High OXPHOS efficiency in RA-FUdr-differentiated SH-SY5Y cells: involvement of cAMP signalling and respiratory supercomplexes.

Neurons are highly dependent on mitochondria to meet their bioenergetic needs and understanding the metabolic changes during the differentiation process is crucial in the neurodegeneration context. Several in vitro approaches have been developed to study neuronal differentiation and bioenergetic changes. The human SH-SY5Y cell line is a widely used cellular model and several differentiation protocols have been developed to induce a neuron-like phenotype including retinoic acid (RA) treatment. In this work we obtained a homogeneous functional population of neuron-like cells by a two-step differentiation protocol in which SH-SY5Y cells were treated with RA plus the mitotic inhibitor 2-deoxy-5-fluorouridine (FUdr). RA-FUdr treatment induced a neuronal phenotype characterized by increased expression of neuronal markers and electrical properties specific to excitable cells. In addition, the RA-FUdr differentiated cells showed an enrichment of long chain and unsaturated fatty acids (FA) in the acyl chain composition of cardiolipin (CL) and the bioenergetic analysis evidences a high coupled and maximal respiration associated with high mitochondrial ATP levels. Our results suggest that the observed high oxidative phosphorylation (OXPHOS) capacity may be related to the activation of the cyclic adenosine monophosphate (cAMP) pathway and the assembly of respiratory supercomplexes (SCs), highlighting the change in mitochondrial phenotype during neuronal differentiation.

Prefrontal dysfunction in post-COVID-19 hyposmia: an EEG/fNIRS study.

Introduction: Subtle cognitive dysfunction and mental fatigue are frequent after severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, characterizing the so-called long COVID-19 syndrome. This study aimed to correlate cognitive, neurophysiological, and olfactory function in a group of subjects who experienced acute SARS-CoV-2 infection with persistent hyposmia at least 12 weeks before the observation. Methods: For each participant (32 post-COVID-19 patients and 16 controls), electroencephalography (EEG) and functional near-infrared spectroscopy (fNIRS) data were acquired using an integrated EEG-fNIRS system during the execution of a P300 odd-ball task and a Stroop test. The Sniffin' Sticks test was conducted to assess subjects' olfactory performance. The Montreal Cognitive Assessment (MoCA) and the Frontal Assessment Battery (FAB) were also administered. Results: The post-COVID-19 group consisted of 32 individuals (20 women and 12 men) with an average education level of 12.9 ± 3.12 years, while the control group consisted of 16 individuals (10 women and 6 men) with an average education level of 14.9 ± 3.2 years. There were no significant differences in gender (X2 = 0, p = 1) or age between the two groups (age 44.81 ± 13.9 vs. 36.62 ± 11.4, p = 0.058). We identified a lower concentration of oxyhemoglobin (p < 0.05) at the prefrontal cortical level in post-COVID-19 subjects during the execution of the Stroop task, as well as a reduction in the amplitude of the P3a response. Moreover, we found that post-COVID-19 subjects performed worst at the MoCA screening test (p = 0.001), Sniffin's Sticks test (p < 0.001), and Stroop task response latency test (p < 0.001). Conclusions: This study showed that post-COVID-19 patients with persistent hyposmia present mild deficits in prefrontal function, even 4 months after the end of the infection. These deficits, although subtle, could have long-term implications for quality of life and cognitive wellbeing. It is essential to continue monitoring and evaluating these patients to better understand the extent and duration of cognitive impairments associated with long COVID-19.

Case report: Variability in clinical features as a potential pitfall for the diagnosis of Barth syndrome.

Background: Barth syndrome is a rare genetic disease characterized by cardiomyopathy, skeletal muscle weakness, neutropenia, growth retardation and organic aciduria. This variable phenotype is caused by pathogenic hemizygous variants of the TAFAZZIN gene on the X chromosome, which impair metabolism of the mitochondrial phospholipid cardiolipin. Although most patients are usually diagnosed in the first years of life, the extremely variable clinical picture and the wide range of clinical presentations may both delay diagnosis. This is the case reported here of a man affected with severe neutropenia, who was not diagnosed with Barth syndrome until adulthood. Case presentation: We describe herein a family case, specifically two Caucasian male cousins sharing the same mutation in the TAFAZZIN gene with a wide phenotypic variability: an infant who was early diagnosed with Barth syndrome due to heart failure, and his maternal cousin with milder and extremely different clinical features who has received the same diagnosis only at 33 years of age. Conclusions: Our report supports the underestimation of the prevalence of Barth syndrome, which should be always considered in the differential diagnosis of male patients with recurrent neutropenia with or without signs and symptoms of cardiomyopathy.

Beneficial effects of SS-31 peptide on cardiac mitochondrial dysfunction in tafazzin knockdown mice.

Barth Syndrome (BTHS), a genetic disease associated with early-onset cardioskeletal myopathy, is caused by loss-of-function mutations of the TAFAZZIN gene, which is responsible for remodeling the mitochondrial phospholipid cardiolipin (CL). Deregulation of CL biosynthesis and maturation in BTHS mitochondria result in a dramatically increased monolysocardiolipin (MLCL)/CL ratio associated with bioenergetic dysfunction. One of the most promising therapeutic approaches for BTHS includes the mitochondria-targeted tetrapeptide SS-31, which interacts with CL. Here, we used TAFAZZIN knockdown (TazKD) mice to investigate for the first time whether in vivo administration of SS-31 could affect phospholipid profiles and mitochondrial dysfunction. The CL fingerprinting of TazKD cardiac mitochondria obtained by MALDI-TOF/MS revealed the typical lipid changes associated with BTHS. TazKD mitochondria showed lower respiratory rates in state 3 and 4 together with a decreased in maximal respiratory rates. Treatment of TazKD mice with SS-31 improved mitochondrial respiratory capacity and promoted supercomplex organization, without affecting the MLCL/CL ratio. We hypothesize that SS-31 exerts its effect by influencing the function of the respiratory chain rather than affecting CL directly. In conclusion, our results indicate that SS-31 have beneficial effects on improving cardiac mitochondrial dysfunction in a BTHS animal model, suggesting the peptide as future pharmacologic agent for therapy.

Fingerprinting Cardiolipin in Leukocytes by Mass Spectrometry for a Rapid Diagnosis of Barth Syndrome.

Cardiolipin (CL), a dimeric phospholipid carrying four fatty acid chains in its structure, is the lipid marker of mitochondria, wherein it plays a crucial role in the functioning of the inner membrane. Its metabolite monolysocardiolipin (MLCL) is physiologically nearly absent in the lipid extract of animal cells and its appearance is the hallmark of the Barth syndrome (BTHS), a rare and often misdiagnosed genetic disease that causes severe cardiomyopathy in infancy. The method described here generates a "cardiolipin fingerprint" and allows a simple assay of the relative levels of CL and MLCL species in cellular lipid profiles. In the case of leukocytes, only 1 mL of blood is required to measure the MLCL/CL ratio via matrix-assisted laser desorption ionization - time-of-flight/mass spectrometry (MALDI-TOF/MS) just within 2 h from blood withdrawal. The assay is straightforward and can be easily integrated into the routine work of a clinical biochemistry laboratory to screen for BTHS. The test shows 100% sensitivity and specificity for BTHS, making it a suitable diagnostic test.

A Lipidomic Approach to Identify Potential Biomarkers in Exosomes From Melanoma Cells With Different Metastatic Potential.

Melanoma, one of the most lethal cutaneous cancers, is characterized by its ability to metastasize to other distant sites, such as the bone. Melanoma cells revealed a variable in vitro propensity to be attracted toward bone fragments, and melanoma-derived exosomes play a role in regulating the osteotropism of these cells. We have here investigated the lipid profiles of melanoma cell lines (LCP and SK-Mel28) characterized by different metastatic propensities to colonize the bone. We have purified exosomes from cell supernatants by ultracentrifugation, and their lipid composition has been compared to identify potential lipid biomarkers for different migration and invasiveness of melanoma cells. Matrix-assisted laser desorption ionization-time-of-flight/mass spectrometry (MALDI-TOF/MS) lipid analysis has been performed on very small amounts of intact parental cells and exosomes by skipping lipid extraction and separation steps. Statistical analysis has been applied to MALDI mass spectra in order to discover significant differences in lipid profiles. Our results clearly show more saturated and shorter fatty acid tails in poorly metastatic (LCP) cells compared with highly metastatic (SK-Mel28) cells, particularly for some species of phosphatidylinositol. Sphingomyelin, lysophosphatidylcholine, and phosphatidic acid were enriched in exosome membranes compared to parental cells. In addition, we have clearly detected a peculiar phospholipid bis(monoacylglycero)phosphate as a specific lipid marker of exosomes. MALDI-TOF/MS lipid profiles of exosomes derived from the poorly and highly metastatic cells were not significantly different.

Alteration of Cholesterol Sulfate/Seminolipid Ratio in Semen Lipid Profile of Men With Oligoasthenozoospermia.

The reduction of sperm motility and count, or oligoasthenozoospermia, is one of the major causes of reduced fertility or infertility in men. Lipid composition of spermatozoa is important in determining their functional characteristics, in particular on motility, acrosomal exocytosis or fusogenic properties of the sperm. Here we investigated the levels of semen lipids in 11 infertile patients with severe oligoasthenozoospermia and 9 normozoospermic subjects with normal motility values. Sperm polar and neutral lipids were analyzed by thin-layer chromatography (TLC) and matrix-assisted laser desorption and ionization time-of-flight mass spectrometry (MALDI-TOF/MS). Semen of patients with oligoasthenozoospermia showed a reduction of the degree of fatty acid unsaturation in the phospholipids chains that might affect the membrane fluidity. Furthermore, a significant higher cholesterol sulfate/seminolipid ratio was found in semen of oligoasthenozoospermic patients than in subjects with normal motility values, suggesting a critical role of sulfolipids in semen quality. The results may facilitate the understanding of the role of lipids on male fertility and offer interesting perspectives to find innovative treatments for oligoasthenozoospermia.

Lipid Profile Changes During the Development of Artemia franciscana, From Cysts to the First Two Naupliar Stages.

The brine shrimp Artemia is an interesting experimental system for studies of developmental processes. Hatching of dormant cysts gives rise to shrimp larvae called nauplii, characterized by numerous naupliar stages representing the first forms of brine shrimp life cycle. Here combined Thin Layer Chromatography (TLC) and Matrix-Assisted Laser Desorption Ionization-Time-of-Flight/Mass Spectrometry (MALDI-TOF/MS) analyses have been performed to gain information on the lipid profiles of cysts and two naupliar stages. Lipid bands isolated after preparative TLC of the lipid extracts have been analyzed to detect various species of each lipid class; in addition Post-Source Decay (PSD) analyses allowed the identification of phospholipid chains. We compared the relative abundance of various polar and neutral lipid species in the lipid extracts, proving for the first time that during the development of nauplii there is an increase of cardiolipin (CL) and lysophospholipid levels; in parallel, the amount of phosphatidylcholine (PC) decreases. In addition, as regards neutral lipids, we found an increase of diacylglycerols (DAGs) in correspondence of the decrease of triacylglycerols (TAGs). Data reflect the fact that naupliar stages, being an active form of life, are more metabolically active and offer a platform to develop further studies on the importance of lipid metabolic pathways and bioactive lipids during the development.

Assessing olfactory functions in patients with Barth syndrome.

Barth syndrome is a rare X-linked disease affecting less than 200 individuals worldwide. Several comorbidities have been associated with the pathology and, among those, cardiac myopathy and neutropenia are the most life threatening. The appropriate nutritive support is important to sustain the everyday life of Barth syndrome patients given the chronic fatigue they experience. Since they often prefer salty and fried food, and avoid vegetables and fruits, their eating habit and food preferences do not always provide the proper amount of vitamins and amino acids. It has been indeed reported that Barth syndrome patients have altered taste sensitivity. As olfaction also contributes to food consumption and flavor perception, we decided to investigate their olfactory abilities using the "Sniffin' sticks' extended test". We found no significant difference in any of the tested olfactory abilities between the group of Barth syndrome patients and the healthy controls. In summary, altered food preference of Barth boys could not be easily explained with an altered olfactory perception.

Lipid profiling of parkin-mutant human skin fibroblasts.

Parkin mutations are a major cause of early-onset Parkinson's disease (PD). The impairment of protein quality control system together with defects in mitochondria and autophagy process are consequences of the lack of parkin, which leads to neurodegeneration. Little is known about the role of lipids in these alterations of cell functions. In the present study, parkin-mutant human skin primary fibroblasts have been considered as cellular model of PD to investigate on possible lipid alterations associated with the lack of parkin protein. Dermal fibroblasts were obtained from two unrelated PD patients with different parkin mutations and their lipid compositions were compared with that of two control fibroblasts. The lipid extracts of fibroblasts have been analyzed by combined matrix-assisted laser desorption/ionization-time-of-flight mass spectrometry (MALDI-TOF/MS) and thin-layer chromatography (TLC). In parallel, we have performed direct MALDI-TOF/MS lipid analyses of intact fibroblasts by skipping lipid extraction steps. Results show that the proportions of some phospholipids and glycosphingolipids were altered in the lipid profiles of parkin-mutant fibroblasts. The detected higher level of gangliosides, phosphatidylinositol, and phosphatidylserine could be linked to dysfunction of autophagy and mitochondrial turnover; in addition, the lysophosphatidylcholine increase could represent the marker of neuroinflammatory state, a well-known component of PD.

Cardiolipin fingerprinting of leukocytes by MALDI-TOF/MS as a screening tool for Barth syndrome.

Barth syndrome (BTHS), an X-linked disease associated with cardioskeletal myopathy, neutropenia, and organic aciduria, is characterized by abnormalities of card-iolipin (CL) species in mitochondria. Diagnosis of the disease is often compromised by lack of rapid and widely available diagnostic laboratory tests. The present study describes a new method for BTHS screening based on MALDI-TOF/MS analysis of leukocyte lipids. This generates a "CL fingerprint" and allows quick and simple assay of the relative levels of CL and monolysocardiolipin species in leukocyte total lipid profiles. To validate the method, we used vector algebra to analyze the difference in lipid composition between controls (24 healthy donors) and patients (8 boys affected by BTHS) in the high-mass phospholipid range. The method of lipid analysis described represents an important additional tool for the diagnosis of BTHS and potentially enables therapeutic monitoring of drug targets, which have been shown to ameliorate abnormal CL profiles in cells.

Haloferax volcanii, as a Novel Tool for Producing Mammalian Olfactory Receptors Embedded in Archaeal Lipid Bilayer.

The aim of this study was to explore the possibility of using an archaeal microorganism as a host system for expressing mammalian olfactory receptors (ORs). We have selected the archaeon Haloferax volcanii as a cell host system and one of the most extensively investigated OR, namely I7-OR, whose preferred ligands are short-chain aldehydes, such as octanal, heptanal, nonanal. A novel plasmid has been constructed to express the rat I7-OR, fused with a hexahistidine-tag for protein immunodetection. The presence of the recombinant receptor at a membrane level was demonstrated by immunoblot of the membranes isolated from the transgenic archaeal strain. In addition, the lipid composition of archaeonanosomes containing ORs has been characterized in detail by High-Performance Thin-Layer Chromatography (HPTLC) in combination with Matrix-Assisted Laser Desorption Ionization-Time-Of-Flight/Mass Spectrometry (MALDI-TOF/MS) analysis.

MALDI-TOF MS lipid profiles of cytochrome c oxidases: cardiolipin is not an essential component of the Paracoccus denitrificans oxidase.

Lipids of cytochrome c oxidase (COX) of Paracoccus denitrificans have been identified by MALDI-TOF MS direct analyses of isolated protein complexes, avoiding steps of lipid extraction or chromatographic separation. Two different COX preparations have been considered in this study: the enzyme core consisting of subunits I and II (COX 2-SU) and the complete complex comprising all four subunits (COX 4-SU). In addition, MALDI-TOF MS lipid profiles of bacterial COX are also compared with those of the isolated mitochondrial COX and bacterial bc1 complex. We show that the main lipids associated with bacterial COX 4-SU are phosphatidylglycerol (PG) and phosphatidylcholine (PC), and minor amounts of cardiolipin (CL). PG and PC are absent in the COX 2-SU preparation lacking subunits III and IV, whereas CL is still present. Quantitative analyses indicate that at variance from mitochondrial COX, cardiolipin is present in substoichiometric amounts in bacterial COX, at a CL:COX molar ratio of ∼1:10. We conclude that bacterial COX does not require CL for structure or its activity.

Deciphering archaeal glycolipids of an extremely halophilic archaeon of the genus Halobellus by MALDI-TOF/MS.

Polar membrane lipids of an archaeal microorganism recently isolated from the natural salt lake Fuente de Piedra (Málaga, Spain) have been studied by means of TLC in combination with MALDI-TOF mass spectrometry. The major phospholipids are the ether lipids phosphatidylglycerophosphate methyl ester and phosphatidylglycerosulfate, while phosphatidylglycerol is barely detectable; in addition the bisphosphatidylglycerol (archaeal cardiolipin) has been detected for the first time in a representative of the genus Halobellus. The structures of glycolipids, including a glycosyl-cardiolipin, have been elucidated by post source decay (PSD) mass spectrometry analysis. Besides the monosulfated diglycosyl diphytanylglyceroldiether, two variants of a bis-sulfated diglycosyl diphytanylglyceroldiether have been identified; furthermore the glycosyl-cardiolipin is found to have the same structure of the analogue present in Halorubrum trapanicum and Haloferax volcanii. The role of the abundant sulfated glycolipids in facing high extracellular salinity is discussed.

Force measurements on natural membrane nanovesicles reveal a composition-independent, high Young's modulus.

Mechanical properties of nano-sized vesicles made up of natural membranes are crucial to the development of stable, biocompatible nanocontainers with enhanced functional, recognition and sensing capabilities. Here we measure and compare the mechanical properties of plasma and inner membrane nanovesicles ∼80 nm in diameter obtained from disrupted yeast Saccharomyces cerevisiae cells. We provide evidence of a highly deformable behaviour for these vesicles, able to support repeated wall-to-wall compressions without irreversible deformations, accompanied by a noticeably high Young's modulus (∼300 MPa) compared to that obtained for reconstituted artificial liposomes of similar size and approaching that of some virus particles. Surprisingly enough, the results are approximately similar for plasma and inner membrane nanovesicles, in spite of their different lipid compositions, especially on what concerns the ergosterol content. These results point towards an important structural role of membrane proteins in the mechanical response of natural membrane vesicles and open the perspective to their potential use as robust nanocontainers for bioapplications.

Relationship between cardiolipin metabolism and oxygen availability in Bacillus subtilis.

We report changes of the content of anionic phospholipids in Bacillus subtilis in response to hypoxic conditions and inhibition of terminal respiration. Cardiolipin accumulates rapidly when bacteria are suspended in non-growth medium under reduced aeration or exposed to the inhibitor cyanide; the increase of cardiolipin occurs at the expense of its precursor phosphatidylglycerol and is temperature-dependent. Depending on the extent of hypoxic stress, membranes containing different levels of cardiolipin can be isolated from B. subtilis cells. The NADH oxidase activity in cardiolipin-enriched membranes is cyanide-resistant; furthermore O2 consumption measurements indicated that cardiolipin-enriched cells are resistant to cyanide. Results point out a possible interdependence between the effect of cyanide on cardiolipin metabolism and the effect of cardiolipin on the effectiveness of cyanide inhibition.

Structural studies on archaeal phytanyl-ether lipids isolated from membranes of extreme halophiles by linear ion-trap multiple-stage tandem mass spectrometry with electrospray ionization.

The structures of archaeal glycerophospholipids and glycolipids are unique in that they consist of phytanyl substituents ether linked to the glycerol backbone, imparting stability to the molecules. In this contribution, we described multiple-stage linear ion-trap combined with high resolution mass spectrometry toward structural characterization of this lipid family desorbed as lithiated adduct ions or as the [M-H](-) and [M-2H](2-) ions by ESI. MS(n) on various forms of the lithiated adduct ions yielded rich structurally informative ions leading to complete structure identification of this lipid family, including the location of the methyl branches of the phytanyl chain. By contrast, structural information deriving from MS(n) on the [M-H](-) and [M-2H](2-) ions is not complete. The fragmentation pathways in an ion-trap, including unusual internal loss of glycerol moiety and internal loss of hexose found for this lipid family were proposed. This mass spectrometric approach provides a simple tool to facilitate confident characterization of this unique lipid family.

Adjusting membrane lipids under salt stress: the case of the moderate halophilic organism Halobacillus halophilus.

The lipid composition of Halobacillus halophilus was investigated by combined thin-layer chromatography and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry analyses of the total lipid extract. Main polar lipids were found to be sulfoquinovosyldiacylglycerol and phosphatidylglycerol, while cardiolipin was a minor lipid together with phosphatidic acid, alanyl-phosphatidylglycerol and two not yet fully identified lipid components. In addition the analyses of residual lipids, associated with denatured proteins after the lipid extraction, revealed the presence of significant amounts of cardiolipin, indicating that it is a not readily extractable phospholipid. Post decay source mass spectrometry analyses allowed the determination of acyl chains of main lipid components. On increasing the culture medium salinity, an increase in the shorter chains and the presence of chain unsaturations were observed. These changes in the lipid core structures might compensate for the increase in packing and rigidity of phospholipid and sulfoglycolipid polar heads in high-salt medium, therefore contributing to the homeostasis of membrane fluidity and permeability in salt stress conditions.

Coupled TLC and MALDI-TOF/MS analyses of the lipid extract of the hyperthermophilic archaeon Pyrococcus furiosus.

The lipidome of the marine hyperthermophilic archaeon Pyrococcus furiosus was studied by means of combined thin-layer chromatography and MALDI-TOF/MS analyses of the total lipid extract. 80-90% of the major polar lipids were represented by archaeol lipids (diethers) and the remaining part by caldarchaeol lipids (tetraethers). The direct analysis of lipids on chromatography plate showed the presence of the diphytanylglycerol analogues of phosphatidylinositol and phosphatidylglycerol, the N-acetylglucosamine-diphytanylglycerol phosphate plus some caldarchaeol lipids different from those previously described. In addition, evidence for the presence of the dimeric ether lipid cardiolipin is reported, suggesting that cardiolipins are ubiquitous in archaea.