Biophysical and structural characterization of the impacts of MET phosphorylation on tepotinib binding

The receptor tyrosine kinase MET is activated by hepatocyte growth factor binding, followed by phosphorylation of the intracellular kinase domain (KD) mainly within the activation loop (A-loop) on Y1234 and Y1235. Dysregulation of MET can lead to both tumor growth and metastatic progression of cancer cells. Tepotinib is a highly selective, potent type Ib MET inhibitor and approved for treatment of non-small cell lung cancer harboring METex14 skipping alterations. Tepotinib binds to the ATP site of unphosphorylated MET with critical π-stacking contacts to Y1230 of the A-loop, resulting in a high residence time. In our study, we combined protein crystallography, biophysical methods (surface plasmon resonance, differential scanning fluorimetry), and mass spectrometry to clarify the impacts of A-loop conformation on tepotinib binding using different recombinant MET KD protein variants. We solved the first crystal structures of MET mutants Y1235D, Y1234E/1235E, and F1200I in complex with tepotinib. Our biophysical and structural data indicated a linkage between reduced residence times for tepotinib and modulation of A-loop conformation either by mutation (Y1235D), by affecting the overall Y1234/Y1235 phosphorylation status (L1195V and F1200I) or by disturbing critical π-stacking interactions with tepotinib (Y1230C). We corroborated these data with target engagement studies by fluorescence cross-correlation spectroscopy using KD constructs in cell lysates or full-length receptors from solubilized cellular membranes as WT or activated mutants (Y1235D and Y1234E/1235E). Collectively, our results provide further insight into the MET A-loop structural determinants that affect the binding of the selective inhibitor tepotinib.

Extract2Chip-Bypassing Protein Purification in Drug Discovery Using Surface Plasmon Resonance

Modern drug discovery relies on combinatorial screening campaigns to find drug molecules targeting specific disease-associated proteins. The success of such campaigns often relies on functional and structural information of the selected therapeutic target, only achievable once its purification is mastered. With the aim of bypassing the protein purification process to gain insights on the druggability, ligand binding, and/or characterization of protein-protein interactions, herein, we describe the Extract2Chip method. This approach builds on the immobilization of site-specific biotinylated proteins of interest, directly from cellular extracts, on avidin-coated sensor chips to allow for the characterization of molecular interactions via surface plasmon resonance (SPR). The developed method was initially validated using Cyclophilin D (CypD) and subsequently applied to other drug discovery projects in which the targets of interest were difficult to express, purify, and crystallize. Extract2Chip was successfully applied to the characterization of Yes-associated protein (YAP): Transcriptional enhancer factor TEF (TEAD1) protein-protein interaction inhibitors, in the validation of a ternary complex assembly composed of Dyskerin pseudouridine synthase 1 (DKC1) and RuvBL1/RuvBL2, and in the establishment of a fast-screening platform to select the most suitable NUAK family SNF1-like kinase 2 (NUAK2) surrogate for binding and structural studies. The described method paves the way for a potential revival of the many drug discovery campaigns that have failed to deliver due to the lack of suitable and sufficient protein supply.

Discovery of Cycloalkyl[c]thiophenes as Novel Scaffolds for Hypoxia-Inducible Factor-2α Inhibitors

Hypoxia-inducible factors (HIFs) are heterodimeric transcription factors induced in diverse pathophysiological settings. Inhibition of HIF-2α has become a strategy for cancer treatment since the discovery that small molecules, upon binding into a small cavity of the HIF-2α PAS B domain, can alter its conformation and disturb the activity of the HIF dimer complex. Herein, the design, synthesis, and systematic SAR exploration of cycloalkyl[c]thiophenes as novel HIF-2α inhibitors are described, providing the first chemotype featuring an alkoxy-aryl scaffold. X-ray data confirmed the ability of these inhibitors to induce perturbation of key amino acids by appropriately presenting key pharmacophoric elements in the hydrophobic cavity. Selected compounds showed inhibition of VEGF-A secretion in cancer cells and prevention of Arg1 expression and activity in IL4-stimulated macrophages. Moreover, in vivo target gene modulation was demonstrated with compound 35r. Thus, the disclosed HIF-2α inhibitors represent valuable tools for investigating selective HIF-2α inhibition and its effect on tumor biology.

B-lines by lung ultrasound is associated with pulmonary symptoms and cardiac function in acute malaria: a prospective cohort study

Background

Malaria patients are at risk of cardiopulmonary complications, but diagnosis and management are difficult in resource limited environments. B-lines by lung ultrasonography (LUS) can identify pulmonary alterations, however, little is known about the usefulness in malaria.

Purpose

We aimed to investigate the occurrence of B-lines in acute malaria patients at baseline and at follow-up, and whether they are associated with shortness of breath and impaired left ventricular ejection fraction (LVEF).

Methods

Adult patients with non-severe acute malaria were prospectively enrolled from June to December 2020 in community healthcare clinics in a remote area. Patients were age- and sex-matched to controls without a prior history of malaria. We examined patients prior to anti-malaria treatment and at follow-up. Malaria treatment was administered according to national guidelines. Patients were excluded if they were pregnant, had concomitant infections or recent chest trauma. Patients underwent LUS (8-zones), echocardiography and peripheral blood smear. Measurements were blinded to clinical variables and outcomes.

Results

We included a total of 99 patients (median age 40±15 years, 55% men). Patients suffered from Plasmodium vivax (n=75), P. falciparum (n=22), and a mix of the two (n=2) and median parasite density was 1,595 parasites/mL (interquartile range [IQR] 528–6,585/mL). Follow-up was completed in 71 patients and the median follow-up time was 31 days (IQR 27–40 days).

Patients with acute malaria had significantly more B-lines at baseline than matched controls (P-value<0.001) and fewer B-lines at follow-up (P-value<0.001) (Figure 1). In acute malaria patients, number of B-lines at baseline correlated significantly with shortness of breath (OR 1.20, [1.04 to 1.39], P-value=0.01) and with LVEF (adjusted for age and sex: +8% [+1% to +15%], P-value=0.016 per 1% decrease in LVEF). There was no correlation between number of B-lines and parasite density (+2% [−5% to +11%], P-value=0.53 per 1000 increase in parasite density).

Conclusion

B-lines detected by LUS are more frequent in patients with acute malaria than in age- and sex-matched controls and decrease in response to treatment. B-lines also correlate with shortness of breath and lower LVEF at baseline. Because LUS is a quick and accessible examination, it may potentially facilitate risk stratification and therapeutic decisions regarding cardiopulmonary complications in patients with acute malaria.

Funding Acknowledgement

Type of funding sources: Foundation. Main funding source(s): Danish Heart Association

Diagnostic value of electrocardiograms to identify pericardial effusion in acute malaria: a cross-sectional study

Background

Patients with acute malaria are at risk of pericarditis and may benefit from timely identification of pericardial effusion. However, diagnostic imaging tools, such as echocardiography, are not always available in malaria endemic regions.

Purpose

The aim of this study is to examine the diagnostic yield of pathology in electrocardiograms (ECG) to identify pericardial effusion in acute malaria.

Methods

We enrolled adult acute malaria patients in community healthcare clinics in a remote area in South America. All patients underwent ECG, echocardiography, and peripheral blood smears. We excluded patients on anti-malarial medication, suspected concomitant infection and pregnant women. All ECGs were examined for the following criteria: (i) PR-depression >0.5mm and/or ST-elevation 0.5–1mm (I, II, aVL, aVF, V2–6) (ii) PR-elevation >0.5mm (only aVR), (iii) ST/T-ratio >0.25 (only V6), (v) low voltage, defined as QRS amplitude <5 mm in limb leads or <10 mm in precordial leads, and (vi) Spodick's sign (all leads). A criterion was positive when present in ≥2 leads. Information on shortness of breath and/or chest pain was also collected. Pericardial effusion was diagnosed by echocardiography and had to be ≥0.5cm in width.

Results

We included 99 non-severe malaria patients (age 40±15 years, 55% men, median parasite density 1517/mm3, [interquartile range 528 to 6,585/mm3]) who suffered from Plasmodium vivax (n=75), falciparum (n=22 falciparum) and mixed vivax/falciparum (n=2). The ECGs showed a mean frequency of 78±16bpm, PR-interval 147±20ms, QRS 88±11ms and QT-interval 376±34ms. A total of 11 patients displayed pericardial effusion (mean width 0.9±0.3cm, n=7 vivax, n=2 falciparum, n=2 mixed). Patients with effusion were older (mean age 39 vs 53 years, P=0.003), but displayed no difference in sex, parasite density or parasite species compared to patients without pericardial effusion (P>0.05). Distribution of ECG findings and symptoms are displayed in figure 1A. PR-depression had a sensitivity and specificity for diagnosing pericardial effusion of 73% and 90%, respectively. The sensitivity and specificity for other ECG findings and clinical symptoms are displayed in Figure 1B.

Conclusion

ECG findings may aid in identifying pericardial effusion in acute malaria, specifically PR depression which had a diagnostic yield of 73% sensitivity and 90% specificity. Based on this, ECG in acute malaria may improve treatment and risk stratification when echocardiography is not an option.

Funding Acknowledgement

Type of funding sources: Foundation. Main funding source(s): Novo Nordisk Foundation, Independent Research Fund Denmark ECG findings in malaria patients

Patient reported health status and cardiovascular risk factors in a remote area of South America: a cross-sectional study

Background

Several studies have indicated that self-perception of health is related to cardiovascular disease. Despite cardiovascular disease is the leading cause of mortality in South America, the relationship between patient reported health and cardiovascular risk is sparsely explored, specifically in indigenous areas.

Purpose

We assessed if self-rated health is associated with cardiovascular risk factors in a remote area in South America.

Methods

We included participants by cluster-randomization of community health care clinics from June to December 2020. Sociodemographic variables and information on cardiovascular risk factors were collected by questionnaires and physical examination. All participants rated their present health status according to the validated EQ5D-VAS instrument, ranging from 0 (worst) to 100 (best).

Results

A total of 492 participants (mean age 41±15 years; 38% men) were included. The mean value of self-rated health was 80 (range 0 to 100) and the prevalence of cardiovascular risk factors were: Hypertension (19%), hypercholesterolemia (15%), smoking (37%), low intake of vegetables (defined as <3 times per week; 54%), no sport activity (62%), diabetes (6%) and obesity (24%). In logistic regression models adjusted for sex, age and socioeconomic status, higher self-rated health was significantly associated with lower risk of hypertension, hypercholesterolemia, smoking, obesity and greater vegetable intake (P<0.05; Figure 1). No association was found with sport activity or diabetes. The total number of cardiovascular risk factors increased with lower self-rated health (beta = 0.100 [0.04 to 0.15], P<0.001 per 10 decrease in self-reported health).

Conclusion

Self-rated health was significantly associated with a greater burden of cardiovascular risk factors and may influence ideal cardiovascular health. Future studies should assess if patient reported health status constitutes an independent risk factor for heart disease in this specific population, and studies elucidating gaps on self-perception of cardiovascular health are encouraged.

Funding Acknowledgement

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): The Independent Research Fund Denmark

Discovery of 5-{2-[5-Chloro-2-(5-ethoxyquinoline-8-sulfonamido)phenyl]ethynyl}-4-methoxypyridine-2-carboxylic Acid, a Highly Selective in Vivo Useable Chemical Probe to Dissect MCT4 Biology

Due to increased lactate production during glucose metabolism, tumor cells heavily rely on efficient lactate transport to avoid intracellular lactate accumulation and acidification. Monocarboxylate transporter 4 (MCT4/SLC16A3) is a lactate transporter that plays a central role in tumor pH modulation. The discovery and optimization of a novel class of MCT4 inhibitors (hit 9a), identified by a cellular screening in MDA-MB-231, is described. Direct target interaction of the optimized compound 18n with the cytosolic domain of MCT4 was shown after solubilization of the GFP-tagged transporter by fluorescence cross-correlation spectroscopy and microscopic studies. In vitro treatment with 18n resulted in lactate efflux inhibition and reduction of cellular viability in MCT4 high expressing cells. Moreover, pharmacokinetic properties of 18n allowed assessment of lactate modulation and antitumor activity in a mouse tumor model. Thus, 18n represents a valuable tool for investigating selective MCT4 inhibition and its effect on tumor biology.

Optimization of a Screening Hit toward M2912, an Oral Tankyrase Inhibitor with Antitumor Activity in Colorectal Cancer Models

Constitutive activation of the canonical Wnt signaling pathway, in most cases driven by inactivation of the tumor suppressor APC, is a hallmark of colorectal cancer. Tankyrases are druggable key regulators in these malignancies and are considered as attractive targets for therapeutic interventions, although no inhibitor has been progressed to clinical development yet. We continued our efforts to develop tankyrase inhibitors targeting the nicotinamide pocket with suitable drug-like properties for investigating effects of Wnt pathway inhibition on tumor growth. Herein, the identification of a screening hit series and its optimization through scaffold hopping and SAR exploration is described. The systematic assessment delivered M2912, a compound with an optimal balance between excellent TNKS potency, exquisite PARP selectivity, and a predicted human PK compatible with once daily oral dosing. Modulation of cellular Wnt pathway activity and significant tumor growth inhibition was demonstrated with this compound in colorectal xenograft models in vivo.

Large-Scale Assessment of Binding Free Energy Calculations in Active Drug Discovery Projects

Accurate ranking of compounds with regards to their binding affinity to a protein using computational methods is of great interest to pharmaceutical research. Physics-based free energy calculations are regarded as the most rigorous way to estimate binding affinity. In recent years, many retrospective studies carried out both in academia and industry have demonstrated its potential. Here, we present the results of large-scale prospective application of the FEP+ method in active drug discovery projects in an industry setting at Merck KGaA, Darmstadt, Germany. We compare these prospective data to results obtained on a new diverse, public benchmark of eight pharmaceutically relevant targets. Our results offer insights into the challenges faced when using free energy calculations in real-life drug discovery projects and identify limitations that could be tackled by future method development. The new public data set we provide to the community can support further method development and comparative benchmarking of free energy calculations.

Ablation of the ASCT2 (SLC1A5) gene encoding a neutral amino acid transporter reveals transporter plasticity and redundancy in cancer cells

The neutral amino acid transporter solute carrier family 1 member 5 (SLC1A5 or ASCT2) is overexpressed in many cancers. To identify its roles in tumors, we employed 143B osteosarcoma cells and HCC1806 triple-negative breast cancer cells with or without ASCT2 deletion. ASCT2ko 143B cells grew well in standard culture media, but ASCT2 was required for optimal growth at <0.5 mm glutamine, with tumor spheroid growth and monolayer migration of 143B ASCT2ko cells being strongly impaired at lower glutamine concentrations. However, the ASCT2 deletion did not affect matrix-dependent invasion. ASCT2ko 143B xenografts in nude mice exhibited a slower onset of growth and a higher number of small tumors than ASCT2wt 143B xenografts, but did not differ in average tumor size 25 days after xenotransplantation. ASCT2 deficiency was compensated by increased levels of sodium neutral amino acid transporter 1 (SNAT1 or SLC38A1) and SNAT2 (SLC38A2) in ASCT2ko 143B cells, mediated by a GCN2 EIF2α kinase (GCN2)-dependent pathway, but this compensation was not observed in ASCT2ko HCC1806 cells. Combined SNAT1 silencing and GCN2 inhibition significantly inhibited growth of ASCT2ko HCC1806 cells, but not of ASCT2ko 143B cells. Similarly, pharmacological inhibition of l-type amino acid transporter 1 (LAT1) and GCN2 significantly inhibited growth of ASCT2ko HCC1806 cells, but not of ASCT2ko 143B cells. We conclude that cancer cells with reduced transporter plasticity are more vulnerable to disruption of amino acid homeostasis than cells with a full capacity to up-regulate redundant transporters by an integrated stress response.

Functional analysis of Hsp70 inhibitors

The molecular chaperones of the Hsp70 family have been recognized as targets for anti-cancer therapy. Since several paralogs of Hsp70 proteins exist in cytosol, endoplasmic reticulum and mitochondria, we investigated which isoform needs to be down-regulated for reducing viability of cancer cells. For two recently identified small molecule inhibitors, VER-155008 and 2-phenylethynesulfonamide (PES), which are proposed to target different sites in Hsp70s, we analyzed the molecular mode of action in vitro. We found that for significant reduction of viability of cancer cells simultaneous knockdown of heat-inducible Hsp70 (HSPA1) and constitutive Hsc70 (HSPA8) is necessary. The compound VER-155008, which binds to the nucleotide binding site of Hsp70, arrests the nucleotide binding domain (NBD) in a half-open conformation and thereby acts as ATP-competitive inhibitor that prevents allosteric control between NBD and substrate binding domain (SBD). Compound PES interacts with the SBD of Hsp70 in an unspecific, detergent-like fashion, under the conditions tested. None of the two inhibitors investigated was isoform-specific.

Structural and biophysical characterization of the Syk activation switch

Syk is an essential non-receptor tyrosine kinase in intracellular immunological signaling, and the control of Syk kinase function is considered as a valuable target for pharmacological intervention in autoimmune or inflammation diseases. Upon immune receptor stimulation, the kinase activity of Syk is regulated by binding of phosphorylated immune receptor tyrosine-based activating motifs (pITAMs) to the N-terminal tandem Src homology 2 (tSH2) domain and by autophosphorylation with consequences for the molecular structure of the Syk protein. Here, we present the first crystal structures of full-length Syk (fl-Syk) as wild type and as Y348F,Y352F mutant forms in complex with AMP-PNP revealing an autoinhibited conformation. The comparison with the crystal structure of the truncated Syk kinase domain in complex with AMP-PNP taken together with ligand binding studies by surface plasmon resonance (SPR) suggests conformational differences in the ATP sites of autoinhibited and activated Syk forms. This hypothesis was corroborated by studying the thermodynamic and kinetic interaction of three published Syk inhibitors with isothermal titration calorimetry and SPR, respectively. We further demonstrate the modulation of inhibitor binding affinities in the presence of pITAM and discuss the observed differences of thermodynamic and kinetic signatures. The functional relevance of pITAM binding to fl-Syk was confirmed by a strong stimulation of in vitro autophosphorylation. A structural feedback mechanism on the kinase domain upon pITAM binding to the tSH2 domain is discussed in analogy of the related family kinase ZAP-70 (Zeta-chain-associated protein kinase 70). Surprisingly, we observed distinct conformations of the tSH2 domain and the activation switch including Tyr348 and Tyr352 in the interdomain linker of Syk in comparison to ZAP-70.

Fragment-based discovery of hydroxy-indazole-carboxamides as novel small molecule inhibitors of Hsp90

Inhibitors of the Hsp90 molecular chaperone are showing considerable promise as potential molecular therapeutic agents for the treatment of cancer. Here we describe the identification of novel small molecular weight inhibitors of Hsp90 using a fragment based approach. Fragments were selected by docking, tested in a biochemical assay and the confirmed hits were crystallized. Information gained from X-ray structures of these fragments and other chemotypes was used to drive the fragment evolution process. Optimization of these high μM binders resulted in 3-benzylindazole derivatives with significantly improved affinity and anti-proliferative effects in different human cancer cell lines.

In-depth biophysical analysis of interactions between therapeutic antibodies and the extracellular domain of the epidermal growth factor receptor

Targeting of the epidermal growth factor receptor (EGFR) with monoclonal antibodies has become an established antitumor strategy in clinical use or in late stages of drug development. The mAbs effector mechanisms have been widely analyzed based on in vivo or cell studies. Hereby we intend to complement these functional studies by investigating the mAb-EGFR interactions on a molecular level. Surface plasmon resonance, isothermal titration calorimetry, and static light scattering were employed to characterize the interactions of matuzumab, cetuximab, and panitumumab with the extracellular soluble form ecEGFR. The kinetic and thermodynamic determinants dissected the differences in mAbs binding mechanism toward ecEGFR. The quantitative stoichiometric data clearly demonstrated the bivalent binding of the mAbs to two ecEGFR molecules. Our results complement earlier studies on simultaneous binding of cetuximab and matuzumab. The antibodies retain their bivalent binding mode achieving a 1:2:1 complex formation. Interestingly the binding parameters remain nearly constant for the individual antibodies in this ternary assembly. In contrast the binding of panitumumab is almost exclusive either by directly blocking the accessibility for the second antibody or by negative allosteric modulation. Overall we provide a comprehensive biophysical dataset on binding parameters, the complex assembly, and relative epitope accessibility for therapeutic anti-EGFR antibodies.

[fs-Lentotomy: presbyopia reversal by generating gliding planes inside the crystalline lens]

Based on the Helmholtz theory for accommodation, increasing sclerosis of the lens nucleus and cortex is the main cause for the development of presbyopia. Existing therapies, however, do not reverse the stiffness of the crystalline lens and thus do not regain real accommodation ability. A new approach to restore the flexibility of the lens has been realised by utilising the non-linear interaction of ultrafast laser pulses with transparent tissue, the so-called photodisruption. This process has been used to create micro-incisions which act as gliding planes inside the crystalline lens without opening the eye globe. This treatment method, known as fs-lentotomy, enables regeneration of real dynamic accommodation. For the first time, 3D structures for gliding planes were successfully generated in experiments with human donor lenses of different ages. An average increase in anterior-posterior lens thickness of 100 mum accompanied by a decrease of equatorial lens diameter was observed as a direct consequence of fs-lentotomy. This is attributed to the increased flexibility, as the force of the capsule bag moulds the lens tissue more spherically. Moreover, in vivo experiments on rabbit eye lenses did not induce an increasing opacification (cataract) over a six-month follow-up period. However, the incisions were still detectable using Scheimpflug imaging and histopathological techniques, although the visibility of the incisions was declining. Furthermore, no side effects were observed during the wound healing process and during a six-months follow-up period. Based on these findings fs-lentotomy might have the potential to become a procedure for the reversal of presbyopia.

On the ultrastructure and functional morphology of the male chelicerae (gonopods) in Parasitina and Dermanyssina mites (Acari: Gamasida)

Males of Parasitina and Dermanyssina (Gamasida=Mesostigmata) have chelicerae modified to function as gonopods. The slit-like spermatotreme in the movable digit of the chela in males of Parasitina was studied in three species: in Pergamasus quisquiliarum and Holoparasitus sp. a rather simple slit is indeed present, whereas in Vulgarogamasus kraepelini the structure is represented by a fine duct traversing the movable digit. The spermatodactyl studied in two phytoseioid species (Phytoseiulus persimilis, Blattisocius dentriticus) of Dermanyssina is a slender process arising from the movable digit and containing a fine duct which is formed by cuticular folds. The spermatodactyl of these species thus differs remarkably from that described in Veigaia sp. The diversity of these structures seen in the few taxa studied up to now is discussed under functional and systematic aspects.

Analysis of CheA histidine phosphorylation and its influence on protein stability by high-resolution element and electrospray mass spectrometry

A combination of electrospray mass spectrometry (ESI-MS) and element mass spectrometry (ICPMS) with phosphorus detection was used to characterize histidine phosphorylation (His-48) of the chemotaxis protein CheA quantitatively. The phosphorylation at His-48 was found to be responsible for a stabilization of the protein. For this investigation, the acceptor domain and the kinase domain of the bacterial chemotaxis protein CheA were recombinantly expressed as single proteins. Using in vitro kinase assay conditions, the acceptor domain CheA-H was phosphorylated by the kinase domain CheA-C. The degree of histidine phosphorylation was determined by nanoelectrospray mass spectrometry of intact CheA-H, and was found to be limited to a maximum value of approximately 50%. The site specificity of CheA-H phosphorylation was controlled by nanoESI-MS/MS of the [M + 16H](16+) ion of intact (pHis)-CheA-H and allowed localization of the pHis residue to the region between residues 32 and 86, containing candidates His-48 and His-67, for which His-48 phosphorylation has been described. Analysis of the tryptic digest of in vitro histidine-phosphorylated CheA-H by capillary chromatography coupled to ESI-MS and to ICPMS with phosphorus detection revealed a truncated (pHis)-CheA-H protein as the only phosphorus-containing analyte. Since the truncated (pHis)-CheA-H in the digest was found to exhibit a higher degree of phosphorylation than could be generated by in vitro phosphorylation without trypsin treatment, it is concluded that histidine phosphorylation at His-48 strongly interferes with structural properties of the CheA-H domain in particular with respect to proteolytic degradation by trypsin.

Lower limits of fluorescein and indocyanine green dye for digital cSLO fluorescence angiography

BACKGROUND

With the advent of digital confocal scanning laser ophthalmoscopy it is possible to detect low levels of fluorescence. Here we used a novel confocal scanning laser ophthalmoscope (cSLO) to determine lower limits of dye required for fluorescein (FL) and indocyanine green (ICG) angiography.

METHODS

A cSLO (Heidelberg retina angiograph 2, Heidelberg Engineering, Dossenheim, Germany) with an optically pumped solid state laser (488 nm) for FL and a diode laser (790 nm) for ICG angiography (FL/ICG-A) was used. 62 FL-As were performed in 53 patients and 45 ICG-As were performed in 39 patients with neovascular age related macular degeneration. The volume and overall dye content of bolus injections was gradually tapered (FL: 500 mg, 250 mg, 200 mg, 166 mg, 100 mg; ICG: 25 mg, 20 mg, 15 mg, 10 mg, 5 mg, 2.5 mg), while dye concentrations were kept constant at 100 mg/ml for FL and at 5 mg/ml for ICG. Images were obtained 1, 5, 15, and 30 minutes after dye injection. Image quality was evaluated by two independent readers using standardised criteria.

RESULTS

For amounts down to 166 mg for FL and to 5 mg for ICG, sufficient image quality was achieved during all phases following injection. Only late phase images showed less contrast compared to typically used dye amounts, which was irrelevant for interpretation and clinical management.

CONCLUSIONS

With the increased sensitivity of this novel cSLO system, amounts of injected dye during FL-A can be reduced to one third for FL and to one fifth for ICG without relevant loss of image quality or information compared to conventionally used dye levels. These amounts can be used for routine angiography and allow relevant savings for units performing FL-A.

Effects of dietary deficiency of selective amino acids on the function of the cornea and lens in rats

Effects of dietary deficiencies of tryptophan and methionin on the transparency of cornea and lens were investigated in young rats (Brown-Norway, BN; Sprague-Dawley, SD) over 3 months. Transparency of the cornea and lens were evaluated in weekly intervals using a photo-slitlamp microscope. After sacrifice and lens fresh weight determination the lenses were prepared for histopathology. Methionin deficiency had no effect on the parameters investigated. Tryptophan deficiency caused severe loss of body weight in both strains, with additional loss of hair in SD rats. These developed corneal neovascularisations and cataracts. BN rats showed an enhanced zone of discontinuity in the lens. Diet intermission arrested the pathological processes in the eye which restarted when feeding the diet again. This observation is supported by lens fresh weight data. DNA staining evidenced that tryptophan deficiency arrested lens fiber maturation in both strains but stimulated corneal neovascularisation only in SD rats.

[Cataract prevention. Therapeutic approaches and critical review of current status]

Research on the pathophysiology of the lens already in the early days of the last century led to first attempts to clinically influence cataract development with vitamins. More detailed investigation of lens aging and its interaction with internal and external cataract risk factors led to two different therapeutic strategies: (1) compounds or mixtures expected to slow down the aging processes in the lens (food additives) and (2) compounds to reduce or even arrest the effect of a specific harmful factor. Various mixtures expected to influence aging processes were even developed into approved OTC drugs although their effectiveness was never demonstrated. Among those compounds designed to act on a specific pathomechanism, mainly aldose reductase inhibitors were designed and successfully tested in animal studies. None of these,however, could be developed into a market-approved drug. Larger controlled clinical studies have been performed with various compositions of food additives, but also with nonsteroidal anti-inflammatory drugs such as salicylic acid and ibuprofen. None of the clinical trials,however, evidenced any convincing anti-cataract effect of the compounds or mixtures tested such that a successful anti-cataract drug still remains to be developed.

Frequency and nature of spontaneous age-related eye lesions observed in a 2-year inhalation toxicity study in rats

A group of 160 Wistar rats (both sexes) from a larger chronic inhalation toxicity study was monitored at baseline and after 1 and 2 years with a photo-slitlamp microscope and a direct ophthalmoscope to record spontaneous age-related eye lesions and treatment-related eye lesions over a period of 24 months. A second group from the same study was monitored at the start and after 5 months of a 6-month posttreatment period immediately following the inhalation period. Rats were nose-only exposed for 6 h/day, 7 days/week, for 2 years to low (3 microg/l) or high (10 microg/l) total particulate matter concentrations of room-aged cigarette sidestream smoke (RASS) or diesel engine exhaust (DEE). Control animals were exposed to filtered fresh air. All ophthalmological examinations were performed in mydriasis, and relevant observations were documented on color slide film. At baseline, all animals with eye lesions were excluded from the study. After 1 year, only minor lesions were found: retrolental opacities (14%) and a few cases of corneal dryness with reddish lid margins. After 2 years, 23% of the animals had unilateral or bilateral retrolental opacities, but the most frequent eye lesions were posterior subcapsular cataracts (PSC, 32%). Water clefts and spokes were found in 11% of the lenses and mature cataracts in 6%. All other eye lesions observed were much less frequent. There were a few cases of glaucoma, corneal dryness and stromal neovascularization. The frequency and type of lesion in animals monitored from the start of the posttreatment period was comparable to what was seen after 2 years. Toward the end of this period the frequency of mature cataracts went up to 9% and that of (secondary) glaucomas to 5%. None of the eye lesions observed showed any association in frequency or severity of expression to the treatment, either RASS or DEE, or to the sex of the animals. In comparison to the (limited) literature data available, far fewer corneal lesions were found in this study, but PSCs and mature cataracts were more frequent. Strain differences may influence these parameters. This study provided valuable information on the nature and frequency of spontaneous age-related eye lesions (0-56%, depending on the tissue) in long-term toxicity studies in Wistar rats.

Age-related light scattering in rat lenses observed in a 2-year inhalation toxicity study

Normal light scattering in the eye is determined primarily by the size of alpha-crystalline molecules. Ageing effects appear as an increase in normal lens light scattering in distinct layers. Subliminal effects of toxins on lens transparency can also cause an increase in light scattering due to protein molecule aggregation before visible opacities appear. Scheimpflug photography of the anterior eye segment with subsequent densitometric image analysis is the method of choice to evaluate such effects. To gain more insight into normal ageing and the potential effects of complex aerosols, a subset of Wistar rats (both sexes) belonging to a larger chronic inhalation toxicity study was documented at baseline and after 2 years with a Topcon SL-45 Scheimpflug camera on Kodak T(max) 400 ISO film. The recording procedure, film development, and microdensitometric image analysis were all performed according to standard protocol. A second group from the same study was documented at the start and after 5 months of a 6-month posttreatment period immediately following the inhalation period. Rats were nose-only exposed for 6 h/day, 7 days/week, for 2 years to low (3 microg/l) or high (10 microg/l) concentrations of room-aged cigarette sidestream smoke or diesel engine exhaust. Control animals were exposed to filtered fresh air. At the baseline examination, there were no relevant differences between groups with respect to corneal density or density of defined layers in the lens capsule (1), epithelium and superficial cortex (2), deep cortex (3), supranuclear layer (4) and nucleus (5). At the 2-year examination, mean corneal density was significantly lower in females than in males. This same trend, although not significant, was also found in most layers of the lens. The most prominent differences in density over time were measured in lens layers 3 and 4, but neither corneal density nor lenticular density showed any consistent treatment-related effects in any of the layers. The data from the posttreatment period confirmed the results of the 2-year study. The depth of the anterior chamber increased constantly over the 2.5-year period, but again, treatment did not affect this. This study provided completely new data on age-related light scattering in the cornea and in defined layers of the lens in long-term toxicity studies in Wistar rats.

Light scattering in normal and cataractous lenses of farmed Atlantic salmon (Salmo salar): a slit lamp and Scheimpflug photographic study

To investigate normal light scattering and cataract formation, the anterior eye segments of farmed Atlantic salmon (Salmo salar) reared in fresh water and sea water were documented in vivo for the first time with a Topcon SL-45 Scheimpflug camera. A total of 40 fish from the fresh-water-rearing period, obtained from 2 groups of identical age but showing a different growth rate, and 24 fish from the sea-water-rearing period, sampled from 2 groups with identical age but being fed different food brands, were included in this study. The fish were anaesthetized before examination. Due to the naturally wide pupil, no mydriatic compound was applied. All fish were removed from the water for photography, which was performed for each eye in 0 degrees = vertical slit position. Images were recorded on Kodak Tmax 400 black-and-white film. Microdensitometric image analysis of all negatives was performed using a Joyce-Loebl online microdensitometer. In spite of the virtual absence of an anterior chamber gap between cornea and lens and very little light scattering in the normal fish lens, a small number of distinct layers could be reproducibly identified in the lens. While there was little abnormal light scattering which could point to cataract development in young fish from the fresh water period, the evaluation of the lenses from the 2 sea water groups showed the presence of specific forms of cataract especially in the cortical and supranuclear layers. There were significant differences between the groups fed different food brands at the sea water site. In conclusion, Scheimpflug photography proved to be applicable to eye research in fish in vivo. It is suggested that this method should be employed for reproducible documentation as an extension to slit lamp monitoring in experimental research to reveal causative factors for cataracts in farmed fish.

[Image analysis and Sheimpflug photography of anterior segment of the eye--a review]

BACKGROUND

Light scattering properties of the cornea and lens change in relation to age. This process is influenced by noxious factors which may induce the formation of cataracts. Four different camera types based on the Scheimpflug principle have been developed for documentation and evaluation of light scattering in the eye. Topcon SL-45. Zeiss SLC, Oxford CASE 2000, Nidek EAS 1000. Only the SL-45 and EAS 1000, however, have found a wider application in clinical and experimental studies.

MATERIAL AND METHODS

Documentation of the eye with a Scheimpflug system is performed in a dark room after mydriasis induction. The rotating axis of the camera is aligned to the optical axis of the eye with fixation devices. Four meridians have been found appropriate for routine documentation. Image analysis is based on peak height and distance evaluation of 2 layers in the cornea and 10 layers in the lens. Standardization devices allow correction of technical differences in the recording process.

RESULTS

Evaluation of the ageing properties of the lens has evidenced typical density developments for each individual layer, the cortex increasing in density earlier than the nucleus. Cataract classification using a Scheimpflug camera provides an objective characterization of cataract type and progression. The outcome of surgical procedures changing the refractive power of the eye can be evaluated with a Scheimpflug camera as well. Its application in studies dealing with the ocular effects of Quinolones and HMG-CoA-reductase inhibitors, has demonstrated that Scheimpflug photography is the method of choice for establishment of a safety profile for a new drug.

CONCLUSIONS

Scheimpflug photography has proven to be ideal for objective documentation of the anterior eye segment in human and animal eyes, although both documentation and image analysis demand technical expertise to be reproducible.

Light scattering in the human lens in childhood and adolescence

The age-related increase in normal light scattering in the adult human lens has frequently been documented with Scheimpflug imaging techniques. There are only insufficient data on lens light scattering, however, from the first 2 decades of human life. After having obtained informed consent from their parents, the anterior eye segments of 26 children of both genders were documented with a Topcon SL-45 Scheimpflug camera on Kodak Tmax 400 ASA black-and-white film in 3 meridians. The age of the children, who had either a normal visual acuity or best corrected visual acuity, ranged from 4 to 18 years. Thirty minutes prior to photography, maximal mydriasis was induced by 3-fold instillation of Mydriaticum Roche(R). Parallel to the Scheimpflug photographic documentation, all eyes were subjected to a basic ophthalmological examination. All images obtained were evaluated with microdensitometry as described earlier. The density data in young children demonstrate that there is very little light scattering in the central lens parts and only a faint zone of discontinuity apart from the 2 signals caused by the anterior and posterior capsules. Starting at the age of 14-15 years, the first separations occur in the zones of discontinuity, thus the first age-correlated increase in light scattering. The data obtained demonstrate that the development of light scattering in the young lens differs from that in the adult lens. Our results point to the assumption that the development of protein light scattering in the lens correlates with physical life-time of the individual and not with the period of life in different species with various life expectancies.

Radiotherapy for age related macular degeneration causes transient lens transparency changes

AIM

Evaluation of potential side effects of photon radiotherapy on the transparency of the lens.

METHODS

The anterior segments of 14 phakic eyes from patients suffering from subfoveal neovascularisation as a result of age related macular degeneration (AMD) were documented by Scheimpflug photography (Topcon SL-45, Kodak Tmax 400) before the start of radiotherapy as well as 6 and 12 months afterwards. All negatives were evaluated by microdensitometry, and peak heights for distinct layers of the lens were used for statistical comparison. External beam radiotherapy (6 MeV photons) consisted of a total dose of 20 Gy, delivered as 10 fractions of 2 Gy.

RESULTS

Six and 12 months following irradiation statistical comparison of the ratios in density change of lenses from irradiated versus non-irradiated fellow eyes revealed statistically significant (p</=0.05) loss of transparency of layers 5 and 7 of the nuclear region. In layer 1 (capsuloepithelial complex) the changes were close to significance. At the 12 month examination, however, all of these significant changes had disappeared.

CONCLUSION

Six months following radiotherapy for AMD, both the anterior capsuloepithelial region and the nuclear layers showed precataractous changes. As most of these significant differences had disappeared after 12 months, it is obvious that these findings reflect acute radiation damage to the lens epithelial cells and an ionising effect on the proteins of the lens nucleus. Long term studies will have to be carried out to demonstrate whether or not this acute radiation damage, which is expressed as a transient increase in light scattering of some layers of the lens, actually does lead to permanent transparency changes, thus reflecting radiation cataractogenesis, and if so, after what time interval and to what extent cataract occurs.

UV damage to the eye lens: further results from animal model studies: a review

UV irradiation has the potential to induce the development of lens opacities. This has been demonstrated since long with animal experiments. Unfortunately these animal cataracts did not explain or elucidate the epidemiological observation that the frequency of human cataracts--such as the so called senile cataract--is remarkably higher in regions with increased cosmic UV irradiation or in the population being in close professional contact with UV-irradiation. The main problem was that the type of UV induced animal cataracts differs remarkably with respect to onset, localization of the opacity, size and its timely progression from the cataract classes observed in human. The research of the last 10 years comes to the conclusion that beside the direct (acute) damage--as seen in animal studies due to high UV dosages--we have to realize a syn- or co-cataractogenic potential of UV irradiation even below the threshold dose which is able to accumulate in the lens and to initiate together with other risk factors (chronic damage) the opacification of the lens. The mechanism for the animal cataract and the human cataract (with an UV risk participation) are different. The epidemiological research about cataract frequency in different regions of the world have to take into account that UV irradiation--even below a threshold dose--is a possible risk among the multifactorial pathogenesis of human cataract.

Protein size resolution in human eye lenses by dynamic light scattering after in vivo measurements

Dynamic light scattering (DLS) measurements were conducted with lowest intensity levels on human eye lenses (3.2 mW/cm2) within measurement times of 3-5 s. A characterisation of the human eye under in-vivo conditions along the optical axis is given and a careful interpretation of the data is made, referring not only to in-vitro results of investigated solutions of lens chemistry and various crystallin fractions but also to measurements performed on intact human lenses under various scattering angles. The clinical study was expanded to 79 subjects with ages varying from 9 to 85 years with no serious diseases of the ocular lenses. A normalisation of Scheimpflug photography density data to the data obtained by DLS enables comparison of the two techniques and shows good agreement. The bimodal character of the viscoelastic properties of healthy eye lenses was confirmed; with an assumed viscosity of 2 cP, the mean size parameter of the smaller component is 5.13 +/- 1.6 nm and of the polymeric fraction 690 nm.

Effects of UV-B radiation on a hereditary suture cataract in mice

UV-B (290-320 um, lambda max = 305 nm) radiation and the Cat2ns (suture cataract) mutation in mice affect both the anterior lens epithelium and the formation of the suture. A low dose of UV-B radiation (2.2 Jcm-2) induces similar anterior subcapsular and cortical lens opacities in wild type as in heterozygous mutant mice. The UV-B treatment of the mutant lenses, however, leads to an increase in the number of epithelial cell layers in the anterior central part as compared to the wild type indicating a more severe form of the cataract formation in mutants. In addition, mutants demonstrate a predisposition for a rupture of the posterior lens capsule, because from 2.9 Jcm-2 and higher, this phenomenon could always be observed in the UV-B treated mutants, but never in the treated wild type mice. The protein biochemical analyses were performed by gel electrophoresis and isoelectric focusing of extracts of total lenses or from defined areas of the lens (lens slice technique). These covered the patterns of those proteins already synthesized before irradiation, which in irradiated lenses in no case evidenced a difference to the untreated control, neither in the wild type nor in the mutants. In contrast, by analysing specifically those proteins, which are synthesised after irradiation, in both treated groups a protein with a molecular mass of about 31 kDa becomes discernable in both treated groups. In addition, the cataractous lenses demonstrate a significantly enhanced overall synthesis of water-soluble proteins after irradiation, which might promote the rupture of the posterior capsule at the posterior pole. The present study offers for the first time the possibility to discriminate between endogeneous (genetic) effects and exogeneous (environmental) effects in cataractogenesis and to study their interactive effects. The first set of experiments demonstrated a clear intensification of the hereditary cataract by the UV-B treatment. The study supports the hypothesis that environmental stress (like UV-B radiation) enhanced the severity of genetically triggered eye disease.

Molecular cloning of ozone-inducible protein from Pinus sylvestris L. with high sequence similarity to vertebrate 3-hydroxy-3-methylglutaryl-CoA-synthase

We have isolated a Pinus sylvestris cDNA encoding a globular protein of 474 amino acids with a predicted molecular weight of 52,995 Da. The deduced amino acid sequence showed 41.9% identity and 13.6% similarity to mammalian cytosolic 3-hydroxy-3-methylglutaryl-CoA-synthase (HMGS). Treatment of Scots pine seedlings with ozone resulted in a transient increase of a 1.95 kb transcript, whereas a 1.2 kb mRNA decreased transiently, indicating a possible influence of ozone on isoprenoid biosynthesis.

Use of subjective and nonsubjective methodologies to evaluate lens radiation damage in exposed populations--an overview

The general epidemiological acceptability of prevalence, or incidence, for assessing risk of radiation cataract development has dictated an almost exclusive dependence on cataract onset as a measure of cataractogenicity for given doses of radiation. The advent of instrumentation capable of acquiring images amenable to quantitative analyses offers the possibility of exploiting "relative opacification" as an added, if not exclusive, parameter. This development is particularly important in efforts to assess populations such as that in the Altai, which are temporally far removed from their exposure and among whom there exists a large subset with extant cataracts. The new technologies, Scheimpflug and retroillumination imaging, combined with the application of the appropriate analytical algorithms can not only provide quantitative and nonsubjective assessment of lens transparency, but also serve as a means to immortalize the state of the pathology at the time of acquisition. Highly relevant to the assessment of an aging exposed population is the use of lens epithelial fragments as potential dosimeters. The material is routinely available as a result of cataract extraction procedures and is amenable to the application of a modified micronucleus (MN) assay. The MN assay in the lens has tremendous advantages over its use in other tissues for a number of reasons, not least of which is that lens MNs are extremely long-lived. Given the relative ease of application and its potential as a radiation bioindicator, the lens MN assay should be considered in any follow-up of populations exposed to ionizing radiation.

Effects of allopurinol and steroids on inflammation and oxidative tissue damage in experimental lens induced uveitis: a biochemical and morphological study

AIMS

To evaluate the effects of allopurinol in lens induced uveitis (LIU) by morphological methods and to compare these effects with those of steroids and a combination of both drugs biochemically and morphologically.

METHODS

Lipid peroxides (LPO) of the retinal tissue were determined by two different methods (thiobarbituric acid assay (TBA) and high performance liquid chromatography expressed as malondialdehyde-like substances). Myeloperoxidase (MPO) activity in the iris/ciliary body complex was analysed spectrophotometrically. Histological changes on three morphological levels of LIU eyes were evaluated.

RESULTS

Both allopurinol and the combination of allopurinol/prednisolone led to a significant reduction in the increaed retinal LPO values. Prednisolone only revealed significant effects on retinal LPO when being measured with the TBA method. MPO activity in iris and ciliary body was significantly reduced in all therapy groups. The morphological evaluation of the sections by two masked investigators revealed a significant reduction (p < 0.05) in the inflammation score in all therapy groups. Morphometric studies using the QUANTIMED system (Leica, Cambridge) showed significantly reduced values (p < 0.05) in the allopurinol group and in the group receiving prednisolone and allopurinol. Prednisolone alone did not lead to a significant reduction in the values.

CONCLUSIONS

The findings show that both allopurinol and steroids exert positive effects on the variables determined in LIU. The effects of steroids are believed to be mostly due to their direct action on inflammatory cells. The recently reported scavenging effects of methylprednisolone should play a minor role in this disease model. Allopurinol and oxypurinol act as direct scavengers of free radicals and hypochlorous acid, which is produced via MPO catalysis, thus leading to a reduction in tissue inflammation and tissue damage.

Imaging of the spatial density distribution on the capsule of the lens with Scheimpflug photography

The density characteristics of the anterior and posterior surfaces of the lens, although of primary importance for its optical quality, are difficult to determine. Scheimpflug photography, however, allows distinct density measurements from the optical axis towards the periphery with the only limitation of a sufficient mydriasis, so that a 3-dimensional scatter profile of both capsular surfaces can be calculated via multilinear densitometric evaluation of a sufficient number of meridians. On this methodical basis, we analysed Scheimpflug images recorded with the Topcon SL-45 on Kodak T-Max 400 film from 25 patients in an age range between 19 and 63 years. Images from the 0 degree + 45 degree meridians were scanned with multilinear microdensitometry and the data computed to get a density profile. In general, most scattering profiles show a marked interindividual variability. Nevertheless, a general trend can be established between the periphery and the center of the anterior and posterior capsules: (a) the anterior capsule generally has a higher density than the posterior; (b) in most cases, the center of the posterior capsule has a higher density than the periphery; (c) the anterior capsule has a more uniform spatial density distribution in all cases. From the cases evaluated, it can be concluded that the density of the peripheral posterior capsule is more importantly influenced by shading effects of the iris, so that geometrical correction is needed.

Anterior chamber angle biometry: a comparison of Scheimpflug photography and ultrasound biomicroscopy

Scheimpflug photography and ultrasound biomicroscopy allow measurement of anterior chamber angle width. To analyze the value of both diagnostic tools, measurements of the same subjects were correlated. Anterior chamber angle width in both eyes of 20 volunteers without any ophthalmological case history was measured in eight meridians. Scheimpflug photographs were recorded on Kodak T-max 400 black-and-white film using a Topcon SL-45 camera. Measurement of chamber angle was done with the aid of a self-programmed PC software. Ultrasound biomicroscopic measurements were obtained using a Humphrey UBM 840 system with a 50-MHz transducer. The chamber angle was measured as described by Pavlin et al. The data of both methods were correlated and analysed for statistically significant differences using a paired t test (level of significance p < or = 0.05). Both methods showed similar changes in chamber angle width and were able to document a variation in angle width with regard to location. The correlation averaged at 0.64. In 4 meridians significant differences were found between the two methods. Scheimpflug photography, however, is unable to visualize directly the angle itself. Both methods are limited by the fact that the angle is defined by curvilinear structures, i.e. posterior corneal surface and anterior iris surface. Scheimpflug photography is able to document changes in angle configuration. Ultrasound biomicroscopy, however, is a more precise method, because it allows direct documentation of all structures involved in chamber angle configuration.

Clinical, histological and ultrastructural characteristics of a spontaneous corneal opacity in Sprague-Dawley rats

The eyes of 200 rats (Mol:SPRD, Moellegaard Ltd., Skensvet, Denmark), 8 weeks of age and of both sexes, were examined routinely with a photo-slitlamp microscope (Zeiss) and opthalmoscope (Heine) 3-4 times in the course of four different 12-week toxicity studies. The animals were kept under constant lighting conditions at a room temperature of 20 +/- 2 degrees C and 55 +/- 5% humidity on a standard diet. More than 70% of the animals were found to have more or less prominent corneal opacities already at the beginning of the study. These were morphologically characterized as meshwork-like alterations of the deeper corneal epithelium, mostly located in the central and nasal region. The temporal, upper and lower periphery remained always unaffected. Male animals were more frequently and more intensively affected than the females. The occurrence of the opacity was totally independent of the treatment scheme (controls and drug dosages, respectively), showing a slight increase in density in some of the animals of all groups and remaining stable in others. Regression was rarely observed. Light and electron microscopical investigations demonstrated focal degenerations of the basal epithelial cell layer as well as alterations of its basement membrane. The lesion was not associated with inflammation or irritation. Therefore, we considered that a genetically determined metabolic disorder of the basal epithelial cells might have led to the impairment of basement membrane synthesis. Further screenings performed in conjunction with the breeder evidenced that these opacities are probably caused by a spontaneous mutation with a complex, not X-linked genetic background.