Mass spectrometric analysis of lipid A obtained from the lipopolysaccharide ofPasteurella multocida

Identification of a Chimera Mass Spectrum of Isomeric Lipid A Species Using Negative Ion Tandem Mass Spectrometry

The toxic nature of bacterial endotoxins is affected by the structural details of lipid A, including the variety and position of acyl chains and phosphate group(s) on its diglucosamine backbone. Negative-ion mode tandem mass spectrometry is a primary method for the structure elucidation of lipid A, used independently or in combination with separation techniques. However, it is challenging to accurately characterize constitutional isomers of lipid A extracts by direct mass spectrometry, as the elemental composition and molecular mass of these molecules are identical. Thus, their simultaneous fragmentation leads to a composite, so-called chimera mass spectrum. The present study focuses on the phosphopositional isomers of the classical monophosphorylated, hexaacylated Escherichia coli-type lipid A. Collision-induced dissociation (CID) was performed in an HPLC-ESI-QTOF system. Energy-resolved mass spectrometry (ERMS) was applied to uncover the distinct fragmentation profiles of the phosphorylation isomers. A fragmentation strategy applying multi-levels of collision energy has been proposed and applied to reveal sample complexity, whether it contains only a 4'-phosphorylated species or a mixture of 1- and 4'-phosphorylated variants. This comparative fragmentation study of isomeric lipid A species demonstrates the high potential of ERMS-derived information for the successful discrimination of co-ionized phosphorylation isomers of hexaacylated lipid A.

Heterogeneity of Lipopolysaccharide as Source of Variability in Bioassays and LPS-Binding Proteins as Remedy

Lipopolysaccharide (LPS), also referred to as endotoxin, is the major component of Gram-negative bacteria's outer cell wall. It is one of the main types of pathogen-associated molecular patterns (PAMPs) that are known to elicit severe immune reactions in the event of a pathogen trespassing the epithelial barrier and reaching the bloodstream. Associated symptoms include fever and septic shock, which in severe cases, might even lead to death. Thus, the detection of LPS in medical devices and injectable pharmaceuticals is of utmost importance. However, the term LPS does not describe one single molecule but a diverse class of molecules sharing one common feature: their characteristic chemical structure. Each bacterial species has its own pool of LPS molecules varying in their chemical composition and enabling the aggregation into different supramolecular structures upon release from the bacterial cell wall. As this heterogeneity has consequences for bioassays, we aim to examine the great variability of LPS molecules and their potential to form various supramolecular structures. Furthermore, we describe current LPS quantification methods and the LPS-dependent inflammatory pathway and show how LPS heterogeneity can affect them. With the intent of overcoming these challenges and moving towards a universal approach for targeting LPS, we review current studies concerning LPS-specific binders. Finally, we give perspectives for LPS research and the use of LPS-binding molecules.

Sarcococca saligna Hydroalcoholic Extract Ameliorates Arthritis in Complete Freund's Adjuvant-Induced Arthritic Rats via Modulation of Inflammatory Biomarkers and Suppression of Oxidative Stress Markers

Traditionally, Sarcococca saligna has been used for the treatment of arthritis and many other inflammatory disorders. The current study was planned to give scientific evidence to this traditional use of S. saligna. Phytochemical profiling of SSME was carried out by using electrospray ionization mass spectrometry (ESI-MS/MS). Complete Freund's adjuvant (CFA), 150 μL was injected in the subplantar region of the left hind paw to induce arthritis in rats. Aqueous methanolic extract of S. saligna (SSME) was administered orally at 250, 500, or 1000 mg/kg dose from the 7th day to the 28th day of the study to explore its anti-arthritic potential. Histopathological and radiographic assessment of joints and enzyme-linked immunosorbent assay (ELISA) and real-time polymerase chain reaction (RT-PCR) analyses were performed. Determination of oxidative stress biomarkers in the serum was also carried out. ESI-MS/MS identified ten such phytoconstituents which have reported strong anti-inflammatory and anti-arthritic activity. The SSME extract considerably reduced paw inflammation and arthritic index, subdued cachexia, and significantly improved biochemical and hematological changes. Oxidative stress decreased in SSME administered rats dose-dependently. Histopathological and radiographic evaluations also showed the anti-arthritic activity of SSME, which was associated with the downregulation of tumor necrosis factor (TNF)-α, nuclear factor (NF)-kB, COX-2, interleukin (IL)-6, and IL-1β and upregulation of I-kB, IL-4, and IL-10, in contrast to disease group rats. The outcomes of the study proposed that S. saligna have anti-arthritic potential, supporting its traditional use for rheumatoid arthritis treatment.

Ziziphus Oxyphylla hydro-methanolic extract ameliorates hypertension in L-NAME induced hypertensive rats through NO/cGMP pathway and suppression of oxidative stress related inflammatory biomarkers

ETHNOPHARMACOLOGICAL RELEVANCE

Ziziphus Oxyphylla belongs to family Ziziphus and has been used traditionally in hypertension. It is enriched with quercetin and kaempferol derivatives, catechin and cyclopeptide alkaloids.

AIM

The current research evaluates the antihypertensive potential of aqueous methanolic extract of Z. oxyphylla (AMEZO) in NG-nitro-L-arginine methyl ester (LNAME) induced hypertension in rats.

MATERIAL AND METHODOLOGY

Phytochemical analysis of AMEZO was carried out using high performance liquid chromatography (HPLC) and electrospray ionization mass spectrometry (ESI-MS/MS). Antihypertensive activities of AMEZO (200 and 400 mg/kg) and Kaempferol were assessed in L-NAME (185 μmol/kg, intraperitoneal) injected hypertensive rats. In normotensive rats, blood pressure was assessed using Power Lab data system. Serum and tissue samples were preserved for estimation of nitric oxide (NO), Cyclic guanosine monophosphate (cGMP), interleukin-6 (IL-6), tumor necrosis factor (TNF- α) and oxidative stress markers respectively. mRNA levels of eNOS, ACE, COX-2 and NF-kB genes were assessed through qPCR.

RESULTS

The HPLC and ESI-MS/MS identified kaempferol, quercetin, catechin, ceanothic acid, zizybernalic acid and oxyphylline F. Chronic administration of AMEZO and kaempferol in L-NAME induced hypertensive rats significantly (p < 0.001) reduced systolic, diastolic and mean blood pressure. AMEZO and kaempferol caused meaningfully improved (p < 0.001) serum NO and cGMP levels. AMEZO administration also noticeably decrease the elevated IL-6 and TNF- α concentration in hypertensive animals. Administration of AMEZO and kaempferol also improved oxidative stress markers (MDA, CAT, SOD, GSH). The antihypertensive activity of AMEZO also resulted in upregulation of eNOS and downregulation of ACE.

CONCLUSION

These data depict that AMEZO and kaempferol showed antihypertensive activity in LNAME induced hypertensive rats possibly mediated through improvement in NO and cGMP levels, modulation of mRNA expression of eNOS, ACE, COX-2 and NF-kB and suppression of oxidative stress related inflammatory markers, proposing a defensive role in cardiovascular diseases.

Study on the CID Fragmentation Pathways of Deprotonated 4'-Monophosphoryl Lipid A

Lipid A, the membrane-bound phosphoglycolipid component of bacteria, is held responsible for the clinical syndrome of gram-negative sepsis. In this study, the fragmentation behavior of a set of synthetic lipid A derivatives was studied by electrospray ionization multistage mass spectrometry (ESI-MSn), in conjunction with tandem mass spectrometry (MS/MS), using low-energy collision-induced dissociation (CID). Genealogical insight about the fragmentation pathways of the deprotonated 4'-monophosphoryl lipid A structural analogs led to proposals of a number of alternative dissociation routes that have not been reported previously. Each of the fragment ions was interpreted using various possible mechanisms, consistent with the principles of reactions described in organic chemistry. Specifically, the hypothesized mechanisms are: (i) cleavage of the C-3 primary fatty acid leaves behind an epoxide group attached to the reducing sugar; (ii) cleavage of the C-3' primary fatty acid (as an acid) generates a cyclic phosphate connected to the nonreducing sugar; (iii) cleavage of the C-2' secondary fatty acid occurs both in acid and ketene forms; iv) the C-2 and C-2' primary fatty acids are eliminated as an amide and ketene, respectively; (v) the 0,2A2 cross-ring fragment contains a four-membered ring (oxetanose); (vi) the 0,4A2 ion is consecutively formed from the 0,2A2 ion by retro-aldol, retro-cycloaddition, and transesterification; and (vii) formations of H2PO4- and PO3- are associated with the formation of sugar epoxide. An understanding of the relation between 0,2A2 and 0,4A2-type sugar fragments and the different cleavage mechanisms of the two ester-linked primary fatty acids is invaluable for distinguishing lipid A isomers with different locations of a single ester-linked fatty acid (i.e., at C-3 or C-3'). Thus, in addition to a better comprehension of lipid A fragmentation processes in mass spectrometers, our observations can be applied for a more precise elucidation of naturally occurring lipid A structures.