Lack of iNOS induction in a severe model of transient focal cerebral ischemia in rats

Minocycline neuroprotection in a rat model of asphyxial cardiac arrest is limited

OBJECTIVE

The study investigated a possible neuroprotective potency of minocycline in an experimental asphyxial cardiac arrest (ACA) rat model. Clinically important survival times were evaluated thus broadening common experimental approaches.

METHODS

Adult rats were subjected to 5 min of ACA followed by resuscitation. There were two main treatment groups: ACA and sham operated. Relating to minocycline treatment each group consisted of three sub-groups: pre-, post-, and sans-mino, with three different survival times: 4, 7, and 21 days. Neurodegeneration and microgliosis were monitored by immunohistochemistry. Alterations of microglia-associated gene expression were analyzed by quantitative RT-PCR.

RESULTS

ACA induced massive nerve cell loss and activation of microglia/macrophages in hippocampal CA1 cell layer intensifying with survival time. After 7 days, minocycline significantly decreased both, neuronal degeneration and microglia response in dependence on the application pattern; application post ACA was most effective. After 21 days, neuroprotective effects of minocycline were lost. ACA significantly induced expression of the microglia-associated factors Ccl2, CD45, Mac-1, F4-80, and Tnfa. Independent on survival time, minocycline affected these parameters not significantly. Expression of iNOS was unaffected by both, ACA and minocycline.

CONCLUSIONS

In adult rat hippocampus microglia was significantly activated by ACA. Minocycline positive affected neuronal survival and microglial response temporary, even when applied up to 18 h after ACA, thus defining a therapeutically-relevant time window. As ACA-induced neuronal cell death involves acute and delayed events, longer minocycline intervention targeting also secondary injury cascades should manifest neuroprotective potency, a question to be answered by further experiments.

Supplementation of deprenyl attenuates age associated alterations in rat cerebellum

Aging, a multifactorial process of enormous complexity is characterised by physio-chemical and biological aspects of cellular functions. It is closely associated with changes in metabolism of various biological molecules in the system. In the present study, we have investigated the effect of deprenyl on cerebellum during ageing process in male Wistar rats with respect to the changes in levels of protein, glycoproteins and amino acids in experimental rats of three age groups (6, 12 and 18 months old). Intraperitoneal administration of liquid deprenyl (2 mg/kg body weight/day for a period of 15 days i.p., significantly P < 0.05) attenuated age-associated alterations in the levels of amino acids (taurine, aspartate, glutamate, arginine, hydroxy proline and homocysteine), protein content and glycoprotein components (hexose and hexosamine) in the rat cerebellum. The results of the present investigation indicate that the protective effect of deprenyl is probably related to its ability to strengthen the neuronal membrane by its membrane stabilizing action or to a counteraction of free radicals by its antioxidant property.

Inducible nitric oxide synthase does not mediate brain damage after transient focal cerebral ischemia in mice

Nitric oxide produced by the inducible nitric oxide synthase (iNOS) is believed to participate in the pathogenic events after cerebral ischemia. In this study, we examined the expression of iNOS in the brain after transient focal cerebral ischemia in mice. We detected differential expression of exons 2 and 3 of iNOS mRNA (16-fold upregulation at 24 to 72 h after middle cerebral artery occlusion, MCAO) compared with exons 6 to 8, 12 to 14, 21 to 22, and 26 to 27 (2- to 5-fold upregulation after 72 and 96 h), which would be compatible with alternative splicing. Expression levels of iNOS mRNA were too low for detection by the Northern blot analysis. Using specific antibodies, we did not detect any iNOS immunoreactivity in the mouse brain 1 to 5 days after MCAO, although we detected iNOS immunoreactivity in the lungs of mice with stroke-associated pneumonia, and in mouse and rat dura mater after lipopolysaccharide administration. In chimeric iNOS-deficient mice transplanted with wild-type bone marrow (BM) cells expressing the green fluorescent protein (GFP) or in wild-type mice transplanted with GFP(+) iNOS-deficient BM cells, no expression of iNOS was detected in GFP(+) leukocytes invading the ischemic brain or in resident brain cells. Moreover, both experimental groups did not show any differences in infarct size. Analysis of three different strains of iNOS-deficient mice and wild-type controls confirmed that infarct size was independent of iNOS deletion, but strongly confounded by the genetic background of mouse strains. In conclusion, our data suggest that iNOS is not a universal mediator of brain damage after cerebral ischemia.