8 to 125%. The immunoreactivity of unknown amounts of purified SP subjected to the preparative procedure yielded a coefficient of variance of 9.4%. The EIA yielded reproducible standard curves having an interassay (n = 8) correlation coefficient of 0.984. The evaluation of normal adult control serum yielded a mean value of 51 pg/ml (range, 35 to 61 pg/ml). The evaluation of 3.33 x concentrates of serum-derived partially purified SP provided uncorrected SP values of 117 to 201 pg/ml, which fell within the midpoint of the three-decalog standard curve. These studies indicate that both the preparative and quantitative procedures are required for the detection of SP in plasma or serum samples collected from patients with several clinical disorders.

Application of [(125)I]-[Tyr8]-substance P prepared by the chloramine-T method to receptor-binding experiments after subsequent reduction with mercaptoethanol and purification by reversed-phase liquid chromatography

Radiolabeling of [Tyr8]-substance P ([Tyr8]-SP) with the (125)I-isotope was performed by use of the chloramine-T technique. The primary formed radiolabeled product, having been quantitatively converted to the corresponding sulfoxide yielding [(125)I]-[Tyr8]-(Met11-->O)-SP completely lacked any binding to proteins rich in SP receptor populations. However, after reductive treatment with mercaptoethanol for about 2 h, a complete reconstitution of the Met11 thioether structure was observed. The reduced peptide, consisting of [(125)I]-[Tyr8]-(Met11)-SP was separated from its by-products by reversed-phase high-performance liquid chromatography on octadecylsilyl silica gel with 100 mM triethyl ammonium formate buffer containing 22% acetonitrile (pH 2.2). The labeled SP derivative prepared by this two-step synthesis was obtained in 73% overall yield related to the [Tyr8]-SP starting material and exhibited a specific activity of 1.9-10(6) Ci/M. In contrast to [(125)I]-[Tyr8]-->(Met11-->O)-SP, satisfactory receptor-binding was now observed with the [(125)I]-->[Tyr8]-(Met11)-SP derivative.