Salwa Abid

Ochratoxin a and human chronic nephropathy in Tunisia: is the situation endemic?

Ochratoxin A (OTA) is a nephrotoxic mycotoxin that is being increasingly considered as the main causal agent of Balkan endemic nephropathy (BEN), a fatal kidney disease associated with the end stage of urothelial tumours. However, despite the considerable amount of data, it is still controversial whether OTA plays a causative or only a subordinate role in the induction of this human nephropathy. Tunisia for years had to confront a very similar human nephropathy, which is tentatively called chronic interstitial nephropathy of unknown cause. This study tends firstly to consolidate the suspected link between this Tunisian chronic interstitial nephropathy (CIN) of unknown cause and the presence of OTA in the blood and food of such patients, and second to enlighten the endemic character of this particular nephropathy. Therefore, in four consecutive inquiries, performed within the period 1991-2000, blood and food OTA contaminations were assayed and compared for 954 nephropathy patients and 205 healthy subjects from the Tunisian general population. This survey was also designed to show that, although the whole population is likely to be exposed to OTA, specific people living in conditions showing similarities with the Balkans do have a kidney disease apparently linked to ochratoxin in food. The results showed that the highest incidences were found in patients with CIN of unknown cause. Indeed, the percentages of OTA-positive samples ranged from 93% to 100%, whereas it was only from 62% to 82% in healthy subjects. Mean OTA concentrations were also higher in patients with CIN of unknown cause than in controls (44.4±-19 mg/L to 55.6±-19 mg/L as opposed to 1.22±-1.2 mg/L to 3.35±-2.32 mg/L, respectively). This study emphasizes further the implication of OTA on this particular human nephropathy and underlines the probable causative role of OTA in the onset of this disease. It is important to note that the highest levels of food OTA contamination were found in the group presenting with CIN of unknown cause, indicating that, similar to the case in the Balkans, people are exposed to OTA essentially by their food.

Karyomegaly of tubular cells as early stage marker of the nephrotoxicity induced by ochratoxin A in rats

Cases of karyomegaly were described by Sclare30 and by Mihatch31 in patients affected with tubular-interstitial nephropathy. The Karyomegalic cells showed enlarged nuclei with accumulation of genetic material. No aetiology was suggested. Our study of rats experimentally intoxicated by ochratoxin A, a well-known nephrotoxic compound, indicates the presence of karyomegaly with alteration of the tubular tissue. In control animals no karyomegalic cells were detected. These observations suggest that karyomegaly with megacytosis may be caused by the nephrotoxic ochratoxin A in the kidney. In addition abnormal mitosis together with karyomegalic cells were observed at an earlier stage of the intoxication (30 days) suggesting possible regeneration if the OTA insults are stopped. After 90 days of treatment, the degeneration increased and only karyomegalic and apoptotic-like cells were observed indicating that the regeneration no longer occurs and that the degeneration becomes irreversible.

Ochratoxin A levels in spices and dried nuts consumed in Tunisia.

A total of 112 samples of spices (24 caraway, 20 coriander, 25 curcuma, 20 black pepper and 23 red pepper) and 110 samples of dried nuts (44 almonds, 42 peanuts and 24 pistachio) purchased from popular markets in 24 regions of Tunisia were analyzed for ochratoxin A (OTA) by fluorescence HPLC. The average levels of contamination of OTA found in spice samples were 244, 206, 290, 274 and 203 µg/kg, respectively, for caraway, coriander, curcuma, black pepper and red pepper. Concerning dried nut samples, the average levels were 61, 60 and 89 µg/kg, respectively, for almonds, peanuts and pistachio. Contamination levels were higher than the usual norms (10.0 OTA µg/kg) established by the European Commission in 2005. This survey is the first to be carried out on the natural occurrence of OTA in the main spices and dried nuts consumed by the Tunisian population.

Induction of cytotoxicity of Pelagia noctiluca venom causes reactive oxygen species generation, lipid peroxydation induction and DNA damage in human colon cancer cells

BackgroundThe long-lasting and abundant blooming of Pelagia noctiluca in Tunisian coastal waters compromises both touristic and fishing activities and causes substantial economic losses. Determining their molecular mode of action is, important in order to limit or prevent the subsequent damages. Thus, the aim of the present study was to investigate the propensity of Pelagia noctiluca venom to cause oxidative damage in HCT 116 cells and its associated genotoxic effects.ResultsOur results indicated an overproduction of ROS, an induction of catalase activity and an increase of MDA generation. We looked for DNA fragmentation by means of the comet assay. Results indicated that venom of Pelagia noctiluca induced DNA fragmentation. SDS-PAGE analysis of Pelagia noctiluca venom revealed at least 15 protein bands of molecular weights ranging from 4 to 120 kDa.ConclusionOxidative damage may be an initiating event and contributes, in part, to the mechanism of toxicity of Pelagia noctiluca venom.

Is cell death induced by nematocysts extract of medusa pelagia noctiluca related to oxidative stress

Pelagia noctiluca, a jellyfish widely distributed in the Mediterranean waters, especially in coastal areas of Tunisia, has garnered attention because of its stinging capacity and the resulting public health hazard. Crude extracts of P. noctiluca nematocysts have been tested for their cytotoxicity on Vero cells. Our results clearly showed that nematocysts induced cell mortality in a dose‐ and time‐dependent manner. A cytoprotective effect against cell mortality was obtained when Vero cells were treated with Vitamin E. This process was further confirmed by the generation of reactive oxygen species (ROS) and the induction of Hsp 70 and 27 protein expressions. Thus, our findings suggested that oxidative stress is involved in the toxicity of pelagia nematocysts and may therefore constitute the major mechanism of this medusa nematocysts toxicity.

Presence of ochratoxin A in Tunisian blood nephropathy patients. Exposure level to OTA.

Ochratoxin A (OTA) produced by Aspergillus and Penicillium genera contaminates cereals and different food compounds. OTA presents a wide range of toxic effects, especially nephrotoxicity. It is also considered to be the main causal agent of Balkan Endemic Nephropathy (BEN) which is similar to the Chronic Interstitial Nephropathy with unknown aetiology seen in Tunisia. In this study, we attempted to confirm the relationship between OTA blood levels and the development of renal pathology. Hence, serum OTA levels were measured in several groups of patients having different renal diseases: a group presenting Chronic Interstitial Nephropathy (CIN) with unknown aetiology, a group presenting Chronic Interstitial Nephropathy (CIN) with known aetiology, a group presenting Chronic Glomerular Nephropathy (CGN), and a group presenting Chronic Vascular Nephropathy (CVN). Each group was compared to a healthy control group. In the healthy group, 49% of individuals showed OTA concentrations ranging from 1.7 to 8.5 ng/ml, with a mean value of 3.3±1.5 ng/ml. However, among nephropathic patients, the group with CIN of unknown aetiology showed the highest incidence (76%), ranging from 1.8 to 65 ng/ml with a mean value of 18±7 ng/ml. Even in the healthy group, the calculated Daily Intake (DI) ranged from 5.0 to 24.9 ng/kgb.w./day when compared to the recommended DI by the scientific committee on foods of 5 ng/kgb.w./day, indicating a high degree of exposure to OTA in the Tunisian population. Our study confirms the involvement of this nephrotoxic mycotoxin, present at high blood levels in the Tunisian population, in the outcome of this particular human nephropathy (CIN with unknown aetiology) which is similar to BEN.

Analgesic and antibutyrylcholinestrasic activities of the venom prepared from the Mediterranean jellyfish Pelagia noctiluca (Forsskal, 1775)

BackgroundToxins derived from jellyfishes have been exploited as a model for the development of new drug promising applications to treat neurodegenerative diseases. The present work is aimed to evaluate the acute toxicity of crude venom of Pelagia noctiluca and then to screen the analgesic and antibutyrylcholinestrasic (anti-BuChE) activities of the crude venom and its fractions.MethodsSephadex G75 gel was used to separate crude venom of Pelagia noctiluca, which led to some fractions. In addition, in vivo analgesic and in vitro plasma antibutyrylcholinestrasic activities were carried out with Pelagia crude venom and its fractions respectively.ResultsThe crude venom and its fractions displayed analgesic and anti-BuChE activities at different doses without inducing acute toxicity. Fraction 2 possesses the highest analgesic and antibutyrylcholinestrasic properties. The crude venom and fraction 1 had shown to possess less significant inhibitory activity against analgesic and antibutyrylcholinestrasic models.ConclusionsBased on this study, the crude venom of Pelagia noctiluca is found to be a useful tool for probing pharmacological activity. The purification and the determination of chemical structures of compounds of active fractions of the venom are under investigation.

The mycotoxin zearalenone enhances cell proliferation, colony formation and promotes cell migration in the human colon carcinoma cell line HCT116

Zearalenone (ZEN) and Aflatoxin B1 (AFB1) are fungal secondary metabolites produced by Fusarium and Aspergillus genera, respectively. These mycotoxins are found world-wide as corn and wheat contaminants. AFB1 is probably the most toxic and carcinogenic mycotoxin. It has been demonstrated to be mutagenic, genotoxic, and hepatocarcinogenic. ZEN is a non-steroidal estrogenic mycotoxin that displays hepatotoxicity, immunotoxicity and genotoxicity. Its mutagenic and carcinogenic properties have so far remained controversial and questionable. Using the colon carcinoma cell line HCT116, we will show here that ZEN, at low concentrations, enhances cell proliferation, increases colony formation and fastens cell migration after wound healing. The highest effect of ZEN was observed at a concentration 10 times lower as compared to AFB1. Our findings suggest thus that this mycotoxin exhibits carcinogenesis-like properties in HCT116 cells.

Dichlorvos-induced toxicity in HCT116 cells: Involvement of oxidative stress and apoptosis

Organophosphorous (OP) pesticides are widely used in the agriculture and home. Among those pesticides, Dichlorvos (DDVP) is a worldwide used insecticide for pest control. DDVP is commonly used as an insecticide for maintenance and growth of agricultural products, to control the internal and external parasites of farm animals, and to eradicate insects threatening the household, public health, and stored products. Although substantial information is available regarding the environmental and ecological impact of DDVP, not much is known in regard to its toxicity in the mammalian system. Therefore a study was conducted for the assessment of cytotoxic and genotoxic effects of DDVP in human colon carcinoma (HCT116) cell line. We demonstrated that DDVP significantly decreased cell viability as assessed by the MTT assay. The increase in cell death was accompanied by a reduction in the mitochondrial membrane potential. Besides, pretreatment with Z-VAD-FMK, a general caspases inhibitor, decreased significantly the DDVP-induced cell death. We also shown that DDVP induced reactive oxygen species (ROS) generation followed by lipid peroxidation as evidenced by an increase in the MDA levels. Our results also indicate that DDVP induced a concentration-dependent increase in DNA damage as evident by the comet assay. These data indicate that DDVP produces cytotoxicity and DNA damage in mammalian cells and should be used with caution.

Cell death in relation to DNA damage after exposure to the jellyfish Pelagia noctiluca nematocysts

Studies on the toxicity of Mediterranean jellyfish have gained attention owing to their weak toxic properties. Our research has been mainly performed on the Scyphomedusae. Pelagia noctiluca is a scyphozoan jellyfish which causes a danger to sea bathers and fishery damages in the Mediterranean Sea. To check whether the cytotoxicity of Pelagia noctiluca nematocysts was associated to DNA lesions, we have looked for DNA fragmentation by means of the Comet and chromosome aberration assays. To specify cell death pathway, we have investigated caspase‐3 activation. Our results have shown that nematocysts reduced cell viability and induced DNA fragmentation in a concentration‐dependent manner with a maximum effect at 150 000 nematocysts mL−1. The high percentage of chromosome aberrations also emphasized the genotoxic character of Pelagia noctiluca nematocysts in Vero cells. This fragmentation was correlated to apoptosis induction which was confirmed by caspase‐3 activation. In conclusion, the present report has suggested that Pelagia noctiluca nematocysts were able to promote apoptosis in Vero cells and therefore may be useful in cancer therapy.