Acute liver injury in ducklings and rats as a result of ochratoxin poisoning

Melatonin alleviates Ochratoxin A-induced liver inflammation involved intestinal microbiota homeostasis and microbiota-independent manner

Melatonin (MEL) shows an anti-inflammatory effect and regulates intestinal microbiota communities in animals and humans; Ochratoxin A (OTA) induces liver inflammation through intestinal microbiota. However, it remains to know whether MEL alleviates the liver inflammation induced by OTA. In this study, MEL reversed various adverse effects induced by OTA. MEL recovered the swarming and motility of intestinal microbiota, decreased the accumulation of lipopolysaccharide (LPS), enhanced the tight junction proteins of jejunum and cecum segments; ultimately alleviated OTA-induced liver inflammation in ducks. However, it is worth noting that MEL still had positive effects on the OTA-exposed ducks after antibiotic treatment. These results suggest that both the maintenance of intestinal microbiota homeostasis and intestinal microbiota-independent manner involved the MEL anti-inflammatory function in OTA-induced liver inflammation. MEL represent a promising protective approach for OTA, even other mycotoxins.

Ochratoxin A at nanomolar concentrations: A signal modulator in renal cells

Ochratoxin A (OTA) is a ubiquitous fungal metabolite with nephrotoxic, carcinogenic, and apoptotic potential. Toxicokinetics make the kidney the primary target organ for OTA. Due to its widespread occurrence in improperly stored foodstuff the complete and safe avoidance of OTA for humans is impossible. There are several reports showing a significant correlation between OTA exposure and certain forms of nephropathies. At nanomolar concentrations OTA leads to specific changes of function and phenotype in renal cells. The toxin interacts with certain cellular "key-molecules" (e. g., mitogen-activated protein (MAP) kinases, Ca2+), thereby disturbing cellular signalling and regulation events as well as mitochondrial function. Moreover, OTA has the ability to modulate physiological signals (e. g., angiotensin II or TNFalpha) and thereby influences cell function and cell growth and may even stable re-program the cells (e. g., altered distribution of chromosomes). This review concentrates on the effects of OTA in the nanomolar range and its interactions with cellular signalling networks in different renal cells proposing OTA to act as a signal modulator.

Histopathologic and electron microscopic studies on the acute toxicity of ochratoxin A in rats

Ochratoxin A was given by gavage to male rats. Moribund and dead animals were necropsied, and the surviving rats, including the controls, were killed 48 hours after dosing. Many of the principal rats were moribund, or began dying, within 12 to 24 hours after dosing. Lesions suggestive of disseminated intravascular coagulation were seen by light microscopy as early as 12 hours after dosing; fibrin deposits were in the spleen, brain choroid plexus, glomerular capillaries, liver, and heart. Renal tubular nephrosis, hepatic and lymphoid necrosis, and necrotic enteritis with villous atrophy were also seen. Electron microscopy demonstrated fibrin strands mixed with degranulated platelets, necrotic leukocytes, and swollen endothelial cells in glomerular capillaries. Myocardial changes included focal supercontracted sarcomeres adjacent to intercalated disks. Swollen sarcolemma, lysed myofibrils and fragmented Z-bands with interstitial edema, vascular thrombosis, and endothelial damage were also seen. The acute pathologic changes induced by ochratoxin A in the intestine, liver, and lymphoid tissues were more obvious than the tubular nephrosis, and the development of a disseminated intravascular coagulation-like syndrome with myocardial changes was a complicating factor.

Hematological changes produced in mice by ochratoxin A and citrinin

The effect of 6 weekly injections of ochratoxin A (5 mg/kg) and citrinin (20 mg/kg) on the following hematological indices of mice was studied: erythrocyte sedimentation rate, hematocrit percentage, mean corpuscular values, red cell indices, platelet count, total count of bone marrow cells, differential count of bone marrow cells, total count of splenic cells, spleen weight, and serum calcium. These mycotoxins resulted in a significant decrease in platelet count and hematocrit values. On the other hand, they increased erythrocyte sedimentation rate, mean corpuscular values and red cell indices. Weight of the spleen and the splenic cell count decreased significantly in ochratoxin A and citrinin treated mice. Total count of bone marrow cells, erythrocyte precursors, leucocyte precursors and megakaryocyte precursors of femoral bone marrow decreased significantly in toxin treated mice. Calcium concentration in the serum of toxin treated mice also was decreased significantly.

Natural occurrences of ochratoxicosis in poultry

Five independent episodes of ochratoxicosis in about 970,000 turkeys, two episodes in about 70,000 laying hens, and two episodes in about 12,000,000 broiler chickens were investigated. Ochratoxin A concentrations in suspect feed and ingredients ranged from less than .2 to 16 ppm. Feed samples tested for T-2 toxin, F-2 toxin, heavy metals, and polychlorinated biphenyls were negative. Minor amounts of aflatoxin (less than 60 ppb) were found in suspect feed from two episodes. The main symptoms in turkeys were mortality (up to 59%), nephrotoxicity (pale, swollen kidneys that became tan colored in the sequel to acute toxicity), decreased feed consumption (as little as 20% of the normal feed intake) prior to death, and secondary air sacculitis. Histopathology revealed edema and necrosis of the proximal tubules of the kidneys and no changes in the liver or other organs. Suspect feed containing 2 ppm ochratoxin A increased uric acid levels in serum when fed to poults in the laboratory. The episodes in laying hens were characterized by reduced egg production, poor egg shell quality, and nephropathy. The episodes in broiler chickens were characterized by poor growth rate, poor feed conversion efficiency, poor pigmentation, nephropathy, and increased incidence of air sacculitis. Obtaining feed and ingredients free of ochratoxin, cleaning the feed and ingredient handling equipment, and adding antifungal agents to the feed proved beneficial. Eight of the 9 episodes were traced to the corn supply and the ninth episode was traced to corn gluten meal that became contaminated during storage after manufacture. Evidence was obtained that the ochratoxin was unstable and declined in concentration during storage. Aqueous acetone was a better solvent for extracting ochratoxin than was the recommended phosphoric acid: chloroform. The ochratoxin extracted from high potency samples consisted of ochratoxins A, B, and C in ratios of about 90:8:2.

Decreased glycogen mobilization during ochratoxicosis in broiler chickens

Graded doses of pure ochratoxin A (0, 0.5, 1.0, 2.0, 4.0, and 8.0 microgram of toxin per g of feed) were incorporated into a commercial diet which was fed to chickens from hatching to 3 weeks of age, at which time the experiments were terminated. Liver glycogen levels were elevated significantly (P less than 0.05) by 4.0 and 8.0 microgram/g but not lower doses. Glucagon stimulation of glycogen mobilization was inhibited at the same concentrations. Histopathological examination revealed cytoplasmic but not nuclear deposits of glycogen in cells at the periphery of liver lobes. These data demonstrated that ochratoxin inhibited glycogenolysis. Impaired ability to generate glucose from glycogen could account for the increased susceptibility to cold stress previously reported to occur in ochratoxicosis. Based on present and prior observations, it seems possible that ochratoxin induces a syndrome which mimics the glycogen storage disease of type X which is caused by a deficiency in the cyclic AMP-dependent enzyme of the glycogenolytic enzymatic cascade.

The pharmacokinetics of ochratoxin A in rats

The absorption and tissue distribution of ochratoxin A (OCT A) following a single oral dose of OCT A were investigated in adult, male Wistar rats. In experiments concerning excretory patterns of OCT A, 14C-OCT A was used. A relatively large amount of OCT A was found in the circulating blood 48 hours after dosing. The patterns of absorption, tissue distribution and excretion of OCT A were affected by acute catarrhal enteritis produced by OCT A and/or ochratoxin alpha(OCT alpha). Quantitative data show that OCT A is distributed mostly in the kidney and this finding is closely associated with the tissue specifity of OCT A-induced nephrotoxicity. OCT A was found to be hydrolyzed to its major metabolite, OCT alpha by addition of the homogenate of pancreas, duodenum and ileum. Approximately 56% of OCT A administered was excreted in both urine and feces as the unchanged toxin and OCT alpha during 120 hours following dosing. A relatively larger amount of OCT alpha was detected as compared with that of OCT A.

Ochratoxin A and citrinin induced nephrosis in Beagle dogs. III. Terminal renal ultrastructural alterations

The extent and type of renal ultrastructural changes in Beagle dogs varied with the administration of ochratoxin A and citrinin alone and in the two dosage combinations. The three predominant changes were cytoplasmic vacuolation, myelin figure formation and lesions designated as cytoplasmic disarray. These changes were mainly of the endomembane system of the tubular epithelial cells. Cytoplasmic vacuoles were within proximal and distal tubules and collecting ducts and were most numerous in dogs given 10 mg/kg critrinin. Vacuolation of similar distribution, but less severe, was seen in renal tubular cells of dogs given the higher dose of the combined mycotoxins (0.2 mg/kg ochratoxin A + 10 mg/kg citrinin). This damage was limited to the proximal tubular cells in dogs given only ochratoxin A (0.1 or 0.2 mg/kg). Myelin figures were in proximal epithelial cells of dogs given ochratoxin A alone or combined with citrinin. There was cytoplasmic disarray in dogs of all groups except for dogs given 5 mg/kg citrinin. This lesions was usually limited to the proximal tubules. The lesions, however, was found in cells of the distal tubules of dogs given 10 mg/kg citrinin alone.

Ochratoxin A and citrinin induced nephrosis in Beagle dogs. II. Pathology

Beagle dogs were given ochratoxin A (0.1 and 0.2 mg/kg) and citrinin (5 and 10 mg/kg) alone and in two dose combinations for 14 days. The gross lesions included focal peritonitis and intestinal intussusceptions in dogs given citrinin. Changes in the kidneys of dogs given ochratoxin A were degeneration and necrosis with desquamation of tubular epithelial cells, primarily in the straight segment of the proximal tubules. Dogs given 10 mg/kg citrin had similar changes in the distal tubules and collecting ducts. Dogs given combined doses of citrinin and ochratoxin A had degeneration and necrosis in proximal and distal tubules, and in thin segments and the collecting ducts; there were desquamated cells and granular casts in the lumina. Dogs given ochratoxin A had necrosis of lymphoid tissues in the spleen, tonsil, thymus, peripheral lymph nodes and lymph nodules of the ileum, colon and rectum. There was ulceration of the mucosa of the intestine in dogs given large combined doses of ochratoxin A and citrinin.

Acute oral ochratoxicosis in day-old White Leghorns, turkeys and Japanese Quail

The comparative acute, oral toxicity of ochratoxin A for three day-old avian species is presented. The seven-day LD50 value for White Leghorns was calculated to be 3.4 +/-0.19 mgm./kg., for turkeys to be 5.9 +/- 0.72 mgm./kg., and for Japanese quail to be 16.5 +/- 0.56 mgm./kg., body weight. The dose-response curves are linear and parallel through one standard deviation on either side of the LD50 when log-dose is plotted against probit for survivors. It is suggested that the mechanism of action of ochratoxin A is similar in the three species, though the potency differs. The reduction in weight gain of Leghorn survivors was proportional to dose, and was observed in two separate traials over an overall dosage range from 0.2 mgm./kg. to 5 mgm./kg. The turkeys showed only a slight reduction in weight gain at doses less than 4mgm./kg., a more marked reduction being observed at higher dose levels. The quail did not show reduction of weight gain at dose levels below 10.9 mgm./kg., though the reduction was proportional to dose at higher levels. All birds dying of acute ochratoxicosis revealed a progression of symptoms from listlessness, huddling, occassionally diarrhoea, ataxia, prostration and death. Viscereal gout was observed at necropsy of the Leghorns.

Nephrotoxicity of dietary ochratoxin A in broiler chickens

Graded doses of pure ochratoxin A (0,0.5,1.0,2.0,4.0, and 8.0 mug of toxin per g of feed) were incorporated into a commercial diet which was fed to chicks from 1 day to 3 weeks of age, at which time the experiments were terminated. Growth was inhibited at 2.0 4,0, and 8.0 mug/g, whereas the kidneys were enlarged at doses of 1.0 mug/g and above. Renal function as measured by clearance of phenol red was decreased 15 and 31% by doses of 4.0 and 8.0 mug/g, respectively. Uric acid was increased 38 and 48% over the control values by doses of 4.0 and 8.0 mug/g, respectively. The plasma electrolytes Na, Cl,Ca, and K were measured; however, only K was significantly ( P smaller than 0.05) altered, showing a decrease at doses of 4.0 and 8.0 mug/g. The percentage dry weight of the kidneys decreased significantly at dose levels of 4.0 and 8.0 mug/g, indicative of edema. Histological examination of kidney sections gave the impression of edema and some tubular necrosis. Pathological changes were observed at all dose levels. These data demonstrate that ochratoxin A is a severe nephrotoxin in young broiler chickens.

Ochratoxicosis in Beagle dogs. III. Terminal renal ultrastructural alterations

Three young male Beagle dogs were given daily oral doses of 0.3 mg/kg body weight of crystalline ochratoxin A. Three untreated Beagle dogs served as controls. The principals survived for 11–15 days and were killed. Cytomorphologic alterations were seen primarily in the endomembrane system of the renal epithelial cells of the proximal convoluted tubules. Increased amounts of smooth-surfaced membranes were present as linear and concentric arrays and as large and small vesicles in many proximal tubular epithelial cells. Few basilar infoldings of the plasma membrane were present in proximal tubular epithelial cells of the principals, but extracellular basilar labyrinth was extensive in proximal tubular epithelial cells of the control kidney. Many tubular epithelial cells contained lipid droplets and cytoplasmic accumulations of phospholipids. The mitochondria usually appeared normal. Prominent ultrastructural alterations of the interstitium included separation between tubular basement membranes, increase in the number of interstitial cells, well-developed secretory apparatuses in many interstitial cells, and the presence of collagen and amorphous material. Few alterations were found in the epithelial cells of the distal convoluted tubules, but some contained more lipid droplets than normally. No consistent alterations were found in other parts of the nephron.

Ochratoxin A toxicosis in swine

Ochratoxicosis was induced in young female swine by a diet contaminated with a rice culture of Aspergillus ostianus that contained ochratoxin A and by daily oral doses of 2.0 or 1.0 mg/kg body weight pure ochratoxin A. Mycotoxicosis was characterized early by depression and reduction in feed intake and loss of body weight, followed by diarrhea, polyuria, polydipsia and dehydration. The pigs given pure ochratoxin A were dead or moribund in 5 to 6 days. Packed cell volume, hemoglobin, total plasma protein, and blood urea nitrogen were increased. Progressive leukocytosis, neutrophitia and moderate left shift in the differential count occurred. Concentrations of lactic dehydrogenase, isocitric dehydrogenase and glutamic-oxalacetic transaminase in the serum and urine were increased by the fourth to sixth day, but only the increase in urinary concentrations was significant. Gross findings included dehydration, enteritis, pale tan discoloration of the liver, and edema and hyperemia of the mesenteric and other lymph nodes. Microscopic lesions were most frequent and severe in the kidney and gastrointestinal tract. Necrosis of renal tubular epithelium was most frequent in the convoluted tubules. Many renal tubules were dilated. The intestinal lesions were focal and necrotizing and occurred in mostanat omic regions. Fatty change was demonstrated in most of the livers. In lymphoid tissues the changes were edema, hyperemia and focal necrosis of lymphocytes within germinal centers and around follicles.

Ochratoxicosis in Beagle dogs. II. Pathology

The gross lesions in 23 young male Beagle dogs given daily oral doses of 0.2–3.0 mg/kg body weight ochratoxin A consisted of moderate to severe mucohemorrhagic enteritis of the cecum, colon, and rectum; tonsillitis: and enlargement of lymph nodes, which were edematous, hyperemic and focally necrotic. Histopathologic alterations in the kidneys consisted of necrosis and desquamation of epithelial cells mainly in, but not limited to, proximal convoluted tubules. Many proximal and distal convoluted tubules contained eosinophilic, granular casts. Necrosis of lymphoid tissues was a prominent feature of the mycotoxicosis and focally occurred in, but was not limited to, germinal centers in the spleen, tonsils, thymus, and lymph nodes and the lymphoid nodules of the jejunum, ileum, cecum, colon, rectum and nictitating membrane. Necrosis did not occur in bone marrow. Hepatic alterations consisted of slight to moderate centrilobular necrosis and fatty change and occurred mainly in dogs receiving 0.2–0.3 mg/kg body weight ochratoxin A daily for 11–14 days.

Mellein and 4-hydroxymellein production by Aspergillus ochraceus Wilhelm

Mellein and 4-hydroxymellein are isocoumarin compounds produced by Aspergillus ochraceus Wilhelm. They are structurally similar to the dihydroisocoumarin moiety of ochratoxin A, a toxic metabolite of the same fungus, and they possibly have similar biological properties. Production of mellein and 4-hydroxymellein on synthetic media and natural solid substrates was determined. Several carbon and nitrogen sources supported production of these metabolites in stationary culture. Additional zinc and molybdenum increased production of both metabolites in stationary culture, but were not required for maximum production in shaken culture. Mellein and 4-hydroxymellein were produced on yellow corn, but neither was produced on wheat, peanuts, or soybeans.

Acute toxicity of ochratoxins A and B in chicks

Ochratoxins A and B were given to 1-day-old Babcock B-300 cockerels to evaluate acute toxic effects. Two trials with ochratoxin A gave 7-day oral median lethal dose estimates of 116 mug (3.3 mg/kg) and 135 mug (3.9 mg/kg) per chick. Chicks given daily oral doses of 100 mug of ochratoxin A died on the second day. Single subcutaneous doses of 400 mug of ochratoxin A were also lethal. The 7-day oral median lethal dose of B was estimated at 1,890 mug (54 mg/kg) per chick. Chicks given oral doses of 100 mug of ochratoxin B daily for 10 days survived. Sublethal doses of both ochratoxins A and B resulted in growth suppression which was proportional to the amount of ochratoxin given. Visceral gout was the principal gross finding. Microscopic examinations revealed acute nephrosis, hepatic degeneration or focal necrosis, and enteritis. Suppression of hematopoiesis in the bone marrow and depletion of lymphoid elements from the spleen and bursa of Fabricius were frequently seen. Both ochratoxins appeared to have similar pathological effects. This is the first report on the toxicity of ochratoxin B.

Ochratoxin A: inhibition of mitochondrial respiration

Ochratoxin A is a fungal metabolite which induces pathological changes in animals. The toxin was isolated from cultures of Aspergillus ochraceus and purified by thin-layer chromatography. Ochratoxin A and one of its hydrolysis products, dihydroisocoumarin, severely inhibited coupled respiration when applied at low concentration to rat liver mitochondria.

Mycotoxicity of Aspergillus ochraceus to chicks

Five isolates of Aspergillus ochraceus, obtained from peanuts, were grown separately on sterile, moist corn for 14 days and fed to 1-day-old Babcock B-300 cockerels to evaluate their toxic effects. Two isolates were highly toxic, causing death of all birds during the 1st week of the experiment. Two isolates were moderately toxic, causing severe growth suppression with some deaths occurring throughout the 3-week test period. One isolate had no apparent effect. When the two most toxic isolates (diets) were diluted, survival time increased but severe growth suppression was evident. Postmortem examinations revealed a few small hemorrhages in the proventriculi of birds which died between the 2nd and 5th days. Emaciation, dehydration, and dry, firm gizzard linings were observed throughout the experiment. Extensive hepatic injury consisting of either fatty changes or necrotic foci was the principal microscopic finding. Suppression of bone marrow activity and depletion of lymphoid elements in the spleen and bursa of Fabricius were also found. The severity of the histopathological changes was directly related to the concentration of ochratoxin A in the diets.

Biosynthesis of ochratoxin A

Biosynthesis of ochratoxin A by Aspergillus ochraceus Wilh. was investigated by radiolabeling experiments in which phenylalanine-1-(14)C and sodium acetate-2-(14)C were supplied to the fungus in sucrose-yeast extract medium. Results showed that phenylalanine was incorporated unaltered into the phenylalanine moiety of ochratoxin A, whereas the isocoumarin moiety of ochratoxin A was mostly derived via acetate condensation.

Production of ochratoxin A by Aspergillus ochraceus in a semisynthetic medium

Aspergillus ochraceus NRRL 3174 produced 29 mg of ochratoxin A per 100 ml of nutrient medium consisting of 4% sucrose and 2% yeast extract. Ochratoxin A was the sole metabolite present in the chloroform extracts of the growth medium. Trace amounts of ochratoxin B were produced in a 1% yeast medium, and a comparatively large amount of ochratoxin B was produced in media containing 16 and 32% sucrose.

Ochratoxin A: occurrence as natural contaminant of a corn sample

Ochratoxin A was detected as a natural contaminant for the first time. It was present in a corn sample.