Echoendoscopic ultrasound pancreatic adenocarcinoma diagnosis and theranostic approach: should KRAS mutation research be recommended in everyday practice?

Background

The impact of KRAS mutation testing on pancreatic ductal adenocarcinoma (PDAC) samples by endoscopic ultrasound-guided fine-needle aspiration (EUS-FNA) for reducing the need to repeat EUS-FNA has been demonstrated. Such testing however is not part of standard practice for endoscopic ultrasound-guided fine-needle biopsy (EUS-FNB).

Objectives

We aim to analyse the proportion of non-contributive samples by EUS-FNB and to evaluate the impact of KRAS mutation testing on the diagnosis, theranostics and survival.

Design

In this retrospective study, the impact on diagnosis and survival of KRAS testing for contributive and non-contributive samples by EUS-FNB was analysed.

Methods

The EUS-FNB samples, combined with KRAS testing using the Idylla® technique on liquid-based cytology from patients with PDAC between February 2019 and May 2023, were retrospectively reviewed. The cytology results were classified according to the guidelines of the World Health Organization System for Reporting Pancreaticobiliary Cytopathology (WHOSRPC).

Results

A total of 85 EUS-FNB specimens were reviewed. In all, 25 EUS-FNB samples did not lead to a formal diagnosis of PDAC according to the WHOSRPC (30.2%). Out of these 25, 11 (44%) could have been considered positive for a PDAC diagnosis thanks to the KRAS mutation test without carrying out further diagnosis procedures. The sensitivity of KRAS mutation testing using the Idylla technique was 98.6%. According to the available data, survival rates were not statistically different depending on the type of mutation.

Conclusion

KRAS mutation testing on liquid-based cytology using the Idylla or equivalent technique, combined with the PDAC EUS-FNB sample, should become a standard for diagnosis to avoid delaying treatment by doing another biopsy. Furthermore, knowledge of the KRAS status from treatment initiation could be used to isolate mutations requiring targeted treatments or inclusion in clinical research trials, especially for wild-type KRAS PDAC.

Standardized Pathology Screening of Mature Tertiary Lymphoid Structures in Cancers

Mature tertiary lymphoid structures (mTLSs) are organized lymphoid structures containing B lymphocytes admixed to CD23+ follicular dendritic cells. Their presence has been linked to improved survival and sensitivity to immune checkpoint inhibitors in several cancers, emerging as a promising pancancer biomarker. However, the requirements for any biomarker are clear methodology, proven feasibility, and reliability. In 357 patients' samples, we studied tertiary lymphoid structures (TLSs) parameters using multiplex immunofluorescence (mIF), hematoxylin-eosin-saffron (HES) staining, double CD20/CD23 staining, and single CD23 immunohistochemistry. The cohort included carcinomas (n = 211) and sarcomas (n = 146), gathering biopsies (n = 170), and surgical specimens (n = 187). mTLSs were defined as TLSs containing either a visible germinal center on HES staining or CD23+ follicular dendritic cells. Focusing on 40 TLSs assessed using mIF, double CD20/CD23 staining was less sensitive than mIF to assess maturity in 27.5% (n = 11/40) but was rescued by single CD23 staining in 90.9% (n = 10/11). In 97 patients, several samples (n = 240) were reviewed to characterize TLS distribution. The likelihood of finding TLSs in surgical material was 6.1 higher than in biopsy and 2.0 higher in primary samples than in metastasis after adjustment with a type of sample. Interrater agreement rates over 4 examiners were 0.65 (Fleiss kappa, 95% CI [0.46; 0.90]) for the presence of TLS and 0.90 for maturity (95% CI [0.83;0.99]). In this study, we propose a standardized method to screen mTLSs in cancer samples using HES staining and immunohistochemistry that can be applied to all specimens.

Cystic Granulosa Cell Tumors of the Ovary

CONTEXT.—

Granulosa cell tumors (GCTs) of both adult (AGCT) and juvenile (JGCT) types can rarely be completely or dominantly cystic, creating diagnostic difficulty because the cyst lining epithelium is often denuded.

OBJECTIVE.—

To describe clinical, gross, microscopic, immunohistochemical, and molecular features of cystic GCTs with an emphasis on their differential diagnosis.

DESIGN.—

We report 80 cystic GCTs (24 AGCTs and 56 JGCTs) in patients from ages 3 to 83 years (average ages, 35 years for AGCT and 22 years for JGCT).

RESULTS.—

Nineteen of 43 patients with known clinical information (3 AGCT and 16 JGCT) had androgenic manifestations. All tumors were greater than 8 cm (average, 17 cm) with minimal to absent gross solid component. Denudation of cells lining the cysts was prominent. Invagination of the epithelium into the cyst walls was a key diagnostic feature and was present as cords, trabeculae, solid nests, and small and large follicles and was identified in most tumors (17 AGCTs and 45 JGCTs). Cytologic atypia was essentially absent in AGCTs, whereas 14 JGCTs showed moderate to severe atypia of bizarre type. A theca cell component was present in all tumors and was extensive in 54. A FOXL2 hotspot mutation was identified in 1 of 4 AGCTs tested.

CONCLUSIONS.—

Despite extensive denudation, the finding of typical architectural patterns and cytologic features as well as, in some cases, androgenic manifestations helps differentiate cystic GCTs from follicle cysts, the most common and challenging differential diagnosis, as well as other cystic neoplasms that may enter the differential diagnosis. FOXL2 sequencing may show a false-negative result in cystic AGCT because of the limited number of cells present within the tumor sample.

Breast hamartoma: reassessment of an underrecognized breast lesion

AIMS

Breast hamartomas are an under-recognized lesion because they lack a distinctive microscopic appearance. Microscopic diagnosis can often conclude "no significant lesion" or "normal breast tissue", leading to repeated biopsies and diagnostic delay. We describe the histological, immunohistochemical and radiological features of breast hamartomas in the aim of identifying specific signs to facilitate their diagnosis and to differentiate them from normal breast and fibroepithelial lesions. METHODS AND RESULTS: Forty-seven breast hamartomas were reassessed (histological diagnosis and imaging features). An immunohistochemical study (ER, PR, CD34, HMGA2) was performed. On breast imaging, hamartomas most often presented as probably benign solid masses with circumscribed margins and variable densities. Histologically, breast hamartomas resembled normal breast, although their stromal component was predominant, separating randomly scattered epithelial elements, with areas of pure collagenous stroma. Pseudo angiomatous stromal hyperplasia (PASH) was present in 93.6% of cases and CD34 antibody highlighted intralobular, perilobular and interlobular distribution of CD34-positive fibroblasts. By comparison, CD34 was mostly expressed in the intralobular normal breast tissue stroma. Hamartoma stromal cells expressed HMGA2, ER and PR in 79%, 66% and 76.3% of our cases, respectively, compared to 7.7%, 23% and 19% in normal breast tissue, respectively (P<0.0001; P=0.0005; P<0.0001).

CONCLUSIONS

After ascertaining that core needle biopsy is effectively intralesional, breast hamartomas can be diagnosed with confidence by taking into account the presence of stromal changes, PASH, interlobular distribution of CD34-positive fibroblasts, HMGA2 and hormonal receptor stromal expression.

A subset of epithelioid and spindle cell rhabdomyosarcomas is associated with TFCP2 fusions and common ALK upregulation

Rhabdomyosarcomas with TFCP2 fusions represent an emerging subtype of tumors, initially discovered by RNA-sequencing. We report herein the clinicopathological, transcriptional, and genomic features of a series of 14 cases. Cases were retrospectively and prospectively recruited and studied by immunohistochemistry (MYF4, MYOD1, S100, AE1/E3, ALK), fluorescence in situ hybridization with TFCP2 break-apart probe (n = 10/14), array-comparative genomic hybridization (Agilent), whole RNA-sequencing (Truseq Exome, Illumina), or anchored multiplex PCR-based targeted next-generation sequencing (Archer® FusionPlex® Sarcoma kit). Patient's age ranged between 11 and 86 years, including 5 pediatric cases. Tumors were located in the bone (n = 12/14) and soft tissue (n = 2/14). Most bone tumors invaded surrounding soft tissue. Craniofacial bones were over-represented (n = 8/12). Median survival was 8 months and five patients are currently alive with a median follow-up of 20 months. Most tumors displayed a mixed spindle cell and epithelioid pattern with frequent vesicular nuclei. All tumors expressed keratins and showed a rhabdomyogenic phenotype (defined as expression of MYF4 and/or MYOD1). ALK was overexpressed in all but three cases without underlying ALK fusion on break-apart FISH (n = 5) nor next-generation sequencing (n = 14). ALK upregulation was frequently associated with an internal deletion at genomic level. TFCP2 was fused in 5' either to EWSR1 (n = 6) or FUS (n = 8). EWSR1 was involved in both soft tissue cases. FISH with TFCP2 break-apart probe was positive in all tested cases (n = 8), including one case with unbalanced signal. On array-CGH, all tested tumors displayed complex genetic profiles with genomic indexes ranging from 13 to 107.55 and recurrent CDKN2A deletions. FET-TFCP2 rhabdomyosarcomas clustered together and distinctly from other rhabdomyosarcomas subgroups. Altogether, our data confirm and expand the spectrum of the new family of FET-TFCP2 rhabdomyosarcomas, which are associated with a predilection for the craniofacial bones, an aggressive course, and recurrent pathological features. Their association with ALK overexpression might represent a therapeutic vulnerability.

Hepatotoxicities Induced by Neoadjuvant Chemotherapy in Colorectal Cancer Liver Metastases: Distinguishing the True From the False

Background:

Pre-operative chemotherapy for colorectal liver metastasis (CRLM) is thought to be the cause of hepatotoxicity of non-tumoural parenchyma. Studies on hepatotoxicity are contradictory. We investigated the impact of a single-line pre-operative chemotherapy on non-tumoural liver analysed by an expert hepatico-pancreatico-biliary pathologist, and the consequences on surgical outcomes.

Patients and methods:

Patients operated for CRLM, after a pure first-line pre-operative chemotherapy, were retrospectively included. Two comparative histopathological analyses were performed for vascular toxicity and steatohepatitis.

Results:

Between 2003 and 2015, 147 patients were included. Chemotherapy was based on oxaliplatin (40.1%), irinotecan (55.8%), or both (4.1%). The expert pathologist described 38.8% of vascular lesions including dilation, nodular regeneration, and peliosis. In multivariate analysis, vascular lesions correlated to male sex (P = .01), pre-operative platelets <150 g/L (P = .04), and aspartate aminotransferase to platelet ratio index (APRI) score >0.36 (P = .02). Steatohepatitis was observed in 15 patients (10.2%), more frequently after irinotecan (14.8% vs 3.4%, P = .01; odds ratio [OR] = 7.3; 95% confidence interval [CI] = [1.5-34.7]), and for patients with body mass index (BMI) >25 kg/m² (P = .004; OR = 10.0; 95% CI = [2.1-47.5]). A total of 29 patients (19.7%) developed major complications with 2 risk factors: portal vein obstruction (PVO) and septic surgery. Reproducibility assessment of steatohepatitis and dilated lesions by 2 pathologists showed moderate agreement (Kappa score 0.53 and 0.54, respectively).

Conclusions:

There is a probable association between non-alcoholic steatohepatitis (NASH) and irinotecan. Oxaliplatin seems to lead to higher vascular lesions. Except in the presence of pre-existent comorbidities, liver toxicities should not restrain the use of pre-operative chemotherapy prior to parenchymal-sparing surgery.

GREB1-CTNNB1 fusion transcript detected by RNA-sequencing in a uterine tumor resembling ovarian sex cord tumor (UTROSCT): A novel CTNNB1 rearrangement

Mutations of CTNNB1 have been implicated in tumorigenesis in many organs. However, tumors harboring a CTNNB1 translocation are extremely rare and this translocation has never been reported in a uterine mesenchymal neoplasm. We report a novel translocation t(2;3)(p25;p22) involving the GREB1 (intron 8) and CTNNB1 (exon 3) in a uterine tumor resembling ovarian sex cord tumor (UTROSCT), which exhibited extrauterine metastasis. The translocation detected by RNA-sequencing was validated by RT-PCR, and resulted in nuclear expression of β-catenin. Juxtapositioning with GREB1, which is overexpressed in response to estrogens, resulted in overexpression of a truncated and hypophosphorylated nuclear β-catenin in the primary and recurrent tumors. This accumulation of nuclear β-catenin results in a constitutive activation of the Wnt/β-catenin signaling pathway with a major oncogenic effect. The CTNNB1 gene fusion, promoted by an estrogen-responsive gene (GREB1), could be a potential driver of tumorigenesis in this case and a therapeutic target with adapted inhibitors. RT-PCR and immunohistochemistry performed on 11 additional UTROSCTs showed no CTNNB1 fusion transcript or nuclear β-catenin immunoreactivity.

Parenchymal sparing surgery brings treatment of colorectal liver metastases into the precision medicine era

The treatment of advanced colorectal liver metastases (CRLMs) follows the biphasic pattern characteristic of oncological surgery. A phase of escalation-the therapeutic aggressiveness-is followed by a phase of de-escalation aimed at decreasing the morbidity, while preserving the gains in survival. From a maximum of three lesions, the rule no longer limits the number, provided the intervention does not cause lethal liver failure. Technically feasible non-anatomical resections, two-stage hepatectomies, portal vein obliteration and so forth, have pushed the boundaries of surgery far. However, the impact and the biology of metastatic processes have been long ignored. Parenchymal sparing surgery (PSS) is a de-escalation strategy that targets only metastasis by minimising the risk of stimulating tumour growth, while enabling iterative interventions. Reducing the loss of healthy parenchyma increases the tolerance of the liver to interval chemotherapy. Technically, PSS could use any type of hepatectomy, providing it is centred on the metastatic load alongside intraoperative ablation. The PSS concept sometimes wrongly comes across as a debate between minor versus major hepatectomies. Hence, we propose a clear definition, both quantitative and qualitative, of what PSS is and what it is not. Conversely, the degree of selectivity of PSS as a percentage of the volume of resected metastases versus the volume of total liver removed has not been stopped to date and should be the subject of prospective studies. Ultimately, the treatment of advanced CRLMs, of which PSS is a part, needs to be personalised by the multidisciplinary team by adapting its response to each new recurrence.

Parenchymal sparing surgery for colorectal liver metastases: The need for a common definition

BACKGROUND

The definition of parenchymal sparing surgery (PSS) for colorectal liver metastases (CRLM) diverges requiring a clarification of the concept.

METHOD

A consecutive series of patients were treated by PSS for their CRLMs, either by resection or intra-operative ablation (IOA), whenever possible a one-stage surgery and minimal usage of portal vein embolization. Post-operative complications were the primary endpoint with a special focus on post-operative liver failure.

RESULTS

Three hundred and eighty-seven patients underwent a PSS out of which 328 patients received a median of 9 pre-operative cycles of chemotherapy. One hundred and twenty-eight patients had a major resection, combined with IOA in 137 patients and IOA alone in 50 cases. The 5yr-overall survival was 50.3%. There was no difference in post-operative complications between minor and major resections, validating our PSS definition based on the Tumor burden/Healthy liver ratio and not just the retrieved volume.

CONCLUSIONS

PSS is defined as a high ratio of tumoral burden per specimen retrieved while favoring one-stage surgery approach. Our series, using combined resections and IOAs, matches this definition well. Furthermore, complications were correlated neither to chemotherapy nor to liver-induced toxicities, contrary to extended hepatectomies.

Influence du score de Gleason des marges chirurgicales de prostatectomie totale sur la récidive biologique

OBJECTIVES

The aim of this study was to assess the impact of the aggressiveness of cancer cells at the level of positive surgical margins (PSM) on the biochemical recurrence rate (BRR) by studying the Gleason score (GS) at this level.

METHODS

We included all radical prostatectomy (RP) procedures performed from January 2007 to November 2011. All of the RP specimens with PSM were reviewed to determine the GS at the level of PSM. We compared the GS at PSM with BRR.

RESULTS

A total of 658 RP were analysed, among which 16% had PSM. From the 101 patients with PSM included, 32% had biochemical recurrence (BR) with a median follow-up of 38 months. GS at PSM was significantly associated with earlier BR (P=0.008). Univariate analysis showed that GS at PSM (P=0.013), initial PSA (P<0.0001), pathologic GS (P<0.001), length of PSM (P=0.013), and seminal vesicle invasion (P<0.0001) were predictors of BR. Multivariate analysis confirmed that PSA greater than 10ng/mL and length of PSM greater than 3mm were independent prognostic factors for BR, but GS at the level of PSM was not.

CONCLUSION

GS at PSM was not confirmed as an independent risk factor for BR. Initial PSA greater than 10ng/mL and length of PSM greater than 3mm were the sole independent predictors for BR.

LEVEL OF PROOF

4.

Parenchymal sparing surgery for colorectal liver metastases: The need for a common definition

e15013

Background: Colorectal cancer metastases (CRLM) are major public health issue. Recently, surgeons have advocated the use of parenchymal sparing surgery (PSS) however, a common definition of the concept is lacking.To clarify and try to validate the concept of PSS to treat CRLM through the available retrospectives studies, including ours. Methods: Retrospective analysis of a cohort of patients treated by combined resections and intra-operative ablation (IOA) based on PSS, prospectively recorded in a database from 2003 to 2015 in a regional referral cancer center. All the patients benefited from the same strategy, constituting a homogenous series.PSS consists of using resection or IOA in order to spare the healthy parenchyma. One-stage is favored over two-stage surgery and use of portal vein embolization was restricted to the minimum.Post-operative complications were the primary endpoint with a special focus on post-operative liver failure. Liver toxicities and overall survival were also scrutinized. Results: Three hundred and eighty-seven patients underwent a PSS out of which 348 patients received a median of 9 pre-operative cycles of oxaliplatin or irinotecan with targeted therapies for half of them. Resection was major in 128 patients, combined with IOA in 137 patients and IOA alone in 50 cases. Thirty-eight patients had a PVO by strict necessity. The 5yr-overall survival was 50.3%. Seventy-eight patients had a complication > grade 3 out of which 10 patients died. Nine patients had a liver failure (LF) grade B and C and four died. There was no difference in post-operative complications comparing minor and major resections, validating our PSS definition. Chemotherapy and liver toxicity were not related to more post-operative complications. Only one patient died from a primitive LF. Conclusions: With PSS, healthy liver is no more a target. Routine use of chemotherapy does not impair the results and severe LFs are rare. PSS is the optimal strategy to treat CRLM. Definition of PSS cannot be based just on the retrived volume but on the ratio Tumor burden/Healthy liver. A major hepatectomy can be a PSS and a minor may not be one. That is why PSS defintion must be clarify especially for further prospective validations.

Molecular Pathology of Anaplastic Thyroid Carcinomas: A Retrospective Study of 144 Cases

BACKGROUND

Anaplastic thyroid carcinoma (ATC) is a rare tumor, with poorly defined oncogenic molecular mechanisms and limited therapeutic options contributing to its poor prognosis. The aims of this retrospective study were to determine the frequency of anaplastic lymphoma kinase (ALK) translocations and to identify the mutational profile of ATC including TERT promoter mutations.

METHODS AND MATERIALS

One hundred and forty-four ATC cases were collected from 10 centers that are a part of the national French network for management of refractory thyroid tumors. Fluorescence in situ hybridization analysis for ALK rearrangement was performed on tissue microarrays. A panel of 50 genes using next-generation sequencing and TERT promoter mutations using Sanger sequencing were also screened.

RESULTS

Fluorescence in situ hybridization was interpretable for 90 (62.5%) cases. One (1.1%) case was positive for an ALK rearrangement with a borderline threshold (15% positive cells). Next-generation sequencing results were interpretable for 94 (65.3%) cases, and Sanger sequencing (TERT) for 98 (68.1%) cases. A total of 210 mutations (intronic and exonic) were identified. TP53 alterations were the most frequent (54.4%). Forty-three percent harbored a mutation in the (H-K-N)RAS genes, 13.8% a mutation in the BRAF gene (essentially p.V600E), 17% a PI3K-AKT pathway mutation, 6.4% both RAS and PI3K pathway mutations, and 4.3% both TP53 and PTEN mutations. Nearly 10% of the cases showed no mutations of the RAS, PI3K-AKT pathways, or TP53, with mutations of ALK, ATM, APC, CDKN2A, ERBB2, RET, or SMAD4, including mutations not yet described in thyroid tumors. Genes encoding potentially druggable targets included: mutations in the ATM gene in four (4.3%) cases, in ERBB2 in one (1.1%) case, in MET in one (1.1%) case, and in ALK in one (1.1%) case. A TERT promoter alteration was found in 53 (54.0%) cases, including 43 C228T and 10 C250T mutations. Three out of our cases did not harbor mutations in the panel of genes with therapeutic interest.

CONCLUSION

This study confirms that ALK rearrangements in ATC are rare and that the mutational landscape of ATC is heterogeneous, with many genes implicated in the follicular epithelial cell dedifferentiation process. This may explain the limited effectiveness of targeted therapeutic options tested so far.

An investigation of the role of irinotecan and oxaliplatin in liver toxicity during first-line neoadjuvant chemotherapy

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Background: Neoadjuvant chemotherapy (CT) have been associated with an increased risk of surgery for colorectal liver metastases (CRLM). Irinotecan (IRI) is claimed to induce CT-associated steatohepatitis (CASH) and oxaliplatin (OX) to induce sinusoidal obstruction (SOS). Imputability is sometimes difficult to establish and the impact on postoperative complications is unclear. The objective of this study is to investigate the impact of IRI and OX on induced liver toxicity, and to study the effects of toxicity on surgical outcomes. Methods: Patients (Pts) who received only one line of CT before resection of CRLM were retrospectively included. CASH and SOS were described according to Kleiner and Rubbia-Brandt classifications respectively. Associations were sought between CASH or SOS and various patient and treatment factors, and between patient and treatment factors and the occurrence of post-operative complications grade 3 or over. Results: Among 379 pts operated on for CRLM from 2003 to 2013, 223 were eligible for inclusion; 57 were excluded as there was no healthy hepatic parenchyma to be analyzed. Median age was 64 y [34-88], BMI ≥25 kg/m² for 52%, 8% had diabetes, and 28% had a dyslipidemia. CRLM were synchronous in 76.5%. 65 (39.2%) received Folfox, 95 (57.2%) Folfiri and 6 (3.6%) Folfirinox. Bevacizumab, cetuximab and panitumumab were given in 71 (42.8%), 30 (17.5%), 4 (2.4%) respectively. Extra-hepatic resections were performed in 78 pts (47%). 90-day mortality was 1.8% and 31 pts encountered complications more severe than 3A. Histological hepatoxicity was established for 82 pts (49%) including 33 (19.9%) with grade 2 or 3 SOS and 22 (13%) with CASH. No significant associations were identified between SOS and OX, nor CASH and IRI. BMI ≥ 25 kg/m² was correlated with an increased risk of CASH. Only septic extra-hepatic surgeries were correlated with the prediction of postoperative complications. Conclusions: In this selected series, preoperative CT was not associated to liver toxicity. The presence of histological lesions did not worsen post-operative outcomes. BMI and extra-hepatic surgery were the only co-factors correlated with CASH and post-operative complications respectively.

A reversed-phase high-performance liquid chromatographic method to analyze retinal isomers

A high-performance liquid chromatographic (HPLC) procedure was developed to separate all-trans-, 13-cis-, 11-cis- and 9-cis-retinal isomers. Two reversed-phase Vydac C18 columns in series were used with an isocratic solvent system of 0.1 M ammonium acetate-acetonitrile (40:60, v/v) as mobile phase and all-trans-9-(4-methoxy-2,3,6-trimethylphenyl)-3,7-dimethyl-2,4,6,8-no natetraene-1-ol (TMMP) as internal standard. Prior to HPLC, the retinal isomers were efficiently extracted in their original isomeric conformation using dichloromethane-n-hexane in the presence of formaldehyde. This technique is suitable for the assay of 11-cis- and all-trans-retinal isomers in retina.

Effect of a cGMP-specific phosphodiesterase inhibitor on retinal function

Multiple forms of phosphodiesterase have been reported in many tissues. Phosphodiesterase 6, a cGMP-specific phosphodiesterase, is described as a photoreceptor cell-specific phosphodiesterase. Phosphodiesterase 6 is known to play a crucial role in visual function. A novel phosphodiesterase inhibitor, GF248 (5["(propoxy),7'(4-morpholino)-phenacyl],[1-methyl-3 propyl]pyrazolo[4,3d]pyrimidin-7-one), has been described to be a very potent cGMP-specific phosphodiesterase inhibitor. In the present study, we compared the potency of GF248 and other known cGMP-specific phosphodiesterase inhibitors on phosphodiesterase 5 and phosphodiesterase 6. GF248 displayed an IC50 of 2 and 5 nM for phosphodiesterase 5 and phosphodiesterase 6, respectively. Thereafter, we assessed the effect of GF248 on retinal function, using an ex vivo model of isolated retina electroretinogram recording. Exposure of retina to GF248 resulted in a dose-dependent decrease in electroretinogram amplitude (PIII and b-waves), with no marked modification of PIII and b-wave implicit time. Among other phosphodiesterase inhibitors, DMPPO (1,3-dimethyl-6-(2-propoxy-5-methanesulfonylamidophenyl)pyrazol ol[3,4d]-pyrimidin-4-(5H)-one) and dipyridamole, cGMP-specific phosphodiesterase inhibitors, and IBMQ (1-isobutyl-3-methylimidazol[1,5a]quinoxalin-4-(5H)one), a nonselective phosphodiesterase inhibitor, altered retinal function but less potently than GF248, consistent with their in vitro phosphodiesterase 6 inhibition. Phosphodiesterase 3- and phosphodiesterase 4-selective inhibitors, cilostamide and rolipram, respectively, did not affect retinal function at 10 micromol l(-1). Our conclusion from these data is that GF248, a potent phosphodiesterase 6 inhibitor, could interfere with visual transduction by cGMP accumulation.

Protective effect of a specific PAF antagonist on vincristine-induced experimental retinopathy

The alkaloid vincristine displays considerable toxicity, particularly for the retina. This type of retinopathy being an inflammatory disease, we measured the effects of a new hetrazepine platelet activating factor antagonist, BN 50730, on a vincristine-induced retinopathy in the rat. Retinal impairments were established by recording several parameters of the electroretinogram obtained from isolated retina. Our results indicate that 1) the increase in PIII duration induced by vincristine is significantly reduced by BN 50730 administration 2) the decrease in the amplitude of the PIII/b wave ratio caused by vincristine is partially inhibited by treatment with BN 50730. These experiments suggest that platelet activating factor is implicated in vincristine retinopathy and demonstrate the therapeutic effect of a specific antagonist of the mediator.

Inhibition of platelet-activating factor-induced retinal impairments by cholera and pertussis toxins

Platelet-activating factor (PAF) has been shown to alter the trans-retinal potential recorded from light-stimulated isolated retina. In the present study, we investigated the effect of cholera and pertussis toxins on PAF-induced impairment of the electroretinogram (ERG). Administered alone, 2 x 10(-7) M PAF induced a very marked and rapid drop in the b-wave amplitude. When 75 micrograms/l of cholera toxin was coadministered with PAF in the perfusion solution, no b-wave drop was observed, suggesting that the effect of PAF on retinal function was mediated by GTP-binding protein (G protein). Similarly, a low dose of pertussis toxin (5 micrograms/l) was sufficient to antagonize the action of PAF on the ERG. Our results suggest that the irreversible and deleterious effect of PAF on ERG is mediated by a G protein mechanism, located in the neural retina.

Prevention of chloroquine-induced electroretinographic damage by a new platelet-activating factor antagonist, BN 50730

Chloroquine retinopathy is a severe toxic retinal impairment which may result in loss of vision by alterations of the retinal pigment epithelium and photoreceptors. Currently, there is no specific treatment for this retinopathy. Platelet-activating factor (PAF) is known to modulate retinal function and is one of the major immunomediators of the retina. In order to test the possible involvement of PAF in chloroquine-induced retinopathy and the effectiveness of PAF antagonists in the prevention of this condition, we investigated the effects of BN 50730, a specific PAF antagonist, on the electroretinogram (ERG) of the isolated rat retina exposed to chloroquine. When retinas from normal rats were perfused with chloroquine (10(-6) M), a marked and rapid decrease in b-wave amplitude was observed. In contrast, chloroquine had no effect on the b-wave of the retina isolated from animals pretreated with the PAF antagonist BN 50730 (30 mg/kg/day, i.p., for 5 days). The results obtained indicate that (i) chloroquine is a toxic drug for retinal function, (ii) PAF plays a key role in the mediation of chloroquine retinopathy and (iii) PAF antagonists may constitute valuable agents for the treatment of this retinal impairment.

Effects of platelet-activating factor on electrophysiology of isolated retinas and their inhibition by BN 52021, a specific PAF-acether receptor antagonist

The effects of (R)PAF-acether have been tested on the isolated rat retina model. Results indicate that (R)PAF-acether inhibits the electrophysiological response (electroretinogram) elicited on isolated retina by a brief light flash. Immediately after the administration of (R)PAF-acether, an irreversible decrease of the electroretinogram b-wave amplitude is observed. This effect is dose-dependent (2 X 10(-11) M, 2 X 10(-9) M, 2 X 10(-7) M) and partially inhibited by simultaneous administration of Ginkgolide B (BN 52021; 2 X 10(-5) M). These results suggest the existence of (R)PAF-acether-specific receptors inside the retina.

[Effect of Ginkgo biloba extract on the electrophysiology of the isolated retina from a diabetic rat]

The purposes of the experimental work presented here were to ascertain that diabetes causes impairment of the visual function and to test the protective properties of Ginkgo biloba extract against this impairment. The experimental method selected was the isolated albino rat retina maintained in survival by perfusion. Retinal function was evaluated by electroretinographic recording in response to a light stimulus. The rats were made diabetics by injection of alloxan. After one month of diabetes the electroretinogram amplitude was significantly decreased in diabetic rats as compared with control animals. This decrease in amplitude was more pronounced after 2 months of diabetes, which confirmed that retinal function was worse. In rats treated with Ginkgo biloba extract, after 2 months of diabetes the electroretinograms had a significantly greater amplitude that that observed in untreated rats. These results are attributed to the specific role played by free oxygenated radicals on the retina of diabetic rats and to the free radical scavenger property of Ginkgo biloba extract.

An automatic stimulus generation system for electroretinogram capture and processing

An automated system is presented for on-line capture and processing of the analog signal obtained in response to light or X-ray stimulation of isolated rat retina maintained in survival by perfusion. The most important part of the system is a microcomputer Apple II (48 K Europlus) equipped with interface boards. Basic and assembler programs automatically deliver light or X-ray stimulation every 5 min. Data capture and data processing are carried out following each retinal response. Calculated parameters of the ERG, and 200 values obtained after sampling of an ERG are placed in a data file on a floppy disc. One hundred ERGs can be stored in this way.

Experimental study of the retinal toxicity of hemoglobinic iron

The functional consequences of vitreous hemorrhage on the retina were studied using a rabbit experimental model. The repartition of hemoglobinic iron inside the retina was assessed after the intravitreous injection of 59Fe-labeled erythrocytes. Electroretinographic studies were performed both in vivo after the intravitreous injection of labeled blood and in vitro on albino rat isolated retina treated with Fe ions. Results indicate that hemoglobinic iron migrates from the vitreous to the retina and inside the retinal tissue from ganglion cells to deeper layers. It is also demonstrated that hemoglobinic iron has a significant functional toxicity on the retina.

Electrophysiological consequences of leukotrienes applied on isolated rat retina

Scotopic vision is the result of a cascade of light-dependent biochemical events in rod outer segments (ROS) involving mainly a cGMP-modulation of sodium current. This modification of ionic currents induces changes of membrane potential which generates electroretinographic (ERG) waves. As (i) ERG disturbances are commonly recorded in hypoxic and inflammatory retinal diseases (ii) leukotrienes (LTs), a very potent mediators of inflammation, disturb ionic exchanges in several artificial or natural membrane systems, we undertook the investigation of the effects of LTs on ERG record in mammalian isolated retina. LTB4, LTC4 and LTD4, all induced a dose-dependent marked reduction of the b wave amplitude of ERG. This effect is correlated with a significant decrease in the survival time of the retina. The analysis of the modification of ERG indicates that LTs exhibit a real toxic effect since b wave is mainly affected while P III wave is unchanged. Comparatively with other nervous cells, this phenomenon may be attributed to an increase in Na+ permeability of ROS. It is suggested that LTs may be involved in the development of inflammatory or ischemic retinal diseases.

Effects of lipid peroxidation on the isolated rat retina

The effects of membrane lipid peroxidation are determined in isolated albino rat retina. Lipoperoxidation induced by addition of Fe2+ + ascorbate to the perfusion liquid leads to an irreversible decrease of amplitude in the electroretinogram. The experimental model proposed here provides the possibility to monitor the survival of the retina and demonstrates that ocular lipid peroxidation very notably shortens the survival time. The specific role of the rod membranes for the excitation mechanism in the retina as revealed by these experiments is discussed.