Impact of HIV-1 infection and highly active antiretroviral therapy on the kinetics of CD4+ and CD8+ T cell turnover in HIV-infected patients.

To evaluate the effects of HIV infection on T cell turnover, we examined levels of DNA synthesis in lymph node and peripheral blood mononuclear cell subsets by using ex vivo labeling with BrdUrd. Compared with healthy controls (n = 67), HIV-infected patients (n = 57) had significant increases in the number and fraction of dividing CD4(+) and CD8(+) T cells. Higher percentages of dividing CD4(+) and CD8(+) T cells were noted in patients with the higher viral burdens. No direct correlation was noted between rates of T cell turnover and CD4(+) T cell counts. Marked reductions in CD4(+) and CD8(+) T cell proliferation were seen in 11/11 patients 1-12 weeks after initiation of highly active antiretroviral therapy (HAART). These reductions persisted for the length of the study (16-72 weeks). Decreases in naive T cell proliferation correlated with increases in the levels of T cell receptor rearrangement excision circles. Division of CD4(+) and CD8(+) T cells increased dramatically in association with rapid increases in HIV-1 viral loads in 9/9 patients 5 weeks after termination of HAART and declined to pre-HAART-termination levels 8 weeks after reinitiation of therapy. These data are consistent with the hypothesis that HIV-1 infection induces a viral burden-related, global activation of the immune system, leading to increases in lymphocyte proliferation.

Effects of a phorbol ester and isoquinoline sulfonamides on rabbit parietal cell function.

The role of protein kinase C (PKC) on gastric H+ secretion, as measured by aminopyrine (AP) uptake and other intracellular signal transduction products, was investigated in isolated rabbit parietal cells using the PKC activator 12-0-tetradecanoyl phorbol 13-acetate (TPA) and several PKC inhibitors, including isoquinoline sulfonamides (H-7, H-8, H-89 and HA-1004) and calphostin-C. TPA dose-dependently inhibited histamine (10(-4) M)- and carbachol (10(-4) M)-stimulated AP uptake without affecting the response to dibutyryl cyclic AMP (10(-3) M). H-7 and calphostin-C dose-dependently augmented secretagogue-stimulated AP uptake, whereas H-8 and H-89 inhibited the response to secretagogues, and HA-1004 had no effect. H-7 and calphostin-C-induced augmentation of AP uptake was blocked by a calcium (Ca++) antagonist, lanthanum chloride, which suggests that the enhanced AP response was regulated by extracellular Ca++. Moreover, H-7 treatment partially reversed the TPA (10(-7) M)-induced inhibition of secretagogue-stimulated AP uptake. TPA reduced histamine- and carbachol-stimulated cAMP and inositol 1,4,5-triphosphate production by 50% and 96%, respectively, with a concomitant reduction of adenylate cyclase and intracellular free Ca++ by 44% and 78%. TPA increased the distribution of membrane-associated PKC by 20% and decreased histamine-stimulated PKA by 30%. In contrast, H-7 inhibited both PKC and protein tyrosine kinase activity in vitro but had no effect on these parameters in vivo. The results indicate that TPA-induced inhibition of secretagogue-stimulated AP uptake in PC is presumably mediated by activation of PKC.

Effects of cyclic adenosine monophosphate-dependent protein kinase and calcium-dependent protein kinase modulators on stimulated gastric acid secretion in the perfused rat stomach.

The effects of cyclic adenosine monophosphate-dependent protein kinase (PKA) and calcium-dependent protein kinase (PKC) modulators on secretagogue-stimulated gastric acid secretion were studied in the continuously perfused stomach of the anesthetized rat. Intravenous histamine (0.25 mg/kg/h) and pentagastrin (2 micrograms/kg/h) increased secretion above baseline by three- and fourfold, respectively. Parenteral administration of a PKC activator, 12-o-tetradecanoylphorbol-13-acetate (TPA; 0.1 nmol/h), decreased histamine- and pentagastrin-stimulated secretion by 64 and 40%, respectively. Administration of PKC inhibitors, calphostin C and 1-(5-isoquinolinyl sulfonyl)-2 methylpiperazine (H-7; 10 nmol/h, each), increased histamine- and pentagastrin-stimulated secretion by 115 and 74% and 42 and 79%, respectively, while equimolar concentrations (10 nmol/h) of three other isoquinoline sulfonamides (HA-1004, H-8, and H-89) had no effect, except for H-89 (100 nmol/h) which inhibited the histamine- and penta-gastrin-stimulated acid secretion by 44%. Basal secretion was not significantly altered by the aforementioned drugs. The TPA-induced inhibition of pentagastrin-stimulated secretion was partially reversed by treatment with H-7. These findings support a role of PKA and PKC in the modulation of stimulated gastric acid secretion in vivo.