N-acetyl-l-cysteine sensitizes pancreatic cancers to gemcitabine by targeting the NFκB pathway

First-line therapy for pancreatic cancer is gemcitabine. Although tumors may initially respond to the gemcitabine treatment, soon tumor resistance develops leading to treatment failure. Previously, we demonstrated in human MIA PaCa-2 pancreatic cancer cells that N-acetyl-l-cysteine (NAC), a glutathione (GSH) precursor, prevents NFκB activation via S-glutathionylation of p65-NFκB, thereby blunting expression of survival genes. In this study, we documented the molecular sites of S-glutathionylation of p65, and we investigated whether NAC can suppress NFκB signaling and augment a therapeutic response to gemcitabine in vivo. Mass spectrometric analysis of S-glutathionylated p65-NFκB protein in vitro showed post-translational modifications of cysteines 38, 105, 120, 160 and 216 following oxidative and nitrosative stress. Circular dichroism revealed that S-glutathionylation of p65-NFκB did not change secondary structure of the protein, but increased tryptophan fluorescence revealed altered tertiary structure. Gemcitabine and NAC individually were not effective in decreasing MIA PaCa-2 tumor growth in vivo. However, combination treatment with NAC and gemcitabine decreased tumor growth by approximately 50%. NAC treatment also markedly enhanced tumor apoptosis in gemcitabine-treated mice. Compared to untreated tumors, gemcitabine treatment alone increased p65-NFκB nuclear translocation (3.7-fold) and DNA binding (2.5-fold), and these effects were blunted by NAC. In addition, NAC plus gemcitabine treatment decreased anti-apoptotic XIAP protein expression compared to gemcitabine alone. None of the treatments, however, affected extent of tumor hypoxia, as assessed by EF5 staining. Together, these results indicate that adjunct therapy with NAC prevents NFκB activation and improves gemcitabine chemotherapeutic efficacy.     

Focused antibody response to influenza linked to antigenic drift

The selective pressure that drives antigenic changes in influenza viruses is thought to originate from the human immune response. Here, we have characterized the B cell repertoire from a previously vaccinated donor whose serum had reduced neutralizing activity against the recently evolved clade 6B H1N1pdm09 viruses. While the response was markedly polyclonal, 88% of clones failed to recognize clade 6B viruses; however, the ability to neutralize A/USSR/90/1977 influenza, to which the donor would have been exposed in childhood, was retained. In vitro selection of virus variants with representative monoclonal antibodies revealed that a single amino acid replacement at residue K163 in the Sa antigenic site, which is characteristic of the clade 6B viruses, was responsible for resistance to neutralization by multiple monoclonal antibodies and the donor serum. The K163 residue lies in a part of a conserved surface that is common to the hemagglutinins of the 1977 and 2009 H1N1 viruses. Vaccination with the 2009 hemagglutinin induced an antibody response tightly focused on this common surface that is capable of selecting current antigenic drift variants in H1N1pdm09 influenza viruses. Moreover, amino acid replacement at K163 was not highlighted by standard ferret antisera. Human monoclonal antibodies may be a useful adjunct to ferret antisera for detecting antigenic drift in influenza viruses.     

Salmonella enterica serovar Typhi possesses a unique repertoire of fimbrial gene sequences

Salmonella enterica serotype Typhi differs from nontyphoidal Salmonella serotypes by its strict host adaptation to humans and higher primates. Since fimbriae have been implicated in host adaptation, we investigated whether the serotype Typhi genome contains fimbrial operons which are unique to this pathogen or restricted to typhoidal Salmonella serotypes. This study established for the first time the total number of fimbrial operons present in an individual Salmonella serotype. The serotype Typhi CT18 genome, which has been sequenced by the Typhi Sequencing Group at the Sanger Centre, contained a type IV fimbrial operon, an orthologue of the agf operon, and 12 putative fimbrial operons of the chaperone-usher assembly class. In addition to sef, fim, saf, and tcf, which had been described previously in serotype Typhi, we identified eight new putative chaperone-usher-dependent fimbrial operons, which were termed bcf, sta, stb, ste, std, stc, stg, and sth. Hybridization analysis performed with 16 strains of Salmonella reference collection C and 22 strains of Salmonella reference collection B showed that all eight putative fimbrial operons of serotype Typhi were also present in a number of nontyphoidal Salmonella serotypes. Thus, a simple correlation between host range and the presence of a single fimbrial operon seems at present unlikely. However, the serotype Typhi genome differed from that of all other Salmonella serotypes investigated in that it contained a unique combination of putative fimbrial operons.     

Selective peripheral dopamine-1 receptor stimulation with fenoldopam in human essential hypertension.

SKF 82526-J, or fenoldopam, a benzazepine derivative, is a selective dopamine-1 (DA-1) agonist devoid of activity at dopamine-2, alpha- or beta-adrenergic receptors. We studied SKF 82526-J in 10 patients with essential hypertension and five normal control subjects on constant 150-meq sodium, 60 meq potassium intake. In the hypertensive patients, during a 6-d placebo period supine blood pressure and heart rate were stable at 156 +/- 6/105 +/- 4 mmHg and 76 +/- 5 beats/min, respectively. In response to a single oral dose of 100 mg of SKF 82526-J, supine blood pressure decreased to a nadir of 141 +/- 5/89 +/- 8 mmHg (P less than 0.0001) at 90 min and remained decreased at 145 +/- 6/99 +/- 3 mmHg (P less than 0.0001) at 4 h. Heart rate increased to 91 +/- 5 beats/min (P less than 0.002), but returned to control levels (82 +/- 5 beats/min) at 4 h. Renal blood flow increased from 371 +/- 57 to a peak of 659 +/- 104 ml/min and renal vascular resistance fell from 34 +/- 5 to 19 +/- 2 dyn sec cm-5 X 10(3) (P less than 0.01). Urine volume, sodium and fractional sodium excretion, and plasma renin activity were increased as a result of SKF 82526-J administration. During the ensuing 3 wk of SKF 82526-J, blood pressure remained decreased and returned to control levels after placebo administration. In contrast, in normal subjects SKF 82526-J administration was associated with a small transient reduction in diastolic pressure only. These results suggest that reduced dopaminergic activity expressed at the peripheral DA-1 receptor may contribute to the pathophysiology and/or maintenance of increased blood pressure in essential hypertension. In addition, the results suggest that peripheral DA-1 receptor stimulation with SKF 82526-J may be efficacious in the treatment of human essential hypertension.     

Acute response to bronchodilator. An imperfect guide for bronchodilator therapy in chronic airflow limitation

We conducted a four-period cross-over randomized trial in which we found that patients with chronic airflow limitation demonstrated symptomatic improvement with both inhaled albuterol and oral theophylline. The response, however, was not uniform. We therefore tested the ability of acute change in forced expired volume in one second (FEV1) following inhaled beta agonist to predict long-term symptomatic response to albuterol and theophylline. We found that the reproducibility of acute change in FEV1 over three repetitions was poor (intraclass correlation 0.17). Furthermore, the mean improvement FEV1 following inhaled albuterol across the three repetitions did not relate closely to symptomatic response to either albuterol or theophylline. We conclude that acute response to inhaled beta agonist is not useful for identifying patients with chronic airflow limitation who are likely to benefit from bronchodilator treatment.     

Central blood pressure measurements—an opportunity for efficacy and safety in drug development?

Over a century of experience with brachial blood pressure has produced a substantial amount of information on the role of blood pressure as a factor in heart disease, stroke and kidney failure. Successful interventions lowering blood pressure and reducing damage to vital organs testify further to the importance of this vital sign. In recent years attempts to probe deeper into the value of knowledge of blood pressure levels closer to the heart (central blood pressures) suggest that noninvasive measurement of central aortic blood pressure may improve further efforts directed at both understanding drug benefit and uncovering potential drug safety issues. This commentary is a summary of a one-day meeting with the FDA in which the role of central blood pressure measurements as an adjunct to drug efficacy and safety were addressed.     

Effectiveness of Respondent-Driven Sampling to Recruit High Risk Heterosexual Men Who Have Multiple Female Sexual Partners: Differences in HIV Prevalence and Sexual Risk Behaviours Measured at Two Time Points

Regular HIV bio-behavioural surveillance surveys (BBSS) among high risk heterosexual (HRH) men who have multiple female sexual partners is needed to monitor HIV prevalence and risk behaviour trends, and to improve the provision and assessment of HIV prevention strategies for this population. In 2006 and 2008 we used respondent-driven sampling to recruit HRH men and examine differences in HIV prevalence and risk behaviours between the two time points. In both surveys, the target population had little difficulty in recruiting others from their social networks that were able to sustain the chain-referral process. Key variables reached equilibrium within one to six recruitment waves and homophily indices showed neither tendencies to in-group nor out-group preferences. Between 2006 and 2008 there were significant differences in condom use with main sexual partners; numbers of sexual partners; and alcohol consumption. Further BBSS among this population are needed before more reliable trends can be inferred.