Methylation: a regulator of HIV-1 replication?

Pakistan, the second most populous Muslim nation in the world, has started to finally experience and confront the HIV/AIDS epidemic. The country had been relatively safe from any indigenous HIV cases for around two decades, with most of the infections being attributable to deported HIV positive migrants from the Gulf States. However, the virus finally seems to have found a home-base, as evidenced by the recent HIV outbreaks among the injection drug user community. Extremely high-risk behavior has also been documented among Hijras (sex workers) and long-distance truck drivers. The weak government response coupled with the extremely distressing social demographics of this South-Asian republic also helps to compound the problem. The time is ripe now to prepare in advance, to take the appropriate measures to curtail further spread of the disease. If this opportunity is not utilized right now, little if at all could be done later.     

A Review of the Salivary Proteome and Peptidome and Saliva-derived Peptide Therapeutics

Saliva is a glandular secretion that is vital in the maintenance of healthy oral tissues. In this review we outline the high abundance salivary proteins, summarise the status of the salivary proteome and peptidome, the genetic origin and recognised functions of these proteins, the diseases associated with salivary disorders, and the emerging saliva-derived peptide therapeutics. Different proteomic approaches have reported the identification of over 1,300 proteins in saliva. However there are fewer than 100 high abundance proteins, identified by multiple methods including, two-dimensional polyacrylamide gel electrophoresis and HPLC combined with mass spectrometry. Analysis of the genes coding for the salivary proteins demonstrated a non-uniform chromosomal distribution with chromosome 4 having the largest proportion of genes expressed in salivary glands. Several diseases are associated with salivary disorders including Sjögren’s syndrome, Prader-Willi syndrome, dental caries and stress related disorders. Saliva as a diagnostic medium for various biochemical tests has provided a non-invasive and accessibility advantage over other more regularly tested body fluids such as blood and urine. To-date the emerging saliva-based therapeutics include artificial salivas and antimicrobial agents based on histatins and mucins.     

Intestinal capillariasis

What started out as an isolated report of an unknown intestinal parasitic disease has emerged as another disease of worldwide significance. Capillaria philippinensis was found in the intestines of a Filipino who suffered from an intractable diarrhoea and died in 1963. A few years later epidemics of intestinal cappillariasis erupted and spread to many parts of the Philippines. Thailand was also found to be endemic for the disease and in recent years, a few case reports have come from Japan, Iran and Egypt too. Since small freshwater and brackish water fish are considered to be the natural intermediate hosts, and fish-eating birds potential definitive hosts, John Cross suggests that the spread of the parasite may be attributable to migratory birds.     

An unusual intronic mutation in the CYBB gene giving rise to chronic granulomatous disease

The most common, X-linked, form of chronic granulomatous disease (CGD) is caused by mutations in the CYBB gene located at Xp21.1. The product of this gene is the large subunit of flavocytochrome b558, gp91phox, which forms the catalytic core of the antimicrobial superoxide-generating enzyme, NADPH oxidase. In the overwhelming majority of cases, mutations are family-specific and occur in the exonic regions of the gene, or more rarely at the intron/exon borders. Alternatively, they are large (often multi-gene) deletions. In addition, four mutations have been found in the promoter region. In contrast, very few intronic mutations have been reported. Here we describe an intronic mutation that causes X-linked CGD. A single nucleotide substitution in the middle of intron V creates a novel 5' splice site and results in multiple abnormal mRNA products.     

Inactivation of glutathione S-transferases by nitric oxide-derived oxidants: exploring a role for tyrosine nitration

Reactive intermediates derived from nitric oxide ((*)NO) are thought to play a contributing role in disease states associated with inflammation and infection. We show here that glutathione S-transferases (GSTs), principal enzymes responsible for detoxification of endogenous and exogenous electrophiles, are susceptible to inactivation by reactive nitrogen species (RNS). Treatment of isolated GSTs or rat liver homogenates with either peroxynitrite, the myeloperoxidase/hydrogen peroxide/nitrite system, or tetranitromethane, resulted in loss of GST activity with a concomitant increase in the formation of protein-associated 3-nitrotyrosine (NO(2)Tyr). This inactivation was only partially (<25%) reversible by dithiothreitol, and exposure of GSTs to hydrogen peroxide or S-nitrosoglutathione was only partially inhibitory (<25%) and did not result in protein nitration. Thus, irreversible modifications such as tyrosine nitration may have contributed to GST inactivation by RNS. Since all GSTs contain a critical, highly conserved, active-site tyrosine residue, we postulated that this Tyr residue might present a primary target for nitration by RNS, thus leading to enzyme inactivation. To directly investigate this possibility, we analyzed purified mouse liver GST-mu, following nitration by several RNS, by trypsin digestion, HPLC separation, and matrix-assisted laser desorption/ionization-time of flight analysis, to determine the degree of tyrosine nitration of individual Tyr residues. Indeed, nitration was found to occur preferentially on several tyrosine residues located in and around the GST active site. However, RNS concentrations that resulted in near complete GST inactivation only caused up to 25% nitration of even preferentially targeted tyrosine residues. Hence, nitration of active-site tyrosine residues may contribute to GST inactivation by RNS, but is unlikely to fully account for enzyme inactivation. Overall, our studies illustrate a potential mechanism by which RNS may promote (oxidative) injury by environmental pollutants in association with inflammation.     

In vivo ozone exposure induces antioxidant/stress-related responses in murine lung and skin

Lung and skin are the organs directly exposed to environmental pollution. Ozone (O(3)) is a toxic, oxidant air pollutant, and exposure has been shown to induce antioxidant depletion as well as oxidation of lipids and proteins within the outermost skin layer (stratum corneum) and the lung respiratory tract lining fluids (RTLFs). To further define skin and lung responses to O(3) exposure, SKH-1 hairless mice were exposed to either 0.8 ppm of O(3) (a level occasionally reached in very polluted areas) or ambient air 6 h/day for 6 consecutive days. O(3) exposure resulted in the depletion of alpha-tocopherol in lung and plasma and induction in both skin and lung of heme oxygenase 1, cyclooxygenase 2, and proliferating cell nuclear antigen. O(3)-exposed animals showed a similar extent of upregulation of COX-2 and PCNA in lung and skin, whereas HO-1 was more responsive in skin than in lung (7-fold induction vs. 2-fold induction). In addition to these measures of response to oxidative stress, O(3) exposure led to the activation of nuclear factor kappaB measured as IkappaBalpha phosphorylation in both tissues. We conclude that in this model, O(3) at high pollutant levels is able to affect both lung and skin biology, inducing depletion of alpha-tocopherol and inducing stress-related responses in both skin epidermis and respiratory tract epithelium.     

Mobilization of neutrophil sialidase activity desialylates the pulmonary vascular endothelial surface and increases resting neutrophil adhesion to and migration across the endothelium

The amount of sialic acid on the surface of the neutrophil (PMN) influences its ability to interact with other cells. PMN activation with various stimuli mobilizes intracellular sialidase to the plasma membrane, where it cleaves sialic acid from cell surfaces. Because enhanced PMN adherence, spreading, deformability, and motility each are associated with surface desialylation and are critical to PMN diapedesis, we studied the role of sialic acid on PMN adhesion to and migration across pulmonary vascular endothelial cell (EC) monolayers in vitro. Neuraminidase treatment of either PMN or EC increased adhesion and migration in a dose-dependent manner. Neuraminidase treatment of both PMNs and ECs increased PMN adhesion to EC more than treatment of either PMNs or ECs alone. Moreover, neuraminidase treatment of ECs did not change surface expression of adhesion molecules or release of IL-8 and IL-6. Inhibition of endogenous sialidase by either cross-protective antineuraminidase antibodies (45.5% inhibition) or competitive inhibition with pseudo-substrate (41.2% inhibition) decreased PMN adhesion to ECs; the inhibitable sialidase activity appeared to be associated with activated PMNs. Finally, EC monolayers preincubated with activated PMNs became hyperadhesive for subsequently added resting PMNs, and this hyperadhesive state was mediated through endogenous PMN sialidase activity. Blocking anti-E-selectin, anti-CD54 and anti-CD18 antibodies decreased PMN adhesion to tumor necrosis factor-activated ECs but not to PMN-treated ECs. These data implicate desialylation as a novel mechanism through which PMN-EC adhesion can be regulated independent of de novo protein synthesis or altered adhesion molecule expression. The ability of activated PMNs, through endogenous sialidase activity, to render the EC surface hyperadherent for unstimulated PMNs may provide for rapid amplification of the PMN-mediated host response.