Postoperative cognitive dysfunction and mortality following lung transplantation.

Preliminary evidence suggests that postoperative cognitive dysfunction (POCD) is common after lung transplantation. The impact of POCD on clinical outcomes has yet to be studied. The association between POCD and longer-term survival was therefore examined in a pilot study of posttransplantation survivors. Forty-nine participants from a prior randomized clinical trial underwent a neurocognitive assessment battery pretransplantation and 6 months posttransplantation, including assessments of the domains of Executive Function (Trail Making Test, Stroop, Digit Span), Processing Speed (Ruff 2 and 7 Test, Digit Symbol Substitution Test), and Verbal Memory (Verbal Paired Associates, Logical Memory, Animal Naming, and Controlled Oral Word Association Test). During a 13-year follow-up, 33 (67%) participants died. Greater neurocognition was associated with longer survival (hazard ratio [HR] = 0.49 [0.25-0.96], P = .039), and this association was strongest on tests assessing Processing Speed (HR = 0.58 [0.36-0.95], P = .03) and Executive Function (HR = 0.52 [0.28-0.97], P = .040). In addition, unadjusted analyses suggested an association between greater Memory performance and lower risk of CLAD (HR = 0.54 [0.29-1.00], P = .050). Declines in Executive Function tended to be predictive of worse survival. These preliminary findings suggest that postoperative neurocognition is predictive of subsequent mortality among lung transplant recipients. Further research is needed to confirm these findings in a larger sample and to examine mechanisms responsible for this relationship.

Psychosocial Predictors of Mortality Following Lung Transplantation.

Lung transplantation has become an increasingly common treatment for patients with end-stage lung disease. Few studies have examined psychosocial risk factors for mortality in transplant recipients, despite evidence suggesting that elevated levels of negative affect are associated with greater mortality following major cardiac surgery. We therefore examined the relationship between negative affect early after lung transplantation and long-term survival in a sample of 132 lung transplant recipients (28 cystic fibrosis, 64 chronic obstructive pulmonary disease, 26 idiopathic pulmonary fibrosis, 14 other) followed for up to 13.5 years (median 7.4 years) following transplantation. Patients underwent both medical and psychosocial assessments 6 months following transplantation, which included the Beck Depression Inventory-II (BDI-II), Spielberger Anxiety Inventory, and General Health Questionnaire (GHQ). Over the course of follow-up, 80 (61%) participants died. Controlling for demographic factors, native lung disease, disease severity, family income, education level, social support, and frequency of posttransplant rejection, elevated symptoms of depression (BDI-II: HR = 1.31, p = 0.011) and distress (GHQ: HR = 1.28, p = 0.003) were associated with increased mortality. Higher levels of depression and general distress, but not anxiety, measured 6 months following lung transplantation are associated with increased mortality, independent of background characteristics and medical predictors.

Staging of Bilateral Lung Transplantation for High-Risk Patients With Interstitial Lung Disease: One Lung at a Time.

The choice of a single or bilateral lung transplant for interstitial lung disease (ILD) is controversial, as surgical risk, long-term survival and organ allocation are competing factors. In an effort to balance risk and benefit, our center adopted a staged bilateral lung transplant approach for higher surgical risk ILD patients where the patient has a single lung transplant followed by a second single transplant at a later date. We sought to understand the surgical risk, organ allocation and early outcomes of these staged bilateral recipients as a group and in comparison to matched single and bilateral recipients. Our analysis demonstrates that staged bilateral lung transplant recipients (n = 12) have a higher lung allocation score (LAS), lower pulmonary function tests and a lower glomerular filtration rate prior to the first transplant compared to the second (p < 0.01). There was a shorter length of hospital stay for the second transplant (p = 0.02). The staged bilateral compared to the single and bilateral case-matched controls had comparable short-term survival (p = 0.20) and pulmonary function tests at 1 year. There was a higher incidence of renal injury in the conventional bilateral group compared to the single and staged bilateral groups. The staged bilateral procedure is a viable option in select ILD patients.

Antibody desensitization therapy in highly sensitized lung transplant candidates.

As HLAs antibody detection technology has evolved, there is now detailed HLA antibody information available on prospective transplant recipients. Determining single antigen antibody specificity allows for a calculated panel reactive antibodies (cPRA) value, providing an estimate of the effective donor pool. For broadly sensitized lung transplant candidates (cPRA ≥ 80%), our center adopted a pretransplant multi-modal desensitization protocol in an effort to decrease the cPRA and expand the donor pool. This desensitization protocol included plasmapheresis, solumedrol, bortezomib and rituximab given in combination over 19 days followed by intravenous immunoglobulin. Eight of 18 candidates completed therapy with the primary reasons for early discontinuation being transplant (by avoiding unacceptable antigens) or thrombocytopenia. In a mixed-model analysis, there were no significant changes in PRA or cPRA changes over time with the protocol. A sub-analysis of the median fluorescence intensity (MFI) change indicated a small decline that was significant in antibodies with MFI 5000-10,000. Nine of 18 candidates subsequently had a transplant. Posttransplant survival in these nine recipients was comparable to other pretransplant-sensitized recipients who did not receive therapy. In summary, an aggressive multi-modal desensitization protocol does not significantly reduce pretransplant HLA antibodies in a broadly sensitized lung transplant candidate cohort.

Coronary revascularization in lung transplant recipients with concomitant coronary artery disease.

Coronary artery disease (CAD) is not uncommon among lung transplant candidates. Several small, single-center series have suggested that short-term outcomes are acceptable in selected patients who undergo coronary revascularization prior to, or concomitant with, lung transplantation. Our objective was to evaluate perioperative and intermediate-term outcomes in this patient population at our institution. We performed a retrospective, observational cohort analysis of 898 lung transplant recipients between 1997 and 2010. Pediatric, multivisceral, lobar or repeat transplantations were excluded, resulting in 791 patients for comparative analysis, of which 49 (median age 62, 79.6% bilateral transplant) underwent concurrent coronary artery bypass and 38 (median age 64, 63.2% bilateral transplant) received preoperative percutaneous coronary intervention (PCI). Perioperative mortality, overall unadjusted survival and adjusted hazard ratio for cumulative risk of death were similar among both revascularization groups as well as controls. The rate of postoperative major adverse cardiac events was also similar among groups; however, concurrent coronary artery bypass was associated with longer postoperative length of stay, more time in the intensive care unit and more postoperative days requiring ventilator support. These results suggest that patients with CAD need not be excluded from lung transplantation. Preferential consideration should be given to preoperative PCI when feasible.

In the face of chronic aspiration, prolonged ischemic time exacerbates obliterative bronchiolitis in rat pulmonary allografts.

Aspiration of gastric fluid into the lung mediates the development of obliterative bronchiolitis (OB) in orthotopic WKY-to-F344 rat pulmonary transplants that have been subjected to immunosuppression with cyclosporine. However, the contribution of ischemic time to this process remains unknown. In this study, the effect of long (n = 16) and short (n = 12) ischemic times (average of 6 h and of 73 min, respectively) on rat lung transplants receiving aspiration of gastric fluid was assessed. Long ischemic times (LIT) led to significantly (p < 0.05) greater development of OB (ratio of OB lesions/total airways = 0.45 ± 0.07, mean ± standard error) compared to short ischemic times (ratio = 0.19 ± 0.05). However, the development of OB was dependent on aspiration, as controls receiving aspiration with normal saline showed little development of OB, regardless of ischemic time (p < 0.05). These data suggest that LIT, while insufficient by itself to lead to OB, works synergistically with aspiration of gastric fluid to exacerbate the development of OB.

Changes in neurocognitive functioning following lung transplantation.

Although neurocognitive impairment is relatively common among patients with advanced lung disease, little is known regarding changes in neurocognition following lung transplantation. We therefore administered 10 tests of neurocognitive functioning before and 6 months following lung transplantation and sought to identify predictors of change. Among the 49 study participants, native diseases included chronic obstructive pulmonary disease (n = 22), cystic fibrosis (n = 12), nonfibrotic diseases (n = 11) and other (n = 4). Although composite measures of executive function and verbal memory scores were generally within normal limits both before and after lung transplantation, verbal memory performance was slightly better posttransplant compared to baseline (p < 0.0001). Executive function scores improved in younger patients but worsened in older patients (p = 0.03). A minority subset of patients (29%) exhibited significant cognitive decline (i.e. >1 standard deviations on at least 20% of tests) from baseline to posttransplant. Patients who declined were older (p < 0.004) and tended to be less educated (p = 0.07). Lung transplantation, like cardiac revascularization procedures, appears to be associated with cognitive decline in a subset of older patients, which could impact daily functioning posttransplant.

Successful bilateral lung transplantation for lymphangiomatosis.

Lymphangiomatosis is a rare disease of lymphatic proliferation for which no adequate treatment is known. We report the first successful case of bilateral lung transplantation for the treatment of end-stage pulmonary lymphangiomatosis. A successful outcome was achieved with continued survival beyond 4 years posttransplant and stable lung function. The primary obstacles to significant gains in pulmonary function were thoracic, skeletal and abdominal lymphangiomatosis, which led to pulmonary restriction. Our report demonstrates that pulmonary lymphangiomatosis should be included among those diseases for which lung transplantation is considered potentially beneficial treatment but also emphasizes the importance of screening patients carefully for chest wall and abdominal lymphangiomas that may impede recovery.

Survival after lung transplantation of cystic fibrosis patients infected with Burkholderia cepacia complex.

Within the Burkholderia cepacia complex (Bcc), B. cenocepacia portends increased mortality compared with other species. We investigated the impact of Bcc infection on mortality and re-infection following lung transplant (LT). Species designation for isolates from Bcc-infected patients was determined using 16S rDNA and recA gene analyses. Of 75 cystic fibrosis patients undergoing LT from September 1992 to August 2002, 59 had no Bcc and 16 had Bcc (including 7 B. cenocepacia) isolated in the year before LT. Of the latter, 87.5% had Bcc recovered after transplantation, and all retained their pretransplant strains. Survival was 97%, 92%, 76% and 63% for noninfected patients; 89%, 89%, 67% and 56% for patients infected with Bcc species other than B. cenocepacia; and 71%, 29%, 29% and 29% for patients with B. cenocepacia (p = 0.014) at 1 month, 1 year, 3 years and 5 years, respectively. Patients infected with B. cenocepacia before transplant were six times more likely to die within 1 year of transplant than those infected with other Bcc species (p = 0.04) and eight times than noninfected patients (p < 0.00005). Following LT, infection with Bcc species other than B. cenocepacia does not significantly impact 5-year survival whereas infection with B. cenocepacia pretransplant is associated with decreased survival.

Baseline 6-min walk distance predicts survival in lung transplant candidates.

In a large, prospectively followed, two-center cohort of patients listed for lung transplantation (n = 376), we used Cox proportional hazards models to determine the importance of baseline 6-min walk distance (6MWD) in predicting patient survival. 6MWD used as a continuous variable was a significant predictor of survival after adjusting for other important covariates when transplant was considered as a time-varying covariate (HR for each 500 ft increase in 6MWD = 0.57, 95% CI: 0.43-0.77, p = 0.0002). 6MWD remained an important predictor of survival in models that considered only survival to transplant (HR for each 500 ft increase in 6MWD = 0.41, 95% CI: 0.27-0.62, p < 0.0001) or survival only after transplant (HR for each 500 ft increase in 6MWD = 0.40, 95% CI: 0.22-0.72, p = 0.002). Unadjusted Kaplan-Meier analysis demonstrates significantly different survival by 6MWD tertiles (<900, 900-1200, or >1200 ft, p-value = 0.0001). In the overall model, 6MWD prediction of survival was relatively homogeneous across disease category (6MWD by disease interaction term, p-value = 0.63). Our results demonstrate a significant relationship between baseline 6MWD and survival among patients listed for lung transplantation that exists across all native disease categories and extends through transplantation. The 6MWD is thus a useful measure of both urgency and utility among patients awaiting lung transplantation.

Chronic aspiration of gastric fluid induces the development of obliterative bronchiolitis in rat lung transplants.

Long-term survival of a pulmonary allograft is currently hampered by obliterative bronchiolitis (OB), a form of chronic rejection that is unique to lung transplantation. While tracheobronchial aspiration from gastroesophageal reflux disease (GERD) has clinically been associated with OB, no experimental model exists to investigate this problem. Using a WKY-to-F344 rat orthotopic left lung transplant model, the effects of chronic aspiration on pulmonary allograft were evaluated. Recipients received cyclosporine with or without 8 weekly aspirations of gastric fluid into the allograft. Six (66.7%) of 9 allografts with aspiration demonstrated bronchioles with surrounding monocytic infiltrates, fibrosis and loss of normal lumen anatomy, consistent with the development of OB. In contrast, none of the allografts without aspiration (n = 10) demonstrated these findings (p = 0.002). Of the grafts examined grossly, 83% of the allografts with chronic aspiration but only 20% without aspiration appeared consolidated (p = 0.013). Aspiration was associated with increased levels of IL-1 alpha, IL-1 beta, IL-6, IL-10, TNF-alpha and TGF-beta in BAL and of IL-1 alpha, IL-4 and GM-CSF in serum. This study provides experimental evidence linking chronic aspiration to the development of OB and suggests that strategies aimed at preventing aspiration-related injuries might improve outcomes in clinical lung transplantation.

Chronic aspiration shifts the immune response from Th1 to Th2 in a murine model of asthma.

BACKGROUND: Chronic aspiration associated with gastro oesophageal reflux disease (GERD) is thought to play a substantial role in the development of asthma, the incidence of which is dramatically increasing in industrially developed countries. The majority of data examining the association between aspiration and asthma has been obtained from epidemiological studies, which show that between 50 and 90% of individuals with asthma experience some element of GERD. This study describes the effect of chronic aspiration on a model of experimentally induced airway hypersensitivity in Balb/c mice. MATERIALS AND METHODS: Four experimental groups were utilized: Aspiration/Asthma, Sham/Asthma, Aspiration/Sham and Sham/Sham. Mice were sensitized with aerosolized 1% ovalbumin on days 1 to 10 (sensitization phase), followed by repeated exposure on days 31 to 40 (challenge phase). Aspiration events occurred on days 1, 8,15, 22, 29, 36, 43 and 50. Animals were sacrificed on days 56 and 57. RESULTS: Chronic aspiration of 10 microL of murine gastric fluid per week for eight weeks produced an injury pattern distinct from that of acute aspiration, with lung injury characterized by hyperplasia, neutrophil infiltration of the bronchioles and relative parenchymal sparing. Aspiration during induction of ovalbumin-induced airway hypersensitivity was associated with a trend toward decreased production of antiovalbumin IgG, antiovalbumin IgE, and total IgE. Further, aspiration induced a substantial and significant increase in antiovalbumin IgG1/IgG2a ratios, consistent with a shift toward a predominantly Th2 response. CONCLUSION: These findings indicate that chronic aspiration has a profound effect on the nature of the immune response to aerosolized allergens in a model of experimentally induced airway hypersensitivity.

The role of antibodies in acute vascular rejection of pig-to-baboon cardiac transplants.

Long-term success in xenotransplantation is currently hampered by acute vascular rejection. The inciting cause of acute vascular rejection is not yet known; however, a variety of observations suggest that the humoral immune response of the recipient against the donor may be involved in the pathogenesis of this process. Using a pig-to-baboon heterotopic cardiac transplant model, we examined the role of antibodies in the development of acute vascular rejection. After transplantation into baboons, hearts from transgenic pigs expressing human decay-accelerating factor and CD59 underwent acute vascular rejection leading to graft failure within 5 d; the histology was characterized by endothelial injury and fibrin thrombi. Hearts from the transgenic pigs transplanted into baboons whose circulating antibodies were depleted using antiimmunoglobulin columns (Therasorb, Unterschleisshein, Germany) did not undergo acute vascular rejection in five of six cases. Biopsies from the xenotransplants in Ig-depleted baboons revealed little or no IgM or IgG, and no histologic evidence of acute vascular rejection in the five cases. Complement activity in the baboons was within the normal range during the period of xenograft survival. In one case, acute vascular rejection of a xenotransplant occurred in a baboon in which the level of antidonor antibody rose after Ig depletion was discontinued. This study provides evidence that antibodies play a significant role in the pathogenesis of acute vascular rejection, and suggests that acute vascular rejection might be prevented or treated by therapies aimed at the humoral immune response to porcine antigens.

Beta(2)-adrenergic and several other G protein-coupled receptors in human atrial membranes activate both G(s) and G(i).

Cardiac G protein-coupled receptors that couple to Galpha(s) and stimulate cAMP formation (eg, beta-adrenergic, histamine, serotonin, and glucagon receptors) play a key role in cardiac inotropy. Recent studies in rodent cardiac myocytes and transfected cells have revealed that one of these receptors, the beta(2)-adrenergic receptor (AR), also couples to the inhibitory G protein Galpha(i) (activation of which inhibits cAMP formation). If beta(2)ARs could be shown to couple to Galpha(i) in the human heart, it would have important ramifications, because levels of Galpha(i) increase with age and in failing human heart. Therefore, we investigated whether beta(2)ARs in the human heart activate Galpha(i). By photoaffinity labeling human atrial membranes with [(32)P]azidoanilido-GTP, followed by immunoprecipitation with antibodies specific for Galpha(i), we found that Galpha(i) is activated by stimulation of beta(2)ARs but not of beta(1)ARs. In addition, we found that other Galpha(s)-coupled receptors also couple to Galpha(i), including histamine, serotonin, and glucagon. When coupling of these receptors to Galpha(i) is disrupted by pertussis toxin, their ability to stimulate adenylyl cyclase is enhanced. These data provide the first evidence that beta(2)AR and many other Galpha(s)-coupled receptors in human atrium also couple to Galpha(i) and that abolishing the coupling of these receptors to Galpha(i) increases the receptor-mediated adenylyl cyclase activity.

A randomized, placebo-controlled trial of complement inhibition in ischemia-reperfusion injury after lung transplantation in human beings.

OBJECTIVE: Complement activation has been shown to play a significant role in ischemia-reperfusion injury after lung transplantation. TP-10 (soluble complement receptor 1 inhibitor) inhibits the activation of complement by inactivating C3a and C5a convertases. This was a clinical trial of TP-10 to reduce ischemia-reperfusion injury in lung transplantation. METHODS: In a randomized, double-blinded, multicenter, placebo-controlled trial, 59 patients from four lung transplant programs received TP-10 (10 mg/kg, n = 28) or placebo (n = 31) before reperfusion. This dose achieved 90% complement inhibition for 24 hours, and activity had returned toward normal by 72 hours. RESULTS: At 24 hours, 14 of 28 patients in the TP-10 group (50%) were extubated, whereas only 6 of 31 patients in the placebo group (19%) were (P = .01). The total times on the ventilator and in the intensive care unit both tended to be shorter in the TP-10 group, but these differences did not achieve statistical significance. Among patients requiring cardiopulmonary bypass (n = 5 in placebo group and n = 7 in TP-10 group), the mean duration of mechanical ventilation was reduced by 11 days in the TP-10 group (10.6 +/- 5.0 days vs 21.5 +/- 5.9 days in placebo group, P = .2). Operative deaths, incidences of infection and rejection, and length of hospital stay were not significantly different between the two groups. CONCLUSIONS: Short-term complement inhibition with TP-10 led to early extubation in a significantly higher proportion of lung transplant recipients. The effect of TP-10 was greater among patients undergoing cardiopulmonary bypass, with a large reduction in ventilator days. Complement inhibition thus significantly decreases the duration of mechanical ventilation and could be useful in improving the outcome of lung transplant recipients.

Oral feeding with pig peripheral lymphocytes decreases the xenogeneic delayed type hypersensitivity reaction in galactosyltransferase knockout mice.

PURPOSE: Oral tolerance induction has shown promising results in experimental allotransplantation models but is not well investigated in xenotransplantation. We investigated the possibility to induce tolerance against pig peripheral lymphocytes (pPBL) in galactosyltransferase knockout mice (gal -/-), which produce antibodies against Galalpha1-3Gal. MATERIAL AND METHODS: Female (gal -/-) mice 6 to 8 weeks old weighing 35 to 40 g (n = 10) were fed orally every third day five times with 2 x 10(7) isolated, viable pPBL, or with phosphate-buffered saline (PBS) only (n = 7). They were then immunized subcutaneously on day 0 with a subcellular lysate from 4 x 10(7) isolated, viable pPBL. On day 13, 25 microL of a subcellular lysate corresponding to 1 x 10(7) isolated, viable pPBL was injected in the right dorsal foot pad, and the delayed type hypersensitivity (DTH) reaction was calculated after 24 hours by subtracting the swelling response from 25 microL PBS in the left footpad. Anti-Galalpha1-3Gal immunoglobulin IgG and IgM antibody titers were measured in the serum before oral feeding and at day 14. RESULTS: The DTH reaction of the pPBL fed mice was 0.07 +/- 0.05 mm vs 0.57 +/- 0.23 mm for the controls (P < .001). No significant differences in anti Gal alpha1-3 Gal IgG and IgM antibody titers were seen. CONCLUSIONS: This study demonstrates for the first time that oral delivery of pPBL can counteract the indirect T-cell reaction against xenogeneic subcellular antigens from pPBL. These observations warrant further investigation in immunologically modified mice and perhaps in primate models of xenotransplantation.

Delirium affects length of hospital stay after lung transplantation.

BACKGROUND: Delirium is relatively common after lung transplantation, although its prevalence and prognostic significance have not been systematically studied. The purpose of the present study was to examine pretransplant predictors of delirium and the short-term impact of delirium on clinical outcomes among lung transplant recipients. METHODS: Participants underwent pretransplant cognitive testing using the Repeatable Battery for the Assessment of Neuropsychological Status and the Trail Making Test. After transplant, delirium was assessed using the Confusion Assessment Method until discharge. RESULTS: Sixty-three patients were transplanted between March and November 2013, of which 23 (37%) developed delirium. Among transplanted patients, 48 patients completed pretransplant cognitive testing. Better pretransplant cognitive function was associated with lower risk of delirium (odds ratio, 0.69 [95% confidence interval 0.48, 0.99], P = .043); and demographic and clinical features including native disease (P = .236), the Charlson comorbidity index (P = .581), and the lung allocation score (P = .871) were unrelated to risk of delirium, although there was a trend for women to experience delirium less frequently (P = .071). The presence (P = .006) and duration (P = .027) of delirium were both associated with longer hospital stays. CONCLUSION: Delirium occurs in more than one-third of patients after lung transplantation. Delirium was associated with poorer pretransplant cognitive functioning and longer hospital stays, after accounting for other medical and demographic factors.

Fungal infections in lung and heart-lung transplant recipients. Report of 9 cases and review of the literature.

We reviewed the pattern and incidence of fungal infections in patients undergoing lung and heart-lung transplantation at Duke University Medical Center from September 1992 until August 1995, and present here 9 illustrative cases. Of the 73 lung and heart-lung transplant recipients studied, 59 (81%) had positive fungal cultures at some point after transplantation. The cases presented here illustrate that lung transplant recipients are predisposed to a wide variety of fungal infections. The clinical pattern of these infections ranges from asymptomatic to rapidly progressive fatal disease. In addition to the reactivation of previous fungal infections and recent exposure to new environmental sources, the donor lung itself can be the source of fungal infection, as we showed by using molecular epidemiology techniques. Because of the associated morbidity and mortality, efforts should be directed at investigating prophylactic antifungal regimens in lung transplant recipients. Preliminary reports on the use of itraconazole and aerosolized amphotericin B have been encouraging. Prospective randomized studies are needed to assess the safety and cost effectiveness of different regimens. Fungal infections in patients after lung transplantation can significantly impede recovery and lead to substantial mortality.

Isothiocyanate-substituted benzyl ether opioid receptor ligands derived from 6 beta-naltrexol.

A series of regioisomeric substituted 6-O-benzyl ethers of 6 beta-naltrexol (12) in which isothiocyanate groups were attached directly to or one carbon removed from the aromatic ring of the benzyl group were prepared. These agents were prepared to obtain electrophilic opioid ligands potentially useful in the characterization of opioid receptors and drug-receptor interactions. Preparation of these ligands was accomplished from 3-O-trityl-6 beta-naltrexol (13) via phase transfer-catalyzed alkylation of the regioisomeric o-, m-, and p-nitrobenzyl halides and the o-, m-, and p-cyanobenzyl halides. The intermediates were deprotected and reduced, and formation of the isothiocyanates from the corresponding amines completed the synthesis. The ligands (6-11) were tested in radioligand displacement assays in guinea pig brain homogenate for opioid receptor binding affinity and irreversibility. All six of the isothiocyanates demonstrated significant affinity in the displacement assays for all three opioid receptors. They also appeared to be irreversibly bound at each of the receptor types. Compound 6, the o-isothiocyanatobenzyl ether analog, had the highest affinity, and it demonstrated significant irreversibility at very low concentration. It appears to be suitable for further investigation.

Isothiocyanate-substituted kappa-selective opioid receptor ligands derived from N-methyl-N-[(1S)-1-phenyl-2-(1-pyrrolidinyl)ethyl] phenylacetamide.

The synthesis of isothiocyanate-substituted kappa-selective opioid ligands derived from N-methyl-N-[(1S)-1-phenyl-2-(1-pyrrolidinyl)ethyl]ethyl]phenylacetami de (8) and their effects in radioligand displacement assays are reported. Ligands 3-5 with the S-absolute configuration were prepared with the isothiocyanate functionality at the 2-, 3-, and 4-positions in the phenylacetamide aromatic ring. The 2-isothiocyanato-4,5-dichlorophenylacetamide 6 was prepared to evaluate the effect of 4,5-dichloro substitution in the same aromatic ring as the 2-isothiocyanate function. N-Methyl-N-[(1S)-1-(4-isothiocyanatophenyl)-2-(1-pyrrolidinyl) ethyl]-3,4-dichlorophenylacetamide (7), with the 4-isothiocyanate function in the 1-phenyl ring, was prepared for comparison with the other compounds in the series. Of the prepared ligands, 7 and 8 (IC50s congruent to 1.4-1.8 nM) were approximately equal in affinity with 2 (ICI-199,441), followed by 3 and 6. All of these compounds were more kappa-selective than 2, as well. The binding characteristics of 8 show that the previously reported 4,5-dichloro substitution is not required for high affinity and kappa-selectivity. All of the synthesized isothiocyanate-substituted ligands irreversibly inhibited radioligand binding to guinea pig brain membrane preparations, including compound 2 (ICI-199,441) which had no isothiocyanate functionality.