Dehydroepiandrosterone modulates T-cell response after major abdominal surgery

Background

The immune balance controlled by T-helper (Th)1 and Th2 cells is critical in protecting the host from pathogenic invasion, and its imbalance may increase susceptibility to infection in patients undergoing major surgery. The differentiation of naive T cells to Th1 and Th2 cells is largely driven by cytokines. In addition, steroid hormones have been shown to affect Th1/Th2 balance, particularly in autoimmune diseases. The regulation of Th1/Th2 balance in patients undergoing surgery and its potential clinical relevance remain unclear.

Materials and methods

Blood samples were obtained from patients both before and 2 h after major abdominal surgery. Peripheral blood mononuclear cells were isolated and cultured in wells coated with either anti-CD3 (direct T-cell stimulation) or phytohemagglutinin (PHA) (indirect T-cell stimulation), with or without 10⁻⁵ M dehydroepiandrosterone (DHEA). The release of interleukin (IL)-2, interferon gamma, and IL-10 was measured by an enzyme-linked immunosorbent assay, and the expression of CD4, CD8, and CD69 was determined by flow cytometry.

Results

DHEA decreased the release of IL-2 and IL-10 in directly (anti-CD3) and indirectly (PHA)-stimulated T cells from postoperative samples, whereas the release of interferon gamma in PHA-stimulated T cells was not affected. The distribution of CD4/CD8 was not significantly different after surgery or DHEA. DHEA was associated with a decrease in the expression of the activation marker CD69 on CD4⁺ T cells, whereas the activation of CD8⁺ T cells remained unchanged.

Conclusions

These results demonstrate that DHEA plays a critical role in controlling Th1/Th2 balance in the immediate postoperative period. Attenuation of both the Th1 and Th2 responses has been suggested to have immunoprotective effects. The role of DHEA in the regulation of Th1/Th2 balance in patients undergoing major abdominal surgery may, therefore, also be of significant clinical relevance and warrants further investigation.     

Operating theatre etiquette,sterile technique and surgical site preparation

The operating theatre is an unusual environment and understanding the systems in place there is an important part of surgical training. ‘Non-technical skills’ is a term used to describe everything a surgeon does in the operating theatre, other than the technical aspects of the procedure itself. This includes communication, decision making and leadership. Non-technical skills have become a vital aspect of the development of a surgeon and should form part of training programmes. A fundamental responsibility of the surgeon is the maintenance of sterility. The techniques of the surgical scrub and preparing and draping a patient only become second nature after good teaching and reflection by the surgeon. The purpose of this article is firstly to describe how a surgical trainee can get the most out of an operating session. We will describe what non-technical surgical skills are and why they are important. We will focus on safety in the operating theatre and discuss worldwide strategies such as the ‘Surgical Safety Checklist’ that aims to improve this. Finally we will present data on measures to reduce surgical site infection, such as which surgical scrub solution to use and whether drapes or wound protectors work.     

Effect of low-level laser therapy (808 nm) on markers of muscle damage: a randomized double-blind placebo-controlled trial

The aim of this randomized double-blind placebo-controlled study was to investigate the effect of low-level laser therapy (LLLT) on markers of muscle damage (creatine kinase (CK) and strength performance) in the biceps brachii. Twenty-two physically active men were randomized into two groups: placebo and laser. All volunteers were submitted to an exercise-induced muscle damage protocol for biceps brachii (biceps curl, 10 sets of 10 repetitions with load of 50 % of one-repetition maximum test (1RM)). Active LLLT (808 nm; 100 mW; 35.7 W/cm², 357.14 J/cm² per point, energy of 1 J per point applied for 10 s on four points of the biceps brachii belly of each arm) or placebo was applied between the sets of the biceps curl exercise. CK activity and maximum strength performance (1RM) were measured before, immediately after, 24, 48, and 72 h after the exercise-induced muscle damage protocol. There was an increase in CK activity after the muscle damage protocol in both groups; however, this increase was attenuated in the laser group compared to the placebo group at 72 h (placebo?=?841 vs. laser?=?357 %; p?<?0.05). Maximum strength performance was decreased immediately after the muscle damage protocol in both groups (p?<?0.05), but at 24, 48, and 72 h, and it returned to the baseline level in both groups. In conclusion, the LLLT attenuated CK activity 72 h after the muscle damage protocol but did not have a positive effect on the recovery of strength performance.     

Molecular profiling of Mycobacterium tuberculosis identifies tuberculosinyl nucleoside products of the virulence-associated enzyme Rv3378c

To identify lipids with roles in tuberculosis disease, we systematically compared the lipid content of virulent Mycobacterium tuberculosis with the attenuated vaccine strain Mycobacterium bovis bacillus Calmette–Guérin. Comparative lipidomics analysis identified more than 1,000 molecular differences, including a previously unknown, Mycobacterium tuberculosis-specific lipid that is composed of a diterpene unit linked to adenosine. We established the complete structure of the natural product as 1-tuberculosinyladenosine (1-TbAd) using mass spectrometry and NMR spectroscopy. A screen for 1-TbAd mutants, complementation studies, and gene transfer identified Rv3378c as necessary for 1-TbAd biosynthesis. Whereas Rv3378c was previously thought to function as a phosphatase, these studies establish its role as a tuberculosinyl transferase and suggest a revised biosynthetic pathway for the sequential action of Rv3377c-Rv3378c. In agreement with this model, recombinant Rv3378c protein produced 1-TbAd, and its crystal structure revealed a cis-prenyl transferase fold with hydrophobic residues for isoprenoid binding and a second binding pocket suitable for the nucleoside substrate. The dual-substrate pocket distinguishes Rv3378c from classical cis-prenyl transferases, providing a unique model for the prenylation of diverse metabolites. Terpene nucleosides are rare in nature, and 1-TbAd is known only in Mycobacterium tuberculosis. Thus, this intersection of nucleoside and terpene pathways likely arose late in the evolution of the Mycobacterium tuberculosis complex; 1-TbAd serves as an abundant chemical marker of Mycobacterium tuberculosis, and the extracellular export of this amphipathic molecule likely accounts for the known virulence-promoting effects of the Rv3378c enzyme.With a mortality rate exceeding 1.5 million deaths annually, Mycobacterium tuberculosis remains one of the world''s most important pathogens (1). M. tuberculosis succeeds as a pathogen because of productive infection of the endosomal network of phagocytes. Its residence within the phagosome protects it from immune responses during its decades long infection cycle. However, intracellular survival depends on active inhibition of pH-dependent killing mechanisms, which occurs for M. tuberculosis but not species with low disease-causing potential (2). Intracellular survival is also enhanced by an unusually hydrophobic and multilayered protective cell envelope. Despite study of this pathogen for more than a century, the spectrum of natural lipids within M. tuberculosis membranes is not yet fully defined. For example, the products of many genes annotated as lipid synthases remain unknown (3), and mass spectrometry detects hundreds of ions that do not correspond to known lipids in the MycoMass and LipidDB databases (4, 5).To broadly compare the lipid profiles of virulent and avirulent mycobacteria, we took advantage of a recently validated metabolomics platform (4). This high performance liquid chromatography–mass spectrometry (HPLC-MS) system uses methods of extraction, chromatography, and databases that are specialized for mycobacteria. After extraction of total bacterial lipids into organic solvents, HPLC-MS enables massively parallel detection of thousands of ions corresponding to diverse lipids that range from apolar polyketides to polar phosphoglycolipids. Software-based (XCMS) ion finding algorithms report reproducibly detected ions as molecular features. Each feature is a 3D data point with linked mass, retention time, and intensity values from one detected molecule or isotope. All features with equivalent mass and retention time from two bacterial lipid extracts are aligned, allowing pairwise comparisons of MS signal intensity to enumerate molecules that are overproduced in one strain with a false-positive rate below 1% (4).This comparative lipidomics system allowed an unbiased, organism-wide analysis of lipids from M. tuberculosis and the attenuated vaccine strain, Mycobacterium bovis Bacillus Calmette–Guérin (BCG). BCG was chosen because of its worldwide use as a vaccine and its genetic similarity to M. tuberculosis (6). We reasoned that any features that are specifically detected in M. tuberculosis might be clinically useful as markers to distinguish tuberculosis-causing bacteria from vaccines. Furthermore, given the differing potential for productive infection by the two strains, any M. tuberculosis-specific compounds would be candidate virulence factors. Comparative genomics of M. tuberculosis and BCG successfully identified “regions of deletion” (RD) that encode genes that were subsequently proven to promote productive M. tuberculosis infection (7), including the 6-kDa early secreted antigenic target (ESAT-6) secretion system-1 (ESX-1) (8, 9). We reasoned that a metabolite-based screen might identify new virulence factors because not all functions of RD genes are known. Also, biologically important metabolites could emerge from complex biosynthetic pathways that cannot be predicted from single-gene analysis.Comparison of M. tuberculosis and BCG lipid profiles revealed more than 1,000 differences, among which we identified a previously unknown M. tuberculosis-specific diterpene-linked adenosine and showed that it is produced by the enzyme Rv3378c. Previously, Rv3378c was thought to generate free tuberculosinol and isotuberculosinol (10–12). This discovery revises the enzymatic function of Rv3378c, which acts as a virulence factor to inhibit phagolysosome fusion (13). Whereas current models of prenyl transferase function emphasize iterative lengthening of prenyl pyrophosphates using one binding pocket, the crystal structure of Rv3378c identifies two pockets in the catalytic site, establishing a mechanism for heterologous prenyl transfer to nonprenyl metabolites.