A new paradigm to understand and treat diabetic neuropathy.

The clinical symptoms of diabetic neuropathy (DN) manifest in a time dependent manner as a positive symptoms (i. e. pain, hypersensitivity, tingling, cramps, cold feet etc.) during its early stages and by a loss of function (i. e. loss of sensory perception, delayed wound healing etc.) predominating in the later stages. Elevated blood glucose alone cannot explain the development and progression of DN and the lowering of blood glucose is insufficient in preventing and/or reversing neuropathy in patients with type 2 diabetes. Recently it has been shown that the endogenous reactive metabolite methylglyoxal (MG) can contribute to the gain of function via post-translational modification in DN of neuronal ion channels involved in chemosensing and action potential generation in nociceptive nerve endings. Dicarbonyls, such as MG, that are elevated in diabetic patients, modify DNA as well as extra- and intracellular proteins, leading to the formation of advanced glycation endproducts (AGEs). Increased formation of AGEs leads to increased cellular stress, dysfunction and ultimately cell death. The interaction of AGE-modified proteins through cell surface receptors, such as RAGE, can lead to increased cellular activation and sustained inflammatory responses, which are the molecular hallmarks of the later, degenerative, stages of DN. The direct and indirect effects of dicarbonyls on nerves or neuronal microvascular network provides a unifying mechanism for the development and progression of DN. Targeting the accumulation of MG and/or prevention of RAGE interactions may therefore provide new, more effective, therapeutic approaches for the treatment of DN.

Bone marrow dendritic cells internalize live RF-81 bovine rotavirus and rotavirus-like particles (RF 2/6-GFP-VLP and RF 8*2/6/7-VLP) but are only activated by live bovine rotavirus.

Dendritic cells (DC) represent the link between innate and adaptive immunity. They are classified as antigen-presenting cells (APC) and can initiate and modulate the immune response. To investigate the interaction with DCs, live RF-81 bovine rotavirus strain (RFV) and rotavirus-like particles (rota-VLP), RF 2/6-GFP-VLP and rota RF 8*2/6/7-VLP, were added in vitro to murine bone marrow-derived DCs (bmDCs). Live RFV, RF 2/6-GFP-VLP and RF 8*2/6/7-VLP all bound to bmDC and were internalized but only live RFV stimulated phenotypic maturation of the bmDCs as shown by the upregulation of the co-stimulatory molecule CD86. Even though bmDCs internalized RF 2/6-GFP-VLP and RF 8*2/6/7-VLP as efficiently as live RFV, these rota-VLP were not able to activate the cells. Supernatants derived from bmDC cultures treated with live RFV, RF 2/6-GFP-VLP or RF 8*2/6/7-VLP were examined for TNF-alpha production. At 6, 18 and 24 h post-infection, TNF-alpha concentrations were significantly increased in cultures treated with live RFV and rota-VLP compared with untreated cultures. In conclusion, this study showed that live RF-81 bovine rotavirus strain was internalized and induced bmDCs activation, whereas both RF 2/6-GFP-VLP and RF 8*2/6/7-VLP were internalized by bmDCs without triggering their activation.

Particle-enhanced membrane uptake of a polynuclear aromatic hydrocarbon: a possible role in cocarcinogenesis.

One possible mechanism by which cocarcinogenesis occurs was investigated. The effect of a particulate, silica, upon the rate of membrane uptake of a polynuclear aromatic hydrocarbon, benz[a]anthracene (BA), was studied. The fluorescence emission spectrum and quantum yield of BA, when adsorbed to silica, underwent spectral shifts upon addition of phospholipid vesicles. These spectral changes appeared to result from the transfer of BA from the silica surface into the lipid bilayer. We used these spectral changes to measure the rates of membrane uptake of BA from the silica-adsorbed state and from the crystalline and microcrystalline states of BA. Our studies demonstrated that adsorption of BA to silica resulted in an increased rate of uptake of BA into dipalmitoyl-L-alpha-phosphatidylcholine vesicles compared to the uptake rate into these vesicles from crystalling states. Such particle-enhanced membrane uptake of chemical carcinogens may be of importance in explaining the enhanced carcinogenicity of the polynuclear aromatic hydrocarbons in the presence of particulate matter.

Particulate enhanced membrane uptake of 1,2-benzanthracene observed by fluorescence spectroscopy: a possible role in co-carcinogenesis.

In recognition of the co-carcinogenic effects of particulate matter and chemical carcinogens, we investigated the effect of particulate silica on the rates of membrane uptake of 1,2-benzanthracene. The fluorescence emission spectra and the apparent quantum yields of benzanthracene and dependent upon adsorption to silica and upon the surface density of benzanthracene on the silica. The fluorescence spectral shifts which occur upon transfer of benzanthracene from the silica surface to phospholipid vesicles provided a convenient means to quantitate the membrane uptake of benzanthracene from particulates. The rate of benzanthracene uptake by dipalmitoyl-L-alpha-phosphatidylcholine vesicles was independent of the concentration of lipid, indicating that the rate-limiting step may involve its solubilization in the aqueous phase. These uptake rates were also independent of the surface density of benzanthracene on the silica, indicating that the benzathracene molecules are dispersed uniformly on the silica surface. Rates of membrane uptake of benzanthracene from the crystalline, microcrystalline, and the silica-absorbed states were compared, and are greatly enhanced by a reduction in crystal size. Silica-adsorbed benzanthracene had the most rapid rate of membrane uptake. Silica did not cause disruption of the lipid vesicles. These results indicate that particulates can enhance the cellular availability of the chemical carcinogens.