Keratopathy after oral administration of tilorone hydrochloride

Alveolar Proteinosis and Phospholipidoses of the Lungs

Three pulmonary disease conditions result from the accumulation of phospholipids in the lung. These conditions are the human lung disease known as pulmonary alveolar proteinosis, the lipoproteinosis that arises in the lungs of rats during acute silicosis, and the phospholipidoses induced by numerous cationic amphiphilic therapeutic agents. In this paper, the status of phospholipid metabolism in the lungs during the process of each of these lung conditions has been reviewed and possible mechanisms for their establishment are discussed. Pulmonary alveolar proteinosis is characterized by the accumulation of tubular myelin-like multilamellated structures in the alveoli and distal airways of patients. These structures appear to be formed by a process of spontaneous assembly involving surfactant protein A and surfactant phospholipids. Structures similar to tubular myelin-like multilamellated structures can be seen in the alveoli of rats during acute silicosis and, as with the human condition, both surfactant protein A and surfactant phospholipids accumulate in the alveoli. Excessive accumulation of surfactant protein A and surfactant phospholipids in the alveoli could arise from their overproduction and hypersecretion by a subpopulation of Type II cells that are activated by silica, and possibly other agents. Phospholipidoses caused by cationic amphiphilic therapeutic agents arise as a result of their inhibition of phospholipid catabolism. Inhibition of phospholipases results in the accumulation of phospholipids in the cytoplasm of alveolar macrophages and other cells. While inhibition of phospholipases by these agents undoubtedly occurs, there are many anomalous features, such as the accumulation of extracellular phospholipids and surfactant protein A, that cannot be accounted for by this simplistic hypothesis.

Counteraction of the Embryolethal Effects, But Not the Maternal Toxicity, of Bropirimine and Tilorone by Coadministration of Indomethacin

Bropirimine and tilorone are immunomodulators with experimental antiviral and antitumor activities. In earlier studies, treatment with bropirimine resulted in either death of the entire litter, if given once on specific days during or prior to the period of organogenesis, or litter survival comparable with that of controls. For example, bropirimine and tilorone were both found to be embryolethal when administered orally at 400 mg/kg to Upj:TUC(SD)spf rats on day 10 of gestation. Previous studies also have shown that coadministration of progesterone with either of these immunomodulators could prevent the embryolethality but not the pronounced maternal toxicity seen concurrently. Thus, bropirimine and tilorone appear to affect maternal support of the pregnancy rather than having a direct effect on the embryos. Since administration of bropirimine or tilorone appears to mimic the luteolytic effects of prostaglandin F2a, it was hypothesized that coadministration of the prostaglandin synthesis inhibitor indomethacin might prevent such embryolethality. Thus, indomethacin was administered s.c. in combination with bropirimine or tilorone (400 mg/kg orally on day 10 of gestation), at 0.4 or 0.8 mg/rat on days 9-11 (bropirimine experiment) or days 9-12 of gestation; the dams were killed on day 13, at which time the status of each conceptus was ascertained. Although unable to prevent maternal toxicity, which was found 24 h after administration of either immunomodulator, coadministration of indomethacin resulted in a decrease in the embryolethality associated with administration of either immunomodulator on day 10 of gestation. No live embryos were found on day 13 of gestation in five of six pregnant dams given bropirimine only, whereas in the drug-combination groups six of seven (indomethacin at 0.4 mg/day) and six of eight (indomethacin at 0.8 mg/day) pregnant dams had litters containing live embryos. In the tilorone experiment, six of eight litters were completely lost in utero in the group receiving the immunomodulator only. However, only one of four surviving dams had no live embryos in the drug-combination group that received indomethacin at 0.4 mg/day, with all eight surviving dams having live embryos in the group that received 0.8 mg/day of this drug. The results of this study and of earlier combination experiments with progesterone support the following hypothesis: bropirimine or tilorone administration to Upj:TUC-(SD)spf rats on day 10 of gestation inhibits progesterone production by the corpora lutea by a mechanism involving prostaglandin synthesis, resulting in a disruption in maternal support to the pregnant uterus and subsequent embryolethality.

Di-22:6-bis(monoacylglycerol)phosphate: A clinical biomarker of drug-induced phospholipidosis for drug development and safety assessment

The inability to routinely monitor drug-induced phospholipidosis (DIPL) presents a challenge in pharmaceutical drug development and in the clinic. Several nonclinical studies have shown di-docosahexaenoyl (22:6) bis(monoacylglycerol) phosphate (di-22:6-BMP) to be a reliable biomarker of tissue DIPL that can be monitored in the plasma/serum and urine. The aim of this study was to show the relevance of di-22:6-BMP as a DIPL biomarker for drug development and safety assessment in humans. DIPL shares many similarities with the inherited lysosomal storage disorder Niemann-Pick type C (NPC) disease. DIPL and NPC result in similar changes in lysosomal function and cholesterol status that lead to the accumulation of multi-lamellar bodies (myeloid bodies) in cells and tissues. To validate di-22:6-BMP as a biomarker of DIPL for clinical studies, NPC patients and healthy donors were classified by receiver operator curve analysis based on urinary di-22:6-BMP concentrations. By showing 96.7-specificity and 100-sensitivity to identify NPC disease, di-22:6-BMP can be used to assess DIPL in human studies. The mean concentration of di-22:6-BMP in the urine of NPC patients was 51.4-fold (p ≤ 0.05) above the healthy baseline range. Additionally, baseline levels of di-22:6-BMP were assessed in healthy non-medicated laboratory animals (rats, mice, dogs, and monkeys) and human subjects to define normal reference ranges for nonclinical/clinical studies. The baseline ranges of di-22:6-BMP in the plasma, serum, and urine of humans and laboratory animals were species dependent. The results of this study support the role of di-22:6-BMP as a biomarker of DIPL for pharmaceutical drug development and health care settings.

Bone morphogenetic protein-inducer tilorone identified by high-throughput screening is antifibrotic in vivo

Idiopathic pulmonary fibrosis (IPF) is a progressive lung disease with a poor prognosis and very few therapeutic options. On the molecular level, patients with IPF have increased amounts of the bone morphogenetic protein (BMP) inhibitor gremlin in their lungs, which results in decreased BMP signaling, and an increase in transforming growth factor-β signaling. Based on these findings, we hypothesized that restoration of the impaired BMP signaling would offer a novel strategy for the prevention of fibrosis progression or for the treatment of pulmonary fibrosis. We used reporter cell lines and high-throughput screening of a chemical compound library as an approach to finding molecules that increase BMP signaling in lung epithelial cells, without increasing transforming growth factor-β signaling. The most promising candidate drug was analyzed further by studying its effects on BMP target gene expression, Smad protein phosphorylation, and a mouse model of silica-induced pulmonary fibrosis. The most promising drug candidate, tilorone, induced BMP signaling in the reporter cells and increased the expression of BMP-7 and a BMP target gene, Id3, in lung epithelial A549 cells. In a mouse model of pulmonary fibrosis, tilorone decreased lung hydroxyproline content and the expression of collagen genes Col1A1 and Col3A1. Mice treated with tilorone showed markedly decreased histological changes, compared with untreated mice. These findings indicate that tilorone has biologically significant antifibrotic properties.

Monitoring the accumulation of fluorescently labeled phospholipids in cell cultures provides an accurate screen for drugs that induce phospholipidosis

A large number of cationic amphiphilic drugs (CADs) are known to cause phospholipidosis (PLD) in vivo. In the present study, we have built upon our previous findings to further qualify the use of a fluorescently labeled phospholipid-based cell-culture assay to detect PLD-inducing drugs. In this paper, we demonstrate that 12 PLD-negative compounds and 11 drugs known to cause PLD in vivo are all correctly identified by using this assay. Interestingly, we found that in cells treated with certain CADs, the fluorescent phospholipid was sequestered in a very specific punctate pattern, which overlapped strongly with the staining pattern seen with a lysosomal marker protein. Our data also show that false positives can be generated with the fluorescence assay when compounds are used at concentrations that cause a >30% decrease in cell number in this assay. Confocal microscopy demonstrated that the staining pattern of fluorescent phospholipids in these cases may be differentiated from those of true positives by the fact that diffuse, rather than punctuate, fluorescence is observed. These studies confirm and expand our previous results showing that the fluorescent phospholipid assay is a highly sensitive, specific tool for detecting PLD-inducing drugs, if care is taken to rule out cytotoxicity-related artifact.

Evaluation of a Published in Silico Model and Construction of a Novel Bayesian Model for Predicting Phospholipidosis Inducing Potential

The identification of phospholipidosis (PPL) during preclinical testing in animals is a recognized problem in the pharmaceutical industry. Depending on the intended indication and dosing regimen, PPL can delay or stop development of a compound in the drug discovery process. Therefore, for programs and projects where a PPL finding would have adverse impact on the success of the project, it would be desirable to be able to rapidly identify and screen out those compounds with the potential to induce PPL as early as possible. Currently, electron microscopy is the gold standard method for identifying phospholipidosis, but it is low-throughput and resource-demanding. Therefore, a low-cost, high-throughput screening strategy is required to overcome these limitations and be applicable in the drug discovery cycle. A recent publication by Ploemen et al. (Exp. Toxicol. Pathol. 2004, 55, 347-55) describes a method using the computed physicochemical properties pKa and ClogP as part of a simple calculation to determine a compound's potential to induce PPL. We have evaluated this method using a set of 201 compounds, both public and proprietary, with known in vivo PPL-inducing ability and have found the overall concordance to be 75%. We have proposed simple modifications to the model rules, which improve the model's concordance to 80%. Finally, we describe the development of a Bayesian model using the same compound set and found its overall concordance to be 83%.

Drug-induced corneal complications

PURPOSE OF REVIEW

To review the common corneal manifestations of systemic medications in order to describe the characteristic clinical features associated with particular systemic drugs, the indications for drug cessation, and the risks for irreversible ocular toxicity.

RECENT FINDINGS

Systemic medications may reach the cornea via the tear film, aqueous humor, and limbal vasculature. The corneal changes are often the result of the underlying chemical properties of medications. Amphiphilic medications (amiodarone, chloroquine, suramin, clofazimine, etc.) may produce a drug-induced lipidosis and development of a vortex keratopathy. Antimetabolites (cytarabine) may lead to a degeneration of basal epithelial cells with formation of epithelial microcysts. Additionally, systemically administered medications and drug metabolites may lead to a stromal or endothelial deposition. Corneal changes may result in reduced visual acuity, photophobia, and ocular irritation, though these symptoms typically resolve following drug cessation. Corneal manifestations of systemic medications are often dose related, and may reflect the potential risk for lenticular or retinal changes.

SUMMARY

Corneal changes secondary to systemic medications may affect all layers of the cornea. While corneal deposition is typically not an indication for drug cessation, patients receiving particular medications should be monitored for symptoms related to corneal deposition as well as for signs of irreversible ocular toxicity.

Drug-induced phospholipidosis: are there functional consequences?

Phospholipidosis induced by drugs with a cationic amphiphilic structure is a generalized condition in humans and animals that is characterized by an intracellular accumulation of phospholipids and the concurrent development of concentric lamellar bodies. The primary mechanism responsible for the development of phospholipidosis is an inhibition of lysosomal phospholipase activity by the drugs. While the biochemical and ultrastructural features of the condition have been well characterized, much less effort has been directed toward understanding whether the condition has adverse effects on the organism. While there are a few cationic amphiphilic drugs that have been reported to cause phospholipidosis in humans, the principal concern with this condition is in the pharmaceutical industry during preclinical testing. While this class of drugs should technically be referred to as cationic lipophilic, the term cationic amphiphilic is widely used and recognized in this field, and for this reason, the terminology cationic amphiphilic drugs (CADs) will be employed in this Minireview. The aim of this Minireview is to provide an evaluation of the state of knowledge on the functional consequences of CAD-induced phospholipidosis.

Time course of the tilorone-induced lysosomal accumulation of sulphated glycosaminoglycans in cultured fibroblasts

Dicationic amphiphilic drugs such as the immunomodulator tilorone [2,7-bis-[2-(diethylamino)ethoxy]fluoren-9-one] are accumulated in lysosomes and disturb the degradation of sulphated glycosaminoglycans (GAGs) thus leading to generalized lysosomal GAG storage (mainly dermatan sulphate) in vivo and in cultured cells. In the present study, the time course of the tilorone-induced GAG storage was determined in cultured bovine corneal fibroblasts by a radiochemical approach and by morphological examination. In contrast to the rapid lysosomal accumulation of the drug as reported previously, it took approximately 42 h to reach 50% of the GAG storage obtained after 96 h. This is thought to be due to the fact that the temporal development of storage of undigested GAGs depends on the natural delivery of GAGs towards the lysosomal apparatus.

Lysosomal glycosaminoglycan storage as induced by dicationic amphiphilic drugs: investigation into the mechanisms underlying the slow reversibility

Several dicationic amphiphilic compounds, such as the immunomodulator tilorone and analogues, impair the lysosomal catabolism of sulphated glycosaminoglycans (GAGs). Thereby they cause lysosomal GAG storage in rats and in cultured fibroblasts of several species including man. The GAG storage is rather slowly reversible in vivo; it persists for months after discontinuance of drug treatment. In the present study, we investigated the mechanisms underlying the slow reversibility. Cultured bovine corneal fibroblasts were pretreated for 4 days with tilorone (5 and 20 microM) or with compound CL-90.100 (3 and 10 microM) and further cultured in drug-free medium for periods up to 11 days. The intracellular GAG storage was analysed biochemically and demonstrated histochemically. The subcellular drug distribution (CL-90.100) was demonstrated by fluorescence microscopy. Dermatan sulphate (DS) provided the predominant contribution towards the GAG storage. After pretreatments with the low, as well as the high concentrations of either drug, the storage of DS was irreversible during the period of observation, whereas the minor storage of heparan sulphate was resolved. The enhanced secretion of the lysosomal enzyme beta-hexosaminidase (E.C. 3.2.1.52) caused by pretreatment with the high concentration of tilorone was also readily reversible. Thus, enzyme deprivation could not be the explanation for the sustained DS storage. The localization of the drug-related fluorescence within perinuclear cell organelles, presumably lysosomes, resembled that of the stored GAGs as visualized by histochemical staining. Both, the fluorescence and the positive GAG staining persisted with unchanged intracellular distribution throughout the recovery period. The present results suggest that the persistence of the DS storage is due to the formation of long-lived, non-degradable DS-drug complexes within the lysosomes.

Drug-induced lysosomal storage of sulphated glycosaminoglycans

1. Certain compounds (e.g., the immunomodulator tilorone and congeners) are able to induce lysosomal storage of sulphated glycosaminoglycans (GAG), thus, producing cytological and biochemical alterations reminiscent of the inherited mucopolysaccharidoses. The drug-induced GAG storage has been studied in cultured fibroblasts of several species and in rats, and it is likely to occur also in humans. 2. The cytological hallmarks of GAG storage are enlarged lysosomes congested with material that is intensely stained by cationic dyes. With respect to fixation techniques, one has to keep in mind that the GAGs are highly water-soluble and are leached during conventional fixation and tissue processing. Biochemically, the elevation of GAG contents in tissues and cultured fibroblasts is due to storage of dermatan sulphate, predominantly. 3. The molecular structure of the potent inducers of GAG storage is characterized by a planar tricyclic aromatic ring system that is symmetrically substituted with two side chains of 4-5 sigma bond length, each carrying a protonizable nitrogen atom. The lysosomal storage of GAG is accompanied by lysosomal accumulation of the inducing drug, with the molar ratio of drug to GAG-disaccharide unit amounting to > 1:1. The reversibility of GAG storage is rather slow. 4. The pathogenic mechanisms underlying the drug side effects are discussed and the following hypothesis is put forward: The compounds in question are lysosomotropic weak bases. They get trapped in the acidic lysosomes and accumulate highly there. Physicochemical data suggest that the drugs form complexes with the sulphated GAGs, particularly with dermatan sulphate: The positively charged nitrogen atoms of the drug side chains interact with the negative charges of sulphate and carboxy groups of the GAGs, thereby crosslinking at least two GAG helices. Moreover, the interlinking drug molecules form parallel stacks resulting from interaction of the aromatic pi-electrons of the planar ring systems. This further stabilizes the complexes. The GAGs within the complexes are thought to be resistant to the degrading lysosomal enzymes. 5. Drug-induced GAG storage has not been directly demonstrated in man. Yet, clinical reports on keratopathy and basophilic cytoplasmic inclusions in blood lymphocytes of tilorone-treated patients suggest that this drug side effect may also occur in man.

Lysosomal storage of sulphated glycosaminoglycans induced by dicationic amphiphilic drug molecules: significance of the central planar ring system

The immunomodulatory drug tilorone (2,7-bis[2-(diethylamino)ethoxy]fluoren-9-one) and several congeners are known to disturb the lysosomal degradation of sulphated glycosaminoglycans and thereby induce lysosomal storage of glycosaminoglycans in cultured cells and intact organisms. The molecules of tilorone and congeners consist of a planar aromatic ring system symmetrically substituted with two aliphatic side chains each carrying a protonizable nitrogen. In a previous study it was proposed that non-degradable glycosaminoglycan-drug complexes are formed by electrostatic interactions and that additionally intermolecular interactions between the drug molecules due to electronic coupling of their central planar ring system are important for formation and stabilization of the glycosaminoglycan-drug complexes and thus for the drug side effect in question. The significance of the central planar ring system was tested in the present study by comparing tilorone and the compound bis(beta-diethylamino-ethylether)hexestrol (DH) with respect to their potencies to cause lysosomal glycosaminoglycan storage in cultured bovine corneal fibroblasts. DH has the same side chains as tilorone, but its central apolar moiety lacks planarity. At a concentration (1.75 muM) which did not cause enhanced secretion of the lysosomal enzyme beta-hexosaminidase (E.C. 3.2.1.52), DH was significantly less potent than tilorone in causing storage of [35S]glycosaminoglycans. This is taken as support of the hypothesis that the planar tricyclic ring system is essential for the high potency of tilorone and its congeners to exert this adverse action.

The antimalarials quinacrine and chloroquine induce weak lysosomal storage of sulphated glycosaminoglycans in cell culture and in vivo

The antimalarial agents quinacrine and chloroquine are well known as potent inducers of lysosomal storage of polar lipids (lipidosis) in cell culture and in vivo. In previous experiments on cultured fibroblasts, chloroquine was shown to additionally cause weak lysosomal storage of sulphated glycosaminoglycans (GAGs) thus inducing mucopolysaccharidosis (MPS). In the present study, quinacrine was investigated for this ability, because we wished to know whether or not the acridine ring system in quinacrine would enhance the MPS-inducing potency as compared to chloroquine carrying an isoquinoline ring system. Tilorone (2,7-bis[2-(diethylamino)ethoxy]fluoren-9-one) known as a potent inducer of MPS served as reference compound. The compounds were compared at a concentration (3 microM) which did not enhance the secretion of the lysosomal enzyme beta-hexosaminidase (E.C. 3.2.1.52), since this would be an indication of unspecific drug effects upon the endosomal/lysosomal compartments of the cell. Additionally the liver of quinacrine- and chloroquine-treated rats was examined with the question whether the lysosomal GAG storage induced by either drug in cell culture had an equivalent in intact organisms. Both, in cell culture and in vivo, quinacrine was found to be a more potent inducer of lysosomal GAG storage than was chloroquine. The results suggest that the acridine ring system favours this drug side effect as compared with the bicyclic isoquinoline ring system. On the other hand, quinacrine was significantly less potent than tilorone and the Symmetrically substituted acridine derivative 3,6-bis[2-(diethylamino)ethoxy]acridine investigated previously. This suggests that the asymmetric structure of the quinacrine molecule reduces the potency as compared to the symmetrically substituted bisbasic compounds with planary tricyclic ring systems such as tilorone and congeners.

Tilorone-induced lysosomal lesions: the bisbasic character of the drug is essential for its high potency to cause storage of sulphated glycosaminoglycans

The immunomodulatory agent tilorone -2,7-bis-[2-(diethyl-amino)ethoxy]fluoren-9-one- and congeners are potent inducers of lysosomal storage of sulphated glycosaminoglycans (GAGs) in animals and cultured fibroblasts of animals and man. All potent inducers of GAG storage hitherto described are bisbasic polycyclic aromatic compounds. They are accumulated in lysosomes and disturb the degradation of GAGs, mainly dermatan sulphate. It has been proposed that the drugs cross-link the polyanionic GAG chains giving rise to undergradable drug-GAG complexes. This hypothesis implies that the bisbasic character of the drug molecules is essential for the side effect in question. In the present study, this was tested by comparing tilorone and its monobasic derivative (MT) with respect to (i) induction of GAG storage in cultured bovine corneal fibroblasts and (ii) physicochemical interactions with GAGs in vitro. The intralysosomal concentration of MT achieved after 1-3 days was of the same order of magnitude as previously shown for tilorone. Nevertheless, under conditions that did not enhance the secretion of a lysosomal enzyme (beta-hexosaminidase, EC 3.2.1.52), the ability of MT to cause storage of [35S]GAGs was significantly lower than that of tilorone. Morphological observations showed that MT was much more potent in causing lysosomal storage of polar lipids than of GAGs. CD spectroscopy with tilorone revealed that the presence of GAGs caused the primarily achiral drug molecules to display CD. This suggested a helical orientation of the tilorone molecules within GAG-drug complexes, and short intermolecular distances which allowed electronic coupling of the aromatic ring systems of adjacent drug molecules. In contrast, MT failed to display any induced optical activity, indicating the absence of highly ordered GAG-drug complexes. In conclusion, the present results show that the substitution of the planar aromatic ring system with two basic side chains is essential for the high potency of tilorone in inducing lysosomal GAG storage. This is paralleled by, and presumably causally related to, strong physicochemical interactions with GAGs.

Tilorone-induced lysosomal storage of sulphated glycosaminoglycans can be separated from tilorone-induced enhancement of lysosomal enzyme secretion

This investigation deals with a drug side-effect. The immunomodulatory drug tilorone (2,7-bis[2-(diethylamino)ethoxy]fluoren-9-one) and congeners induce lysosomal storage of sulphated glycosaminoglycans (GAGs) in animals and in cultured cells. At high tilorone concentrations, GAG storage in cultured fibroblasts was previously reported to be accompanied, and presumably caused by, disturbance of intracellular targeting of lysosomal enzyme precursors, which leads to enhanced secretion and thus loss of lysosomal enzymes. The purpose of the present study was to examine whether the GAG storage induced in cultured bovine fibroblasts by low tilorone concentrations is also accompanied by enhanced lysosomal enzyme release. Enhanced secretion of beta-hexosaminidase (EC 3.2.1.52) was taken as indicating the intracellular mistargeting of lysosomal enzyme precursors. Dose-response curves were established for (a) the intracellular accumulation of 35S-GAGs and (b) the release of beta-hexosaminidase after exposure (72 hr) to tilorone (1-35 microM). For positive controls, the classical lysosomotropic agents NH4Cl (1-30 mM) and chloroquine (1-60 microM) were used. With NH4Cl, 35S-GAG storage was accompanied by enhanced enzyme release throughout the concentration range (EC50 at 3.3 mM for either effect). With chloroquine, low concentrations (< or = 5 microM) caused a small increase in 35S-GAG accumulation without abnormal enzyme secretion; at higher concentrations both drug effects were produced (EC50 around 15 microM for either effect). With tilorone, low concentrations (< or = 5 microM) caused marked 35S-GAG accumulation without enhancement of enzyme release. The EC50 for tilorone-induced 35S-GAG storage was 3 microM, as opposed to 15 microM for enzyme release. The results indicate that GAG storage induced by low concentrations of tilorone is due to mechanisms other than mistargeting and loss of lysosomal enzymes. On the basis of previous results it may be hypothesized that tilorone and other symmetrically substituted dicationic compounds form complexes with the polyanionic GAG chains and thereby impair their enzymic degradation.

Corneal lipidosis in patients with the acquired immunodeficiency syndrome

PURPOSE

Certain drugs bind to anionic phospholipids of lysosomal membranes and produce progressive intracellular accumulation of lamellar inclusions. We studied two patients treated for opportunistic infections associated with the acquired immunodeficiency syndrome (AIDS), who developed bilateral ocular surface changes suggestive of drug-induced corneal lipidosis.

METHODS

Two patients with AIDS had translucent vacuoles within the corneal epithelium and mild conjunctival hyperemia. Because the differential diagnosis included microsporidial keratoconjunctivitis, biopsies of the ocular surface were performed for histopathologic analysis.

RESULTS

Transmission electron microscopy of corneal epithelial debridement and conjunctival biopsy specimens showed intracellular, electron-dense lipoidal bodies and multilaminated lysosomal inclusions suggestive of a drug-induced lipidosis. Both patients also had tubuloreticular inclusions in conjunctival capillary endothelial cells. The ocular surface changes resolved within one to three months after dosage reduction or discontinuation of systemic ganciclovir and acyclovir.

CONCLUSIONS

Drug-induced phospholipidosis is a cause of punctate corneal epitheliopathy during AIDS, but the responsible agent remains to be identified.

Development of atypical amiodarone keratopathy in a corneal graft

The presence of fine epithelial deposits in a whorled pattern (cornea verticillata) as a consequence of treatment with amiodarone is well documented. We present a case of amiodarone keratopathy in a grafted cornea which is atypical in that the orientation of the pattern is rotated through nearly 90 degrees to that normally observed. This observation runs counter to the hypothesis that cornea verticillata is a manifestation of the line of lid closure. We speculate on the mechanism directing the migrational pathways of epithelial cells.

Lysosomal storage of sulfated glycosaminoglycans in cultured fibroblasts exposed to immunostimulatory acridine derivatives

The purpose of the present cytological and radiochemical study was to investigate whether the immunomodulatory agent 3,6-bis[2-(diethylamino)ethoxy]acridine (CL-90.100) and three congeners induce lysosomal storage of sulfated glycosaminoglycans (sGAG) in cultured rat corneal fibroblasts. The reason for asking this question was as follows: The four acridine derivatives have molecular similarities with the dicationic amphiphilic compound tilorone, which has previously been shown to cause sGAG storage in cultured cells and in intact rats. The cells were exposed to the drugs for 72 hr. Tilorone served as reference. All acridine derivatives caused cytological alterations which, on the basis of the cytochemical results, were indicative of lysosomal sGAG storage. The threshold concentrations ranged from 0.3 to 0.7 microM. Radiochemical experiments showed that CL-90.100 up to 10 microM induced [35S]GAG storage in a dose-dependent manner, with an EC50 of 2 microM. Concentrations above 10 microM were cytotoxic. Experiments with equimolar concentrations (3 microM) demonstrated that three of the acridine derivatives were more potent and one was less potent than tilorone. Additionally, CL-90.100 was tested on bovine corneal fibroblasts, with cytochemical and radiochemical results similar to those in rat cells. The present findings show that (a) the four acridine derivatives induce lysosomal sGAG storage; (b) the acridine ring, compared with the fenfluorenone ring (tilorone), enhances this potency; and (c) the substituents at the nitrogens can have some influence on the potency to induce sGAG storage.

Drug-induced lysosomal storage of sulfated glycosaminoglycans in cultured bovine and human fibroblasts

Several di-cationic amphiphilic compounds are known to cause lysosomal accumulation of sulfated glycosaminoglycans (sGAG) in intact rats and in cultured rat fibroblasts. The purpose of the present investigation was to examine whether this drug side effect also occurs in bovine and human cells. Cultured fibroblasts from both species were exposed to tilorone (3 microM and 5 microM) for 72 h; lysosomal sGAG-storage was demonstrated by cytochemical staining with cuprolinic blue and by measuring the intracellular accumulation of [35S]-GAG. The cytological alterations as well as the radiochemical results in both species were in good agreement with previous data from rat fibroblasts. The present findings indicate that the drug-induced lysosomal storage of sGAG is a species-independent phenomenon. Thus, cultured bovine and human fibroblasts are a suitable model for further studies concerning the as yet unknown molecular mechanisms underlying this adverse drug action.

Cultured corneal fibroblasts as a model system for the demonstration of drug-induced mucopolysaccharidosis

The purpose of the present investigation was to establish a cell culture system suitable for demonstrating the drug-induced lysosomal storage of sulfated glycosaminoglycans (GAGs). This is a drug side-effect which was previously studied in animals treated with the di-cationic amphiphilic compound tilorone and congeners, and which is likely to occur in humans, too. Cultured corneal fibroblasts of rats were exposed to tilorone for 72 h. They developed histochemical and cytochemical alterations indicative of mucopolysaccharidosis and resembling those occurring in vivo. The threshold drug concentration was found to be below 0.7 microM. The reversibility of the lysosomal GAG storage was low. An increase in the drug concentration to 10 microM produced additional unspecific lysosomal alterations, while the mucopolysaccharidosis-like lesions became less prominent. Concentrations of 40 microM and 80 microM caused unspecific cytoplasmic vacuolation and cell death, respectively. The present model system appears suitable for screening investigations of newly developed drugs with respect to their mucopolysaccharidosis-inducing potential and for investigating the structure-activity relationships underlying this adverse drug effect. Care should be taken not to use too high drug concentrations which cause unspecific lysosomal lesions.

Ocular complications of systemic cancer chemotherapy

Cancer chemotherapy has changed rapidly in recent years. New agents are constantly being developed. Established agents are being used with increased frequency, in new combinations, at higher dosages, and via new routes of administration. Enhanced survival, as well as increased drug toxicity, has resulted. Ocular toxicity is not uncommon and can greatly impact on quality of life. Practitioners in all fields are increasingly caring for patients who are receiving cancer chemotherapy. The recognition of eye disease resulting from chemotherapy is essential to appropriate patient management. We provide a review of the rapidly growing body of literature on the ocular toxicity of systemic cancer chemotherapy with particular attention to context, clinical course, mechanism, prevention and treatment.

Mucopolysaccharidosis and lipidosis in rats treated with tilorone analogues

The experimental immunomodulatory agent tilorone was previously reported to induce generalized mucopolysaccharidosis (lysosomal storage of sulfated glycosaminoglycans) and lipidosis in rats. While lipidosis is a side effect common to many cationic amphiphilic compounds, none of them except tilorone has been known to cause mucopolysaccharidosis in intact animals. The purpose of the present histochemical and ultrastructural study was to examine whether or not mucopolysaccharidosis can be induced by tilorone analogues. Three analogues were selected and administered to rats in short-term and subchronic experiments, and liver, spleen, kidney, and cornea were examined. The analogues caused generalized cellular lesions which had the same histochemical and cytological characteristics and the same distribution as the lesions produced by tilorone. The results show that the ability to induce mucopolysaccharidosis is not a unique property of tilorone; this drug side effect should be taken into account when developing new drugs with molecular structures resembling that of tilorone.

Keratopathy in rats after treatment with tilorone

According to clinical reports, the antitumor drug tilorone induces corneal opacities in patients. The present communication shows that keratopathy can be experimentally reproduced in rats and describes the cellular alterations underlying the corneal opacities. Tilorone was applied either orally (60-90 mg/kg) for several weeks or topically (2%) for a few days. Biomicroscopic examination performed after treatment for 6 weeks or longer revealed fine punctate opacities throughout the corneal stroma. Ultrastructurally, the keratocytes were swollen due to large, optically empty vacuoles in the cytoplasm. Similar, albeit smaller, vacuoles were also numerous in the endothelium and less frequent in the epithelium. Histochemical experiments showed that the cellular alterations represented lysosomal storage of polyanionic substances, most probably sulfated glycosaminoglycans, thus mimicking the cytological picture of mucopolysaccharidosis. Upon discontinuation of drug treatment, the alterations tended not to recede. This keratopathy in rats is part of a generalized mucopolysaccharidosis-like disorder induced by tilorone.

Tilorone-induced lysosomal storage mimicking the features of mucopolysaccharidosis and of lipidosis in rat liver

This ultrastructural and histochemical study deals with the lysosomal storage phenomena occurring in the rat liver after repeated oral administration of tilorone, an agent with anti-tumor and anti-viral activities. In the sinusoidal endothelium and in Kupffer cells, the lysosomes were changed into large vacuoles which contained material with the histochemical characteristics of acid glycosaminoglycans. The alterations closely resembled those previously observed in the splenic red pulp of tilorone-treated rats. In hepatocytes, the lysosomes were converted into large multilamellated inclusions indicating storage of polar lipids. The results show that, in the rat liver, tilorone induces cellular alterations mimicking those of inherited mucopolysaccharidoses and lipidoses. After discontinuing drug treatment the two storage phenomena gradually faded at different rates: The lipidosis disappeared within 2 to 4 weeks, whilst mucopolysaccharidosis-like changes were still found 15 weeks after drug withdrawal. The occurrence of lipidosis is not surprising, since by its molecular structure tilorone can be regarded as belonging to the group of amphiphilic cationic drugs which often have this side effect. Much more surprising is the occurrence of mucopolysaccharidosis-like alterations. The exact biochemical identification of the polyanionic storage material and the molecular mechanisms responsible for this drug side effect remain to be established.

Histochemical evidence for lysosomal storage of acid glycosaminoglycans in splenic cells of rats treated with tilorone

Tilorone, an agent with antiviral and antitumor activities, has previously been reported to produce clear cytoplasmic vacuoles in many cell types of the rat. The present study on rat spleen was planned to investigate the ultrastructural and histochemical features of the tilorone-induced vacuoles occurring in sinus endothelium, trabecular smooth muscle cells, and macrophages of the red pulp. Evidence was obtained that the vacuoles represent lysosomes overloaded with acid glycosaminoglycans (aGAG). The main purpose of the present study was to overcome the technical difficulties of preserving the intralysosomal storage materials which were highly water-soluble and non-fixable by aldehyde fixatives. Preservation, at least for the light microscopical level, was achieved by freeze drying and by means of cationic dyes which served also to characterize the storage materials on the basis of their acidities. Tissue slices were used to determine the critical MgCl2 concentration necessary to abolish Alcian blue staining; cartilage and mast cells served as references. For the storage material in sinus endothelium, the critical MgCl2 concentration was found to be greater than 0.7 M, as compared to greater than 0.5 M for cartilage and greater than 0.9 M for mast cells. The storage materials in trabecular cells and macrophages were slightly less acidic than cartilaginous matrix and more heterogeneous than that in sinus endothelium. Ultrastructurally, positive staining with high iron diamine (HID) confirmed the presence of aGAG within the tilorone-induced vacuoles.

Phase II trials of Baker's antifol, bleomycin, CCNU, streptozotocin, tilorone, and 5-fluorodeoxyuridine plus arabinosyl cytosine in metastatic breast cancer

A total of 202 patients with advanced breast cancer were entered into two prospectively randomized Phase II trials conducted by the Eastern Cooperative Oncology Group, in an effort to identify promising agents and combinations for previously treated cases. Patients in Study 1 received bleomycin, CCNU, or streptozotocin and those in Study 2 received tilorone, Baker's antifol, or a combination of 5-fluorodeoxyuridine plus arabinosyl cytosine. Partial responses were seen only with bleomycin, Baker's antifol, and 5-fluorodeoxyuridine plus arabinosyl cytosine. The median times to treatment failure ranged from 3.6 weeks to 5.7 weeks, and the median survival times, from 8 weeks to 25 weeks for tilorone and bleomycin, respectively. Toxic reactions was primarily hematologic and gastrointestinal, but skin, neurologic, respiratory, and renal abnormalities were noted in some treatment arms. The treatment schedules outlined and the toxic effects noted provide background information that might prove useful in designing complex new chemotherapeutic programs, since there is pharmacological rationale for incorporating some of the agents tested into present standard combination chemotherapy regimens.

Retinopathy after tilorone hydrochloride

Two patients, a 34-year-old woman and a 50-year-old woman, received tilorone HCl, an experimental antitumor drug. After taking the drug orally (total dose, 152 g), the first patient developed corneal subepithelial infiltrates and toxic retinopathy characterized by fine pigment mottling of the peripheral fundus and macula with mild arteriolar narrowing. Although visual acuity was 6/6 (20/20) throughout treatment, Goldmann perimetry showed marked peripheral constriction of the visual fields and results of an electroretinogram and an electro-oculogram were abnormal. After taking the drug orally (total dose, 189 g), the second patient developed corneal subepithelial infiltrates, severe bilateral arteriolar narrowing, and mild pigment mottling of the macula. ERG and EOG were moderately attenuated. Visual fields by Goldman perimetry were within normal limits. Tilorone HCl, like chloroquine, may be an antioxidant that affects the free radical scavenging mechanism of the retinal pigment epithelium. Extensive testing should be done on all patients taking tilorone HCl in order to detect the initial manifestations of retinopathy.