Organomegaly and histopathology in an animal model of mucopolysaccharidosis induced by suramin

The Polyanionic Drug Suramin Neutralizes Histones and Prevents Endotheliopathy

Drugs are needed to protect against the neutrophil-derived histones responsible for endothelial injury in acute inflammatory conditions such as trauma and sepsis. Heparin and other polyanions can neutralize histones but challenges with dosing or side effects such as bleeding limit clinical application. In this study, we demonstrate that suramin, a widely available polyanionic drug, completely neutralizes the toxic effects of individual histones, but not citrullinated histones from neutrophil extracellular traps. The sulfate groups on suramin form stable electrostatic interactions with hydrogen bonds in the histone octamer with a dissociation constant of 250 nM. In cultured endothelial cells (Ea.Hy926), histone-induced thrombin generation was significantly decreased by suramin. In isolated murine blood vessels, suramin abolished aberrant endothelial cell calcium signals and rescued impaired endothelial-dependent vasodilation caused by histones. Suramin significantly decreased pulmonary endothelial cell ICAM-1 expression and neutrophil recruitment caused by infusion of sublethal doses of histones in vivo. Suramin also prevented histone-induced lung endothelial cell cytotoxicity in vitro and lung edema, intra-alveolar hemorrhage, and mortality in mice receiving a lethal dose of histones. Protection of vascular endothelial function from histone-induced damage is a novel mechanism of action for suramin with therapeutic implications for conditions characterized by elevated histone levels.

Antitumor activity and structure-activity relationship of heparanase inhibitors: Recent advances

Heparanase (HPSE)-directed tumor progression plays a crucial role in mediating tumor-host crosstalk and priming the tumor microenvironment, leading to tumor growth, metastasis and chemo-resistance. HPSE-mediated breakdown of structural heparan sulfate (HS) networks in the extracellular matrix (ECM) and basement membranes (BM) directly facilitates tumor growth and metastasis. Lysosome HPSE also induces multi-drug resistance via enhanced autophagy. Therefore, HPSE inhibitors development has become an attractive topic to block tumor growth and metastasis or eliminate drug resistance. In this review, we summarize HPSE inhibitors applied experimentally and clinically according to interaction with the binding sites of HPSE and participation of growth factors. The antitumor activity and structure-activity relationship (SAR) are also emphasized.

The role of heparanase in diseases of the glomeruli

The glomerular basement membrane (GBM) is a kind of net that remains in a state of dynamic equilibrium. Heparan sulfate proteoglycans (HSPGs) are among its most important components. There are much data indicating the significance of these proteoglycans in protecting proteins such as albumins from penetrating to the urine, although some new data indicate that loss of proteoglycans does not always lead to proteinuria. Heparanase is an enzyme which cleaves beta 1,4 D: -glucuronic bonds in sugar groups of HSPGs. Thus it is supposed that heparanase may have an important role in the pathogenesis of proteinuria. Increased heparanase expression and activity in the course of many glomerular diseases was observed. The most widely documented is the significance of heparanase in the pathogenesis of diabetic nephropathy. Moreover, heparanase acts as a signaling molecule and may influence the concentrations of active growth factors in the GBM. It is being investigated whether heparanase inhibition may cause decreased proteinuria. The heparanase inhibitor PI-88 (phosphomannopentaose sulfate) was effective as an antiproteinuric drug in an experimental model of membranous nephropathy. Nevertheless, this drug is burdened by some toxicity, so further investigations should be considered.

Purine receptor antagonist modulates serology and affective behaviors in lupus-prone mice: evidence of autoimmune-induced pain?

Neurologic and psychiatric (NP) manifestations are severe complications of systemic lupus erythematosus (SLE). As commonly seen in patients, spontaneous disease onset in the MRL/MpJ-Fas(lpr)/J (MRL-lpr) mouse model of NP-SLE is accompanied by increased autoantibodies, pro-inflammatory cytokines and behavioral dysfunction which precede neuroinflammation and structural brain lesions. The role of purinergic receptors in the regulation of immunity and behavior remains largely unexplored in the field of neuropsychiatry. To examine the possibility that purinoception is involved in the development of affective behaviors, the P2X purinoceptor antagonist, suramin, was administered to lupus-prone mice from 5 to 14 weeks of age. In addition to food and water measures, novel object and sucrose preference tests were performed to assess neophobic anxiety- and anhedonic-like behaviors. Enzyme-linked immunosorbant assays for anti-nuclear antibodies (ANA) and pro-inflammatory cytokines were employed in immunopathological analyses. Changes in dendritic morphology in the hippocampal CA1 region were examined by a Golgi impregnation method. Suramin significantly lowered serum ANA and prevented behavioral deficits, but did not prevent neuronal atrophy in MRL-lpr animals. In a new batch of asymptomatic mice, systemic administration of corticosterone was found to induce aberrations in CA1 dendrites, comparable to the "stress" of chronic disease. The precise mechanism(s) through which purine receptor inhibition exerted beneficial effects is not known. The present data supports the hypothesis that activation of the peripheral immune system induces nociceptive-related behavioral symptomatology which is attenuated by the analgesic effects of suramin. Hypercortisolemia may also initiate neuronal damage, and metabolic perturbations may underlie neuro-immuno-endocrine imbalances in MRL-lpr mice.

Respiratory Tract

The chapter describes different aspects of the respiratory tract. In preclinical safety studies, pathologies of the respiratory system can be a result of an intercurrent disease or can be induced by systemically administered drugs. Intranasal or inhalation modes of therapy pose particular challenges in terms of the formulations and technologies required to administer a drug. A complex technology is developed to support the assessment of adverse effects of inhaled substances in rodent and nonrodent species, and the extrapolation of experimental findings to humans. The nasal chambers are the structures that are first to be subjected to the effects of inhaled substances, whether microorganisms or chemical substances. In rodents, the relatively small size of the nose and nasal sinuses facilitates a histological examination. Findings show that infectious agents cause inflammation in the nose and nasal sinuses, and this may be associated with inflammation in the conjunctiva, the middle ear, and the oral cavity. It has been observed that a particular response of the rodent nasal mucosa to some irritant substances, including pharmaceutical agents, is the formation of rounded eosinophilic inclusions in the cytoplasm of sustentacular cells of the olfactory epithelium, and to a lesser extent in respiratory and glandular epithelial cells.

Lysosomal-storage disorder induced by elmiron following 90-days gavage administration in rats and mice

Elmiron, a highly sulfated, semisynthetic pentose polysaccharide with properties similar to heparin, is used for the treatment of interstitial cystitis. Thirteen-week gavage studies were conducted by administering the drug in deionized water to F344/N rats and B6C3F1 mice once daily, 5 days per week for up to 13 consecutive weeks, at doses of 0, 63, 125, 250, 500, and 1,000 mg/kg body weight. No significant drug-related effects were observed in body weight, survival, clinical, and necropsy results. Significant organ weight increases were seen in the liver, lungs, and spleen of both species and the kidneys of rats, mainly in groups treated with 250 mg/kg/day and above. Hematological analysis indicated increases for both species in the white blood cell and lymphocyte counts. Sites of toxicity identified histopathologically were the rectum, liver, mesenteric and mandibular lymph nodes (both sexes), spleen (mice only), and lungs and kidneys (rats only). Lesions consisted mainly of infiltration into multiple tissues of vacuolated histiocytes, which, by histochemical investigation, indicated the presence of neutral and acidic mucins and lipidic material within the vacuoles. Transmission electron microscopy identified these vacuoles as lysosomal structures that exhibited a variety of contents. On the basis of our findings, we propose that Elmiron was absorbed through the focally disrupted rectal mucosa, was deposited in the lamina propria, accumulated within macrophages, and then was distributed by these cells or as a free chemical via the lymphatics and blood, to the various organ sites manifesting histiocytic infiltration. The cytoplasmic membrane-bound structures within macrophages were lysosomes containing membranous material of cellular origin and, perhaps, remnants of the deposited test material, Elmiron.

Suramin-induced neuropathy in an animal model

Suramin is being used either alone, or in combination with other chemotherapeutic agents, in the treatment of hormone-refractory or metastatic prostate cancer. Use of this potentially valuable chemotherapy is limited by a dose-dependent polyneuropathy. It has been difficult in human studies to characterize peripheral suramin toxicity separately from cancer-related neuropathy. To characterize suramin-induced neuropathy in a rat model, adult rats were given either a single dose of 500 mg/kg (high dose) or 50 mg/kg (low dose) weekly suramin for 2 months. Electrophysiology and peroneal/sural nerve morphometry were performed. In high dose animals, neuropathy developed within 2 weeks, most severe in the digital sensory responses (DSR) (p<0.05) and tail and hind limb compound muscle action potential (p<0.001). Histologically, there was evidence of axonal degeneration and axon atrophy. With low dose suramin, the DSR (p<0.05) and tail distal sensory and motor responses (p<0.01) were most severely affected at 2 months. Axonal degeneration was seen in teased fibers from most animals. With TEM, there were abundant characteristic lysosomal inclusion bodies in DRG and Schwann cells. Electrophysiological and histological evidence of peripheral demyelination was rare, being observed in only one animal. Suramin induced a length, dose and time-dependent axonal sensorimotor polyneuropathy associated with axonal degeneration, atrophy, and accumulation of glycolipid lysosomal inclusions.

Effects of purinergic and adrenergic antagonists in a rat model of painful peripheral neuropathy

In previous studies, pain behaviors produced in the spinal nerve ligation rat model of neuropathic pain were partly reduced by surgical lumbar sympathectomy. However, systemic injection of phentolamine, an alpha-adrenoceptor blocker, was not effective in reducing pain behaviors, at least in the Sprague-Dawley strain of rats. This suggests that sympathectomy removes not only adrenoceptor function but also other factors that must contribute importantly to the generation of neuropathic pain behaviors. Since the purinergic substance adenosine 5'-triphosphate (ATP) is known to be co-released with norepinephrine (NE) from the sympathetic nerve terminals, we hypothesized that ATP might be involved in the sympathetic dependency of neuropathic pain. The present study tested this hypothesis by examining the effects of systemic injection of an adrenoceptor blocker (phentolamine), a purinoceptor blocker (suramin), and a combination of these two on behavioral signs of mechanical allodynia in the spinal nerve ligation model of neuropathic pain. The results of the present study showed two novel findings. First, the mechanical hypersensitivity (allodynia) resulting from the L5/6 spinal nerve ligation can be reduced either by sympathetic block accomplished by application of a local anesthetic or by surgical sympathectomy of the L2-L6 sympathetic ganglia. Second, suramin (at 100 mg/kg, i.p.) can reduce mechanical hypersensitivity in neuropathic rats when given in combination with 5 mg/kg of phentolamine. This effect was observed in a subset of neuropathic rats, and the drug responses were consistent in repeated treatments within the animal group. Neither phentolamine nor suramin changed the mechanical sensitivity of neuropathic rats when given alone. The data suggest that the purinergic substance ATP is co-released with NE from sympathetic nerve terminals and these two are together involved, at least in part, in the maintenance of the sympathetically dependent component of pain behaviors in some neuropathic rats.

Activation of the high affinity nerve growth factor receptor by two polyanionic chemotherapeutic agents: role in drug induced neurotoxicity

Suramin is a polyanionic chemotherapeutic agent which causes severe peripheral neuropathy. The mechanisms of antineoplastic and neurotoxic activities are still poorly understood. Interference with growth factor receptor function has been suggested for suramin's chemotherapeutic function. Previous studies from our laboratory have demonstrated that suramin interfered with the function of nerve growth factor (NGF) and induced lysosomal storage defects within dorsal root ganglion neurons. Pentosan polysulfate (PPS) was used as another polyanionic agent, to compare these two cellular functions; NGF receptor interaction and disruption in glycolipid metabolism. Like suramin and NGF, PPS induced neurite outgrowth from the PC12 cell line which correlated with tyrosine phosphorylation of the high affinity NGF receptor (TrkA/gpl40) and ERK-1/MAP kinase. Ultrastructural studies of dorsal root ganglion exposed to PPS for various time periods were normal. This contrasted with suramin exposed cultures which consistently developed lamellar inclusion bodies (LIB) within 6 h. LIB formation with suramin treatment was associated with neuronal cell death, while PPS treatment did not cause any neurotoxic effects. These results indicated that PPS mimicked the effect of suramin on NGF receptors but did not cause similar accumulation of LIB. This suggested that the effect of polyanionic compounds on TrkA was not involved in LIB accumulation and subsequent induction of neurotoxicity.

Co-localization of suramin and serum albumin in lysosomes of suramin-treated human colon cancer cells

Suramin is a polysulfonated compound currently under investigation for the treatment of various types of cancer. Pharmacokinetic studies from clinical trials in humans have shown that most of the circulating drug is associated with serum albumin. The objective of the present study was to investigate the intracellular localization of suramin and serum albumin in human colon cancer cells (HT-29-D4) upon suramin treatment. For this purpose, combined gold labeling and autoradiographic methods were performed on HT-29-D4 cells grown in serum free medium containing both [3H]suramin and colloidal gold-albumin. These morphological experiments demonstrated for the first time that suramin and serum albumin were co-localized in the same cellular compartment (i.e. the lysosomal system) of the suramin-treated HT-29-D4 cells. The albumin-directed targeting of suramin in lysosomes may allow the drug to inhibit the activity of several lysosomal hydrolases, resulting in a lysosomal storage disorder.

Intracellular localisation of suramin, an anticancer drug, in human colon adenocarcinoma cells: a study by quantitative autoradiography

Suramin is a polysulphonated naphthylurea currently investigated for the treatment of advanced malignancy. In the present study, we have analysed the uptake and the intracellular localisation of tritiated suramin in human colon adenocarcinoma cells (HT-29-D4), using quantitative autoradiographic techniques at the optical and electron microscopy levels. Our results show that the drug is able to enter both undifferentiated and differentiated HT-29-D4 cells. The process of suramin uptake is time-dependent, and significantly inhibited by the presence of the suramin-binding protein serum albumin in the culture medium of HT-29-D4 cells. Autoradiographic analysis revealed two distinct patterns of intracellular localisation of tritiated suramin labelling, according to the presence or absence of serum albumin. Indeed, in the absence of serum albumin, the labelling of free suramin was distributed over the nucleus, the Golgi apparatus and the mitochondria, while it was restricted to the lysosomal system when suramin was complexed with albumin. These data show that a serum factor, i.e. albumin, influences the biological activity of suramin by determining its intracellular localisation. The presence of suramin in a given compartment may account for specific effects of the drug including mitochondrial hypertrophy, altered gene expression and lysosomal perturbation.

Lipids in predentine and dentine

Using two histochemical methods, malachite green-aldehyde and iodoplatinate, phospholipids were visualized in the predentine of rat incisors in the spaces located between collagen fibers and in dentine as needle-like structures located along individual or groups of mineralizing collagen fibers. The same staining pattern was seen with phospholipase A2-gold. Autoradiographic investigation using 3H choline as labelled precursor, visualized the incorporation of membrane-associated and extracellular choline-containing phosphatidyl choline and sphingomyelin. The cell and membrane-associated labelling decreased gradually between 24 and 4 days, whereas incorporation of the labelled precursor as stable extracellular matrix component was seen in dentine. In addition to these investigations, pharmacologically induced (suramine) and genetically (Krabbe's disease) lysosomal storage pathology was investigated. Defects due to lipid metabolism alterations were seen in predentine and/or in dentine. The major differences visualized here between the non-mineralized and mineralized compartments and interactions between phospholipids and proteoglycans, support the view that phospholipids as matrix components play an important role in the mechanisms of dentine formation and mineralization.

Liver damaging effect of suramin in normal and carbon-tetrachloride treated rats

Male Fischer 344 (F344) rats were treated with phenobarbital + carbon tetrachloride (CCl4) for 16 weeks to induce liver cirrhosis. Another group of rats received 50 mg/kg iv suramin once a week for 16 weeks. The third group of rats was treated with both phenobarbital + CCl4 and suramin. After 16 weeks of suramin treatment, a massive periportal infiltration composed of macrophages, many of them containing glycosaminoglycans in their cytoplasm, mast cells, and other inflammatory cells were observed. This lesion was added to the liver cirrhosis caused by CCl4 in the group treated with suramin and CCl4. The changes in glycosaminoglycan metabolism caused by suramin did not influence the CCl4 cirrhosis. Since suramin has been reported to be a prototype of a new generation of antitumor compounds, we suggest caution in the use of chronic suramin treatment, especially in patients with livers which are already damaged.

Nephrotoxicity screening in rats: a validation study

A validation of our non-invasive screening test for the detection of renal damage (Zbinden et al. 1988) is presented. The test is based on repetitive, quantitative urine analysis in groups of six female Sprague-Dawley rats treated on 5 consecutive days with low doses of test substances. Higher doses were administered in the following weeks until nephrotoxic effects or signs of general toxicity were observed. Thirteen reference substances (hexachloro-1:3-butadiene [HCBD], cisplatin, carboplatin, suramin, chloroform, neomycin, rifampicin, phenacetin, phenylbutazone, methicilline, sodium oxalate, ethylene glycol and furosemide) were used. The percentage of rats reaching the test criteria, i.e., pathologic values defined on the basis of measured control values, was determined. In the controls, the overall percentage of rats reaching or exceeding the test criteria was 4.48%, a value that is close to the expected 5%. Evidence of nephrotoxicity was found with all reference compounds. Elevated excretion of cells and occurrence of cylinders were the most sensitive indicators of renal damage. Hematuria was the most frequent finding. Of the other urine constituents measured the enzyme malate dehydrogenase (MDH) was frequently increased. Water consumption, urine volume, pH and specific gravity were occasionally, and protein, glucose, electrolytes, amino acids and gamma-glutamyl-transpeptidase (GGT) were only rarely changed. It is concluded that the screening which is based on quantitative and repeated urine analysis is a useful procedure to detect nephrotoxic chemicals acting by a variety of mechanisms. The histopathological examination of the kidneys contributed useful information of the nature of the toxic effects, but as a screening tool it is less sensitive than quantitative urine analysis.

On the alcianophilia of the drug suramin used as a tool for inducing experimental mucopolysaccharidosis

The trypanocidal drug suramin was previously reported to induce mucopolysaccharidosis in rats; apart from the biochemical demonstration of increased tissue concentrations of sulfated glycosaminoglycans (GAGs), a strongly positive staining reaction with the cationic dye Alcian Blue was taken as indicating GAG-storage (Constantopoulos et al. 1983). The purpose of the present report is to point out a methodical pitfall. In model experiments it was found that suramin itself, being a polysulfated compound, gives a strongly positive reaction with Alcian Blue at pH 1. It is known that suramin is accumulated in the lysosomes and that high drug concentrations are retained in the tissues for weeks. Therefore a positive staining reaction with Alcian Blue observed in a given cell cannot be conclusively attributed to the storage of sulfated GAGs as has been done in the past. The present report may be a warning that, in the case of the suramin-induced animal model of mucopolysaccharidosis, the usual histochemical strategy, i.e. staining with cationic dyes, is not suitable for analysing the cellular distribution pattern of GAG-storage, since the inducing drug by itself reacts with the indicator dye.

The suramin-treated rat as a model of mucopolysaccharidosis. Variation in the reversibility of biochemical and morphological changes among different organs

We have examined the reversibility of the biochemical and pathological changes induced in the spleen, kidney and lung of the suramin-treated rat which we have previously proposed as a useful model of the human condition, mucopolysaccharidosis (MPS). Rats were injected with a single intravenous dose of suramin (250 mg/kg) and allowed to survive for periods of up to 6 months. The organs were examined for suramin content, pathological changes, biochemical storage of glycosaminoglycans (GAGs) and for the blockage of the relevant hydrolytic enzymes. The extent and rate of suramin accumulation and the retention of the drug varied considerably between organs with the greatest concentration of suramin (4,000 micrograms/g) occurring in the kidney 2 weeks after injection. Suramin persisted at gradually decreasing levels in all organs for the duration of the experiment, remaining at the highest level (1,150 micrograms/g) in the kidney. The concentration of GAGs peaked 10-18 days after administration of the drug, in all organs. Within 6 months the level had returned to normal in the liver, spleen and lung, but remained elevated in the kidney. The activities of beta-glucuronidase and acid phosphatase were decreased in all organs at diminishing levels throughout the experiment. There was a significant increase in the activity of arylsulphatase B, except in the kidney, where the predominant effect was a reduction of activity. Recovery from the morphological changes was evident in all organs except the lung within 6 months of suramin administration. The reversibility of the biochemical and pathological changes in the various tissues is discussed and compared with the earlier results described for the liver (Rees et al. 1986) and the implications of using suramin for the treatment of human trypanosomiasis, onchocerciasis and AIDS are considered.

The suramin-treated rat as a model of mucopolysaccharidosis: reversibility of biochemical and morphological changes in the liver

Rats treated with the trypanocidal drug suramin, a potent inhibitor of several lysosomal enzymes, develop a storage disorder which mimics the features of mucopolysaccharidosis (Constantopoulos et al. 1983). In this paper we have examined the reversibility of the biochemical and pathological changes induced in the liver of the suramin-treated rat. Rats were injected with a single intravenous dose of suramin (250 mg/kg) and allowed to survive for periods of up to 6 months. The liver was examined for suramin content, pathological changes, biochemical storage of glycosaminoglycans (GAGs) and for the blockade of the relevant hydrolytic enzymes. GAG storage in the liver peaked at approximately 14 days after administration of suramin when there was a five-fold increase in the GAG content. Thereafter GAGs decreased in parallel with the fall of suramin concentrations so that within 6 months the content had returned to control levels. The activity of most of the enzymes tested had also returned to control levels within 6 months. The pathological changes which are evident in the liver 1-2 weeks after administration of the drug had diminished considerably within 6 months. These results indicate that significant reversibility of both the biochemical and pathological changes induced by suramin occurs and they support the suitability of the suramin treated rat as a model to assess the value of therapeutic treatments of mucopolysaccharidosis.

Morphological and enzymatic heterogeneity of suramin-induced lysosomal storage disease in some tissues of mice and rats

Suramin-induced lysosomal storage disease reproduced in the rat was extended to the mouse with the attempt to characterize enzymatically and morphologically heterogeneous responses of various organs to the drug. Suramin administration strikingly decreased (3-6 days afterward) the activity of beta-glucuronidase in all tissues studied (kidney, liver, heart, and skeletal muscle). The enzymatic responses were small in the activities of beta-N-acetyl-glucosaminidase. The activity of arylsulfatase A decreased to a varying degree in mouse tissues, but in rats the activity increased in liver and skeletal muscle. The activity of cathepsin D increased in rat tissues. Suramin induced morphological changes characteristic to lysosomal storage diseases in kidney and liver but not in heart and skeletal muscle of both mice and rats. Kidney was appreciably more susceptible to suramin than liver. The occurrence of lysosomal accumulations, membranous lamellar inclusions, and granular material were most prominent in tubular cells of kidney and in Kupffer cells of liver. These cells also presented intensive Alcian blue staining. Interestingly, the enzymatic and morphological responses did not correlate with each other, which may reflect differences in the regulation of lysosomal functions in various cell types.