Protective role of natural killer cells in neuropathic pain conditions.

ABSTRACT: During the past few years, the research of chronic neuropathic pain has focused on neuroinflammation within the central nervous system and its impact on pain chronicity. As part of the ERA-Net NEURON consortium, we aimed to identify immune cell patterns in the cerebrospinal fluid (CSF) of patients with herpes zoster neuralgia and patients with polyneuropathy (PNP), which may contribute to pain chronicity in these neuropathic pain conditions. Cerebrospinal fluid of 41 patients (10 herpes zoster and 31 PNP) was analyzed by flow cytometry identifying lymphocyte subsets: CD4+ (T-helper cells), CD8+ (cytotoxic T cells), CD19+ (B cells), and CD56+ (natural killer [NK]) cells. At baseline and at follow-up, the somatosensory phenotype was assessed with quantitative sensory testing. In addition, the patients answered epidemiological questionnaires and the PainDETECT questionnaire. Immune cell profiles and somatosensory profiles, as well as painDETECT questionnaire scores, were analyzed and correlated to determine specific immune cell patterns, which contribute to chronic pain. We found a negative correlation (P = 0.004, r = -0.596) between the frequency of NK cells and mechanical pain sensitivity (MPS), one of the most relevant quantitative sensory testing markers for central sensitization; a high frequency of NK cells correlated with low MPS. The analysis of the individual follow-up showed a worsening of the pain condition if NK-cell frequency was low. Low NK-cell frequency is associated with signs of central sensitization (MPS), whereas high NK-cell frequency might prevent central sensitization. Therefore, NK cells seem to play a protective role within the neuroinflammatory cascade and may be used as a marker for pain chronicity.

A comparison of metabolic health parameters in ICSI-conceived and naturally conceived adolescents.

RESEARCH QUESTION: Are there differences in the cardiometabolic health of ICSI-conceived adolescents compared with a control group, taking parental risk factors into account? DESIGN: ICSI-conceived adolescents (n = 272), their mothers (n = 273) and naturally conceived control adolescents (n = 273) and their mothers (n = 273) provided a blood test and answered a health-related questionnaire. The adolescents also attended a physical examination. RESULTS: ICSI-conceived males showed significantly higher mean weight (72.6 ± 15.1 versus 67.7 ± 12.6 kg, P = 0.005), body mass index (BMI) (22.2 ± 3.7 versus 21.0 ± 3.2 kg/m2, P = 0.007) and waist circumference (79.1 ± 11.6 versus 74.5 ± 8.7 cm, P < 0.001). The mean values for weight and BMI were also significantly higher in the ICSI parents. In the ICSI-conceived females significant differences in high-density lipoprotein cholesterol (1.5 ± 0.3 versus 1.6 ± 0.3 mmol/l, P = 0.033) and triglyceride values (1.1 ± 0.5 versus 1.0 ± 0.4 mmol/l, P = 0.013) were observed. ICSI mothers also had significantly higher triglycerides (P = 0.002), higher glutamate pyruvate transaminase/alanine aminotransferase (P < 0.001) and higher alkaline phosphatase values (P < 0.001). CONCLUSIONS: Increased values for weight were found in the male and differences in lipid parameters in the female ICSI-conceived adolescents, which were reflected in the values of their parents. Adjustment for parental risk factors generally attenuated the differences between the ICSI and the control groups, but did not completely remove them. Whether these observed differences are clinically relevant for the future health of the participants requires further study. To increase knowledge in this area, future studies should also include parental data.

Construction and characterization of a gradually inducible expression vector for Halobacterium salinarum, based on the kdp promoter.

Gradually inducible expression vectors which are governed by variations of growth conditions are powerful tools for gene expression of conditionally lethal mutants. Furthermore, controlled expression allows monitoring of overproduction of proteins at various stages in their expressing hosts. For Halobacterium salinarum, which is often used as a paradigm for halophilic archaea, such an inducible expression system is not available to date. Here we show that the kdp promoter (Pkdp), which facilitates gene expression upon K(+) limitation, can be used to establish such a system for molecular applications. Pkdp features a rather high expression rate, with an approximately 50-fold increase that can be easily varied by K(+) concentrations in the growth medium. Besides the construction of an expression vector, our work describes the characterization of expression patterns and, thus, offers a gradually inducible expression system to the scientific community.

An ATP-driven potassium pump promotes long-term survival of Halobacterium salinarum within salt crystals.

Many extremely halophilic archaea belonging to the Halobacteriales have remarkable longevity. They are even known to persist for millions of years within fluid inclusions of salt crystals. However, the key systems responsible for this remarkable ability and the underlying physiological mechanisms have not yet been deciphered. This study revealed that the ATP-dependent K(+) uptake system KdpFABC of Halobacterium salinarum is essential for survival under desiccation and salt crystal inclusion and, thus, can be identified as at least one of these systems in this organism. The presence of the kdp genes promoted survival of H. salinarum entombed in halite, compared with cells in which these genes were deleted. Expression of the kdp operon was found to be induced already under desiccating conditions without halite entombment. The morphology of cells included in halite resembled that of cells grown under potassium limitation. Therefore, a steady potassium supply, even under unfavourable energetic conditions, plays a key role in long-term survival and desiccation tolerance.

Archaeal transcriptional regulation of the prokaryotic KdpFABC complex mediating K(+) uptake in H. salinarum.

The genome of the halophilic archaeon Halobacterium salinarum encodes the high-affinity ATP-dependent K(+) uptake system Kdp. Previous studies have shown that the genes coding for the KdpFABC complex are arranged in a kdpFABCQ gene cluster together with an additional gene kdpQ. In bacteria, expression of the kdpFABC genes is generally regulated by the dedicated sensor kinase/response regulator pair KdpD/KdpE, which are absent in H. salinarum. Surprisingly, H. salinarum expresses the kdp genes in a manner which is strikingly similar to Escherichia coli. In this study, we show that the halobacterial kdpFABCQ genes constitute an operon and that kdpFABCQ expression is subject to a complex regulatory mechanism involving a negative transcriptional regulator and is further modulated via a so far unknown mechanism. We describe how the regulation of kdp gene expression is facilitated in H. salinarum in contrast to its bacterial counterparts. Whereas the Kdp system fulfils the same core function as an ATP-driven K(+) uptake system in both archaea and bacteria, the different mechanisms involved in the regulation of gene expression appear to have evolved separately, possibly reflecting a different physiological role of ATP-driven K(+) uptake in halophilic archaea.