Exploring the remarkable protective effects of Polysaccharide of Atractylodes macrocephala Koidz (PAMK) on chicken spleen under heat stress
As global temperatures continue to rise, heat stress has become one of the most significant challenges facing modern poultry production. When chickens are exposed to high temperatures, their immune organs suffer damage, leading to increased disease susceptibility and substantial economic losses for farmers.
In the search for solutions, scientists have turned to traditional wisdom, focusing on a remarkable natural compound: the Polysaccharide of Atractylodes macrocephala Koidz (PAMK). This extract from a classic Chinese herb shows extraordinary potential in protecting chickens from the damaging effects of heat stress.
Through sophisticated molecular mechanisms that reduce oxidative stress and inhibit programmed cell death, PAMK offers a natural solution to one of agriculture's most pressing problems 1 .
Unlike humans, chickens cannot sweat to cool themselves. When environmental temperatures climb, they resort to panting and spreading their wings to try to dissipate heat. But these adaptations often prove insufficient, especially in intensive farming conditions.
The consequences extend beyond mere discomfort—heat stress triggers a cascade of cellular damage that compromises the entire immune system 2 .
The spleen serves as a critical immune surveillance center in chickens, producing antibodies and filtering pathogens from the blood. Under heat stress, this vital organ undergoes structural and functional damage.
Scientists have observed that heat-stressed chickens experience reduced spleen weight and fewer germinal centers—the specialized areas where immune cells multiply to fight infections 1 .
Heat stress disrupts the delicate balance between reactive oxygen species production and the antioxidant defenses that neutralize them. This imbalance leads to accumulation of hydrogen peroxide and hydroxyl radicals—dangerous molecules that damage proteins, lipids, and DNA 1 .
The mitochondria, known as cellular powerplants, are particularly vulnerable to heat stress. Their delicate membranes deteriorate, and the energy-producing complexes within them become less efficient. This results in reduced ATP production—essentially creating a cellular energy crisis 1 .
Heat stress triggers an unhealthy immune response characterized by elevated pro-inflammatory cytokines including interleukin 1 and tumor necrosis factor-alpha, while simultaneously suppressing beneficial cytokines like interleukin 2 and interferon gamma 1 .
These cellular disturbances ultimately activate the apoptosis pathway—a programmed cell death sequence that further compromises immune function 1 .
Atractylodes macrocephala Koidz, known as Baizhu in Traditional Chinese Medicine, has a documented history dating back to the Warring States period (476-221 BCE). Ancient medical texts record its use for treating digestive disorders, water retention, and arthritis.
The herb has been cultivated primarily in southern China for centuries, valued for its diverse therapeutic properties 3 .
While Baizhu contains multiple active compounds including lactones and glycosides, modern research has particularly focused on its polysaccharide fraction (PAMK). Polysaccharides are complex carbohydrates consisting of long chains of sugar molecules that exhibit remarkable biological activity 6 .
Previous studies have demonstrated that PAMK possesses immunomodulatory properties—in pigs, it improved metabolic status and immune function, while in mouse splenocytes, it enhanced immune response by increasing IgG and cytokine production 1 .
How PAMK Protects the Chicken Spleen
To understand exactly how PAMK protects against heat stress, researchers designed a comprehensive study with four distinct groups of chickens:
Kept at normal temperatures
Received PAMK supplementation
Exposed to elevated temperatures
Received PAMK and heat exposure
This elegant design allowed scientists to isolate the effects of both heat stress and PAMK treatment 1 4 .
To visualize ultrastructural changes
To detect and quantify apoptotic cells
To measure antioxidant enzyme activities
To assess gene expression patterns
To evaluate energy production systems 1
The results provided compelling evidence for PAMK's protective effects. Under heat stress, spleen cells showed severe mitochondrial damage—the organelles were swollen with broken cristae (the inner folds where energy production occurs).
The PAMK+heat stress group showed some mitochondrial damage, but it was significantly less severe than in the heat stress-only group 1 .
The TUNEL assay revealed that heat stress dramatically increased the rate of programmed cell death in spleen tissue, while PAMK supplementation significantly reduced this effect, bringing apoptosis levels closer to normal 1 .
| Parameter | Control Group | Heat Stress Group | PAMK+Heat Stress Group |
|---|---|---|---|
| Catalase (CAT) Activity | Normal | Significantly Decreased | Partially Restored |
| Total Antioxidant Capacity (T-AOC) | Normal | Significantly Decreased | Partially Restored |
| Hydrogen Peroxide (H₂O₂) Content | Normal | Significantly Increased | Significantly Reduced |
| Hydroxyl Radical (·OH) Inhibition | Normal | Significantly Decreased | Partially Restored |
The data clearly demonstrate that PAMK helps maintain the antioxidant defense system under challenging conditions, reducing the oxidative damage that triggers broader cellular dysfunction 1 .
The mitochondria serve as the cellular powerplants, and their proper function is essential for immune cells to effectively combat pathogens. The research revealed that heat stress significantly reduces the activities of key mitochondrial complexes (I, II, and V) and ATPases—the enzymes responsible for energy production.
PAMK supplementation markedly enhanced the activities of these critical complexes compared to the heat stress group, though it didn't completely restore them to normal levels 1 .
| Enzyme | Control Group | Heat Stress Group | PAMK+Heat Stress Group |
|---|---|---|---|
| Complex I | Normal | Significantly Decreased | Significantly Improved |
| Complex II | Normal | Significantly Decreased | Significantly Improved |
| Complex V | Normal | Significantly Decreased | Significantly Improved |
| Na+-K+-ATPase | Normal | Significantly Decreased | Significantly Improved |
| Ca2+-ATPase | Normal | Significantly Decreased | Significantly Improved |
One of the most critical aspects of PAMK's activity is its ability to modulate immune function. Heat stress created a dysfunctional immune environment in the spleen, with increased pro-inflammatory cytokines (IL-1β and TNF-α) and decreased beneficial cytokines (IL-2 and IFN-γ).
PAMK treatment significantly reversed this pattern, reducing the damaging inflammation while enhancing the cytokines necessary for effective immune response 1 .
The effect on immune function isn't limited to heat stress scenarios. Separate research has shown that Atractylodis macrocephalae polysaccharides can enhance lymphocyte proliferation, increase the CD4+/CD8+ ratio (an indicator of immune competence), and potentially serve as effective vaccine adjuvants in chickens 7 .
At the most fundamental level, PAMK exerts its effects by regulating gene expression. The study examined numerous genes related to mitochondrial dynamics and apoptosis, finding that heat stress downregulated both mitochondrial fission- and fusion-related genes while activating pro-apoptotic factors.
PAMK treatment counteracted these changes, promoting expression of genes that maintain mitochondrial health and prevent programmed cell death 1 .
| Factor | Function | Effect of Heat Stress | Effect of PAMK |
|---|---|---|---|
| Bax | Pro-apoptotic | Increased | Significantly Reduced |
| Bak | Pro-apoptotic | Increased | Significantly Reduced |
| Bcl-xl | Anti-apoptotic | Decreased | Significantly Increased |
| Caspase-3 | Executioner of apoptosis | Increased | Significantly Reduced |
The implications of PAMK research extend far beyond poultry spleen protection. Scientists are discovering that plant polysaccharides more broadly represent a promising class of natural compounds with diverse biological activities.
These complex carbohydrates show potential for direct anticancer activity, immune system modulation, and even serving as drug delivery vehicles in nanomedicine 6 .
Interestingly, the protective effects of PAMK aren't limited to heat stress. Recent research demonstrates that it can also alleviate splenic ferroptosis (an iron-dependent form of cell death) in goslings induced by lipopolysaccharide exposure.
This suggests that PAMK's mechanisms may be effective against multiple forms of cellular stress 8 .
The study of how polysaccharides interact with biological systems has revealed fascinating connections to the gut microbiome. Similar polysaccharides from other medicinal herbs have been shown to modulate gut microbiota composition, enhancing the production of beneficial short-chain fatty acids that support overall health .
While this particular aspect hasn't been thoroughly investigated for PAMK specifically, it represents an exciting direction for future research.
The discovery of PAMK's protective effects against heat stress damage represents a perfect marriage of traditional herbal wisdom and cutting-edge molecular biology. By understanding exactly how this natural polysaccharide reduces oxidative stress, enhances mitochondrial function, and inhibits apoptosis, scientists have provided a solid scientific foundation for its use in poultry production.
As climate change increases the frequency and intensity of heat waves, natural solutions like PAMK become increasingly valuable. They offer a sustainable approach to maintaining animal health and productivity without resorting to synthetic chemicals or pharmaceuticals.
While significant progress has been made in understanding PAMK's mechanisms, many questions remain. Future research may explore how combining PAMK with other natural compounds might enhance its efficacy, how it affects other organs and systems beyond the spleen, and whether similar polysaccharides from other plants offer comparable benefits.
What remains clear is that nature provides powerful solutions to agricultural challenges—we need only look closely enough to find them.
Induces oxidative damage and mitochondrial dysfunction
Enhances antioxidant defenses
Preserves energy production complexes
Reduces programmed cell death
Normalizes cytokine balance and immune function
Heat stress causes substantial economic losses in poultry production worldwide. PAMK offers a natural, sustainable solution to this growing problem exacerbated by climate change.
Poultry affected by heat stress in warm climates