The introduction of lumbar puncture into clinical medicine over 100 years ago marks the beginning of the study of central nervous system diseases using the human cerebrospinal fluid (CSF). Ever since, CSF has been analyzed extensively to elucidate the physiological and biochemical bases of neurological disease. The proximity of CSF to the brain makes it a good target for studying the pathophysiology of brain functions, but the barrier function of the CSF also impedes its diagnostic value. Today, measurements to determine alterations in the composition of CSF are central in the differential diagnosis of specific diseases of the central nervous system (CNS). In particular, the analysis of the CSF protein composition provides crucial information in the diagnosis of CNS diseases. This enables the assessment of the physiology of the blood-CSF barrier and of the immunology of intrathecial responses. Besides those routine measurements, protein compositional studies of CSF have been extended recently to many other proteins in the expectation that comprehensive analysis of lower abundance CSF proteins will lead to the discovery of new disease markers. Disease marker discovery by molecular profiling of the CSF tissue has the enormous potential of providing many new disease relevant molecules. New developments in protein profiling techniques hold promise for the discovery and validation of relevant disease markers. In this review, we summarize the current efforts and progress in CSF protein profiling measurements using conventional and current protein analysis tools. We also discuss necessary development in methodology in order to have the highest impact on the study of the molecular composition of CSF proteins.

This paper describes the profiling of human growth hormone (hGH) in human plasma in order to assess the dynamic range of the ion-trap mass spectrometer for proteomic studies of complex biological samples. Human growth hormone is an example of a low-level plasma protein in vivo, present at subfemtomole levels. This study was performed on a plasma sample in which hGH has been spiked at 10-fold above the natural level, that is approximately 16 pg/microL of plasma. Initially, the measurement was carried out without any sample enrichment and consisted of the following steps: the full set of plasma proteins were reduced, alkylated, and digested with trypsin, and the resulting peptides were separated on a capillary C-18 column and then detected by ion-trap mass spectrometry (1D LC/MS). In addition, this study provided a global view of the serum proteome with over 200 plasma proteins being preliminarily identified. In the MS/MS analysis, hGH was detected by characterization of the first tryptic peptide (T1). The initial identification was confirmed by alternative approaches, which also allowed the evaluation of different sample purification protocols. First, the plasma sample containing hGH was fractionated on a reversed-phase HPLC column and digested, and hGH could now be identified by MS/MS measurements of two tryptic peptides (T1 and T4) by the same 1D LC/MS protocol. In addition, the assignment of peptide identity was made with higher certainty (as measured by an algorithm score). The plasma sample was also fractionated by 1D and 2D gel electrophoresis, the selected bands were digested and analyzed again by the 1D LC/MS protocol. In both cases using the gel prepurifications, hGH was identified with additional peptides. Finally, the plasma sample was analyzed by 2D chromatography (ion exchange and reversed phase) on a new instrumental platform (ProteomeX), and hGH was identified by the observation of five tryptic peptides. In conclusion, these experiments were able to detect growth hormone in the low femtomole level with a dynamic range of 1 in 40 000 by several independent approaches. The amount of growth hormone, while 10-fold above normal in vivo levels, represents concentrations that may be present in disease states (such as acromegaly) and also in doping control measurements. These studies have demonstrated that shotgun sequencing approaches (LC/MS/MS) not only can profile high-abundance proteins in complex biological fluids but also have the potential to identify and quantitate low-level proteins present in such complex mixtures without extensive prepurification protocols. A key to such studies, however, is to use targeted approaches that reduce the complexity of the solute mixture that is presented to the mass spectrometer at a given time point. The various sample preparation protocols described here all improved the quality of the hGH measurement, although in this study the 2D chromatographic approach gave the greatest sequence coverage.

Lipids comprise the bulk of the dry mass of the brain. In addition to providing structural integrity to membranes, insulation to cells and acting as a source of energy, lipids can be rapidly converted to mediators of inflammation or to signaling molecules that control molecular and cellular events in the brain. The advent of soft ionization procedures such as electrospray ionization (ESI) and atmospheric pressure chemical ionization (APCI) have made it possible for compositional studies of the diverse lipid structures that are present in brain. These include phospholipids, ceramides, sphingomyelin, cerebrosides, cholesterol and their oxidized derivatives. Lipid analyses have delineated metabolic defects in disease conditions including mental retardation, Parkinson's Disease (PD), schizophrenia, Alzheimer's Disease (AD), depression, brain development, and ischemic stroke. In this review, we examine the structure of the major lipid classes in the brain, describe methods used for their characterization, and evaluate their role in neurological diseases. The potential utility of characterizing lipid markers in the brain, with specific emphasis on disease mechanisms, will be discussed. Additionally, we describe several proteomic strategies for characterizing lipid-metabolizing proteins in human cerebrospinal fluid (CSF). These proteins may be potential therapeutic targets since they transport lipids required for neuronal growth or convert lipids into molecules that control brain physiology. Combining lipidomics and proteomics will enhance existing knowledge of disease pathology and increase the likelihood of discovering specific markers and biochemical mechanisms of brain diseases.

Background: Cerebrospinal fluid (CSF) contacts many brain regions and may mediate humoral signaling distinct from synaptic neurotransmission. However, synthesis and transport mechanisms for such signaling are not defined. The purpose of this study was to investigate whether human CSF contains discrete structures that may enable the regulation of humoral transmission.

Background.-Pharmaceuticals with calcium-or sodium-channel-blocking activity have proven useful for migraine prophylaxis, and calcium channel, sodium transporter, and sodium channel gene mutations have been found in familial hemiplegic migraine. However, it is not known whether calcium or sodium homeostasis is altered in migraine.Objective.-To compare levels of sodium, calcium, potassium, and magnesium in cerebrospinal fluid (CSF) and blood plasma between migraineurs and controls.Methods.-We recruited 20 migraineurs without aura and 11 controls prospectively, and studied migraineurs in sick (MH + ) and well (MH − ) states. We collected lumbar CSF and venous blood plasma, quantified elements with ion-selective electrodes or colorimetry, and determined osmolality by depression of freezing point. We compared levels of Na + , Ca 2+ , K + , and Mg among and also within subjects who were studied in both MH + and MH − states.Results.-Mean CSF Na + levels were increased by 3 mmol/L in MH + compared with MH − and by 4 mmol/L compared to controls (P < 0.005). In 4 subjects who were sampled in both MH + and MH − states, mean CSF Na + concentration increased by 2 mmol/L in the MH + state compared with the MH − state (P < 0.05). Simultaneous plasma Na + levels did not differ among the 3 clinical groups, nor did osmolality, total Ca and Ca 2+ , K + , and total Mg levels in CSF.Conclusions.-Compared to both controls and the MH − state, CSF Na + concentration increased in MH + independently from other clinical or pharmacological fluctuations, CSF concentrations of Ca 2+ , Mg, and K + , and blood plasma Na + levels. These results implicate a deviation of Na + homeostasis in migraine. The modestly elevated extracellular Na + in MH + may cause the neural changes that underlie clinical features of migraine.