Ghrelin Alleviates Tilmicosin-Induced Myocardial Oxidative Stress in Rats

Potential inhibitory effect of geraniol isolated from lemongrass (Cymbopogon commutatus Stapf) on tilmicosin-induced oxidative stress in cardiac tissue

An experimental study has been conducted to investigate the efficacy of geraniol (GNL) isolated from lemomgrass in protecting against cardiac toxicity induced by tilmicosin (TIL) in albino mice. Compared to TIL-treated mice, those supplemented with GNL had a thicker left ventricular wall and a smaller ventricular cavity. Studies of TIL animals treated with GNL showed that their cardiomyocytes had markedly changed in diameter and volume, along with a reduction in numerical density. After TIL induction, animals showed a significant increase in the protein expression of TGF-β1, TNF-α, nuclear factor kappa B (NF-kB), by 81.81, 73.75 and 66.67%, respectively, and hypertrophy marker proteins ANP, BNP, and calcineurin with respective percentages of 40, 33.34 and 42.34%. Interestingly, GNL significantly decreased the TGF-β1, TNF-α, NF-kB, ANP, BNP, and calcineurin levels by 60.94, 65.13, 52.37, 49.73, 44.18 and 36.84%, respectively. As observed from histopathology and Masson's trichrome staining, supplementation with GNL could rescue TIL-induced cardiac hypertrophy. According to these results, GNL may protect the heart by reducing hypertrophy in mice and modulating biomarkers of fibrosis and apoptosis.

Exploration of Tilmicosin Cardiotoxicity in Rats and the Protecting Role of the Rhodiola rosea Extract: Potential Roles of Cytokines, Antioxidant, Apoptotic, and Anti-Fibrotic Pathways

Tilmicosin (TIL) is a common macrolide antibiotic in veterinary medicine. High doses of TIL can have adverse cardiovascular effects. This study examined the effects of Rhodiola rosea (RHO) that have anti-inflammatory, antioxidant, and anti-fibrotic effects on tilmicosin (TIL)-induced cardiac injury targeting anti-inflammatory, antioxidant, apoptotic, and anti-apoptotic signaling pathways with anti-fibrotic outcomes. Thirty-six male Wistar albino rats were randomly divided into groups of six rats each. Rats received saline as a negative control, CARV 1 mL orally (10 mg/kg BW), and RHO 1 mL orally at 400 mg/kg BW daily for 12 consecutive days. The TIL group once received a single subcutaneous injection (SC) dose of TIL (75 mg/kg BW) on the sixth day of the experiment to induce cardiac damage. The standard group (CARV + TIL) received CARV daily for 12 consecutive days with a single TIL SC injection 1 h after CARV administration only on the sixth day of study and continued for another six successive days on CARV. The protective group (RHO + TIL) received RHO daily for the same period as in CARV + TIL-treated rats and with the dosage mentioned before. Serum was extracted at the time of the rat's scarification at 13 days of study and examined for biochemical assessments in serum lactate dehydrogenase (LDH), cardiac troponin I (cTI), and creatine phosphokinase (CK-MB). Protein carbonyl (PC) contents, malondialdehyde (MDA), and total antioxidant capacity (TAC) in cardiac homogenate were used to measure these oxidative stress markers. Quantitative RT-PCR was used to express interferon-gamma (INF-γ), cyclooxygenase-2 (COX-2), OGG1, BAX, caspase-3, B-cell lymphoma-2 (Bcl-2), and superoxide dismutase (SOD) genes in cardiac tissues, which are correlated with inflammation, antioxidants, and apoptosis. Alpha-smooth muscle actin (α-SMA), calmodulin (CaMKII), and other genes associated with Ca2+ hemostasis and fibrosis were examined using IHC analysis in cardiac cells (myocardium). TIL administration significantly increased the examined cardiac markers, LDH, cTI, and CK-MB. TIL administration also increased ROS, PC, and MDA while decreasing antioxidant activities (TAC and SOD mRNA) in cardiac tissues. Serum inflammatory cytokines and genes of inflammatory markers, DNA damage (INF-γ, COX-2), and apoptotic genes (caspase-3 and BAX) were upregulated with downregulation of the anti-apoptotic gene Bcl-2 as well as the DNA repair OGG1 in cardiac tissues. Furthermore, CaMKII and α-SMA genes were upregulated at cellular levels using cardiac tissue IHC analysis. On the contrary, pretreatment with RHO and CARV alone significantly decreased the cardiac injury markers induced by TIL, inflammatory and anti-inflammatory cytokines, and tissue oxidative-antioxidant parameters. INF-γ, COX-2, OGG1, BAX, and caspase-3 mRNA were downregulated, as observed by real-time PCR, while SOD and Bcl-2 mRNA were upregulated. Furthermore, the CaMKII and α-SMA genes' immune reactivities were significantly decreased in the RHO-pretreated rats.

Protective effect of ghrelin against tilmicosin-induced left ventricular dysfunction in rats

This study was conducted to investigate the possible protective effects of ghrelin against tilmicosin-induced acute ventricular dysfunction in rats. Forty adult male Sprague Dawley rats were randomly divided into 4 equal groups: control, ghrelin, tilmicosin, and ghrelin + tilmicosin. The left ventricular structural and functional parameters together with cardiac biomarker levels were evaluated. The results showed that tilmicosin treatment alone significantly decreased the left ventricular fractional shortening, left ventricular ejection fraction, left ventricular stroke volume, and cardiac output when compared with control group. In addition, tilmicosin led to a significant increase in left ventricular internal dimension in systole and left ventricular fractional end-systolic volume. At the same time, serum lactate dehydrogenase, creatine kinase, and creatine kinase-myocardial B fraction levels were significantly increased in tilmicosin-treated group when compared with control group. However, ghrelin pretreatment significantly prevented the left ventricular internal dimension in systole, left ventricular fractional end-systolic volume, left ventricular stroke volume, left ventricular ejection fraction, left ventricular fractional shortening, and cardiac output changes caused by tilmicosin. Moreover, ghrelin pretreatment could reduce significantly serum lactate dehydrogenase, creatine kinase, and creatine kinase-myocardial B fraction levels. These data indicated that ghrelin treatment may provide a protective effect against tilmicosin-induced left ventricular systolic dysfunction.

Macrolides induce severe cardiotoxicity and developmental toxicity in zebrafish embryos

Macrolide antibiotics (MALs) are widely used for both human and animal health. Most MALs and their metabolites transfer into aquatic organisms and environment resulting in violent consequences. Previous studies show that MALs cause cardiotoxicity in humans and mammals. However, the potential risk of these chemicals in aquatic organisms remains unclear. Here, we used zebrafish embryos as a model to evaluate the toxicity of MALs. Zebrafish embryos were exposed to four typical MALs including azithromycin (AZM), clarithromycin (CLR), tilmicosin (TMS) and tylosin (TYL) to study their cardiotoxicity. The heart rate of zebrafish embryos showed similar biphasic distribution in the presence of four MALs at 2 days post-fertilization (dpf). The heart rate increased significantly at low levels of MALs while decreased obviously at high levels. Subsequently, TMS was chose to study its acute toxicity and developmental toxicity, which caused pericardial edema and spinal curvature in zebrafish embryos at 4 dpf. Furthermore, we found that TMS triggered oxidative stress, with decreased SOD activities and increased MDA contents. Lastly, apoptosis was observed in zebrafish embryos under TMS treatment, with up-regulation of apoptosis associated genes such as p53, bcl 2, bax, caspase 3 and caspase 9, confirmed by increased protein expression based on Western blot analysis. Taken together, these data indicate that MALs can cause serious toxicity in the development of zebrafish. Great caution should be taken due to the huge consumption of MALs for food animal production and treatments with TMS for infections in aquaculture.