Temporal modulation of nephrotoxicity, feeding, and drinking in gentamicin-treated rats

Gingerol fraction from Zingiber officinale protects against gentamicin-induced nephrotoxicity

Nephrotoxicity is the main complication of gentamicin (GM) treatment. GM induces renal damage by overproduction of reactive oxygen species and inflammation in proximal tubular cells. Phenolic compounds from ginger, called gingerols, have been demonstrated to have antioxidant and anti-inflammatory effects. We investigated if oral treatment with an enriched solution of gingerols (GF) would promote a nephroprotective effect in an animal nephropathy model. The following six groups of male Wistar rats were studied: (i) control group (CT group); (ii) gingerol solution control group (GF group); (iii) gentamicin treatment group (GM group), receiving 100 mg/kg of body weight intraperitoneally (i.p.); and (iv to vi) gentamicin groups also receiving GF, at doses of 6.25, 12.5, and 25 mg/kg, respectively (GM+GF groups). Animals from the GM group had a significant decrease in creatinine clearance and higher levels of urinary protein excretion. This was associated with markers of oxidative stress and nitric oxide production. Also, there were increases of the mRNA levels for proinflammatory cytokines (tumor necrosis factor alpha [TNF-α], interleukin-1β [IL-1β], IL-2, and gamma interferon [IFN-γ]). Histopathological findings of tubular degeneration and inflammatory cell infiltration reinforced GM-induced nephrotoxicity. All these alterations were attenuated by previous oral treatment with GF. Animals from the GM+GF groups showed amelioration in renal function parameters and reduced lipid peroxidation and nitrosative stress, in addition to an increment in the levels of glutathione (GSH) and superoxide dismutase (SOD) activity. Gingerols also promoted significant reductions in mRNA transcription for TNF-α, IL-2, and IFN-γ. These effects were dose dependent. These results demonstrate that GF promotes a nephroprotective effect on GM-mediated nephropathy by oxidative stress, inflammatory processes, and renal dysfunction.

Effects of Three‐Hour Restricted Food Access during the Light Period on Circadian Rhythms of Temperature, Locomotor Activity, and Heart Rate in Rats

The effects of food on biological rhythms may influence the findings of chronopharmacological studies. The present study evaluated the influence of a restricted food access during the rest (light) span of nocturnally active Wistar rats on the 24 h time organization of biological functions in terms of the circadian rhythms of temperature (T), heart rate (HR), and locomotor activity (LA) in preparation for subsequent studies aimed at evaluating the influence of timed food access on the pharmacokinetics and pharmacodynamics of medications. Ten-wk-old male Wistar rats were housed under controlled 12:12 h light:dark (LD) environmental conditions. Food and water were available ad libitum, excepted during a 3 wk period of restriction. Radiotelemetry transmitters were implanted to record daily rhythms in T, HR, and LA. The study lasted 7 wk and began after a 21-d recovery span following surgery. Control baseline data were collected during the first wk (W1). The second span of 3 wk duration (W2 to W4) consisted of the restricted feeding regimen (only 3 h access to food between 11:00 and 14:00 h daily) during the L (rest span) under 12:12 h LD conditions. The third period of 3 wk duration (W5 to W7) consisted of the recovery span with ad libitium normal feeding. Weight loss in the amount of 5% of baseline was observed during W1 with stabilization of body weight thereafter during the remaining 2 wk of food restriction. The 3 h restricted food access during the L rest span induced a partial loss of circadian rhythmicity and the emergence of 12 h rhythms in T, HR, and LA. Return to ad libitum feeding conditions restored circadian rhythmicity in the manner evidenced during the baseline control span. Moreover, the MESORS and amplitudes of the T, HR, and LA 24 h patterns were significantly attenuated during food restriction (p < 0.001) and then returned to initial values during recovery. These changes may be interpreted as a masking effect, since T, HR, and LA are known to directly react to food intake. The consequences of such findings on the methods used to conduct chronokinetic studies, such as the fasting of animals the day before testing, are important since they may alter the temporal structure of the organism receiving the drug and thereby compromise findings.

Chronobiology and chronotoxicology of antibiotics and aminoglycosides

Few investigators have examined the circadian variation in the symptom intensity of infectious diseases. Seasonal patterns in a variety of infectious are well know. Less appreciated are the circadian patterns in the symptom expression of infections. Studies indicate that fever which accompanies the common cold peaks at 4 p.m., and this is in agreement with other studies indicating that the elevation of body temperature, fever, due to bacterial infections is higher in the evening while that due to viral infections is more likely in the morning. Animal and human studies reveal also administration-time-dependent differences in the pharmacokinetics and toxicity of antimicrobial agents. This is particularly true for the aminoglycosides, as their nephrotoxicity is greatest when administered during the resting period of laboratory animals and human beings. Food intake and low urinary pH has been found to be protective of the toxicity of aminoglycosides at this time of the day. Knowledge of the administration-time-dependence of aminoglycosides and the underlying mechanisms can be used to develop once-a-day formulations that are significantly less toxic, in particular to the kidney, in patients who require around-the-clock antimicrobial therapy.

Dietary protein level alters gentamicin-induced nephrotoxicity in rats

Aminoglycosides (AG) such as gentamicin are antimicrobial drugs widely used in the hospital setting due to their efficacy in the treatment of severe gram-negative bacterial infections. However, all AG have the potential to cause nephrotoxicity. Two studies have been conducted (1) to assess the protein level of a diet that would give the best renal outcome with gentamicin administration, and (2) to get a better idea about the rhythms of food ingestion associated with the different protein levels. Adult female Sprague-Dawley rats fully adapted to a standard chow diet, the standard chow with 20% or 55% added casein were chronically treated for 10 days with a nephrotoxic dose of gentamicin sulfate (40 mg/kg/day, i.p.) or a saline solution. Food ingestion patterns of rats were recorded every hour using a Diet Scan system and gentamicin nephrotoxicity indices were measured. The second study used rats that were fed the same diets and given a sham injection. Corticosterone was assayed to quantify the stress of the animals. Results showed that chronic gentamicin treatment leads to a decrease in food intake and flattening of the rhythms of food ingestion. Also, chow feeding and the 20% casein diet were found to be more protective against gentamicin-induced nephrotoxicity than the 55% casein diet. Therefore, while a protein-rich diet can be protective against gentamicin-induced nephrotoxicity, the present study demonstrates that a diet too high in protein might rather be harmful to the kidneys.

The effect of surface charge on the disposition of liposome-encapsulated gentamicin to the rat liver, brain, lungs and kidneys after intraperitoneal administration

The disposition of gentamicin to the normal rat brain, lung, kidney and liver was studied at intervals of 1, 2, 4, 6 and 8h after intraperitoneal injection of gentamicin encapsulated in positive, negative and neutral liposomes. Compared with the control, which was treated with free gentamicin, liposomes were associated with higher concentrations of gentamicin in the brain and liver, while concentrations were lower in the kidney. The average concentrations of gentamicin in the liver and the brain were highest with positive liposomes, while, gentamicin concentrations in the kidneys and lungs were not influenced by surface charge of the liposomes. These observations have important implications on the selective delivery of gentamicin to tissues and on the intraperitoneal route of administration.

Agents ameliorating or augmenting experimental gentamicin nephrotoxicity: some recent research

Despite its nephrotoxic potential, the aminoglycoside antibiotic gentamicin (GM) is still considered to be an important agent against life-threatening infections. The goal of reducing or protecting against its nephrotoxicity has attracted much effort and attention during the last decade. This article reviews some of the literature published during the last decade on the effects of agents that ameliorate or augment GM nephrotoxicity. Notable among the ameliorating agents are antioxidant agents. These include different classes of compounds that include beta blockers (e.g. carvedilol), superoxide dismutase mimetic agents (e.g. M40403), hormones (e.g. melatonin), iron chelators (e.g. deferrioxamine), vitamins (vitamin C and E) and medicinal plants (e.g. garlic). Other ameliorating agents include antibiotics (e.g. ceftriaxone), antiplatelet drugs (e.g. trapidil) and Ca++ agents that may augment GM nephrotoxicity include cyclosporin and the Ca++-channel blocker verapamil.

Dietary composition alters gentamicin-induced nephrotoxicity in rats

Previous studies have shown temporal variations in gentamicin-induced renal toxicity characterized by a peak when administered during the resting period and a trough during the active period. This time-dependent toxicity was also altered according to the macronutrient composition of dietary regimens offered to female rats. In the present study, adult female Sprague-Dawley rats were adapted to semipurified isocaloric diets containing 20% casein or soy-protein (10% fat each) or to a standard chow diet (18.1% mixed proteins; 4.5% fat). The animals were then chronically treated for 10 days with a nephrotoxic dose of gentamicin sulfate (40 mg/kg/day ip) or a saline solution administered in the middle of their resting period (1200 h) or in the middle of their activity period (0000 h). Body weights of rats injected in the middle of their resting period decreased over the last 6 days of gentamicin treatment. Total 12-h light and 12-h dark food intakes were decreased in gentamicin-treated rats. Rats fed the standard chow diet had significantly lower corticocellular regeneration, serum creatinine and blood urea nitrogen compared to those fed the casein- and soy-containing diets. The present study demonstrates that chronic gentamicin-induced renal toxicity varies temporally according to the time of administration and that a mixed protein diet containing a lower fat level can protect against gentamicin-induced nephrotoxicity.