Cytochemical energy-filtering transmission electron microscopy of mitochondrial free radical formation in paraquat cytotoxicity

Neuroprotective effects of coenzyme Q10 on paraquat-induced Parkinson's disease in experimental animals

Parkinson's disease (PD) affects ∼1-2% of the elderly population. Development of a neuroprotective therapy that may be initiated early in the course of the disease to retard/prevent disease progression is highly desirable. This study aimed to investigate prophylactic treatment with coenzyme Q10 (CoQ10) before paraquat (PQ) exposure, a herbicide known to increase the risk for PD, to attain neuroprotection. In addition, therapeutic intervention with CoQ10 in mice already exposed to PQ (24 h) might halt ongoing neurodegeneration and behavioural deterioration. PD was induced experimentally in mice by an injection of PQ (10 mg/kg, intraperitoneal), twice a week for 3 consecutive weeks, either before or after the initiation of treatment with CoQ10 (200 mg/kg). The results of the sustained supplementation with CoQ10, prophylactically and therapeutically, were compared with L-DOPA (100 mg/kg). A battery of behavioural tests was performed, in addition to estimation of protein carbonyl in the brain. CoQ10 elicited a remarkable improvement in most of the behavioural tests and decreased protein carbonyl content in the brain, particularly when it was initiated before rather than after PQ induction of PD. Therefore, CoQ10, which protects against mitochondrial damage, may be beneficial in slowing the progression of PD, particularly when initiated as prophylactic treatment.

Scanning transmission electron microscopic analysis of nitrogen generated by 3, 3'-diaminobenzidine-besed peroxidase reaction with resin ultrathin sections of rhinoceros parotid gland acinar cells

A 3, 3'-diaminobenzidine (DAB)-based method was used to detect the localization of endogenous peroxidase activity in Indian rhinoceros (Rhinoceros unicornis) parotid gland acinar cells. The tissue had previously been resin-embedded in gelatin capsules for routine electron microscopic observations and thus pre-incubation for endogenous peroxidase analysis was not possible. We attempted to demonstrate the relationship between secretory granules (SGs) in resin ultrathin sections of Indian rhinoceros parotid gland acinar cells and endogenous peroxidase activity. A JEM 1400 Plus scanning transmission electron microscope (STEM) was used to conduct energy dispersive X-ray spectroscopy (EDS) analysis of the presence of nitrogen generated by the DAB reaction in bipartite structural SG consisting of a dense body (or core). The mapping patterns of nitrogen were restricted to the dense body. We observed nitrogen localized in the rough endoplasmic reticulum (ER), nuclear envelope (NE) and several components of the Golgi apparatus (G) of rhinoceros parotid gland acinar cells participating in the synthetic pathway of secretory proteins. Moreover, we established a nitrogen-detection method by EDS analysis of rhinoceros parotid gland. The reliability of the method was validated by comparison of the test group (peroxidase detection in ultrathin resin sections) and the control group (ordinary peroxidase detection in semi-thin sections following glutaraldehyde pre-fixation) of rat submandibular gland. The same mapping patterns of nitrogen were detected by DAB reaction in the SG, ER, NE and G in these two groups. Hence, EDS-STEM approaches for endogenous peroxidase post-incubation analysis will prove useful for advanced cytochemical analysis for the identification of any other resin sections.

Paraquat toxicity induced by voltage-dependent anion channel 1 acts as an NADH-dependent oxidoreductase

Paraquat (PQ), a herbicide used worldwide, causes fatal injury to organs upon high dose ingestion. Treatments for PQ poisoning are unreliable, and numerous deaths have been attributed inappropriate usage of the agent. It is generally speculated that a microsomal drug-metabolizing enzyme system is responsible for PQ toxicity. However, recent studies have demonstrated cytotoxicity via mitochondria, and therefore, the cytotoxic mechanism remains controversial. Here, we demonstrated that mitochondrial NADH-dependent PQ reductase containing a voltage-dependent anion channel 1 (VDAC1) is responsible for PQ cytotoxicity. When mitochondria were incubated with NADH and PQ, superoxide anion (O(2)(*)) was produced, and the mitochondria ruptured. Outer membrane extract oxidized NADH in a PQ dose-dependent manner, and oxidation was suppressed by VDAC inhibitors. Zymographic analysis revealed the presence of VDAC1 protein in the oxidoreductase, and the direct binding of PQ to VDAC1 was demonstrated using biotinylated PQ. VDAC1-overexpressing cells showed increased O(2)(*) production and cytotoxicity, both of which were suppressed in VDAC1 knockdown cells. These results indicated that a VDAC1-containing mitochondrial system is involved in PQ poisoning. These insights into the mechanism of PQ poisoning not only demonstrated novel physiological functions of VDAC protein, but they may facilitate the development of new therapeutic approaches.

Ultrastructural evidence of dermal gadolinium deposits in a patient with nephrogenic systemic fibrosis and end-stage renal disease

BACKGROUND AND OBJECTIVES

The pathogenesis of acquired nephrogenic systemic fibrosis recently described for patients with renal insufficiency and a history of exposition to gadolinium-based magnetic resonance contrast agents is not completely understood. A role for circulating fibroblasts in the fibrosing tissue is hypothetical, and the mechanism of the assumed trigger function of gadolinium remains elusive.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

A skin lesion on a 76-yr-old man with symptoms of nephrogenic systemic fibrosis lasting 5 mo was studied at the ultrastructural level. After confirmation of he diagnosis by histopathologic methods, the presence and distribution of gadolinium, iron, calcium, and magnesium by energy filtering transmission electron microscopy was also examined.

RESULTS

The performed electron spectroscopic imaging and electron energy loss spectroscopic analyses on deparaffinized samples revealed deposition of gadolinium in irregular small aggregates that adhered to cell profiles and collagen fibers of the connective tissue, forming a perivascular "gadolinium-deposit zone" in the skin. Traces of iron signal were demonstrated in singular gadolinium-positive deposits, and iron presence was found in adjacent connective tissue. The ultrastructural cell analysis of the lesion showed among numerous poorly differentiated fibrocytes also higher differentiated cells with myofibroblastic characteristics, including bundles of intermediate filaments and attachment plaques in the cell periphery, indicating an ability of lesional fibroblasts to differentiate into myofibroblastic cells.

CONCLUSIONS

These findings support the pivotal role of gadolinium chelates in the development of nephrogenic systemic fibrosis.

Fermented grain products, production, properties and benefits to health

Fermented foods such as Japanese traditional food "miso (fermented soy bean paste)" have been shown to be rich source of micronutrients with the potential to prevent various human diseases. We have introduced effects of a new dietary supplement of fermented grain foods mixture containing extracts from wheat germ, soybeans, rice bran, tear grass, sesame, wheat, citrus lemon, green tea, green leaf extract and malted rice under the trade name of antioxidant biofactor (AOB). Chemical analysis of AOB shows the presence of various phenolic compounds (catechins, rutin, genistin, daidzin, etc.). AOB has strong antioxidant properties and additional biological effects, which might be of importance in context with the prevention of degenerative diseases. This paper focuses on the effect of supplementing AOB in various animal models and humans.

Environmental risk factors and Parkinson's disease: selective degeneration of nigral dopaminergic neurons caused by the herbicide paraquat

Environmental toxicants and, in particular, pesticides have been implicated as risk factors in Parkinson's disease (PD). The purpose of this study was to determine if selective nigrostriatal degeneration could be reproduced by systemic exposure of mice to the widely used herbicide paraquat. Repeated intraperitoneal paraquat injections killed dopaminergic neurons in the substantia nigra (SN) pars compacta, as assessed by stereological counting of tyrosine hydroxylase (TH)-immunoreactive and Nissl-stained neurons. This cell loss was dose- and age-dependent. Several lines of evidence indicated selective vulnerability of dopaminergic neurons to paraquat. The number of GABAergic cells was not decreased in the SN pars reticulata, and counting of Nissl-stained neurons in the hippocampus did not reveal any change in paraquat-treated mice. Degenerating cell bodies were observed by silver staining, but only in the SN pars compacta, and glial response was present in the ventral mesencephalon but not in the frontal cortex and cerebellum. No significant depletion of striatal dopamine followed paraquat administration. On the other hand, enhanced dopamine synthesis was suggested by an increase in TH activity. These findings unequivocally show that selective dopaminergic degeneration, one of the pathological hallmarks of PD, is also a characteristic of paraquat neurotoxicity. The apparent discrepancy between pathological (i.e., neurodegeneration) and neurochemical (i.e., lack of significant dopamine loss) effects represents another important feature of this paraquat model and is probably a reflection of compensatory mechanisms by which neurons that survive damage are capable of restoring neurotransmitter tissue levels.

Paraquat detoxicative system in the mouse liver postmitochondrial fraction

We examined the paraquat detoxicative system in mouse livers. The survival rate of mice receiving 50 mg/kg paraquat was 41% at 7 days and significantly rose to 88, 64, 69% with pretreatment with phenytoin, phenobarbital, and rifampicin, respectively. Phenytoin induced activity in NADPH-cytochrome P450 reductase, CYP3A, CYP2B, and CYP2C that was 3 to 4 times higher than that of the controls. Phenobarbital induced CYP2B and rifampicin induced CYP3A, respectively, in addition to NADPH-cytochrome P450 reductase. 3-Methylcholanthrene did not induce these enzymes and did not alter the survival rate. All the mice pretreated with CoCl(2) (a CYP synthesis inhibitor) or SKF 525-A (a CYP inhibitor) were dead after 5 days, and troleandomycin (a CYP3A-specific inhibitor) also reduced the survival rate. When cell homogenates were incubated with paraquat and NADPH, paraquat decreased and its metabolic intermediate paraquat-monopyridone was formed. Troleandomycin inhibited the decrease in paraquat and increased the monopyridone. After making a subfraction of the homogenate, monopyridone was produced in the postmicrosomal 105,000g supernatant, but not in the microsomes. The pretreatment of mice with phenytoin decreased the monopyridone in the postmitochondrial fraction, but did not affect the supernatant. These results indicated that paraquat was first metabolized in the postmicrosomal supernatant into monopyridone, and that may have been subsequently hydroxylated by the microsomes. Repeated intravenous injections of alpha-tocopherol to paraquat-loaded mice significantly reduced the paraquat mortality and when these mice were pretreated with rifampicin, 100% of them survived. These studies demonstrate that postmitochondrial fractions play an important role in paraquat detoxication metabolism, and that the combination of CYP induction and alpha-tocopherol administration is highly useful for the survival of paraquat-exposed mice.