Autoantibodies in HIV-infected patients that modulate the cholinergic activity of heart and gut tissue

The impact of HIV/AIDS on compliance with antidepressant treatment in major depressive disorder: A prospective study in a South African private healthcare cohort

BACKGROUND

MDD and HIV/AIDS have a high prevalence worldwide with severe consequences for patients. In both conditions, compliance with treatment is key to successfully treat these disorders. In the current study, we examine the effect of MDD on the compliance with ADs in patients diagnosed with co-morbid HIV/AIDS and how different classes of ADs influence compliance in this group of patients.

METHODS

A prospective, cohort study design was used to analyse nationally representative medicine claims data submitted to a privately-owned South African Pharmaceutical Benefit Management (PBM) company. Two groups were distinguished in the database, namely patients with only MDD and patients with both MDD and HIV/AIDS, over a six-year study period. The study population was determined by the following inclusion criteria: patients older than 18 years, MDD should be diagnosed by a psychiatrist supported by an appropriate ICD-10 code, and all patients have to be on combination antiretroviral treatment (cARV) treatment. The medicine possession ratio (MPR) was used as proxy to determine patient compliance with AD medication.

RESULTS

127 patients (i.e. 0.24%) met the criteria of co-morbid MDD and HIV/AIDS. Females have a significantly higher prevalence of MDD and HIV/AIDS when compared to males. Patients diagnosed with both HIV/AIDS and MDD (74.43. ± 32.03, 95% Cl: 71.51-77.34) have a statistical significantly (p < 0.0001) lower compliance with AD treatment vs. MDD patients (80.94% ± 29.44, 95% Cl: 80.56-81.33), but the practical significance thereof, is low (Cohen's d = 0.2255). In this group only 26.83% of TCA had acceptable compliance compared to the 58.57% of SNRIs. Noteworthy observations were that 75% (p < 0.0217; Cramer's V = 0.0388) of venlafaxine and 28.6% (p < 0.0197; Cramer's V = -0.0705) of the paroxetine items were compliant in patients diagnosed with both HIV/AIDS and MDD.

CONCLUSIONS

AD compliance is statistical significantly lower in depressed HIV/AIDS vs. depressed non-HIV/AIDS patients. However, these differences is of low practical or clinical significance, meaning that depressed HIV/AIDS patients would have missed approximately two AD doses (6.5% of a 30-day treatment period) more than the non-HIV/AIDS depressed patient over the same treatment period.

Functional implications of circulating muscarinic cholinergic receptor autoantibodies in chagasic patients with achalasia

BACKGROUND & AIMS

Autoantibodies against M(2)-muscarinic acetylcholine receptors (M(2) mAChR) have been reported in patients with chronic Chagas' disease who have cardiac dysautonomia. The aim of this study was to investigate the presence of such antibodies in chronic chagasic and non-chagasic patients with esophageal achalasia and their ability to activate M(2) mAChR in the isolated esophagus.

METHODS

Enzyme-linked immunosorbent assay was used to detect serum immunoglobulin (Ig) G antibodies against a synthetic 24-mer peptide corresponding to the second extracellular loop of human M(2) mAChR. The effects of both total serum IgG and affinity-purified antipeptide antibodies on the contractile activity and adenosine 3', 5'-cyclic monophosphate (cAMP) production in rat esophageal strips were also tested.

RESULTS

Circulating IgG antibodies from chagasic achalasia patients recognized the M(2)-peptide more often than those from non-chagasic achalasia patients (P < 0.0005) and normal subjects (P < 0.0001). A strong association between the existence of circulating anti-M(2) mAChR antibodies and the presence of achalasia in chagasic patients was found (P < 0.01). Both the total IgG fraction and anti-M(2)-peptide antibodies increased the basal tone, reduced the relaxant effect of isoproterenol, and decreased cAMP accumulation in esophageal strips, displaying a muscarinic agonist-like activity on M(2) mAChR.

CONCLUSIONS

Patients with chronic Chagas' disease have circulating autoantibodies against M(2) mAChR. These antibodies could be involved in the pathophysiological mechanism of chagasic achalasia.

IgA from HIV+ haemophilic patients triggers intracellular signals coupled to the cholinergic system of the intestine

IgA was obtained from HIV-infected haemophilic patients and the intracellular signals triggered by its reaction with isolated rat intestinal strips were studied. HIV+ IgA stained intestinal microvilli with a granular immunofluorescence pattern and bound to the muscarinic acetylcholine receptor (mAChR), displacing the specific muscarinic cholinergic antagonist QNB in a non-competitive manner. It triggered the signals that are the consequence of mAChR stimulation in the intestine. Thus, it decreased cAMP synthesis and increased guanosine 3':5'-cyclic monophosphate (cGMP) formation and phosphoinositide (PI) turnover of the intestine. In addition, it stimulated prostaglandin E2(PGE2) synthesis by intestinal strips. Through its effect on PGE2 synthesis, HIV+ IgA could have a dual action. On the one hand, it could enhance immunosuppression at a local level, favouring pathogen growth and subsequent intestinal dysfunction. On the other hand, PGE2 could directly increase intestinal motility and electrolyte/fluid loss. Both effects could be involved in intestinal damage in AIDS.

Intracellular signals coupled to different rat ileal muscarinic receptor subtypes

Taking into account that the activation of different subtypes of ileal muscarinic acetylcholine receptors (mAChR) regulate gut functions such as tone, motility, and electrolyte secretion, we characterized the expression of mAChR in ileal-purified membranes. We also studied intracellular signals triggered by mAChR activation. Binding parameters obtained from saturation assays with the nonselective tritiated muscarinic antagonist, quinuclidynil benzilate ([3H]-QNB), were maximal number of binding sites (Bmax): 30 +/- 2 fmol/mg prot and dissociation constant (Kd): 0.2 +/- 0.03 nM. The competitive inhibition of [3H]-QNB specific binding by various nonlabelled muscarinic antagonists was measured and the rank order of potency was: atropine (ATROP) > 4-DAMP > AF-DX 116 > pirenzepine (PZ). The activation of mAChR by carbachol (CARB) increased ileal motility in a concentration-dependent manner (EC50 2 x 10[-7] M). The antagonists' order of potency to displace dose-response curve of CARB was: ATROP > 4-DAMP > AF-DX116 > PZ. Optimal concentration of CARB on ileal strips increased phosphoinositide turnover and cGMP levels by activating ml receptor subtype and decreased isoproterenol (ISO) stimulated levels of cAMP due to M2 receptor activation. We can conclude that the activation of different mAchR subtypes triggers different intracellular signals that could regulate intestinal tone and motility.

Induction of ileum muscarinic cholinoceptor signal transduction pathways by rat interferon-gamma

We have recently shown that rat interferon-gamma (IFN gamma) can trigger a cholinergic muscarinic response upon interaction with isolated rat atria, decreasing both the contractile tension and cAMP synthesis, and increasing cGMP production. Because the intestine is rich in cholinergic muscarinic receptors, and IFN gamma-producing cells are normal components of the mucosal immune system, we investigated whether IFN gamma could also modulate the muscarinic cholinergic activity of the intestine. Our results indicate that IFN gamma may interact with ileum cholinergic muscarinic receptors by inhibiting binding of the radiolabelled antagonist quinuclidinyl benzylate (3H-QNB), decreasing cAMP formation and increasing cGMP synthesis. These effects are associated with increased mechanical activity of the isolated ileum strips, and can be blunted by pretreatment of the tissue with atropine.