GAA•TTC repeat expansion in human cells is mediated by mismatch repair complex MutLγ and depends upon the endonuclease domain in MLH3 isoform one

DNA repeat expansion underlies dozens of progressive neurodegenerative disorders. While the mechanisms driving repeat expansion are not fully understood, increasing evidence suggests a central role for DNA mismatch repair. The mismatch repair recognition complex MutSβ (MSH2-MSH3) that binds mismatched bases and/or insertion/deletion loops has previously been implicated in GAA•TTC, CAG•CTG and CGG•CCG repeat expansion, suggesting a shared mechanism. MutSβ has been studied in a number of models, but the contribution of subsequent steps mediated by the MutL endonuclease in this pathway is less clear. Here we show that MutLγ (MLH1-MLH3) is the MutL complex responsible for GAA•TTC repeat expansion. Lentiviral expression of shRNA targeting MutL nuclease components MLH1, PMS2, and MLH3 revealed that reduced expression of MLH1 or MLH3 reduced the repeat expansion rate in a human Friedreich ataxia cell model, while targeting PMS2 did not. Using splice-switching oligonucleotides we show that MLH3 isoform 1 is active in GAA•TTC repeat expansion while the nuclease-deficient MLH3 isoform 2 is not. MLH3 isoform switching slowed repeat expansion in both model cells and FRDA patient fibroblasts. Our work indicates a specific and active role for MutLγ in the expansion process and reveals plausible targets for disease-modifying therapies.

Induction of tumor necrosis factor α and interleukin-1β in subcutaneously implanted chamber by lipopolysaccharide

Lipopolysaccharide (LPS) is the major component of the outermost membrane of Gram-negative bacteria and is considered to be one of the major virulence factors of these bacteria. While the effect of systemic injection of LPS is well characterized, the characterization of cytokine secretion in response to local injection of LPS is lacking. The present study was designed to determine the local production of tumor necrosis factor α (TNFα) and interleukin-1β (IL-1β) over a 4 day period following injection of LPS into subcutaneous implanted chambers in mice. Mice were challenged by a single or repeated injection of Salmonella typhosa LPS into the chambers. Chamber fluids were aspirated at different time intervals and were used for assessment of leukocyte and cytokine levels. A single injection of LPS was found to induce cell influx into the chamber which peaked after 4 h. TNFα and IL-1β levels increased rapidly, reaching their maximum levels within 4 h. After 24 h, TNFα levels declined markedly and were undetectable at 48 and 96 h. TNFα mRNA levels in the sedimented cells followed a similar pattern. In contrast, IL-1β showed a more gradual decrease with levels significantly different from baseline still being present 96 h post-LPS challenge. Four consecutive daily injections of LPS into the chambers resulted in undetectable levels of TNFα in the chamber fluid, while significant levels of IL-1β were detected. These levels were significantly higher than the levels of IL-1β in the chamber fluid 96 h after a single injection and approximately 60% of the levels measured 24 h after a single intra-chamber injection of LPS. The results emphasize the difference between single and repeated exposure to LPS in vivo, and suggest a role for TNFα in the initial phase of the local inflammatory response and for IL-1β in the later phase.

The effect of mild and moderate renal impairment on the pharmacokinetics of pridopidine, a new drug for Huntington's disease

Aim

Pridopidine, a new oral drug for treatment of patients with motor symptoms associated with Huntington's Disease (HD) is currently under development. In steady‐state conditions, pridopidine elimination is mediated primarily through renal excretion. This study evaluated single dose and steady‐state pharmacokinetics (PK) of a daily dose of pridopidine in subjects with mild and moderate renal impairment and matched healthy subjects.

Methods

Subjects with mild renal impairment (n = 12), moderate impairment (n = 12), or their matched healthy controls (n = 25) participated in this study. Subjects received a single dose of pridopidine (45 mg) on day 1 and a multiple dose cycle of 45 mg once daily on days 5–18. Blood and urine samples were collected on days 1 and 18 for PK analysis.

Results

Mild renal impairment did not affect the PK of pridopidine whilst an increase in exposure was seen in subjects with moderate renal impairment. Subjects with moderate impairment showed reduced plasma clearance (by 44%) and had 68% higher AUC (90% CI 1.22, 2.30) and 26% higher C_max (90% CI 1.02, 1.56) values than those with normal renal function at steady‐state. Pridopidine was safe and well tolerated in healthy subjects and in subjects with mild and moderate renal impairment.

Conclusions

Mild renal impairment has no impact on exposure to pridopidine while moderately impaired renal function resulted in higher pridopidine concentrations.

Pharmacokinetics, pharmacodynamics and safety of empagliflozin, a sodium glucose cotransporter 2 (SGLT2) inhibitor, in subjects with renal impairment

AIMS

Empagliflozin is a selective sodium glucose cotransporter 2 (SGLT2) inhibitor that inhibits renal glucose reabsorption and is being investigated for the treatment of type 2 diabetes mellitus (T2DM).

METHODS

In this open-label study, the effect of renal impairment on the pharmacokinetics, pharmacodynamics and safety of a 50 mg dose of empagliflozin was investigated in 40 subjects, grouped according to estimated glomerular filtration rate (eGFR).

RESULTS

Maximum empagliflozin plasma concentrations were similar in subjects with normal renal function and renal impairment. Area under the empagliflozin concentration-time curve (AUC0 -∞ ) values increased by approximately 18, 20, 66 and 48% in subjects with mild, moderate, severe renal impairment and renal failure/end stage renal disease (ESRD), respectively, in comparison to healthy subjects. This was attributed to decreased renal clearance (CLR ). Urinary glucose excretion (UGE) decreased with increasing renal impairment and correlated with decreased eGFR and CLR . Empagliflozin was well tolerated, with no increase in adverse events associated with renal impairment.

CONCLUSIONS

Renal insufficiency resulted in decreased CLR of empagliflozin, moderately increased systemic exposure and decreased UGE. A single 50 mg dose of empagliflozin was well tolerated in subjects with normal renal function and any degree of renal impairment. The pharmacokinetic results of this study indicate that no dose adjustment of empagliflozin is required in patients with renal impairment.

Multiple-dose tolerability, pharmacokinetics, and pharmacodynamics of ponesimod, an S1P1 receptor modulator: favorable impact of dose up-titration

This multiple-ascending-dose study investigated the safety, tolerability, pharmacokinetics, and pharmacodynamics of ponesimod, an S1P1 receptor modulator and a potential new treatment for autoimmune diseases. In part A, 10 healthy male and female subjects received once daily oral doses of ponesimod (5, 10, or 20 mg) or placebo for 7 days. Sinus bradycardia and, in some subjects, atrioventricular (AV) block occurred primarily on the first day of dosing, as desensitization developed to ponesimod-induced heart rate (HR) reduction and PR-prolongation. This elicited the design of an up-titration schedule in 17 subjects to a dose of 40 mg in part B. The up-titration regimen reduced HR and PQ/PR effects. Reported adverse events were mainly related to the cardiac and respiratory systems. Respiratory effects increased with higher doses. Ponesimod multiple-dose pharmacokinetics were slightly more than dose-proportional and characterized by a time to maximum concentration and an elimination half-life varying from 2.5 to 4.0 hours and 30.9 to 33.5 hours, respectively, and an accumulation of about 2.3-fold. Ponesimod caused a dose-dependent sustained decrease in total lymphocyte count, reversible within 7 days of discontinuation. A pharmacokinetic-pharmacodynamic model enabled comparing day 1 and steady-state conditions. These results warrant further investigation of ponesimod in patients.

DNA mismatch repair complex MutSβ promotes GAA·TTC repeat expansion in human cells

While DNA repair has been implicated in CAG·CTG repeat expansion, its role in the GAA·TTC expansion of Friedreich ataxia (FRDA) is less clear. We have developed a human cellular model that recapitulates the DNA repeat expansion found in FRDA patient tissues. In this model, GAA·TTC repeats expand incrementally and continuously. We have previously shown that the expansion rate is linked to transcription within the repeats. Our working hypothesis is that structures formed within the GAA·TTC repeat during transcription attract DNA repair enzymes that then facilitate the expansion process. MutSβ, a heterodimer of MSH2 and MSH3, is known to have a role in CAG·CTG repeat expansion. We now show that shRNA knockdown of either MSH2 or MSH3 slowed GAA·TTC expansion in our system. We further characterized the role of MutSβ in GAA·TTC expansion using a functional assay in primary FRDA patient-derived fibroblasts. These fibroblasts have no known propensity for instability in their native state. Ectopic expression of MSH2 and MSH3 induced GAA·TTC repeat expansion in the native FXN gene. MSH2 is central to mismatch repair and its absence or reduction causes a predisposition to cancer. Thus, despite its essential role in GAA·TTC expansion, MSH2 is not an attractive therapeutic target. The absence or reduction of MSH3 is not strongly associated with cancer predisposition. Accordingly, MSH3 has been suggested as a therapeutic target for CAG·CTG repeat expansion disorders. Our results suggest that MSH3 may also serve as a therapeutic target to slow the expansion of GAA·TTC repeats in the future.

Effect of renal impairment on the pharmacokinetics of the dipeptidyl peptidase-4 inhibitor linagliptin(*)

AIM

This study assessed the influence of various degrees of renal impairment on the exposure of linagliptin, a dipeptidyl peptidase-4 (DPP-4) inhibitor with a primarily non-renal route of excretion, in subjects with type 2 diabetes mellitus (T2DM).

METHODS

Linagliptin pharmacokinetics was studied under single-dose and steady-state conditions in subjects with mild, moderate and severe renal impairment (with and without T2DM) and end-stage renal disease and compared with the pharmacokinetics in subjects with normal renal function (with and without T2DM).

RESULTS

Renal excretion of unchanged linagliptin was <7% in all groups. Under single-dose conditions, the degree of renal impairment did not affect mean plasma linagliptin concentration-time profiles. These showed a similar decline and almost identical plasma concentrations 24 h postdosing in subjects with mild, moderate or severe renal impairment and in subjects with T2DM with and without renal impairment. Although there was a tendency towards slightly higher (20-60%) exposure in renally impaired subjects (with and without T2DM) compared with subjects with normal renal function, the steady-state AUC and C(max) values showed a large overlap and were not affected by the degree of renal impairment. The accumulation half-life of linagliptin ranged from 14-15 h in subjects with normal renal function to 18 h in severe renal impairment. Only a weak correlation (r(2) = 0.18) was seen between creatinine clearance and steady-state exposure.

CONCLUSIONS

Renal impairment has only a minor effect on linagliptin pharmacokinetics. Consequently, there will be no need for adjusting the linagliptin dose in renally impaired patients with T2DM.

IL-10 gene transfer attenuates P. gingivalis-induced inflammation

IL-10 is an anti-inflammatory cytokine secreted by stimulated Th2 lymphocytes that can down-regulate inflammatory responses to bacterial challenge. We hypothesized that local delivery of IL-10 using gene-transfer will down-regulate inflammatory responses. We examined the effect of IL-10 plasmid injection on the local cytokine response. Two weeks after the implantation of chambers, either IL-10 plasmid or vector was injected into the mice. Four days later, they were challenged with an intra-chamber injection of P. gingivalis. The intra-chamber levels of IL-10, IFNgamma, TNFalpha, and IL-1beta were evaluated after 2 and 24 hrs. The results showed that local IL-10 gene delivery elevated the levels of IL-10 at both time periods. It attenuated the levels of IFNgamma (656 +/- 154 to 218 +/- 144 pg/mL) and TNFalpha (23 +/- 2.0 to 12.5 +/- 2.9 ng/mL) at 2 hrs, and of IL-1beta (21.5 +/- 5.7 to 12.4 +/- 3.0 ng/mL) at 24 hrs. The results suggest the possibility of modulating the local inflammatory response to P. gingivalis by direct IL-10 gene transfer.

Pharmacokinetic interaction between bosentan and the oral contraceptives norethisterone and ethinyl estradiol

OBJECTIVE

Bosentan has been shown in vitro and in vivo to induce the cytochrome P450 enzymes CYP2C9 and CYP3A4. The present study was conducted to investigate the effect of bosentan on the pharmacokinetics of a combined oral contraceptive.

SUBJECTS AND METHODS

In a randomized, 2-way crossover study, 20 healthy female subjects received Treatments A and B. Treatment A consisted of a single dose of OrthoNovum containing 1 mg norethisterone (norethindrone) and 35 microg ethinyl estradiol. Treatment B consisted of bosentan, 125 mg b.i.d. for 7 days plus concomitant norethisterone and ethinyl estradiol on Day 7. Plasma concentrations of norethisterone and ethinyl estradiol were measured on days of oral contraceptive administration.

RESULTS

In the absence of bosentan, the pharmacokinetics of norethisterone and ethinyl estradiol were characterized by Cmax and AUC0-infinity values (95% CI) of 9.8 (8.1, 11.9) ng/ml and 72.9 (57.0, 93.1) ng x h/ml, and 53.0 (47.0, 59.9) pg/ml and 758 (655, 878) pg x h/ml, respectively. Concomitant bosentan did not affect the Cmax but significantly decreased the AUC of norethisterone and ethinyl estradiol by 13.7% (-23.5, -2.6) and 31.0% (-40.5,-20.2), respectively. The maximum decrease in AUC of norethisterone and ethinyl estradiol in an individual subject was 56% and 66%, respectively.

CONCLUSIONS

Bosentan decreases the AUC of norethisterone and ethinyl estradiol in healthy female subjects. In patients treated with bosentan, reduced efficacy of hormonal contraceptives should be considered.

Pharmacokinetics of moxifloxacin, a novel 8-methoxy-quinolone, in patients with renal dysfunction

AIMS

To evaluate the influence of impaired renal function on the plasma and urinary pharmacokinetics of moxifloxacin, a novel 8-methoxy-quinolone antibacterial drug.

METHODS

Twenty male and 12 female subjects (8 healthy subjects, 24 patients with impaired renal function), 18--75 years of age were investigated in parallel fashion with four groups stratified according to creatinine clearance (CLCR; n=8 for each group). The pharmacokinetics of moxifloxacin and the metabolites M1 (sulphonate metabolite) and M2 (glucuronide) in plasma and urine were determined repeatedly up to 96 h after single oral doses of 400 mg. Patients were monitored intensively with regard to clinical and laboratory safety and tolerability.

RESULTS

Single doses of 400 mg moxifloxacin were safe and well tolerated. The urinary excretion of moxifloxacin (Aeur, P: 0.0002) and renal clearance (CLR, P<0.0001) were reduced with decreasing CLCR, mean Cmax was slightly reduced (Cmax-ratio 85.0%, 90% CI 67.9, 106.4% severe renal impairment vs healthy subjects) but the AUC was unchanged even in severe renal impairment (AUC-ratio 101.3%, 90% CI 79.7, 128.6%). The mean AUC of the N-sulphonate M1 was slightly increased (by about 53% for the most severe disease) by impaired renal function, but there was no significant correlation between individual AUC and CLCR, whilst Aeur and CLR were significantly correlated with CLCR. In contrast, for the acylglucuronide M2, Aeur (P: 0.0026), CLR (P<0.0001) and AUC (P: 0.0011) were directly correlated with CLCR.

CONCLUSIONS

Renal dysfunction had little effect on the plasma pharmacokinetics of either moxifloxacin or metabolite M1, although their renal clearance and urinary excretion were reduced. In contrast renal dysfunction did result in changes in the plasma pharmacokinetics of metabolite M2, causing greater and longer exposure. However the extent of these changes is unlikely to be of clinical relevance.

Experimental stress suppresses recruitment of macrophages but enhanced their P. gingivalis LPS-stimulated secretion of nitric oxide

BACKGROUND

Epidemiological studies have suggested that stress can alter the onset and progression of periodontal disease. However, the mechanisms involved are not clear. The present study was designed to examine whether the functional response of mouse macrophages stimulated by Porphyromonas gingivalis lipopolysaccharide (LPS) is affected by experimental stress, and to investigate the role of corticosterone (CS) in the stress-related effects.

METHODS

Two models of stress were used: emotional (isolation) and physical (cold). We measured thioglycollate-induced macrophage recruitment in vivo, and LPS-induced nitric oxide (NO) secretion by the macrophages in vitro. Two groups of mice were exposed to the stress conditions: isolation or cold. A third group was injected daily with CS, and a fourth group was used as a control (no stress). After 3 days of stress conditions, thioglycollate was injected into the peritoneal cavity. Four days later, peritoneal macrophages were isolated, counted, and cultured. The secretion of NO by the cultured cells was evaluated with and without P. gingivalis LPS stimulation.

RESULTS

The number of cells in the peritoneal lavage of stressed mice was significantly reduced in comparison to macrophages isolated from non-stressed animals. The number of macrophages from CS-treated mice did not differ from controls. NO secretion from unstimulated macrophages did not differ between the stressed and control groups. Stimulation of the macrophages with P. gingivalis LPS significantly enhanced NO secretion by macrophages from the control and stressed animals, but not by the CS-treated group. NO levels secreted by P. gingivalis-stimulated cells from the two stressed groups were significantly higher than the levels secreted by controls, and the isolation group released significantly higher levels than the cold group. Stimulation of the macrophages with P. gingivalis LPS and interferon (IFN)-gamma resulted in enhanced NO secretion in the 4 groups compared to LPS alone, with no significant differences between the groups.

CONCLUSIONS

The results suggest that experimental stress modulates the response of macrophages to inflammatory stimulants, and that CS is not the sole mediator involved. The presence of IFN-gamma in the culture may mask the functional differences induced by stress. The stress-induced upregulation of NO secretion might be involved in the accelerated periodontal destruction in stressed subjects.

Repeat bacterial challenge in a subcutaneous chamber model results in augmented tumour necrosis factor-alpha and interferon-gamma response, and suppression of interleukin-10

The present study compared the effect of a single or a repeat challenge with the Gram-negative pathogen Porphyromonas gingivalis on the local inflammatory response within subcutaneous chamber model in mice. Subcutaneous chambers were implanted 2 weeks prior to the final challenge. The repeat-challenge (REP) group received two intrachamber bacterial injections 14 days apart, while the single-injection group (SIN) received only a single bacterial challenge. Injection of saline was used as the control. The cellular contents of the chamber exudates were used for differential cell counts, and the supernatants were analysed for tumour necrosis factor-alpha (TNF-alpha), interferon-gamma (IFN-gamma), and interleukin (IL)-10 levels. Immunoglobulin G1 (IgG1) and IgG2a levels to P. gingivalis in the exudates were also determined. The results showed that the leucocyte counts increased significantly post-challenge, and the REP group showed the highest number of lymphocytes and neutrophils. Both P. gingivalis-challenged groups exhibited significant increase in TNF-alpha and IL-10 levels at day 1 post-challenge. TNF-alpha levels in the chamber exudate were threefold higher in the REP group compared with the SIN group on day 1 post-challenge (P < 0.05). In contrast, IL-10 levels were significantly lower in the REP group 1 day post-challenge compared with the SIN group. The REP group had significantly higher levels of IFN-gamma at baseline, and this difference remained significant 1 day post-challenge. Analysis of antibody levels to P. gingivalis showed that while the control and the SIN groups had no anti-P. gingivalis IgG in the chamber exudate during the 7-day study period, the REP group showed high anti-P. gingivalis IgG levels. In addition, the titres of IgG2a were fivefold higher than the IgG1 titres. The results showed that a repeat local challenge with P. gingivalis augmented the proinflammatory cytokines TNF-alpha and IFN-gamma, while inhibiting the accumulation of the anti-inflammatory cytokine IL-10. This shift towards a T helper 1 (Th1)-dominant response was reflected in the relatively high anti-P. gingivalis IgG2a titres in the local inflammatory environment 7 days post-challenge.

Pharmacokinetics and pharmacodynamics of the acetylcholinesterase inhibitor metrifonate in patients with renal impairment

The aim of this study was to assess the influence of renal function on the pharmacokinetics, pharmacodynamics, safety, and tolerability of the acetylcholinesterase inhibitor metrifonate. Four groups of six age- and gender-matched subjects with varying degrees of renal function (creatinine clearances more than 90, 60-90, 30-60, and less than 30 mL/min/ 1.73 m2, respectively) were administered a single 50-mg oral dose of metrifonate. Blood and urine samples were collected for 24 hours and concentrations of metrifonate and its metabolites dichlorvos, dichloroacetic acid, and M3 were determined. Inhibition of acetylcholinesterase activity in erythrocytes and butyrylcholinesterase in plasma were also measured. Metrifonate was well tolerated in all treatment groups. The urinary excretion of metrifonate and dichlorvos decreased with decreasing renal function but accounted for less than 2% of the elimination. There were no statistically significant differences in primary pharmacokinetic parameters--Cmax, t(max), area under the concentration-time curve (AUC), and t1/2--of metrifonate and dichlorvos among the different groups. The excretion of dichloroacetic acid and M3 was not influenced by renal impairment. Acetylcholinesterase was not inhibited, whereas butyrylcholinesterase was inhibited markedly but independently of renal function. No metrifonate dose adjustments are needed when treating subjects with renal impairment.

Activation of murine macrophages by lipoprotein and lipooligosaccharide of Treponema denticola

We have recently demonstrated that the periodontopathogenic oral spirochete Treponema denticola possesses membrane-associated lipoproteins in addition to lipooligosaccharide (LOS). The aim of the present study was to test the potential of these oral spirochetal components to induce the production of inflammatory mediators by human macrophages, which in turn may stimulate tissue breakdown as observed in periodontal diseases. An enriched lipoprotein fraction (dLPP) from T. denticola ATCC 35404 obtained upon extraction of the treponemes with Triton X-114 was found to stimulate the production of nitric oxide (NO), tumor necrosis factor alpha (TNF-alpha), and interleukin-1 (IL-1) by mouse macrophages in a dose-dependent manner. Induction of NO by dLPP was at 25% of the levels obtained by Salmonella typhosa lipopolysaccharide (LPS) at similar concentrations, while IL-1 was produced at similar levels by both inducers. dLPP-mediated macrophage activation was unaffected by amounts of polymyxin B that neutralized the induction produced by S. typhosa LPS. dLPP also induced NO and TNF-alpha secretion from macrophages isolated from endotoxin-unresponsive C3H/HeJ mice to an extent similar to the stimulation produced in endotoxin-responsive mice. Purified T. denticola LOS also produced a concentration-dependent activation of NO and TNF-alpha in LPS-responsive and -nonresponsive mouse macrophages. However, macrophage activation by LOS was inhibited by polymyxin B. These results suggest that T. denticola lipoproteins and LOS may play a role in the inflammatory processes that characterize periodontal diseases.

The Effect of Stress on the Inflammatory Response toPorphyromonas gingivalisin a Mouse Subcutaneous Chamber Model

BACKGROUND

The impact of emotional stress on the outcome of infectious diseases was studied in animal models and humans, but data related to the effect of stress on periodontal infection are limited. Using the subcutaneous chamber model in mice, the present study was carried out to investigate the effect of stress on the host response to Porphyromonas gingivalis.

METHODS

Mice with subcutaneous chambers (2 per animal) were divided into 4 treatment groups: cold-stress; isolation-stress; corticosterone (CS)-injected; and controls. On the third day of stress conditions, heat-killed P. gingivalis were injected into the chambers. The chambers were sampled 1 and 5 days later and analyzed for leukocyte number, tumor necrosis factor (TNF)-alpha levels, and interferon (IFN)-gamma levels.

RESULTS

Injection of P. gingivalis induced the migration of leukocytes into the chambers and increased the intrachamber levels of IFN-gamma and TNF-alpha. There were no significant differences in cell number and IFN-gamma levels between the different treatment groups, but the levels of TNF-alpha were significantly lower in the isolation-stress and cold-stress groups compared to control animals. CS-injected animals were not different from controls. In addition, the levels of TNF-alpha in the stressed animals were lower on the fifth day post-injection than on the first day, but not in the CS and control group.

CONCLUSIONS

The results suggest that the levels of TNF-alpha induced by P. gingivalis in the infection site are downregulated in stressed animals, and CS is not the sole mediator responsible. The stress-induced reduction in TNF-alpha levels might have an impact on the pathogenesis of periodontal disease in humans experiencing emotional stress.

Effects of tetracyclines on the pathologic activity of endotoxin: in vitro and in vivo studies

Lipopolysaccharide (LPS) is considered to be one of the major virulence factors of Gram-negative bacteria. Recently, tetracyclines (TTCs) were found to prevent the patho-physiological changes associated with LPS in vivo and the secretion of inflammatory mediators in vitro. However, the mechanism by which TTCs prevents LPS-induced pathology in vivo is still unclear. In order to shed light on that problem, we carried out in vitro and in vivo experiments. TTC inhibited the secretion of nitric oxide (NO) and TNF alpha from LPS-stimulated macrophages and inhibited macrophage-induced thymocyte proliferation. However, TTC inhibited NO secretion with use of concentrations five-fold lower than those that inhibited TNF alpha secretion and thymocyte proliferation. The secretion of NO was inhibited by the addition of TTC to the cultures up to 6 hrs post-LPS stimulation. TTC inhibition of LPS-induced NO secretion was not reversed by the addition of recombinant TNF alpha, and TTC inhibition of LPS-induced TNF alpha secretion was not reversed by the addition of NO donor. These results suggest that the inhibition of TNF alpha by TTC is not the result of the inhibition of LPS-induced NO secretion or vice versa. In vivo experiments had shown that TTC prevented mortality in LPS-treated mice, but not in mice pre-sensitized with galactosamine prior to the LPS challenge. These results suggest that TTC activity in vivo is due not to the suppression of synthesis of inflammatory mediators but rather to the induction of acute phase-like response, which antagonizes the LPS-induced activity.

Anti-D immunoglobulin in Rh(D) negative volunteers: clearance of Rh(D) positive red cells and kinetics of serum anti-D levels

Properties of a new anti-D immunoglobulin were assessed in Rh(D) negative healthy male adults. Six volunteers received intravenous, and five volunteers intramuscular injections of 200 micrograms anti-D, 48 hours after pre-treatment with 5 mL of Rh(D) positive erythrocytes. Immediately after intravenous administration of anti-D, a rapid decrease of the Rh(D) positive erythroyctes was noted. After intramuscular injection of anti-D, there was a lag phase of 6 hours until the erythrocytes decreased, and the elimination rate was slower. Twenty-four hours after injection of anti-D, the Rh(D) positive erythrocytes were at the detection limit or no longer detectable in all volunteers. After intravenous administration, anti-D serum levels decreased from 45 ng/mL at 2 hours to 29 ng/mL at 24 hours, whereas after intramuscular administration, anti-D became detectable at 4 hours and increased to 11 ng/mL at 24 hours. During subsequent months, anti-D serum levels decreased at similar rates in both groups. After six months, anti-D was not detectable in any of the volunteers. Thus, the new anti-D immunoglobulin induced elimination of the Rh(D) positive erythrocytes and suggested that Rh(D) immunization of the volunteers was prevented.

Bacterial lipopolysaccharide induces early and late activation of protein kinase C in inflammatory macrophages by selective activation of PKC-epsilon

Experiments from our and other laboratories have shown that specific inhibitors of protein kinase C (PKC) inhibited the secretion of nitric oxide, TNF alpha, and IL-1 beta from lipopolysaccharide (LPS)-stimulated macrophages, suggesting an important role for PKC in the inflammatory response. The present study was designed to investigate the mechanism whereby LPS stimulates PKC activity in inflammatory macrophages. Mouse macrophages were stimulated with 0-1 microgram/ml LPS for 0-18 hours, and PKC activity was detected in cell lysates. PKC isoform specificity was determined by blocking PKC activity with isoform-specific antibodies. Treatment of macrophages with 1 microgram/ml LPS induced a two-fold increase in PKC activity within 15 minutes and an additional more significant peak of PKC activity appeared 3 hours post-LPS stimulation. A lower dose of LPS (10 ng/ml) induced the later peak only. The enhancement in PKC activity induced by LPS occurred in both the cytosol and membrane fractions, but the enhancement in the membrane fraction was significantly greater than in the cytosol. The increase in PKC activity in both peaks was abolished only by the addition of anti-PKC-epsilon antibody. The present experiments suggest that PKC activation is an important pathway in the LPS-induced secretory response of macrophages and that PKC-epsilon is the major isoform involved.

Tetracycline inhibits Porphyromonas gingivalis lipopolysaccharide-induced lesions in vivo and TNF alpha processing in vitro

Lipopolysaccharides (LPS) are considered one of the more important virulence factors related to the pathogenesis of periodontal diseases. Based on tetracycline (TTC) ability to bind divalent metal ions, the present study was designed to examine the effect of TTC on P. gingivalis LPS-induced lesions in vivo and on LPS-induced TNF alpha production in vitro. Subcutaneous injection of 50-100 micrograms of P. gingivalis LPS into BALB/C mice induced a visible lesion within 24 h with evident tissue necrosis. Daily systemic administration of TTC for the first 4 d following LPS challenge reduced the size of the lesion, and total inhibition of lesion formation was observed in 75-100% of the treated mice. A non-related broad spectrum antibiotic, ampicillin, or the IL-1 inhibitor ML-20, had no effect on the lesion size. In order to explore some aspects of the mechanism involved, we tested the effect of TTC on LPS-induced TNF alpha secretion by human monocytes in vitro. TTC (1 mM) was found to block LPS-stimulated TNF alpha secretion. Western blotting of monocyte cytoplasmic membranes for membrane-bound TNF alpha show that TTC causes the retention of membrane-associated TNF alpha on monocyte membranes, thereby preventing the release of TNF alpha into the culture media. The results suggest the TTC is an effective in vivo therapy for preventing P. gingivalis LPS-induced subcutaneous lesion formation in the murine model. The mechanism of TTC treatment probably involves blocking the activity of metalloproteinases, including TNF alpha processing enzyme, thereby preventing LPS-induced tissue destruction.

Human monocyte response to cementum extracts from periodontally diseased teeth: effect of conditioning with tetracycline

Monocyte inflammatory cytokines, such as TNF alpha and IL-1 beta, have been implicated in the pathogenesis of periodontal destruction. The present study was designed to test the ability of extracts of cementum from periodontally diseased teeth to induce the secretion of these mediators by monocytes, to evaluate the role of adsorbed endotoxin in this process, and to test the effect of cementum conditioning with tetracycline on the monocyte response. Human monocytes were incubated with varying concentrations of cementum extracts, and TNF alpha and IL-1 beta levels in the media were measured. The results showed that while extracts of healthy cementum had no effect on monocyte secretion, concentration as low as 0.5 mg/ml of cementum from diseased sites raised the levels of TNF alpha and IL-1 beta secretion 10-fold. This response was dose-dependent. Diseased cementum were found to contain 1.5 ng/mg endotoxin, while endotoxin was not detectable in the extracts of the healthy cementum. However, neutralization of the endotoxin by polymyxin B only partially reduced the monocyte secretory response by 50 to 70%, suggesting that other factors in the extracts are also involved in monocyte stimulation. To simulate the effect of root conditioning, cementum was first agitated in a tetracycline or control solution prior to its extraction in media. Pretreatment of diseased cementum with tetracycline (50 mg/ml) was found to block the secretion of TNF alpha from cementum-stimulated monocytes. Pretreatment of the diseased cementum with 10 mg/ml tetracycline was not more effective than saline and HCI controls, with all treatments reducing cytokine secretion by approximately 80%. The direct addition of tetracycline to cementum-stimulated monocyte culture was found to block TNF alpha secretion in a dose dependent manner. The results suggest that extracts from diseased cementum are potent stimulators of monocyte secretion, and that endotoxin as well as other factor(s) appear to be involved. These factors are partially extracted by washing and a 10 mg/ml tetracycline solution is not more effective than saline in achieving this goal. In addition, tetracycline was found to be a potent inhibitor of TNF alpha secretion by cementum-stimulated monocytes, suggesting a novel mechanism for this drug in periodontal therapy.

Protection against endotoxic shock and lipopolysaccharide-induced local inflammation by tetracycline: correlation with inhibition of cytokine secretion

Septic shock results from excessive stimulation of host immune cells, particularly monocytes and macrophages, by lipopolysaccharide (LPS) released from gram-negative bacteria. Macrophage-derived cytokines, such as tumor necrosis factor alpha (TNF-alpha) and interleukin-1beta (IL-1 beta), have been identified as central mediators in the pathogenesis of septic shock and the resultant mortality. Therefore, these cytokines were targets for experimental therapy for septic shock. Because of tetracycline's ability to intervene in cellular mechanisms involved in cytokine secretion, we tested the effect of tetracycline on LPS-induced septic shock and inflammatory lesions in mice. Tetracycline was found to protect mice against LPS-induced lethality and to abolish clinical signs of LPS-induced inflammatory lesions. This protection correlates with tetracycline's ability to reduce LPS-induced TNF-alpha levels in serum. Furthermore, tetracycline was found to inhibit LPS-induced TNF-alpha and IL-1 beta secretion, but not cytokine mRNA accumulation, in human monocytes in vitro. The results presented here suggest that tetracycline is a potent drug for LPS-induced pathology and that its mechanism of action involves blockage of posttranscriptional events of cytokine production.

Clinical aspects of cardiovascular effects of H2-receptor antagonists

In vitro studies and animal experiments as well as clinical observations in humans concerning cardiovascular effects of H2-receptor antagonists have been published shortly after the development. Thus, clinical studies were performed to investigate these effects. The following review summarizes the results from in vitro studies up to the clinical investigations performed.

Changes in the effects of nizatidine and famotidine on cardiac performance after pretreatment with ranitidine

This was an open, randomized study of the cardiovascular effects of the histamine H2 receptor antagonists ranitidine, famotidine, and nizatidine after single oral doses alone or in combination in healthy volunteers. When compared with placebo ranitidine (450 mg) did not have any haemodynamic effects. Nizatidine (300 mg) caused significant falls in heart rate and cardiac output. Famotidine (40 mg) caused significant falls in stroke volume and cardiac output and an increase in pre-ejection period. Pretreatment with ranitidine abolished the haemodynamic effects of nizatidine and caused a time-shift of 2 h in the onset of the cardiovascular effects of famotidine. The difference in the results for nizatidine and famotidine can be explained by the longer half-life of famotidine. Vascular effects are assumed to be responsible for impairment of cardiac performance by famotidine.

Bunazosin in patients with impaired hepatic or renal function

Following a single oral dose of 6 mg bunazosin, a novel alpha 1-adrenoceptor antagonist, the pharmacokinetics and blood pressure behaviour of 37 patients were studied. 12 subjects had normal renal and hepatic function (mean creatinine clearance (GFR) 107 +/- 240 ml/min, antipyrine clearance (AP Cl) 47 +/- 10.2 ml/min; x +/- SD), 13 subjects had impaired renal function (mean GFR 38 +/- 11.5 ml/min, AP Cl 39 +/- 4.0 ml/min), and 12 patients had liver cirrhosis which was confirmed by liver biopsy (mean AP Cl 18 +/- 9.2 ml/min, GFR 92 +/- 8.1 ml/min). The groups studied were matched for age and body weight. The area under the plasma level time curve (AUC0-infinity) of bunazosin increased from 96.6 +/- 48.7 micrograms.ml-1.h in the normals to 157.0 +/- 101.0 micrograms.ml-1.h in the liver patients and to 298.2 +/- 199.4 micrograms.ml-1.h in patients with impaired renal function (P < 0.05). As there was a close correlation between plasma levels and antihypertensive activity of bunazosin in the present study, dosage adjustment of the alpha 1-receptor blocker in patients with impaired liver and kidney function appears to be mandatory.

Dose-dependent heart rate reducing effect of nizatidine, a histamine H2-receptor antagonist

1. Twelve healthy subjects were treated in a randomised placebo-controlled crossover study with placebo, 150 mg, 300 mg, and 600 mg nizatidine, 100 mg pirenzepine, and 300 mg nizatidine plus 100 mg pirenzepine for 1 week each. 2. On the seventh treatment day, heart rate, blood pressure, systolic time intervals, impedance cardiographic and Doppler ultrasound variables were measured. 3. Stroke volume and blood pressure were not altered by nizatidine and/or pirenzepine. By contrast, heart rate and cardiac output significantly (P < 0.05) decreased in a dose-dependent manner 1.5 and 3 h after administration of 300 and 600 mg nizatidine. Treatment with 150 mg nizatidine led to similar though non-significant trends. 4. While a slightly insignificant rise in heart rate was detected with pirenzepine alone, heart rate and cardiac output remained unchanged upon combined nizatidine and pirenzepine treatment as compared with placebo and baseline values. 5. In conclusion, nizatidine reduced heart rate and cardiac output in a dose-dependent manner, whereas this negative chronotropic effect was counteracted by concurrent administration of the anti-cholinergic drug pirenzepine.

Modulation of lymphocyte subsets due to psychological stress in patients with rheumatoid arthritis

The influence of a 1-hour neuropsychological stress test on the distribution of lymphocyte subpopulations and on plasma catecholamine levels was investigated in 18 patients with rheumatoid arthritis (RA) and 14 sex- and age-matched controls. Despite significant increases in lymphocyte counts in both groups, lymphocyte subsets did not change accordingly. A wide scattering of catecholamine levels in plasma before and after stress was observed. Plasma levels of lymphokines such as interleukin (IL)-1 beta and IL-6 could not be detected in RA patients. Enzyme immunoassay of markers of lymphocyte activation such as HLA-DR and cell-bound IL-2 receptor showed only a significant elevation of HLA-DR marked cells in RA patients at baseline. Significantly higher amounts of the soluble IL-2 receptor were detected in patients with RA before the stress test, but stress testing did not alter this parameter. In conclusion, lymphocyte activation in RA and a defect in the expression of IL-2 receptor on the cell surface of lymphocytes were confirmed in the present study.

Cardiovascular effects of omeprazole and famotidine

In a randomized, placebo-controlled, double-blind, crossover comparison, 12 patients with congestive heart failure (New York Heart Association class II) and dyspeptic complaints were treated orally for 1 week each with placebo, 40 mg omeprazole daily, and 40 mg famotidine daily. Non-invasive haemodynamic measurements were taken on the last day of treatment. Although omeprazole did not alter cardiac performance in impedance cardiography and mechanocardiography, the administration of famotidine led to a significant fall in stroke volume and cardiac output as compared with placebo (both p less than 0.05). Thus, omeprazole did not exert any relevant cardiovascular effects, in contrast to the H2-receptor antagonist famotidine.

Hemodynamic and humoral effects of the novel calcium antagonist Ro 40-5967 in patients with hypertension

The tolerability and hemodynamic and humoral effects of the structurally novel calcium antagonist Ro 40-5967 were investigated in 64 patients with hypertension. In a double-blind, placebo-controlled study, ascending oral doses of 50, 100, 150, or 200 mg were administered once daily for 8 days in a solution. Ro 40-5967 was well tolerated up to 150 mg, but treatment was stopped in one patient in the 200 mg group because of bradycardia. Blood pressure was dose-dependently reduced over the full 24-hour dosing period with more pronounced effects on day 8 than on day 1. The maximum blood pressure reduction was obtained after 150 mg (supine blood pressure, -34/-25 mm Hg, p less than 0.001). Despite a slight decrease in supine heart rate, cardiac output increased. PQ time was dose-dependently increased and concentration-effect analysis showed that relevant atrioventricular conduction disturbances occur only at concentrations much higher than those required to reduce blood pressure. Changes in catecholamines, plasma renin activity, and aldosterone were small and inconsistent. In conclusion, Ro 40-5967 has a long-lasting antihypertensive effect after once-daily administration.

Arachidonic acid channelling in the phospholipid fractions and subcellular compartments of cultured myocardial cells

Arachidonic acid (AA) channeling in cultured heart cells was studied following pulse labelling for 1 h. AA was shown to be esterified immediately and equally distributed between the neutral lipids and phospholipids. A rapid constant flow to various phospholipid classes occurred thereafter, while the AA oxidation was only between 12%. The subcellular distribution of AA was studied by nitrogen cavitation followed by fractionation on 6.7% percoll in sucrose-EDTA. After 1 h pulse labeling and 2 h post-pulse incubation, most of the radioactivity was found in the sarcolemmal fraction with a much smaller amount in the mitochondrial fraction.

Mechanical injury increases eicosanoid production in cultured cardiomyocytes

The release of three stable metabolites of the arachidonic acid cascade was determined in cultures of cardiac myocytes and of non-muscle cells. In both cell types, the main product was 6-keto-PGF1 alpha much less PGE2 was released, while TXB2 was only detected in muscle cells. Preincubation with arachidonic acid increased the release of all the PGs in both types of culture. Mechanical injury had a synergistic effect on the increased PG release in AA-preincubated cells. However, TXB2 was not detected in F-cells in any experimental conditions. These results suggest that PG production serves a functional role in heart preservation during injury.

Maternal immunization with gametocyte antigens as a means of providing protective immunity against Eimeria maxima in chickens

In the present study, we wished to demonstrate the ability of surface gametocyte antigens to induce protective immunity against Eimeria maxima infections in chickens. In order to accomplish this goal, we employed maternal immunization as a means of providing large amounts of specific antibodies to offspring chicks. Upon challenge with sporulated E. maxima oocysts, chicks from hens immunized with affinity-purified gametocyte antigens showed greatly reduced oocyst production compared with chicks from sham-immunized hens. These results suggest that maternal immunization with gametocyte antigens can be used as a means to provide transmission-blocking immunity against E. maxima infections.