Hypothermia attenuates protective effects of ginkgolides on astrocytes from ischemia/reperfusion injury

Hormesis and Ginkgo biloba (GB): Numerous biological effects of GB are mediated via hormesis

Ginkgo biloba (GB) extracts have been shown to commonly induce biphasic dose responses in a range of cell types and endpoints (e.g., cochlea neural stem cells, cell viability, cell proliferation). The magnitude and width of the low dose stimulation of these biphasic dose responses are similar to those reported for hormetic dose responses. These hormetic dose responses occur within direct stimulatory responses as well as in preconditioning experimental protocols, displaying acquired resistance within an adaptive homeodynamic and temporal framework and repeated measurement protocols. The demonstrated GB dose responses further reflect the general occurrence of hormetic dose responses that consistently appear to be independent of the biological model, endpoint, inducing agent, and/or mechanism. These findings have important implications for consideration(s) of study designs involving dose selection, dose spacing, sample size, and statistical power. This illustrates and strengthens the need to characterize the low dose stimulatory response range and optimal dose in order to explore potential public health and clinical applications of plant-derived agents, such as GB.

Molecular and cellular pathways as a target of therapeutic hypothermia: pharmacological aspect

Induced therapeutic hypothermia is the one of the most effective tools against brain injury and inflammation. Even though its beneficial effects are well known, there are a lot of pitfalls to overcome, since the potential adverse effects of systemic hypothermia are still troublesome. Without the knowledge of the precise mechanisms of hypothermia, it will be difficult to tackle the application of hypothermia in clinical fields. Better understanding of the characteristics and modes of hypothermic actions may further extend the usage of hypothermia by developing novel drugs based on the hypothermic mechanisms or by combining hypothermia with other therapeutic modalities such as neuroprotective drugs. In this review, we describe the potential therapeutic targets for the development of new drugs, with a focus on signal pathways, gene expression, and structural changes of cells. Theapeutic hypothermia has been shown to attenuate neuroinflammation by reducing the production of reactive oxygen species and proinflammatory mediators in the central nervous system. Along with the mechanism-based drug targets, applications of therapeutic hypothermia in combination with drug treatment will also be discussed in this review.

Hyperthermia conditioned astrocyte-cultured medium protects neurons from ischemic injury by the up-regulation of HIF-1 alpha and the increased anti-apoptotic ability

It has been demonstrated that conditioned medium from astrocytes challenged by in vitro ischemia (oxygen-glucose deprivation, OGD) improved neuronal survival. In addition, preconditioning stimuli can be cross-tolerant, safeguarding against other types of injury. We therefore hypothesized that hyperthermia-conditioned astrocyte-cultured medium (ACM) might also have protective effect on neurons against ischemic injury. The cultured-media, named 38ACM and 40ACM respectively, were collected after astrocytes had been incubated at 38 °C or 40 °C for 6h, followed by incubation at 37 °C for 24h. It was found that ischemia for 6h induced a significant reduction in the number of neuronal cells and cell-viability, and an increase in lactate dehydrogenase (LDH) release and the percentage of apoptotic nuclei in neurons. Pre-treatment with 38ACM or 40ACM for 24h significantly diminished ischemia injury, enhanced cell viability, reduced LDH release and reversed apoptosis. Western blot analysis showed that treatment with 38ACM or 40ACM for 24h led to a significant increase in hypoxia-inducible factor-1 (HIF-1) alpha expression. The EMSA demonstrated that the ACM increased the binding activity of HIF-1 in ischemic neurons. The data implied that hyperthermia-conditioned ACM protects neurons from ischemic injury by up-regulating HIF-1 alpha, and the increased binding activity of HIF-1 and anti-apoptotic ability.

Hydrogen sulfide attenuates ischemia-reperfusion injury in in vitro and in vivo models of intestine free tissue transfer

BACKGROUND

Ischemia-reperfusion injury is the propagation of injury following reintroduction of oxygen to previously ischemic tissue. The purpose of this study was to evaluate whether hydrogen sulfide provides protection against ischemia-reperfusion injury in enteric tissue.

METHODS

In vitro (enterocyte anoxia-normoxia) and in vivo (rat intestinal ischemia-reperfusion) models of ischemia-reperfusion injury were tested with or without the addition of hydrogen sulfide. Apoptotic index was determined in vitro, and gross appearance, histology, and villus height (a measure of mucosal integrity) were assessed in vivo. Statistical analysis was performed, and significance was defined as p < 0.05.

RESULTS

In vitro, cells treated with 10 microM hydrogen sulfide after 1-hour anoxia experienced a significant decrease in apoptotic index compared with untreated control (0.5 +/- 0.3 percent versus 2.8 +/- 0.7 percent); after 3 hours of anoxia, cells treated with 1 microM, 10 microM, and 100 microM hydrogen sulfide experienced significant decreases in apoptotic index versus untreated control (1.6 +/- 0.8 percent, 1.8 +/- 0.9 percent, and 2.8 +/- 0.7 percent versus 8.6 +/- 1.7 percent). In vivo, intestine treated with [10 microM] or [100 microM] hydrogen sulfide retained normal coloration and villus architecture after 1-hour ischemia; after 2 hours of ischemia, only intestine treated with [10 microM] hydrogen sulfide appeared uninjured. After 1, 2, or 3 hours of ischemia, villus heights of intestine treated with [10 microM] or [100 microM] hydrogen sulfide were significantly higher than heights of non-hydrogen sulfide-treated villi.

CONCLUSIONS

Hydrogen sulfide significantly attenuates ischemia-reperfusion injury in intestinal tissue in vitro and in vivo. These results have significant implications for enteric free tissue transfers and other gastrointestinal procedures in which ischemic intervals may be anticipated.